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| author | Andreas Metzler <ametzler@downhill.at.eu.org> | 2013-09-29 14:39:44 +0200 |
|---|---|---|
| committer | Andreas Metzler <ametzler@downhill.at.eu.org> | 2013-09-29 14:39:44 +0200 |
| commit | f86518405fe4817dc91553856c995c7482a1f4ce (patch) | |
| tree | 6c646a36cf63a4828c75e145ba38550523354365 | |
| parent | 95ddbb39c005c2a1aca7852ccbff2e1eef10aadc (diff) | |
| download | exim4-f86518405fe4817dc91553856c995c7482a1f4ce.tar.gz | |
Add txt docs.
80_addmanuallybuiltdocs.diff: Upstream rc tarball ships empty
filter.txt and spec.txt, replace these with correct handbuilt versions.
| -rw-r--r-- | debian/changelog | 2 | ||||
| -rw-r--r-- | debian/patches/80_addmanuallybuiltdocs.diff | 36053 | ||||
| -rw-r--r-- | debian/patches/series | 1 |
3 files changed, 36056 insertions, 0 deletions
diff --git a/debian/changelog b/debian/changelog index 2f763ca..0892d3a 100644 --- a/debian/changelog +++ b/debian/changelog @@ -15,6 +15,8 @@ exim4 (4.82~rc1-1) UNRELEASED; urgency=low * Appling upstream's default configuration changes to Debian change 30_exim4-config_examples to use tls_in_cipher/tls_out_cipher instead of tls_out_cipher. - exim4-config therefore Breaks exim daemon << 4.82~rc1. + * 80_addmanuallybuiltdocs.diff: Upstream rc tarball ships empty filter.txt + and spec.txt, replace these with correct handbuilt versions. -- Andreas Metzler <ametzler@debian.org> Sat, 28 Sep 2013 13:13:38 +0200 diff --git a/debian/patches/80_addmanuallybuiltdocs.diff b/debian/patches/80_addmanuallybuiltdocs.diff new file mode 100644 index 0000000..45ae0c4 --- /dev/null +++ b/debian/patches/80_addmanuallybuiltdocs.diff @@ -0,0 +1,36053 @@ +Description: Add txt documentation. + Upstream rc tarball ships empty filter.txt and spec.txt, replace these + with correct handbuilt versions. +Author: Andreas Metzler <ametzler@debian.org> +Origin: vendor +Forwarded: http://article.gmane.org/gmane.mail.exim.devel/6412 +Last-Update: <YYYY-MM-DD> + +--- exim4-4.82~rc1.orig/doc/filter.txt ++++ exim4-4.82~rc1/doc/filter.txt +@@ -0,0 +1,1728 @@ ++Exim's interfaces to mail filtering ++ ++Philip Hazel ++ ++Copyright (c) 2010 University of Cambridge ++ ++Revision 4.82 29 Sep 2013 PH ++ ++Abstract ++ ++Exim filtering ++ ++------------------------------------------------------------------------------- ++ ++TABLE OF CONTENTS ++ ++1. Forwarding and filtering in Exim ++ ++ 1.1. Introduction ++ 1.2. Filter operation ++ 1.3. Testing a new filter file ++ 1.4. Installing a filter file ++ 1.5. Testing an installed filter file ++ 1.6. Details of filtering commands ++ ++2. Sieve filter files ++ ++ 2.1. Recognition of Sieve filters ++ 2.2. Saving to specified folders ++ 2.3. Strings containing header names ++ 2.4. Exists test with empty list of headers ++ 2.5. Header test with invalid MIME encoding in header ++ 2.6. Address test for multiple addresses per header ++ 2.7. Semantics of keep ++ 2.8. Semantics of fileinto ++ 2.9. Semantics of redirect ++ 2.10. String arguments ++ 2.11. Number units ++ 2.12. RFC compliance ++ ++3. Exim filter files ++ ++ 3.1. Format of Exim filter files ++ 3.2. Data values in filter commands ++ 3.3. String expansion ++ 3.4. Some useful general variables ++ 3.5. Header variables ++ 3.6. User variables ++ 3.7. Current directory ++ 3.8. Significant deliveries ++ 3.9. Filter commands ++ 3.10. The add command ++ 3.11. The deliver command ++ 3.12. The save command ++ 3.13. The pipe command ++ 3.14. Mail commands ++ 3.15. Logging commands ++ 3.16. The finish command ++ 3.17. The testprint command ++ 3.18. The fail command ++ 3.19. The freeze command ++ 3.20. The headers command ++ 3.21. Obeying commands conditionally ++ 3.22. String testing conditions ++ 3.23. Numeric testing conditions ++ 3.24. Testing for significant deliveries ++ 3.25. Testing for error messages ++ 3.26. Testing a list of addresses ++ 3.27. Testing for personal mail ++ 3.28. Alias addresses for the personal condition ++ 3.29. Details of the personal condition ++ 3.30. Testing delivery status ++ 3.31. Multiple personal mailboxes ++ 3.32. Ignoring delivery errors ++ 3.33. Examples of Exim filter commands ++ ++ ++ ++=============================================================================== ++1. FORWARDING AND FILTERING IN EXIM ++ ++This document describes the user interfaces to Exim's in-built mail filtering ++facilities, and is copyright (c) University of Cambridge 2010. It corresponds ++to Exim version 4.82. ++ ++ ++1.1 Introduction ++---------------- ++ ++Most Unix mail transfer agents (programs that deliver mail) permit individual ++users to specify automatic forwarding of their mail, usually by placing a list ++of forwarding addresses in a file called .forward in their home directories. ++Exim extends this facility by allowing the forwarding instructions to be a set ++of rules rather than just a list of addresses, in effect providing ".forward ++with conditions". Operating the set of rules is called filtering, and the file ++that contains them is called a filter file. ++ ++Exim supports two different kinds of filter file. An Exim filter contains ++instructions in a format that is unique to Exim. A Sieve filter contains ++instructions in the Sieve format that is defined by RFC 3028. As this is a ++standard format, Sieve filter files may already be familiar to some users. ++Sieve files should also be portable between different environments. However, ++the Exim filtering facility contains more features (such as variable ++expansion), and better integration with the host environment (such as the use ++of external processes and pipes). ++ ++The choice of which kind of filter to use can be left to the end-user, provided ++that the system administrator has configured Exim appropriately for both kinds ++of filter. However, if interoperability is important, Sieve is the only choice. ++ ++The ability to use filtering or traditional forwarding has to be enabled by the ++system administrator, and some of the individual facilities can be separately ++enabled or disabled. A local document should be provided to describe exactly ++what has been enabled. In the absence of this, consult your system ++administrator. ++ ++This document describes how to use a filter file and the format of its ++contents. It is intended for use by end-users. Both Sieve filters and Exim ++filters are covered. However, for Sieve filters, only issues that relate to the ++Exim implementation are discussed, since Sieve itself is described elsewhere. ++ ++The contents of traditional .forward files are not described here. They ++normally contain just a list of addresses, file names, or pipe commands, ++separated by commas or newlines, but other types of item are also available. ++The full details can be found in the chapter on the redirect router in the Exim ++specification, which also describes how the system administrator can set up and ++control the use of filtering. ++ ++ ++1.2 Filter operation ++-------------------- ++ ++It is important to realize that, in Exim, no deliveries are actually made while ++a filter or traditional .forward file is being processed. Running a filter or ++processing a traditional .forward file sets up future delivery operations, but ++does not carry them out. ++ ++The result of filter or .forward file processing is a list of destinations to ++which a message should be delivered. The deliveries themselves take place ++later, along with all other deliveries for the message. This means that it is ++not possible to test for successful deliveries while filtering. It also means ++that any duplicate addresses that are generated are dropped, because Exim never ++delivers the same message to the same address more than once. ++ ++ ++1.3 Testing a new filter file ++----------------------------- ++ ++Filter files, especially the more complicated ones, should always be tested, as ++it is easy to make mistakes. Exim provides a facility for preliminary testing ++of a filter file before installing it. This tests the syntax of the file and ++its basic operation, and can also be used with traditional .forward files. ++ ++Because a filter can do tests on the content of messages, a test message is ++required. Suppose you have a new filter file called myfilter and a test message ++in a file called test-message. Assuming that Exim is installed with the ++conventional path name /usr/sbin/sendmail (some operating systems use /usr/lib/ ++sendmail), the following command can be used: ++ ++/usr/sbin/sendmail -bf myfilter <test-message ++ ++The -bf option tells Exim that the following item on the command line is the ++name of a filter file that is to be tested. There is also a -bF option, which ++is similar, but which is used for testing system filter files, as opposed to ++user filter files, and which is therefore of use only to the system ++administrator. ++ ++The test message is supplied on the standard input. If there are no ++message-dependent tests in the filter, an empty file (/dev/null) can be used. A ++supplied message must start with header lines or the "From " message separator ++line that is found in many multi-message folder files. Note that blank lines at ++the start terminate the header lines. A warning is given if no header lines are ++read. ++ ++The result of running this command, provided no errors are detected in the ++filter file, is a list of the actions that Exim would try to take if presented ++with the message for real. For example, for an Exim filter, the output ++ ++Deliver message to: gulliver@lilliput.fict.example ++Save message to: /home/lemuel/mail/archive ++ ++means that one copy of the message would be sent to ++gulliver@lilliput.fict.example, and another would be added to the file /home/ ++lemuel/mail/archive, if all went well. ++ ++The actions themselves are not attempted while testing a filter file in this ++way; there is no check, for example, that any forwarding addresses are valid. ++For an Exim filter, if you want to know why a particular action is being taken, ++add the -v option to the command. This causes Exim to output the results of any ++conditional tests and to indent its output according to the depth of nesting of ++if commands. Further additional output from a filter test can be generated by ++the testprint command, which is described below. ++ ++When Exim is outputting a list of the actions it would take, if any text ++strings are included in the output, non-printing characters therein are ++converted to escape sequences. In particular, if any text string contains a ++newline character, this is shown as "\n" in the testing output. ++ ++When testing a filter in this way, Exim makes up an "envelope" for the message. ++The recipient is by default the user running the command, and so is the sender, ++but the command can be run with the -f option to supply a different sender. For ++example, ++ ++/usr/sbin/sendmail -bf myfilter \ ++ -f islington@never.where <test-message ++ ++Alternatively, if the -f option is not used, but the first line of the supplied ++message is a "From " separator from a message folder file (not the same thing ++as a From: header line), the sender is taken from there. If -f is present, the ++contents of any "From " line are ignored. ++ ++The "return path" is the same as the envelope sender, unless the message ++contains a Return-path: header, in which case it is taken from there. You need ++not worry about any of this unless you want to test out features of a filter ++file that rely on the sender address or the return path. ++ ++It is possible to change the envelope recipient by specifying further options. ++The -bfd option changes the domain of the recipient address, while the -bfl ++option changes the "local part", that is, the part before the @ sign. An ++adviser could make use of these to test someone else's filter file. ++ ++The -bfp and -bfs options specify the prefix or suffix for the local part. ++These are relevant only when support for multiple personal mailboxes is ++implemented; see the description in section 3.31 below. ++ ++ ++1.4 Installing a filter file ++---------------------------- ++ ++A filter file is normally installed under the name .forward in your home ++directory - it is distinguished from a conventional .forward file by its first ++line (described below). However, the file name is configurable, and some system ++administrators may choose to use some different name or location for filter ++files. ++ ++ ++1.5 Testing an installed filter file ++------------------------------------ ++ ++Testing a filter file before installation cannot find every potential problem; ++for example, it does not actually run commands to which messages are piped. ++Some "live" tests should therefore also be done once a filter is installed. ++ ++If at all possible, test your filter file by sending messages from some other ++account. If you send a message to yourself from the filtered account, and ++delivery fails, the error message will be sent back to the same account, which ++may cause another delivery failure. It won't cause an infinite sequence of such ++messages, because delivery failure messages do not themselves generate further ++messages. However, it does mean that the failure won't be returned to you, and ++also that the postmaster will have to investigate the stuck message. ++ ++If you have to test an Exim filter from the same account, a sensible precaution ++is to include the line ++ ++if error_message then finish endif ++ ++as the first filter command, at least while testing. This causes filtering to ++be abandoned for a delivery failure message, and since no destinations are ++generated, the message goes on to be delivered to the original address. Unless ++there is a good reason for not doing so, it is recommended that the above test ++be left in all Exim filter files. (This does not apply to Sieve files.) ++ ++ ++1.6 Details of filtering commands ++--------------------------------- ++ ++The filtering commands for Sieve and Exim filters are completely different in ++syntax and semantics. The Sieve mechanism is defined in RFC 3028; in the next ++chapter we describe how it is integrated into Exim. The subsequent chapter ++covers Exim filtering commands in detail. ++ ++ ++ ++=============================================================================== ++2. SIEVE FILTER FILES ++ ++The code for Sieve filtering in Exim was contributed by Michael Haardt, and ++most of the content of this chapter is taken from the notes he provided. Since ++Sieve is an extensible language, it is important to understand "Sieve" in this ++context as "the specific implementation of Sieve for Exim". ++ ++This chapter does not contain a description of Sieve, since that can be found ++in RFC 3028, which should be read in conjunction with these notes. ++ ++The Exim Sieve implementation offers the core as defined by RFC 3028, ++comparison tests, the subaddress parameter, the copy, envelope, fileinto, ++notify, and vacation extensions, but not the reject extension. Exim does not ++support message delivery notifications (MDNs), so adding it just to the Sieve ++filter (as required for reject) makes little sense. ++ ++In order for Sieve to work properly in Exim, the system administrator needs to ++make some adjustments to the Exim configuration. These are described in the ++chapter on the redirect router in the full Exim specification. ++ ++ ++2.1 Recognition of Sieve filters ++-------------------------------- ++ ++A filter file is interpreted as a Sieve filter if its first line is ++ ++# Sieve filter ++ ++This is what distinguishes it from a conventional .forward file or an Exim ++filter file. ++ ++ ++2.2 Saving to specified folders ++------------------------------- ++ ++If the system administrator has set things up as suggested in the Exim ++specification, and you use keep or fileinto to save a mail into a folder, ++absolute files are stored where specified, relative files are stored relative ++to $home, and inbox goes to the standard mailbox location. ++ ++ ++2.3 Strings containing header names ++----------------------------------- ++ ++RFC 3028 does not specify what happens if a string denoting a header field does ++not contain a valid header name, for example, it contains a colon. This ++implementation generates an error instead of ignoring the header field in order ++to ease script debugging, which fits in with the common picture of Sieve. ++ ++ ++2.4 Exists test with empty list of headers ++------------------------------------------ ++ ++The exists test succeeds only if all the specified headers exist. RFC 3028 does ++not explicitly specify what happens on an empty list of headers. This ++implementation evaluates that condition as true, interpreting the RFC in a ++strict sense. ++ ++ ++2.5 Header test with invalid MIME encoding in header ++---------------------------------------------------- ++ ++Some MUAs process invalid base64 encoded data, generating junk. Others ignore ++junk after seeing an equal sign in base64 encoded data. RFC 2047 does not ++specify how to react in this case, other than stating that a client must not ++forbid to process a message for that reason. RFC 2045 specifies that invalid ++data should be ignored (apparently looking at end of line characters). It also ++specifies that invalid data may lead to rejecting messages containing them (and ++there it appears to talk about true encoding violations), which is a clear ++contradiction to ignoring them. ++ ++RFC 3028 does not specify how to process incorrect MIME words. This ++implementation treats them literally, as it does if the word is correct but its ++character set cannot be converted to UTF-8. ++ ++ ++2.6 Address test for multiple addresses per header ++-------------------------------------------------- ++ ++A header may contain multiple addresses. RFC 3028 does not explicitly specify ++how to deal with them, but since the address test checks if anything matches ++anything else, matching one address suffices to satisfy the condition. That ++makes it impossible to test if a header contains a certain set of addresses and ++no more, but it is more logical than letting the test fail if the header ++contains an additional address besides the one the test checks for. ++ ++ ++2.7 Semantics of keep ++--------------------- ++ ++The keep command is equivalent to ++ ++fileinto "inbox"; ++ ++It saves the message and resets the implicit keep flag. It does not set the ++implicit keep flag; there is no command to set it once it has been reset. ++ ++ ++2.8 Semantics of fileinto ++------------------------- ++ ++RFC 3028 does not specify whether fileinto should try to create a mail folder ++if it does not exist. This implementation allows the sysadmin to configure that ++aspect using the appendfile transport options create_directory, create_file, ++and file_must_exist. See the appendfile transport in the Exim specification for ++details. ++ ++ ++2.9 Semantics of redirect ++------------------------- ++ ++Sieve scripts are supposed to be interoperable between servers, so this ++implementation does not allow mail to be redirected to unqualified addresses, ++because the domain would depend on the system being used. On systems with ++virtual mail domains, the default domain is probably not what the user expects ++it to be. ++ ++ ++2.10 String arguments ++--------------------- ++ ++There has been confusion if the string arguments to require are to be matched ++case-sensitively or not. This implementation matches them with the match type ++:is (default, see section 2.7.1 of the RFC) and the comparator i;ascii-casemap ++(default, see section 2.7.3 of the RFC). The RFC defines the command defaults ++clearly, so any different implementations violate RFC 3028. The same is valid ++for comparator names, also specified as strings. ++ ++ ++2.11 Number units ++----------------- ++ ++There is a mistake in RFC 3028: the suffix G denotes gibi-, not tebibyte. The ++mistake is obvious, because RFC 3028 specifies G to denote 2^30 (which is gibi, ++not tebi), and that is what this implementation uses as the scaling factor for ++the suffix G. ++ ++ ++2.12 RFC compliance ++------------------- ++ ++Exim requires the first line of a Sieve filter to be ++ ++# Sieve filter ++ ++Of course the RFC does not specify that line. Do not expect examples to work ++without adding it, though. ++ ++RFC 3028 requires the use of CRLF to terminate a line. The rationale was that ++CRLF is universally used in network protocols to mark the end of the line. This ++implementation does not embed Sieve in a network protocol, but uses Sieve ++scripts as part of the Exim MTA. Since all parts of Exim use LF as the newline ++character, this implementation does, too, by default, though the system ++administrator may choose (at Exim compile time) to use CRLF instead. ++ ++Exim violates RFC 2822, section 3.6.8, by accepting 8-bit header names, so this ++implementation repeats this violation to stay consistent with Exim. This is in ++preparation for UTF-8 data. ++ ++Sieve scripts cannot contain NUL characters in strings, but mail headers could ++contain MIME encoded NUL characters, which could never be matched by Sieve ++scripts using exact comparisons. For that reason, this implementation extends ++the Sieve quoted string syntax with \0 to describe a NUL character, violating \ ++0 being the same as 0 in RFC 3028. Even without using \0, the following tests ++are all true in this implementation. Implementations that use C-style strings ++will only evaluate the first test as true. ++ ++Subject: =?iso-8859-1?q?abc=00def ++ ++header :contains "Subject" ["abc"] ++header :contains "Subject" ["def"] ++header :matches "Subject" ["abc?def"] ++ ++Note that by considering Sieve to be an MUA, RFC 2047 can be interpreted in a ++way that NUL characters truncating strings is allowed for Sieve ++implementations, although not recommended. It is further allowed to use encoded ++NUL characters in headers, but that's not recommended either. The above example ++shows why. ++ ++RFC 3028 states that if an implementation fails to convert a character set to ++UTF-8, two strings cannot be equal if one contains octets greater than 127. ++Assuming that all unknown character sets are one-byte character sets with the ++lower 128 octets being US-ASCII is not sound, so this implementation violates ++RFC 3028 and treats such MIME words literally. That way at least something ++could be matched. ++ ++The folder specified by fileinto must not contain the character sequence ".." ++to avoid security problems. RFC 3028 does not specify the syntax of folders ++apart from keep being equivalent to ++ ++fileinto "INBOX"; ++ ++This implementation uses inbox instead. ++ ++Sieve script errors currently cause messages to be silently filed into inbox. ++RFC 3028 requires that the user is notified of that condition. This may be ++implemented in the future by adding a header line to mails that are filed into ++inbox due to an error in the filter. ++ ++ ++ ++=============================================================================== ++3. EXIM FILTER FILES ++ ++This chapter contains a full description of the contents of Exim filter files. ++ ++ ++3.1 Format of Exim filter files ++------------------------------- ++ ++Apart from leading white space, the first text in an Exim filter file must be ++ ++# Exim filter ++ ++This is what distinguishes it from a conventional .forward file or a Sieve ++filter file. If the file does not have this initial line (or the equivalent for ++a Sieve filter), it is treated as a conventional .forward file, both when ++delivering mail and when using the -bf testing mechanism. The white space in ++the line is optional, and any capitalization may be used. Further text on the ++same line is treated as a comment. For example, you could have ++ ++# Exim filter <<== do not edit or remove this line! ++ ++The remainder of the file is a sequence of filtering commands, which consist of ++keywords and data values. For example, in the command ++ ++deliver gulliver@lilliput.fict.example ++ ++the keyword is "deliver" and the data value is ++"gulliver@lilliput.fict.example". White space or line breaks separate the ++components of a command, except in the case of conditions for the if command, ++where round brackets (parentheses) also act as separators. Complete commands ++are separated from each other by white space or line breaks; there are no ++special terminators. Thus, several commands may appear on one line, or one ++command may be spread over a number of lines. ++ ++If the character # follows a separator anywhere in a command, everything from # ++up to the next newline is ignored. This provides a way of including comments in ++a filter file. ++ ++ ++3.2 Data values in filter commands ++---------------------------------- ++ ++There are two ways in which a data value can be input: ++ ++ * If the text contains no white space, it can be typed verbatim. However, if ++ it is part of a condition, it must also be free of round brackets ++ (parentheses), as these are used for grouping in conditions. ++ ++ * Otherwise, text must be enclosed in double quotation marks. In this case, ++ the character \ (backslash) is treated as an "escape character" within the ++ string, causing the following character or characters to be treated ++ specially: ++ ++ \n is replaced by a newline ++ \r is replaced by a carriage return ++ \t is replaced by a tab ++ ++Backslash followed by up to three octal digits is replaced by the character ++specified by those digits, and "\x" followed by up to two hexadecimal digits is ++treated similarly. Backslash followed by any other character is replaced by the ++second character, so that in particular, "\"" becomes """ and "\\" becomes "\". ++A data item enclosed in double quotes can be continued onto the next line by ++ending the first line with a backslash. Any leading white space at the start of ++the continuation line is ignored. ++ ++In addition to the escape character processing that occurs when strings are ++enclosed in quotes, most data values are also subject to string expansion (as ++described in the next section), in which case the characters "$" and "\" are ++also significant. This means that if a single backslash is actually required in ++such a string, and the string is also quoted, "\\\\" has to be entered. ++ ++The maximum permitted length of a data string, before expansion, is 1024 ++characters. ++ ++ ++3.3 String expansion ++-------------------- ++ ++Most data values are expanded before use. Expansion consists of replacing ++substrings beginning with "$" with other text. The full expansion facilities ++available in Exim are extensive. If you want to know everything that Exim can ++do with strings, you should consult the chapter on string expansion in the Exim ++documentation. ++ ++In filter files, by far the most common use of string expansion is the ++substitution of the contents of a variable. For example, the substring ++ ++$reply_address ++ ++is replaced by the address to which replies to the message should be sent. If ++such a variable name is followed by a letter or digit or underscore, it must be ++enclosed in curly brackets (braces), for example, ++ ++${reply_address} ++ ++If a "$" character is actually required in an expanded string, it must be ++escaped with a backslash, and because backslash is also an escape character in ++quoted input strings, it must be doubled in that case. The following two ++examples illustrate two different ways of testing for a "$" character in a ++message: ++ ++if $message_body contains \$ then ... ++if $message_body contains "\\$" then ... ++ ++You can prevent part of a string from being expanded by enclosing it between ++two occurrences of "\N". For example, ++ ++if $message_body contains \N$$$$\N then ... ++ ++tests for a run of four dollar characters. ++ ++ ++3.4 Some useful general variables ++--------------------------------- ++ ++A complete list of the available variables is given in the Exim documentation. ++This shortened list contains the ones that are most likely to be useful in ++personal filter files: ++ ++$body_linecount: The number of lines in the body of the message. ++ ++$body_zerocount: The number of binary zero characters in the body of the ++message. ++ ++$home: In conventional configurations, this variable normally contains the ++user's home directory. The system administrator can, however, change this. ++ ++$local_part: The part of the email address that precedes the @ sign - normally ++the user's login name. If support for multiple personal mailboxes is enabled ++(see section 3.31 below) and a prefix or suffix for the local part was ++recognized, it is removed from the string in this variable. ++ ++$local_part_prefix: If support for multiple personal mailboxes is enabled (see ++section 3.31 below), and a local part prefix was recognized, this variable ++contains the prefix. Otherwise it contains an empty string. ++ ++$local_part_suffix: If support for multiple personal mailboxes is enabled (see ++section 3.31 below), and a local part suffix was recognized, this variable ++contains the suffix. Otherwise it contains an empty string. ++ ++$message_body: The initial portion of the body of the message. By default, up ++to 500 characters are read into this variable, but the system administrator can ++configure this to some other value. Newlines in the body are converted into ++single spaces. ++ ++$message_body_end: The final portion of the body of the message, formatted and ++limited in the same way as $message_body. ++ ++$message_body_size: The size of the body of the message, in bytes. ++ ++$message_exim_id: The message's local identification string, which is unique ++for each message handled by a single host. ++ ++$message_headers: The header lines of the message, concatenated into a single ++string, with newline characters between them. ++ ++$message_size: The size of the entire message, in bytes. ++ ++$original_local_part: When an address that arrived with the message is being ++processed, this contains the same value as the variable $local_part. However, ++if an address generated by an alias, forward, or filter file is being ++processed, this variable contains the local part of the original address. ++ ++$reply_address: The contents of the Reply-to: header, if the message has one; ++otherwise the contents of the From: header. It is the address to which normal ++replies to the message should be sent. ++ ++$return_path: The return path - that is, the sender field that will be ++transmitted as part of the message's envelope if the message is sent to another ++host. This is the address to which delivery errors are sent. In many cases, ++this variable has the same value as $sender_address, but if, for example, an ++incoming message to a mailing list has been expanded, $return_path may have ++been changed to contain the address of the list maintainer. ++ ++$sender_address: The sender address that was received in the envelope of the ++message. This is not necessarily the same as the contents of the From: or ++Sender: header lines. For delivery error messages ("bounce messages") there is ++no sender address, and this variable is empty. ++ ++$tod_full: A full version of the time and date, for example: Wed, 18 Oct 1995 ++09:51:40 +0100. The timezone is always given as a numerical offset from GMT. ++ ++$tod_log: The time and date in the format used for writing Exim's log files, ++without the timezone, for example: 1995-10-12 15:32:29. ++ ++$tod_zone: The local timezone offset, for example: +0100. ++ ++ ++3.5 Header variables ++-------------------- ++ ++There is a special set of expansion variables containing the header lines of ++the message being processed. These variables have names beginning with $header_ ++followed by the name of the header line, terminated by a colon. For example, ++ ++$header_from: ++$header_subject: ++ ++The whole item, including the terminating colon, is replaced by the contents of ++the message header line. If there is more than one header line with the same ++name, their contents are concatenated. For header lines whose data consists of ++a list of addresses (for example, From: and To:), a comma and newline is ++inserted between each set of data. For all other header lines, just a newline ++is used. ++ ++Leading and trailing white space is removed from header line data, and if there ++are any MIME "words" that are encoded as defined by RFC 2047 (because they ++contain non-ASCII characters), they are decoded and translated, if possible, to ++a local character set. Translation is attempted only on operating systems that ++have the iconv() function. This makes the header line look the same as it would ++when displayed by an MUA. The default character set is ISO-8859-1, but this can ++be changed by means of the headers command (see below). ++ ++If you want to see the actual characters that make up a header line, you can ++specify $rheader_ instead of $header_. This inserts the "raw" header line, ++unmodified. ++ ++There is also an intermediate form, requested by $bheader_, which removes ++leading and trailing space and decodes MIME "words", but does not do any ++character translation. If an attempt to decode what looks superficially like a ++MIME "word" fails, the raw string is returned. If decoding produces a binary ++zero character, it is replaced by a question mark. ++ ++The capitalization of the name following $header_ is not significant. Because ++any printing character except colon may appear in the name of a message's ++header (this is a requirement of RFC 2822, the document that describes the ++format of a mail message) curly brackets must not be used in this case, as they ++will be taken as part of the header name. Two shortcuts are allowed in naming ++header variables: ++ ++ * The initiating $header_, $rheader_, or $bheader_ can be abbreviated to $h_, ++ $rh_, or $bh_, respectively. ++ ++ * The terminating colon can be omitted if the next character is white space. ++ The white space character is retained in the expanded string. However, this ++ is not recommended, because it makes it easy to forget the colon when it ++ really is needed. ++ ++If the message does not contain a header of the given name, an empty string is ++substituted. Thus it is important to spell the names of headers correctly. Do ++not use $header_Reply_to when you really mean $header_Reply-to. ++ ++ ++3.6 User variables ++------------------ ++ ++There are ten user variables with names $n0 - $n9 that can be incremented by ++the add command (see section 3.10). These can be used for "scoring" messages in ++various ways. If Exim is configured to run a "system filter" on every message, ++the values left in these variables are copied into the variables $sn0 - $sn9 at ++the end of the system filter, thus making them available to users' filter ++files. How these values are used is entirely up to the individual installation. ++ ++ ++3.7 Current directory ++--------------------- ++ ++The contents of your filter file should not make any assumptions about the ++current directory. It is best to use absolute paths for file names; you can ++normally make use of the $home variable to refer to your home directory. The ++save command automatically inserts $home at the start of non-absolute paths. ++ ++ ++3.8 Significant deliveries ++-------------------------- ++ ++When in the course of delivery a message is processed by a filter file, what ++happens next, that is, after the filter file has been processed, depends on ++whether or not the filter sets up any significant deliveries. If at least one ++significant delivery is set up, the filter is considered to have handled the ++entire delivery arrangements for the current address, and no further processing ++of the address takes place. If, however, no significant deliveries are set up, ++Exim continues processing the current address as if there were no filter file, ++and typically sets up a delivery of a copy of the message into a local mailbox. ++In particular, this happens in the special case of a filter file containing ++only comments. ++ ++The delivery commands deliver, save, and pipe are by default significant. ++However, if such a command is preceded by the word "unseen", its delivery is ++not considered to be significant. In contrast, other commands such as mail and ++vacation do not set up significant deliveries unless preceded by the word ++"seen". The following example commands set up significant deliveries: ++ ++deliver jack@beanstalk.example ++pipe $home/bin/mymailscript ++seen mail subject "message discarded" ++seen finish ++ ++The following example commands do not set up significant deliveries: ++ ++unseen deliver jack@beanstalk.example ++unseen pipe $home/bin/mymailscript ++mail subject "message discarded" ++finish ++ ++ ++3.9 Filter commands ++------------------- ++ ++The filter commands that are described in subsequent sections are listed below, ++with the section in which they are described in brackets: ++ ++add increment a user variable (section 3.10) ++deliver deliver to an email address (section 3.11) ++fail force delivery failure (sysadmin use) (section 3.18) ++finish end processing (section 3.16) ++freeze freeze message (sysadmin use) (section 3.19) ++headers set the header character set (section 3.20) ++if test condition(s) (section 3.21) ++logfile define log file (section 3.15) ++logwrite write to log file (section 3.15) ++mail send a reply message (section 3.14) ++pipe pipe to a command (section 3.13) ++save save to a file (section 3.12) ++testprint print while testing (section 3.17) ++vacation tailored form of mail (section 3.14) ++ ++The headers command has additional parameters that can be used only in a system ++filter. The fail and freeze commands are available only when Exim's filtering ++facilities are being used as a system filter, and are therefore usable only by ++the system administrator and not by ordinary users. They are mentioned only ++briefly in this document; for more information, see the main Exim ++specification. ++ ++ ++3.10 The add command ++-------------------- ++ ++ add <number> to <user variable> ++e.g. add 2 to n3 ++ ++There are 10 user variables of this type, with names $n0 - $n9. Their values ++can be obtained by the normal expansion syntax (for example $n3) in other ++commands. At the start of filtering, these variables all contain zero. Both ++arguments of the add command are expanded before use, making it possible to add ++variables to each other. Subtraction can be obtained by adding negative ++numbers. ++ ++ ++3.11 The deliver command ++------------------------ ++ ++ deliver <mail address> ++e.g. deliver "Dr Livingstone <David@somewhere.africa.example>" ++ ++This command provides a forwarding operation. The delivery that it sets up is ++significant unless the command is preceded by "unseen" (see section 3.8). The ++message is sent on to the given address, exactly as happens if the address had ++appeared in a traditional .forward file. If you want to deliver the message to ++a number of different addresses, you can use more than one deliver command ++(each one may have only one address). However, duplicate addresses are ++discarded. ++ ++To deliver a copy of the message to your normal mailbox, your login name can be ++given as the address. Once an address has been processed by the filtering ++mechanism, an identical generated address will not be so processed again, so ++doing this does not cause a loop. ++ ++However, if you have a mail alias, you should not refer to it here. For ++example, if the mail address L.Gulliver is aliased to lg303 then all references ++in Gulliver's .forward file should be to lg303. A reference to the alias will ++not work for messages that are addressed to that alias, since, like .forward ++file processing, aliasing is performed only once on an address, in order to ++avoid looping. ++ ++Following the new address, an optional second address, preceded by "errors_to" ++may appear. This changes the address to which delivery errors on the forwarded ++message will be sent. Instead of going to the message's original sender, they ++go to this new address. For ordinary users, the only value that is permitted ++for this address is the user whose filter file is being processed. For example, ++the user lg303 whose mailbox is in the domain lilliput.example could have a ++filter file that contains ++ ++deliver jon@elsewhere.example errors_to lg303@lilliput.example ++ ++Clearly, using this feature makes sense only in situations where not all ++messages are being forwarded. In particular, bounce messages must not be ++forwarded in this way, as this is likely to create a mail loop if something ++goes wrong. ++ ++ ++3.12 The save command ++--------------------- ++ ++ save <file name> ++e.g. save $home/mail/bookfolder ++ ++This command specifies that a copy of the message is to be appended to the ++given file (that is, the file is to be used as a mail folder). The delivery ++that save sets up is significant unless the command is preceded by "unseen" ++(see section 3.8). ++ ++More than one save command may be obeyed; each one causes a copy of the message ++to be written to its argument file, provided they are different (duplicate save ++commands are ignored). ++ ++If the file name does not start with a / character, the contents of the $home ++variable are prepended, unless it is empty, or the system administrator has ++disabled this feature. In conventional configurations, this variable is ++normally set in a user filter to the user's home directory, but the system ++administrator may set it to some other path. In some configurations, $home may ++be unset, or prepending may be disabled, in which case a non-absolute path name ++may be generated. Such configurations convert this to an absolute path when the ++delivery takes place. In a system filter, $home is never set. ++ ++The user must of course have permission to write to the file, and the writing ++of the file takes place in a process that is running as the user, under the ++user's primary group. Any secondary groups to which the user may belong are not ++normally taken into account, though the system administrator can configure Exim ++to set them up. In addition, the ability to use this command at all is ++controlled by the system administrator - it may be forbidden on some systems. ++ ++An optional mode value may be given after the file name. The value for the mode ++is interpreted as an octal number, even if it does not begin with a zero. For ++example: ++ ++save /some/folder 640 ++ ++This makes it possible for users to override the system-wide mode setting for ++file deliveries, which is normally 600. If an existing file does not have the ++correct mode, it is changed. ++ ++An alternative form of delivery may be enabled on your system, in which each ++message is delivered into a new file in a given directory. If this is the case, ++this functionality can be requested by giving the directory name terminated by ++a slash after the save command, for example ++ ++save separated/messages/ ++ ++There are several different formats for such deliveries; check with your system ++administrator or local documentation to find out which (if any) are available ++on your system. If this functionality is not enabled, the use of a path name ++ending in a slash causes an error. ++ ++ ++3.13 The pipe command ++--------------------- ++ ++ pipe <command> ++e.g. pipe "$home/bin/countmail $sender_address" ++ ++This command specifies that the message is to be delivered to the specified ++command using a pipe. The delivery that it sets up is significant unless the ++command is preceded by "unseen" (see section 3.8). Remember, however, that no ++deliveries are done while the filter is being processed. All deliveries happen ++later on. Therefore, the result of running the pipe is not available to the ++filter. ++ ++When the deliveries are done, a separate process is run, and a copy of the ++message is passed on its standard input. The process runs as the user, under ++the user's primary group. Any secondary groups to which the user may belong are ++not normally taken into account, though the system administrator can configure ++Exim to set them up. More than one pipe command may appear; each one causes a ++copy of the message to be written to its argument pipe, provided they are ++different (duplicate pipe commands are ignored). ++ ++When the time comes to transport the message, the command supplied to pipe is ++split up by Exim into a command name and a number of arguments. These are ++delimited by white space except for arguments enclosed in double quotes, in ++which case backslash is interpreted as an escape, or in single quotes, in which ++case no escaping is recognized. Note that as the whole command is normally ++supplied in double quotes, a second level of quoting is required for internal ++double quotes. For example: ++ ++pipe "$home/myscript \"size is $message_size\"" ++ ++String expansion is performed on the separate components after the line has ++been split up, and the command is then run directly by Exim; it is not run ++under a shell. Therefore, substitution cannot change the number of arguments, ++nor can quotes, backslashes or other shell metacharacters in variables cause ++confusion. ++ ++Documentation for some programs that are normally run via this kind of pipe ++often suggest that the command should start with ++ ++IFS=" " ++ ++This is a shell command, and should not be present in Exim filter files, since ++it does not normally run the command under a shell. ++ ++However, there is an option that the administrator can set to cause a shell to ++be used. In this case, the entire command is expanded as a single string and ++passed to the shell for interpretation. It is recommended that this be avoided ++if at all possible, since it can lead to problems when inserted variables ++contain shell metacharacters. ++ ++The default PATH set up for the command is determined by the system ++administrator, usually containing at least /bin and /usr/bin so that common ++commands are available without having to specify an absolute file name. ++However, it is possible for the system administrator to restrict the pipe ++facility so that the command name must not contain any / characters, and must ++be found in one of the directories in the configured PATH. It is also possible ++for the system administrator to lock out the use of the pipe command ++altogether. ++ ++When the command is run, a number of environment variables are set up. The ++complete list for pipe deliveries may be found in the Exim reference manual. ++Those that may be useful for pipe deliveries from user filter files are: ++ ++DOMAIN the domain of the address ++HOME your home directory ++LOCAL_PART see below ++LOCAL_PART_PREFIX see below ++LOCAL_PART_SUFFIX see below ++LOGNAME your login name ++MESSAGE_ID the unique id of the message ++PATH the command search path ++RECIPIENT the complete recipient address ++SENDER the sender of the message ++SHELL /bin/sh ++USER see below ++ ++LOCAL_PART, LOGNAME, and USER are all set to the same value, namely, your login ++id. LOCAL_PART_PREFIX and LOCAL_PART_SUFFIX may be set if Exim is configured to ++recognize prefixes or suffixes in the local parts of addresses. For example, a ++message addressed to pat-suf2@domain.example may cause the filter for user pat ++to be run. If this sets up a pipe delivery, LOCAL_PART_SUFFIX is "-suf2" when ++the pipe command runs. The system administrator has to configure Exim specially ++for this feature to be available. ++ ++If you run a command that is a shell script, be very careful in your use of ++data from the incoming message in the commands in your script. RFC 2822 is very ++generous in the characters that are permitted to appear in mail addresses, and ++in particular, an address may begin with a vertical bar or a slash. For this ++reason you should always use quotes round any arguments that involve data from ++the message, like this: ++ ++/some/command '$SENDER' ++ ++so that inserted shell meta-characters do not cause unwanted effects. ++ ++Remember that, as was explained earlier, the pipe command is not run at the ++time the filter file is interpreted. The filter just defines what deliveries ++are required for one particular addressee of a message. The deliveries ++themselves happen later, once Exim has decided everything that needs to be done ++for the message. ++ ++A consequence of this is that you cannot inspect the return code from the pipe ++command from within the filter. Nevertheless, the code returned by the command ++is important, because Exim uses it to decide whether the delivery has succeeded ++or failed. ++ ++The command should return a zero completion code if all has gone well. Most ++non-zero codes are treated by Exim as indicating a failure of the pipe. This is ++treated as a delivery failure, causing the message to be returned to its ++sender. However, there are some completion codes that are treated as temporary ++errors. The message remains on Exim's spool disk, and the delivery is tried ++again later, though it will ultimately time out if the delivery failures go on ++too long. The completion codes to which this applies can be specified by the ++system administrator; the default values are 73 and 75. ++ ++The pipe command should not normally write anything to its standard output or ++standard error file descriptors. If it does, whatever is written is normally ++returned to the sender of the message as a delivery error, though this action ++can be varied by the system administrator. ++ ++ ++3.14 Mail commands ++------------------ ++ ++There are two commands that cause the creation of a new mail message, neither ++of which count as a significant delivery unless the command is preceded by the ++word "seen" (see section 3.8). This is a powerful facility, but it should be ++used with care, because of the danger of creating infinite sequences of ++messages. The system administrator can forbid the use of these commands ++altogether. ++ ++To help prevent runaway message sequences, these commands have no effect when ++the incoming message is a bounce (delivery error) message, and messages sent by ++this means are treated as if they were reporting delivery errors. Thus, they ++should never themselves cause a bounce message to be returned. The basic ++mail-sending command is ++ ++mail [to <address-list>] ++ [cc <address-list>] ++ [bcc <address-list>] ++ [from <address>] ++ [reply_to <address>] ++ [subject <text>] ++ [extra_headers <text>] ++ [text <text>] ++ [[expand] file <filename>] ++ [return message] ++ [log <log file name>] ++ [once <note file name>] ++ [once_repeat <time interval>] ++e.g. mail text "Your message about $h_subject: has been received" ++ ++Each <address-list> can contain a number of addresses, separated by commas, in ++the format of a To: or Cc: header line. In fact, the text you supply here is ++copied exactly into the appropriate header line. It may contain additional ++information as well as email addresses. For example: ++ ++mail to "Julius Caesar <jc@rome.example>, \ ++ <ma@rome.example> (Mark A.)" ++ ++Similarly, the texts supplied for from and reply_to are copied into their ++respective header lines. ++ ++As a convenience for use in one common case, there is also a command called ++vacation. It behaves in the same way as mail, except that the defaults for the ++subject, file, log, once, and once_repeat options are ++ ++subject "On vacation" ++expand file .vacation.msg ++log .vacation.log ++once .vacation ++once_repeat 7d ++ ++respectively. These are the same file names and repeat period used by the ++traditional Unix vacation command. The defaults can be overridden by explicit ++settings, but if a file name is given its contents are expanded only if ++explicitly requested. ++ ++Warning: The vacation command should always be used conditionally, subject to ++at least the personal condition (see section 3.27 below) so as not to send ++automatic replies to non-personal messages from mailing lists or elsewhere. ++Sending an automatic response to a mailing list or a mailing list manager is an ++Internet Sin. ++ ++For both commands, the key/value argument pairs can appear in any order. At ++least one of text or file must appear (except with vacation, where there is a ++default for file); if both are present, the text string appears first in the ++message. If expand precedes file, each line of the file is subject to string ++expansion before it is included in the message. ++ ++Several lines of text can be supplied to text by including the escape sequence ++"\n" in the string wherever a newline is required. If the command is output ++during filter file testing, newlines in the text are shown as "\n". ++ ++Note that the keyword for creating a Reply-To: header is reply_to, because Exim ++keywords may contain underscores, but not hyphens. If the from keyword is ++present and the given address does not match the user who owns the forward ++file, Exim normally adds a Sender: header to the message, though it can be ++configured not to do this. ++ ++The extra_headers keyword allows you to add custom header lines to the message. ++The text supplied must be one or more syntactically valid RFC 2822 header ++lines. You can use "\n" within quoted text to specify newlines between headers, ++and also to define continued header lines. For example: ++ ++extra_headers "h1: first\nh2: second\n continued\nh3: third" ++ ++No newline should appear at the end of the final header line. ++ ++If no to argument appears, the message is sent to the address in the ++$reply_address variable (see section 3.3 above). An In-Reply-To: header is ++automatically included in the created message, giving a reference to the ++message identification of the incoming message. ++ ++If return message is specified, the incoming message that caused the filter ++file to be run is added to the end of the message, subject to a maximum size ++limitation. ++ ++If a log file is specified, a line is added to it for each message sent. ++ ++If a once file is specified, it is used to hold a database for remembering who ++has received a message, and no more than one message is ever sent to any ++particular address, unless once_repeat is set. This specifies a time interval ++after which another copy of the message is sent. The interval is specified as a ++sequence of numbers, each followed by the initial letter of one of "seconds", ++"minutes", "hours", "days", or "weeks". For example, ++ ++once_repeat 5d4h ++ ++causes a new message to be sent if at least 5 days and 4 hours have elapsed ++since the last one was sent. There must be no white space in a time interval. ++ ++Commonly, the file name specified for once is used as the base name for ++direct-access (DBM) file operations. There are a number of different DBM ++libraries in existence. Some operating systems provide one as a default, but ++even in this case a different one may have been used when building Exim. With ++some DBM libraries, specifying once results in two files being created, with ++the suffixes .dir and .pag being added to the given name. With some others a ++single file with the suffix .db is used, or the name is used unchanged. ++ ++Using a DBM file for implementing the once feature means that the file grows as ++large as necessary. This is not usually a problem, but some system ++administrators want to put a limit on it. The facility can be configured not to ++use a DBM file, but instead, to use a regular file with a maximum size. The ++data in such a file is searched sequentially, and if the file fills up, the ++oldest entry is deleted to make way for a new one. This means that some ++correspondents may receive a second copy of the message after an unpredictable ++interval. Consult your local information to see if your system is configured ++this way. ++ ++More than one mail or vacation command may be obeyed in a single filter run; ++they are all honoured, even when they are to the same recipient. ++ ++ ++3.15 Logging commands ++--------------------- ++ ++A log can be kept of actions taken by a filter file. This facility is normally ++available in conventional configurations, but there are some situations where ++it might not be. Also, the system administrator may choose to disable it. Check ++your local information if in doubt. ++ ++Logging takes place while the filter file is being interpreted. It does not ++queue up for later like the delivery commands. The reason for this is so that a ++log file need be opened only once for several write operations. There are two ++commands, neither of which constitutes a significant delivery. The first ++defines a file to which logging output is subsequently written: ++ ++ logfile <file name> ++e.g. logfile $home/filter.log ++ ++The file name must be fully qualified. You can use $home, as in this example, ++to refer to your home directory. The file name may optionally be followed by a ++mode for the file, which is used if the file has to be created. For example, ++ ++logfile $home/filter.log 0644 ++ ++The number is interpreted as octal, even if it does not begin with a zero. The ++default for the mode is 600. It is suggested that the logfile command normally ++appear as the first command in a filter file. Once a log file has been obeyed, ++the logwrite command can be used to write to it: ++ ++ logwrite "<some text string>" ++e.g. logwrite "$tod_log $message_id processed" ++ ++It is possible to have more than one logfile command, to specify writing to ++different log files in different circumstances. Writing takes place at the end ++of the file, and a newline character is added to the end of each string if ++there isn't one already there. Newlines can be put in the middle of the string ++by using the "\n" escape sequence. Lines from simultaneous deliveries may get ++interleaved in the file, as there is no interlocking, so you should plan your ++logging with this in mind. However, data should not get lost. ++ ++ ++3.16 The finish command ++----------------------- ++ ++The command finish, which has no arguments, causes Exim to stop interpreting ++the filter file. This is not a significant action unless preceded by "seen". A ++filter file containing only "seen finish" is a black hole. ++ ++ ++3.17 The testprint command ++-------------------------- ++ ++It is sometimes helpful to be able to print out the values of variables when ++testing filter files. The command ++ ++ testprint <text> ++e.g. testprint "home=$home reply_address=$reply_address" ++ ++does nothing when mail is being delivered. However, when the filtering code is ++being tested by means of the -bf option (see section 1.3 above), the value of ++the string is written to the standard output. ++ ++ ++3.18 The fail command ++--------------------- ++ ++When Exim's filtering facilities are being used as a system filter, the fail ++command is available, to force delivery failure. Because this command is ++normally usable only by the system administrator, and not enabled for use by ++ordinary users, it is described in more detail in the main Exim specification ++rather than in this document. ++ ++ ++3.19 The freeze command ++----------------------- ++ ++When Exim's filtering facilities are being used as a system filter, the freeze ++command is available, to freeze a message on the queue. Because this command is ++normally usable only by the system administrator, and not enabled for use by ++ordinary users, it is described in more detail in the main Exim specification ++rather than in this document. ++ ++ ++3.20 The headers command ++------------------------ ++ ++The headers command can be used to change the target character set that is used ++when translating the contents of encoded header lines for insertion by the ++$header_ mechanism (see section 3.5 above). The default can be set in the Exim ++configuration; if not specified, ISO-8859-1 is used. The only currently ++supported format for the headers command in user filters is as in this example: ++ ++headers charset "UTF-8" ++ ++That is, headers is followed by the word "charset" and then the name of a ++character set. This particular example would be useful if you wanted to compare ++the contents of a header to a UTF-8 string. ++ ++In system filter files, the headers command can be used to add or remove header ++lines from the message. These features are described in the main Exim ++specification. ++ ++ ++3.21 Obeying commands conditionally ++----------------------------------- ++ ++Most of the power of filtering comes from the ability to test conditions and ++obey different commands depending on the outcome. The if command is used to ++specify conditional execution, and its general form is ++ ++if <condition> ++then <commands> ++elif <condition> ++then <commands> ++else <commands> ++endif ++ ++There may be any number of elif and then sections (including none) and the else ++section is also optional. Any number of commands, including nested if commands, ++may appear in any of the <commands> sections. ++ ++Conditions can be combined by using the words and and or, and round brackets ++(parentheses) can be used to specify how several conditions are to combine. ++Without brackets, and is more binding than or. For example: ++ ++if ++$h_subject: contains "Make money" or ++$h_precedence: is "junk" or ++($h_sender: matches ^\\d{8}@ and not personal) or ++$message_body contains "this is not spam" ++then ++seen finish ++endif ++ ++A condition can be preceded by not to negate it, and there are also some ++negative forms of condition that are more English-like. ++ ++ ++3.22 String testing conditions ++------------------------------ ++ ++There are a number of conditions that operate on text strings, using the words ++"begins", "ends", "is", "contains" and "matches". If you want to apply the same ++test to more than one header line, you can easily concatenate them into a ++single string for testing, as in this example: ++ ++if "$h_to:, $h_cc:" contains me@domain.example then ... ++ ++If a string-testing condition name is written in lower case, the testing of ++letters is done without regard to case; if it is written in upper case (for ++example, "CONTAINS"), the case of letters is taken into account. ++ ++ <text1> begins <text2> ++ <text1> does not begin <text2> ++e.g. $header_from: begins "Friend@" ++ ++A "begins" test checks for the presence of the second string at the start of ++the first, both strings having been expanded. ++ ++ <text1> ends <text2> ++ <text1> does not end <text2> ++e.g. $header_from: ends "public.com.example" ++ ++An "ends" test checks for the presence of the second string at the end of the ++first, both strings having been expanded. ++ ++ <text1> is <text2> ++ <text1> is not <text2> ++e.g. $local_part_suffix is "-foo" ++ ++An "is" test does an exact match between the strings, having first expanded ++both strings. ++ ++ <text1> contains <text2> ++ <text1> does not contain <text2> ++e.g. $header_subject: contains "evolution" ++ ++A "contains" test does a partial string match, having expanded both strings. ++ ++ <text1> matches <text2> ++ <text1> does not match <text2> ++e.g. $sender_address matches "(bill|john)@" ++ ++For a "matches" test, after expansion of both strings, the second one is ++interpreted as a regular expression. Exim uses the PCRE regular expression ++library, which provides regular expressions that are compatible with Perl. ++ ++The match succeeds if the regular expression matches any part of the first ++string. If you want a regular expression to match only at the start or end of ++the subject string, you must encode that requirement explicitly, using the "^" ++or "$" metacharacters. The above example, which is not so constrained, matches ++all these addresses: ++ ++bill@test.example ++john@some.example ++spoonbill@example.com ++littlejohn@example.com ++ ++To match only the first two, you could use this: ++ ++if $sender_address matches "^(bill|john)@" then ... ++ ++Care must be taken if you need a backslash in a regular expression, because ++backslashes are interpreted as escape characters both by the string expansion ++code and by Exim's normal processing of strings in quotes. For example, if you ++want to test the sender address for a domain ending in .com the regular ++expression is ++ ++\.com$ ++ ++The backslash and dollar sign in that expression have to be escaped when used ++in a filter command, as otherwise they would be interpreted by the expansion ++code. Thus, what you actually write is ++ ++if $sender_address matches \\.com\$ ++ ++An alternative way of handling this is to make use of the "\N" expansion flag ++for suppressing expansion: ++ ++if $sender_address matches \N\.com$\N ++ ++Everything between the two occurrences of "\N" is copied without change by the ++string expander (and in fact you do not need the final one, because it is at ++the end of the string). If the regular expression is given in quotes (mandatory ++only if it contains white space) you have to write either ++ ++if $sender_address matches "\\\\.com\\$" ++ ++or ++ ++if $sender_address matches "\\N\\.com$\\N" ++ ++If the regular expression contains bracketed sub-expressions, numeric variable ++substitutions such as $1 can be used in the subsequent actions after a ++successful match. If the match fails, the values of the numeric variables ++remain unchanged. Previous values are not restored after endif. In other words, ++only one set of values is ever available. If the condition contains several ++sub-conditions connected by and or or, it is the strings extracted from the ++last successful match that are available in subsequent actions. Numeric ++variables from any one sub-condition are also available for use in subsequent ++sub-conditions, because string expansion of a condition occurs just before it ++is tested. ++ ++ ++3.23 Numeric testing conditions ++------------------------------- ++ ++The following conditions are available for performing numerical tests: ++ ++ <number1> is above <number2> ++ <number1> is not above <number2> ++ <number1> is below <number2> ++ <number1> is not below <number2> ++e.g. $message_size is not above 10k ++ ++The <number> arguments must expand to strings of digits, optionally followed by ++one of the letters K or M (upper case or lower case) which cause multiplication ++by 1024 and 1024x1024 respectively. ++ ++ ++3.24 Testing for significant deliveries ++--------------------------------------- ++ ++You can use the delivered condition to test whether or not any previously ++obeyed filter commands have set up a significant delivery. For example: ++ ++if not delivered then save mail/anomalous endif ++ ++"Delivered" is perhaps a poor choice of name for this condition, because the ++message has not actually been delivered; rather, a delivery has been set up for ++later processing. ++ ++ ++3.25 Testing for error messages ++------------------------------- ++ ++The condition error_message is true if the incoming message is a bounce (mail ++delivery error) message. Putting the command ++ ++if error_message then finish endif ++ ++at the head of your filter file is a useful insurance against things going ++wrong in such a way that you cannot receive delivery error reports. Note: ++error_message is a condition, not an expansion variable, and therefore is not ++preceded by "$". ++ ++ ++3.26 Testing a list of addresses ++-------------------------------- ++ ++There is a facility for looping through a list of addresses and applying a ++condition to each of them. It takes the form ++ ++foranyaddress <string> (<condition>) ++ ++where <string> is interpreted as a list of RFC 2822 addresses, as in a typical ++header line, and <condition> is any valid filter condition or combination of ++conditions. The "group" syntax that is defined for certain header lines that ++contain addresses is supported. ++ ++The parentheses surrounding the condition are mandatory, to delimit it from ++possible further sub-conditions of the enclosing if command. Within the ++condition, the expansion variable $thisaddress is set to the non-comment ++portion of each of the addresses in the string in turn. For example, if the ++string is ++ ++B.Simpson <bart@sfld.example>, lisa@sfld.example (his sister) ++ ++then $thisaddress would take on the values "bart@sfld.example" and ++"lisa@sfld.example" in turn. ++ ++If there are no valid addresses in the list, the whole condition is false. If ++the internal condition is true for any one address, the overall condition is ++true and the loop ends. If the internal condition is false for all addresses in ++the list, the overall condition is false. This example tests for the presence ++of an eight-digit local part in any address in a To: header: ++ ++if foranyaddress $h_to: ( $thisaddress matches ^\\d{8}@ ) then ... ++ ++When the overall condition is true, the value of $thisaddress in the commands ++that follow then is the last value it took on inside the loop. At the end of ++the if command, the value of $thisaddress is reset to what it was before. It is ++best to avoid the use of multiple occurrences of foranyaddress, nested or ++otherwise, in a single if command, if the value of $thisaddress is to be used ++afterwards, because it isn't always clear what the value will be. Nested if ++commands should be used instead. ++ ++Header lines can be joined together if a check is to be applied to more than ++one of them. For example: ++ ++if foranyaddress $h_to:,$h_cc: .... ++ ++This scans through the addresses in both the To: and the Cc: headers. ++ ++ ++3.27 Testing for personal mail ++------------------------------ ++ ++A common requirement is to distinguish between incoming personal mail and mail ++from a mailing list, or from a robot or other automatic process (for example, a ++bounce message). In particular, this test is normally required for "vacation ++messages". ++ ++The personal condition checks that the message is not a bounce message and that ++the current user's email address appears in the To: header. It also checks that ++the sender is not the current user or one of a number of common daemons, and ++that there are no header lines starting List- in the message. Finally, it ++checks the content of the Precedence: header line, if there is one. ++ ++You should always use the personal condition when generating automatic ++responses. This example shows the use of personal in a filter file that is ++sending out vacation messages: ++ ++if personal then ++mail to $reply_address ++subject "I am on holiday" ++file $home/vacation/message ++once $home/vacation/once ++once_repeat 10d ++endif ++ ++It is tempting, when writing commands like the above, to quote the original ++subject in the reply. For example: ++ ++subject "Re: $h_subject:" ++ ++There is a danger in doing this, however. It may allow a third party to ++subscribe you to an opt-in mailing list, provided that the list accepts bounce ++messages as subscription confirmations. (Messages sent from filters are always ++sent as bounce messages.) Well-managed lists require a non-bounce message to ++confirm a subscription, so the danger is relatively small. ++ ++If prefixes or suffixes are in use for local parts - something which depends on ++the configuration of Exim (see section 3.31 below) - the tests for the current ++user are done with the full address (including the prefix and suffix, if any) ++as well as with the prefix and suffix removed. If the system is configured to ++rewrite local parts of mail addresses, for example, to rewrite "dag46" as ++"Dirk.Gently", the rewritten form of the address is also used in the tests. ++ ++ ++3.28 Alias addresses for the personal condition ++----------------------------------------------- ++ ++It is quite common for people who have mail accounts on a number of different ++systems to forward all their mail to one system, and in this case a check for ++personal mail should test all their various mail addresses. To allow for this, ++the personal condition keyword can be followed by ++ ++alias <address> ++ ++any number of times, for example: ++ ++if personal alias smith@else.where.example ++ alias jones@other.place.example ++then ... ++ ++The alias addresses are treated as alternatives to the current user's email ++address when testing the contents of header lines. ++ ++ ++3.29 Details of the personal condition ++-------------------------------------- ++ ++The basic personal test is roughly equivalent to the following: ++ ++not error_message and ++$message_headers does not contain "\nList-Id:" and ++$message_headers does not contain "\nList-Help:" and ++$message_headers does not contain "\nList-Subscribe:" and ++$message_headers does not contain "\nList-Unsubscribe:" and ++$message_headers does not contain "\nList-Post:" and ++$message_headers does not contain "\nList-Owner:" and ++$message_headers does not contain "\nList-Archive:" and ++( ++"${if def:h_auto-submitted:{present}{absent}}" is "absent" or ++$header_auto-submitted: is "no" ++) and ++$header_precedence: does not contain "bulk" and ++$header_precedence: does not contain "list" and ++$header_precedence: does not contain "junk" and ++foranyaddress $header_to: ++( $thisaddress contains "$local_part$domain" ) and ++not foranyaddress $header_from: ++( ++$thisaddress contains "$local_part@$domain" or ++$thisaddress contains "server@" or ++$thisaddress contains "daemon@" or ++$thisaddress contains "root@" or ++$thisaddress contains "listserv@" or ++$thisaddress contains "majordomo@" or ++$thisaddress contains "-request@" or ++$thisaddress matches "^owner-[^@]+@" ++) ++ ++The variable $local_part contains the local part of the mail address of the ++user whose filter file is being run - it is normally your login id. The $domain ++variable contains the mail domain. As explained above, if aliases or rewriting ++are defined, or if prefixes or suffixes are in use, the tests for the current ++user are also done with alternative addresses. ++ ++ ++3.30 Testing delivery status ++---------------------------- ++ ++There are two conditions that are intended mainly for use in system filter ++files, but which are available in users' filter files as well. The condition ++first_delivery is true if this is the first process that is attempting to ++deliver the message, and false otherwise. This indicator is not reset until the ++first delivery process successfully terminates; if there is a crash or a power ++failure (for example), the next delivery attempt is also a "first delivery". ++ ++In a user filter file first_delivery will be false if there was previously an ++error in the filter, or if a delivery for the user failed owing to, for ++example, a quota error, or if forwarding to a remote address was deferred for ++some reason. ++ ++The condition manually_thawed is true if the message was "frozen" for some ++reason, and was subsequently released by the system administrator. It is ++unlikely to be of use in users' filter files. ++ ++ ++3.31 Multiple personal mailboxes ++-------------------------------- ++ ++The system administrator can configure Exim so that users can set up variants ++on their email addresses and handle them separately. Consult your system ++administrator or local documentation to see if this facility is enabled on your ++system, and if so, what the details are. ++ ++The facility involves the use of a prefix or a suffix on an email address. For ++example, all mail addressed to lg303-<something> would be the property of user ++lg303, who could determine how it was to be handled, depending on the value of ++<something>. ++ ++There are two possible ways in which this can be set up. The first possibility ++is the use of multiple .forward files. In this case, mail to lg303-foo, for ++example, is handled by looking for a file called .forward-foo in lg303's home ++directory. If such a file does not exist, delivery fails and the message is ++returned to its sender. ++ ++The alternative approach is to pass all messages through a single .forward ++file, which must be a filter file so that it can distinguish between the ++different cases by referencing the variables $local_part_prefix or ++$local_part_suffix, as in the final example in section 3.33 below. ++ ++It is possible to configure Exim to support both schemes at once. In this case, ++a specific .forward-foo file is first sought; if it is not found, the basic ++.forward file is used. ++ ++The personal test (see section 3.27) includes prefixes and suffixes in its ++checking. ++ ++ ++3.32 Ignoring delivery errors ++----------------------------- ++ ++As was explained above, filtering just sets up addresses for delivery - no ++deliveries are actually done while a filter file is active. If any of the ++generated addresses subsequently suffers a delivery failure, an error message ++is generated in the normal way. However, if a filter command that sets up a ++delivery is preceded by the word "noerror", errors for that delivery, and any ++deliveries consequent on it (that is, from alias, forwarding, or filter files ++it invokes) are ignored. ++ ++ ++3.33 Examples of Exim filter commands ++------------------------------------- ++ ++Simple forwarding: ++ ++# Exim filter ++deliver baggins@rivendell.middle-earth.example ++ ++Vacation handling using traditional means, assuming that the .vacation.msg and ++other files have been set up in your home directory: ++ ++# Exim filter ++unseen pipe "/usr/ucb/vacation \"$local_part\"" ++ ++Vacation handling inside Exim, having first created a file called .vacation.msg ++in your home directory: ++ ++# Exim filter ++if personal then vacation endif ++ ++File some messages by subject: ++ ++# Exim filter ++if $header_subject: contains "empire" or ++$header_subject: contains "foundation" ++then ++save $home/mail/f+e ++endif ++ ++Save all non-urgent messages by weekday: ++ ++# Exim filter ++if $header_subject: does not contain "urgent" and ++$tod_full matches "^(...)," ++then ++save $home/mail/$1 ++endif ++ ++Throw away all mail from one site, except from postmaster: ++ ++# Exim filter ++if $reply_address contains "@spam.site.example" and ++$reply_address does not contain "postmaster@" ++then ++seen finish ++endif ++ ++Handle multiple personal mailboxes: ++ ++# Exim filter ++if $local_part_suffix is "-foo" ++then ++save $home/mail/foo ++elif $local_part_suffix is "-bar" ++then ++save $home/mail/bar ++endif ++ +--- exim4-4.82~rc1.orig/doc/spec.txt ++++ exim4-4.82~rc1/doc/spec.txt +@@ -0,0 +1,34311 @@ ++Specification of the Exim Mail Transfer Agent ++ ++Exim Maintainers ++ ++Copyright (c) 2012 University of Cambridge ++ ++Revision 4.82 29 Sep 2013 EM ++ ++Abstract ++ ++The Exim MTA ++ ++------------------------------------------------------------------------------- ++ ++TABLE OF CONTENTS ++ ++1. Introduction ++ ++ 1.1. Exim documentation ++ 1.2. FTP and web sites ++ 1.3. Mailing lists ++ 1.4. Exim training ++ 1.5. Bug reports ++ 1.6. Where to find the Exim distribution ++ 1.7. Limitations ++ 1.8. Run time configuration ++ 1.9. Calling interface ++ 1.10. Terminology ++ ++2. Incorporated code ++3. How Exim receives and delivers mail ++ ++ 3.1. Overall philosophy ++ 3.2. Policy control ++ 3.3. User filters ++ 3.4. Message identification ++ 3.5. Receiving mail ++ 3.6. Handling an incoming message ++ 3.7. Life of a message ++ 3.8. Processing an address for delivery ++ 3.9. Processing an address for verification ++ 3.10. Running an individual router ++ 3.11. Duplicate addresses ++ 3.12. Router preconditions ++ 3.13. Delivery in detail ++ 3.14. Retry mechanism ++ 3.15. Temporary delivery failure ++ 3.16. Permanent delivery failure ++ 3.17. Failures to deliver bounce messages ++ ++4. Building and installing Exim ++ ++ 4.1. Unpacking ++ 4.2. Multiple machine architectures and operating systems ++ 4.3. PCRE library ++ 4.4. DBM libraries ++ 4.5. Pre-building configuration ++ 4.6. Support for iconv() ++ 4.7. Including TLS/SSL encryption support ++ 4.8. Use of tcpwrappers ++ 4.9. Including support for IPv6 ++ 4.10. Dynamically loaded lookup module support ++ 4.11. The building process ++ 4.12. Output from "make" ++ 4.13. Overriding build-time options for Exim ++ 4.14. OS-specific header files ++ 4.15. Overriding build-time options for the monitor ++ 4.16. Installing Exim binaries and scripts ++ 4.17. Installing info documentation ++ 4.18. Setting up the spool directory ++ 4.19. Testing ++ 4.20. Replacing another MTA with Exim ++ 4.21. Upgrading Exim ++ 4.22. Stopping the Exim daemon on Solaris ++ ++5. The Exim command line ++ ++ 5.1. Setting options by program name ++ 5.2. Trusted and admin users ++ 5.3. Command line options ++ ++6. The Exim run time configuration file ++ ++ 6.1. Using a different configuration file ++ 6.2. Configuration file format ++ 6.3. File inclusions in the configuration file ++ 6.4. Macros in the configuration file ++ 6.5. Macro substitution ++ 6.6. Redefining macros ++ 6.7. Overriding macro values ++ 6.8. Example of macro usage ++ 6.9. Conditional skips in the configuration file ++ 6.10. Common option syntax ++ 6.11. Boolean options ++ 6.12. Integer values ++ 6.13. Octal integer values ++ 6.14. Fixed point numbers ++ 6.15. Time intervals ++ 6.16. String values ++ 6.17. Expanded strings ++ 6.18. User and group names ++ 6.19. List construction ++ 6.20. Changing list separators ++ 6.21. Empty items in lists ++ 6.22. Format of driver configurations ++ ++7. The default configuration file ++ ++ 7.1. Main configuration settings ++ 7.2. ACL configuration ++ 7.3. Router configuration ++ 7.4. Transport configuration ++ 7.5. Default retry rule ++ 7.6. Rewriting configuration ++ 7.7. Authenticators configuration ++ ++8. Regular expressions ++9. File and database lookups ++ ++ 9.1. Examples of different lookup syntax ++ 9.2. Lookup types ++ 9.3. Single-key lookup types ++ 9.4. Query-style lookup types ++ 9.5. Temporary errors in lookups ++ 9.6. Default values in single-key lookups ++ 9.7. Partial matching in single-key lookups ++ 9.8. Lookup caching ++ 9.9. Quoting lookup data ++ 9.10. More about dnsdb ++ 9.11. Pseudo dnsdb record types ++ 9.12. Multiple dnsdb lookups ++ 9.13. More about LDAP ++ 9.14. Format of LDAP queries ++ 9.15. LDAP quoting ++ 9.16. LDAP connections ++ 9.17. LDAP authentication and control information ++ 9.18. Format of data returned by LDAP ++ 9.19. More about NIS+ ++ 9.20. SQL lookups ++ 9.21. More about MySQL, PostgreSQL, Oracle, and InterBase ++ 9.22. Specifying the server in the query ++ 9.23. Special MySQL features ++ 9.24. Special PostgreSQL features ++ 9.25. More about SQLite ++ ++10. Domain, host, address, and local part lists ++ ++ 10.1. Expansion of lists ++ 10.2. Negated items in lists ++ 10.3. File names in lists ++ 10.4. An lsearch file is not an out-of-line list ++ 10.5. Named lists ++ 10.6. Named lists compared with macros ++ 10.7. Named list caching ++ 10.8. Domain lists ++ 10.9. Host lists ++ 10.10. Special host list patterns ++ 10.11. Host list patterns that match by IP address ++ 10.12. Host list patterns for single-key lookups by host address ++ 10.13. Host list patterns that match by host name ++ 10.14. Behaviour when an IP address or name cannot be found ++ 10.15. Temporary DNS errors when looking up host information ++ 10.16. Host list patterns for single-key lookups by host name ++ 10.17. Host list patterns for query-style lookups ++ 10.18. Mixing wildcarded host names and addresses in host lists ++ 10.19. Address lists ++ 10.20. Case of letters in address lists ++ 10.21. Local part lists ++ ++11. String expansions ++ ++ 11.1. Literal text in expanded strings ++ 11.2. Character escape sequences in expanded strings ++ 11.3. Testing string expansions ++ 11.4. Forced expansion failure ++ 11.5. Expansion items ++ 11.6. Expansion operators ++ 11.7. Expansion conditions ++ 11.8. Combining expansion conditions ++ 11.9. Expansion variables ++ ++12. Embedded Perl ++ ++ 12.1. Setting up so Perl can be used ++ 12.2. Calling Perl subroutines ++ 12.3. Calling Exim functions from Perl ++ 12.4. Use of standard output and error by Perl ++ ++13. Starting the daemon and the use of network interfaces ++ ++ 13.1. Starting a listening daemon ++ 13.2. Special IP listening addresses ++ 13.3. Overriding local_interfaces and daemon_smtp_ports ++ 13.4. Support for the obsolete SSMTP (or SMTPS) protocol ++ 13.5. IPv6 address scopes ++ 13.6. Disabling IPv6 ++ 13.7. Examples of starting a listening daemon ++ 13.8. Recognizing the local host ++ 13.9. Delivering to a remote host ++ ++14. Main configuration ++ ++ 14.1. Miscellaneous ++ 14.2. Exim parameters ++ 14.3. Privilege controls ++ 14.4. Logging ++ 14.5. Frozen messages ++ 14.6. Data lookups ++ 14.7. Message ids ++ 14.8. Embedded Perl Startup ++ 14.9. Daemon ++ 14.10. Resource control ++ 14.11. Policy controls ++ 14.12. Callout cache ++ 14.13. TLS ++ 14.14. Local user handling ++ 14.15. All incoming messages (SMTP and non-SMTP) ++ 14.16. Non-SMTP incoming messages ++ 14.17. Incoming SMTP messages ++ 14.18. SMTP extensions ++ 14.19. Processing messages ++ 14.20. System filter ++ 14.21. Routing and delivery ++ 14.22. Bounce and warning messages ++ 14.23. Alphabetical list of main options ++ ++15. Generic options for routers ++16. The accept router ++17. The dnslookup router ++ ++ 17.1. Problems with DNS lookups ++ 17.2. Declining addresses by dnslookup ++ 17.3. Private options for dnslookup ++ 17.4. Effect of qualify_single and search_parents ++ ++18. The ipliteral router ++19. The iplookup router ++20. The manualroute router ++ ++ 20.1. Private options for manualroute ++ 20.2. Routing rules in route_list ++ 20.3. Routing rules in route_data ++ 20.4. Format of the list of hosts ++ 20.5. Format of one host item ++ 20.6. How the list of hosts is used ++ 20.7. How the options are used ++ 20.8. Manualroute examples ++ ++21. The queryprogram router ++22. The redirect router ++ ++ 22.1. Redirection data ++ 22.2. Forward files and address verification ++ 22.3. Interpreting redirection data ++ 22.4. Items in a non-filter redirection list ++ 22.5. Redirecting to a local mailbox ++ 22.6. Special items in redirection lists ++ 22.7. Duplicate addresses ++ 22.8. Repeated redirection expansion ++ 22.9. Errors in redirection lists ++ 22.10. Private options for the redirect router ++ ++23. Environment for running local transports ++ ++ 23.1. Concurrent deliveries ++ 23.2. Uids and gids ++ 23.3. Current and home directories ++ 23.4. Expansion variables derived from the address ++ ++24. Generic options for transports ++25. Address batching in local transports ++26. The appendfile transport ++ ++ 26.1. The file and directory options ++ 26.2. Private options for appendfile ++ 26.3. Operational details for appending ++ 26.4. Operational details for delivery to a new file ++ 26.5. Maildir delivery ++ 26.6. Using tags to record message sizes ++ 26.7. Using a maildirsize file ++ 26.8. Mailstore delivery ++ 26.9. Non-special new file delivery ++ ++27. The autoreply transport ++ ++ 27.1. Private options for autoreply ++ ++28. The lmtp transport ++29. The pipe transport ++ ++ 29.1. Concurrent delivery ++ 29.2. Returned status and data ++ 29.3. How the command is run ++ 29.4. Environment variables ++ 29.5. Private options for pipe ++ 29.6. Using an external local delivery agent ++ ++30. The smtp transport ++ ++ 30.1. Multiple messages on a single connection ++ 30.2. Use of the $host and $host_address variables ++ 30.3. Use of $tls_cipher and $tls_peerdn ++ 30.4. Private options for smtp ++ 30.5. How the limits for the number of hosts to try are used ++ ++31. Address rewriting ++ ++ 31.1. Explicitly configured address rewriting ++ 31.2. When does rewriting happen? ++ 31.3. Testing the rewriting rules that apply on input ++ 31.4. Rewriting rules ++ 31.5. Rewriting patterns ++ 31.6. Rewriting replacements ++ 31.7. Rewriting flags ++ 31.8. Flags specifying which headers and envelope addresses to rewrite ++ 31.9. The SMTP-time rewriting flag ++ 31.10. Flags controlling the rewriting process ++ 31.11. Rewriting examples ++ ++32. Retry configuration ++ ++ 32.1. Changing retry rules ++ 32.2. Format of retry rules ++ 32.3. Choosing which retry rule to use for address errors ++ 32.4. Choosing which retry rule to use for host and message errors ++ 32.5. Retry rules for specific errors ++ 32.6. Retry rules for specified senders ++ 32.7. Retry parameters ++ 32.8. Retry rule examples ++ 32.9. Timeout of retry data ++ 32.10. Long-term failures ++ 32.11. Deliveries that work intermittently ++ ++33. SMTP authentication ++ ++ 33.1. Generic options for authenticators ++ 33.2. The AUTH parameter on MAIL commands ++ 33.3. Authentication on an Exim server ++ 33.4. Testing server authentication ++ 33.5. Authentication by an Exim client ++ ++34. The plaintext authenticator ++ ++ 34.1. Plaintext options ++ 34.2. Using plaintext in a server ++ 34.3. The PLAIN authentication mechanism ++ 34.4. The LOGIN authentication mechanism ++ 34.5. Support for different kinds of authentication ++ 34.6. Using plaintext in a client ++ ++35. The cram_md5 authenticator ++ ++ 35.1. Using cram_md5 as a server ++ 35.2. Using cram_md5 as a client ++ ++36. The cyrus_sasl authenticator ++ ++ 36.1. Using cyrus_sasl as a server ++ ++37. The dovecot authenticator ++38. The gsasl authenticator ++ ++ 38.1. gsasl auth variables ++ ++39. The heimdal_gssapi authenticator ++ ++ 39.1. heimdal_gssapi auth variables ++ ++40. The spa authenticator ++ ++ 40.1. Using spa as a server ++ 40.2. Using spa as a client ++ ++41. Encrypted SMTP connections using TLS/SSL ++ ++ 41.1. Support for the legacy "ssmtp" (aka "smtps") protocol ++ 41.2. OpenSSL vs GnuTLS ++ 41.3. GnuTLS parameter computation ++ 41.4. Requiring specific ciphers in OpenSSL ++ 41.5. Requiring specific ciphers or other parameters in GnuTLS ++ 41.6. Configuring an Exim server to use TLS ++ 41.7. Requesting and verifying client certificates ++ 41.8. Revoked certificates ++ 41.9. Configuring an Exim client to use TLS ++ 41.10. Use of TLS Server Name Indication ++ 41.11. Multiple messages on the same encrypted TCP/IP connection ++ 41.12. Certificates and all that ++ 41.13. Certificate chains ++ 41.14. Self-signed certificates ++ ++42. Access control lists ++ ++ 42.1. Testing ACLs ++ 42.2. Specifying when ACLs are used ++ 42.3. The non-SMTP ACLs ++ 42.4. The SMTP connect ACL ++ 42.5. The EHLO/HELO ACL ++ 42.6. The DATA ACLs ++ 42.7. The SMTP DKIM ACL ++ 42.8. The SMTP MIME ACL ++ 42.9. The QUIT ACL ++ 42.10. The not-QUIT ACL ++ 42.11. Finding an ACL to use ++ 42.12. ACL return codes ++ 42.13. Unset ACL options ++ 42.14. Data for message ACLs ++ 42.15. Data for non-message ACLs ++ 42.16. Format of an ACL ++ 42.17. ACL verbs ++ 42.18. ACL variables ++ 42.19. Condition and modifier processing ++ 42.20. ACL modifiers ++ 42.21. Use of the control modifier ++ 42.22. Summary of message fixup control ++ 42.23. Adding header lines in ACLs ++ 42.24. Removing header lines in ACLs ++ 42.25. ACL conditions ++ 42.26. Using DNS lists ++ 42.27. Specifying the IP address for a DNS list lookup ++ 42.28. DNS lists keyed on domain names ++ 42.29. Multiple explicit keys for a DNS list ++ 42.30. Data returned by DNS lists ++ 42.31. Variables set from DNS lists ++ 42.32. Additional matching conditions for DNS lists ++ 42.33. Negated DNS matching conditions ++ 42.34. Handling multiple DNS records from a DNS list ++ 42.35. Detailed information from merged DNS lists ++ 42.36. DNS lists and IPv6 ++ 42.37. Rate limiting incoming messages ++ 42.38. Ratelimit options for what is being measured ++ 42.39. Ratelimit update modes ++ 42.40. Ratelimit options for handling fast clients ++ 42.41. Limiting the rate of different events ++ 42.42. Using rate limiting ++ 42.43. Address verification ++ 42.44. Callout verification ++ 42.45. Additional parameters for callouts ++ 42.46. Callout caching ++ 42.47. Sender address verification reporting ++ 42.48. Redirection while verifying ++ 42.49. Client SMTP authorization (CSA) ++ 42.50. Bounce address tag validation ++ 42.51. Using an ACL to control relaying ++ 42.52. Checking a relay configuration ++ ++43. Content scanning at ACL time ++ ++ 43.1. Scanning for viruses ++ 43.2. Scanning with SpamAssassin ++ 43.3. Calling SpamAssassin from an Exim ACL ++ 43.4. Scanning MIME parts ++ 43.5. Scanning with regular expressions ++ 43.6. The demime condition ++ ++44. Adding a local scan function to Exim ++ ++ 44.1. Building Exim to use a local scan function ++ 44.2. API for local_scan() ++ 44.3. Configuration options for local_scan() ++ 44.4. Available Exim variables ++ 44.5. Structure of header lines ++ 44.6. Structure of recipient items ++ 44.7. Available Exim functions ++ 44.8. More about Exim's memory handling ++ ++45. System-wide message filtering ++ ++ 45.1. Specifying a system filter ++ 45.2. Testing a system filter ++ 45.3. Contents of a system filter ++ 45.4. Additional variable for system filters ++ 45.5. Defer, freeze, and fail commands for system filters ++ 45.6. Adding and removing headers in a system filter ++ 45.7. Setting an errors address in a system filter ++ 45.8. Per-address filtering ++ ++46. Message processing ++ ++ 46.1. Submission mode for non-local messages ++ 46.2. Line endings ++ 46.3. Unqualified addresses ++ 46.4. The UUCP From line ++ 46.5. Resent- header lines ++ 46.6. The Auto-Submitted: header line ++ 46.7. The Bcc: header line ++ 46.8. The Date: header line ++ 46.9. The Delivery-date: header line ++ 46.10. The Envelope-to: header line ++ 46.11. The From: header line ++ 46.12. The Message-ID: header line ++ 46.13. The Received: header line ++ 46.14. The References: header line ++ 46.15. The Return-path: header line ++ 46.16. The Sender: header line ++ 46.17. Adding and removing header lines in routers and transports ++ 46.18. Constructed addresses ++ 46.19. Case of local parts ++ 46.20. Dots in local parts ++ 46.21. Rewriting addresses ++ ++47. SMTP processing ++ ++ 47.1. Outgoing SMTP and LMTP over TCP/IP ++ 47.2. Errors in outgoing SMTP ++ 47.3. Incoming SMTP messages over TCP/IP ++ 47.4. Unrecognized SMTP commands ++ 47.5. Syntax and protocol errors in SMTP commands ++ 47.6. Use of non-mail SMTP commands ++ 47.7. The VRFY and EXPN commands ++ 47.8. The ETRN command ++ 47.9. Incoming local SMTP ++ 47.10. Outgoing batched SMTP ++ 47.11. Incoming batched SMTP ++ ++48. Customizing bounce and warning messages ++ ++ 48.1. Customizing bounce messages ++ 48.2. Customizing warning messages ++ ++49. Some common configuration settings ++ ++ 49.1. Sending mail to a smart host ++ 49.2. Using Exim to handle mailing lists ++ 49.3. Syntax errors in mailing lists ++ 49.4. Re-expansion of mailing lists ++ 49.5. Closed mailing lists ++ 49.6. Variable Envelope Return Paths (VERP) ++ 49.7. Virtual domains ++ 49.8. Multiple user mailboxes ++ 49.9. Simplified vacation processing ++ 49.10. Taking copies of mail ++ 49.11. Intermittently connected hosts ++ 49.12. Exim on the upstream server host ++ 49.13. Exim on the intermittently connected client host ++ ++50. Using Exim as a non-queueing client ++51. Log files ++ ++ 51.1. Where the logs are written ++ 51.2. Logging to local files that are periodically "cycled" ++ 51.3. Datestamped log files ++ 51.4. Logging to syslog ++ 51.5. Log line flags ++ 51.6. Logging message reception ++ 51.7. Logging deliveries ++ 51.8. Discarded deliveries ++ 51.9. Deferred deliveries ++ 51.10. Delivery failures ++ 51.11. Fake deliveries ++ 51.12. Completion ++ 51.13. Summary of Fields in Log Lines ++ 51.14. Other log entries ++ 51.15. Reducing or increasing what is logged ++ 51.16. Message log ++ ++52. Exim utilities ++ ++ 52.1. Finding out what Exim processes are doing (exiwhat) ++ 52.2. Selective queue listing (exiqgrep) ++ 52.3. Summarizing the queue (exiqsumm) ++ 52.4. Extracting specific information from the log (exigrep) ++ 52.5. Selecting messages by various criteria (exipick) ++ 52.6. Cycling log files (exicyclog) ++ 52.7. Mail statistics (eximstats) ++ 52.8. Checking access policy (exim_checkaccess) ++ 52.9. Making DBM files (exim_dbmbuild) ++ 52.10. Finding individual retry times (exinext) ++ 52.11. Hints database maintenance ++ 52.12. exim_dumpdb ++ 52.13. exim_tidydb ++ 52.14. exim_fixdb ++ 52.15. Mailbox maintenance (exim_lock) ++ ++53. The Exim monitor ++ ++ 53.1. Running the monitor ++ 53.2. The stripcharts ++ 53.3. Main action buttons ++ 53.4. The log display ++ 53.5. The queue display ++ 53.6. The queue menu ++ ++54. Security considerations ++ ++ 54.1. Building a more "hardened" Exim ++ 54.2. Root privilege ++ 54.3. Running Exim without privilege ++ 54.4. Delivering to local files ++ 54.5. Running local commands ++ 54.6. IPv4 source routing ++ 54.7. The VRFY, EXPN, and ETRN commands in SMTP ++ 54.8. Privileged users ++ 54.9. Spool files ++ 54.10. Use of argv[0] ++ 54.11. Use of %f formatting ++ 54.12. Embedded Exim path ++ 54.13. Dynamic module directory ++ 54.14. Use of sprintf() ++ 54.15. Use of debug_printf() and log_write() ++ 54.16. Use of strcat() and strcpy() ++ ++55. Format of spool files ++ ++ 55.1. Format of the -H file ++ ++56. Support for DKIM (DomainKeys Identified Mail) ++ ++ 56.1. Signing outgoing messages ++ 56.2. Verifying DKIM signatures in incoming mail ++ ++57. Adding new drivers or lookup types ++ ++ ++ ++=============================================================================== ++1. INTRODUCTION ++ ++Exim is a mail transfer agent (MTA) for hosts that are running Unix or ++Unix-like operating systems. It was designed on the assumption that it would be ++run on hosts that are permanently connected to the Internet. However, it can be ++used on intermittently connected hosts with suitable configuration adjustments. ++ ++Configuration files currently exist for the following operating systems: AIX, ++BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd, GNU/ ++Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD, ++OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4, ++Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware. ++Some of these operating systems are no longer current and cannot easily be ++tested, so the configuration files may no longer work in practice. ++ ++There are also configuration files for compiling Exim in the Cygwin environment ++that can be installed on systems running Windows. However, this document does ++not contain any information about running Exim in the Cygwin environment. ++ ++The terms and conditions for the use and distribution of Exim are contained in ++the file NOTICE. Exim is distributed under the terms of the GNU General Public ++Licence, a copy of which may be found in the file LICENCE. ++ ++The use, supply or promotion of Exim for the purpose of sending bulk, ++unsolicited electronic mail is incompatible with the basic aims of the program, ++which revolve around the free provision of a service that enhances the quality ++of personal communications. The author of Exim regards indiscriminate ++mass-mailing as an antisocial, irresponsible abuse of the Internet. ++ ++Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the ++experience of running and working on the Smail 3 code, I could never have ++contemplated starting to write a new MTA. Many of the ideas and user interfaces ++were originally taken from Smail 3, though the actual code of Exim is entirely ++new, and has developed far beyond the initial concept. ++ ++Many people, both in Cambridge and around the world, have contributed to the ++development and the testing of Exim, and to porting it to various operating ++systems. I am grateful to them all. The distribution now contains a file called ++ACKNOWLEDGMENTS, in which I have started recording the names of contributors. ++ ++ ++1.1 Exim documentation ++---------------------- ++ ++This edition of the Exim specification applies to version 4.82 of Exim. ++Substantive changes from the 4.80 edition are marked in some renditions of the ++document; this paragraph is so marked if the rendition is capable of showing a ++change indicator. ++ ++This document is very much a reference manual; it is not a tutorial. The reader ++is expected to have some familiarity with the SMTP mail transfer protocol and ++with general Unix system administration. Although there are some discussions ++and examples in places, the information is mostly organized in a way that makes ++it easy to look up, rather than in a natural order for sequential reading. ++Furthermore, the manual aims to cover every aspect of Exim in detail, including ++a number of rarely-used, special-purpose features that are unlikely to be of ++very wide interest. ++ ++An "easier" discussion of Exim which provides more in-depth explanatory, ++introductory, and tutorial material can be found in a book entitled The Exim ++SMTP Mail Server (second edition, 2007), published by UIT Cambridge (http:// ++www.uit.co.uk/exim-book/). ++ ++This book also contains a chapter that gives a general introduction to SMTP and ++Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date ++with the latest release of Exim. (Note that the earlier book about Exim, ++published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.) ++ ++If you are using a Debian distribution of Exim, you will find information about ++Debian-specific features in the file /usr/share/doc/exim4-base/README.Debian. ++The command man update-exim.conf is another source of Debian-specific ++information. ++ ++As the program develops, there may be features in newer versions that have not ++yet made it into this document, which is updated only when the most significant ++digit of the fractional part of the version number changes. Specifications of ++new features that are not yet in this manual are placed in the file doc/ ++NewStuff in the Exim distribution. ++ ++Some features may be classified as "experimental". These may change ++incompatibly while they are developing, or even be withdrawn. For this reason, ++they are not documented in this manual. Information about experimental features ++can be found in the file doc/experimental.txt. ++ ++All changes to the program (whether new features, bug fixes, or other kinds of ++change) are noted briefly in the file called doc/ChangeLog. ++ ++This specification itself is available as an ASCII file in doc/spec.txt so that ++it can easily be searched with a text editor. Other files in the doc directory ++are: ++ ++OptionLists.txt list of all options in alphabetical order ++dbm.discuss.txt discussion about DBM libraries ++exim.8 a man page of Exim's command line options ++experimental.txt documentation of experimental features ++filter.txt specification of the filter language ++Exim3.upgrade upgrade notes from release 2 to release 3 ++Exim4.upgrade upgrade notes from release 3 to release 4 ++ ++The main specification and the specification of the filtering language are also ++available in other formats (HTML, PostScript, PDF, and Texinfo). Section 1.6 ++below tells you how to get hold of these. ++ ++ ++1.2 FTP and web sites ++--------------------- ++ ++The primary site for Exim source distributions is currently the University of ++Cambridge's FTP site, whose contents are described in Where to find the Exim ++distribution below. In addition, there is a web site and an FTP site at ++exim.org. These are now also hosted at the University of Cambridge. The ++exim.org site was previously hosted for a number of years by Energis Squared, ++formerly Planet Online Ltd, whose support I gratefully acknowledge. ++ ++As well as Exim distribution tar files, the Exim web site contains a number of ++differently formatted versions of the documentation. A recent addition to the ++online information is the Exim wiki (http://wiki.exim.org), which contains what ++used to be a separate FAQ, as well as various other examples, tips, and ++know-how that have been contributed by Exim users. ++ ++An Exim Bugzilla exists at http://bugs.exim.org. You can use this to report ++bugs, and also to add items to the wish list. Please search first to check that ++you are not duplicating a previous entry. ++ ++ ++1.3 Mailing lists ++----------------- ++ ++The following Exim mailing lists exist: ++ ++exim-announce@exim.org Moderated, low volume announcements list ++exim-users@exim.org General discussion list ++exim-dev@exim.org Discussion of bugs, enhancements, etc. ++exim-cvs@exim.org Automated commit messages from the VCS ++ ++You can subscribe to these lists, change your existing subscriptions, and view ++or search the archives via the mailing lists link on the Exim home page. If you ++are using a Debian distribution of Exim, you may wish to subscribe to the ++Debian-specific mailing list pkg-exim4-users@lists.alioth.debian.org via this ++web page: ++ ++http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users ++ ++Please ask Debian-specific questions on this list and not on the general Exim ++lists. ++ ++ ++1.4 Exim training ++----------------- ++ ++Training courses in Cambridge (UK) used to be run annually by the author of ++Exim, before he retired. At the time of writing, there are no plans to run ++further Exim courses in Cambridge. However, if that changes, relevant ++information will be posted at http://www-tus.csx.cam.ac.uk/courses/exim/. ++ ++ ++1.5 Bug reports ++--------------- ++ ++Reports of obvious bugs can be emailed to bugs@exim.org or reported via the ++Bugzilla (http://bugs.exim.org). However, if you are unsure whether some ++behaviour is a bug or not, the best thing to do is to post a message to the ++exim-dev mailing list and have it discussed. ++ ++ ++1.6 Where to find the Exim distribution ++--------------------------------------- ++ ++The master ftp site for the Exim distribution is ++ ++ftp://ftp.csx.cam.ac.uk/pub/software/email/exim ++ ++This is mirrored by ++ ++ftp://ftp.exim.org/pub/exim ++ ++The file references that follow are relative to the exim directories at these ++sites. There are now quite a number of independent mirror sites around the ++world. Those that I know about are listed in the file called Mirrors. ++ ++Within the exim directory there are subdirectories called exim3 (for previous ++Exim 3 distributions), exim4 (for the latest Exim 4 distributions), and Testing ++for testing versions. In the exim4 subdirectory, the current release can always ++be found in files called ++ ++exim-n.nn.tar.gz ++exim-n.nn.tar.bz2 ++ ++where n.nn is the highest such version number in the directory. The two files ++contain identical data; the only difference is the type of compression. The ++.bz2 file is usually a lot smaller than the .gz file. ++ ++The distributions will be PGP signed by an individual key of the Release ++Coordinator. This key will have a uid containing an email address in the ++exim.org domain and will have signatures from other people, including other ++Exim maintainers. We expect that the key will be in the "strong set" of PGP ++keys. There should be a trust path to that key from Nigel Metheringham's PGP ++key, a version of which can be found in the release directory in the file ++nigel-pubkey.asc. All keys used will be available in public keyserver pools, ++such as pool.sks-keyservers.net. ++ ++At time of last update, releases were being made by Phil Pennock and signed ++with key 0x403043153903637F, although that key is expected to be replaced in ++2013. A trust path from Nigel's key to Phil's can be observed at https:// ++www.security.spodhuis.org/exim-trustpath. ++ ++The signatures for the tar bundles are in: ++ ++exim-n.nn.tar.gz.asc ++exim-n.nn.tar.bz2.asc ++ ++For each released version, the log of changes is made separately available in a ++separate file in the directory ChangeLogs so that it is possible to find out ++what has changed without having to download the entire distribution. ++ ++The main distribution contains ASCII versions of this specification and other ++documentation; other formats of the documents are available in separate files ++inside the exim4 directory of the FTP site: ++ ++exim-html-n.nn.tar.gz ++exim-pdf-n.nn.tar.gz ++exim-postscript-n.nn.tar.gz ++exim-texinfo-n.nn.tar.gz ++ ++These tar files contain only the doc directory, not the complete distribution, ++and are also available in .bz2 as well as .gz forms. ++ ++ ++1.7 Limitations ++--------------- ++ ++ * Exim is designed for use as an Internet MTA, and therefore handles ++ addresses in RFC 2822 domain format only. It cannot handle UUCP "bang ++ paths", though simple two-component bang paths can be converted by a ++ straightforward rewriting configuration. This restriction does not prevent ++ Exim from being interfaced to UUCP as a transport mechanism, provided that ++ domain addresses are used. ++ ++ * Exim insists that every address it handles has a domain attached. For ++ incoming local messages, domainless addresses are automatically qualified ++ with a configured domain value. Configuration options specify from which ++ remote systems unqualified addresses are acceptable. These are then ++ qualified on arrival. ++ ++ * The only external transport mechanisms that are currently implemented are ++ SMTP and LMTP over a TCP/IP network (including support for IPv6). However, ++ a pipe transport is available, and there are facilities for writing ++ messages to files and pipes, optionally in batched SMTP format; these ++ facilities can be used to send messages to other transport mechanisms such ++ as UUCP, provided they can handle domain-style addresses. Batched SMTP ++ input is also catered for. ++ ++ * Exim is not designed for storing mail for dial-in hosts. When the volumes ++ of such mail are large, it is better to get the messages "delivered" into ++ files (that is, off Exim's queue) and subsequently passed on to the dial-in ++ hosts by other means. ++ ++ * Although Exim does have basic facilities for scanning incoming messages, ++ these are not comprehensive enough to do full virus or spam scanning. Such ++ operations are best carried out using additional specialized software ++ packages. If you compile Exim with the content-scanning extension, ++ straightforward interfaces to a number of common scanners are provided. ++ ++ ++1.8 Run time configuration ++-------------------------- ++ ++Exim's run time configuration is held in a single text file that is divided ++into a number of sections. The entries in this file consist of keywords and ++values, in the style of Smail 3 configuration files. A default configuration ++file which is suitable for simple online installations is provided in the ++distribution, and is described in chapter 7 below. ++ ++ ++1.9 Calling interface ++--------------------- ++ ++Like many MTAs, Exim has adopted the Sendmail command line interface so that it ++can be a straight replacement for /usr/lib/sendmail or /usr/sbin/sendmail when ++sending mail, but you do not need to know anything about Sendmail in order to ++run Exim. For actions other than sending messages, Sendmail-compatible options ++also exist, but those that produce output (for example, -bp, which lists the ++messages on the queue) do so in Exim's own format. There are also some ++additional options that are compatible with Smail 3, and some further options ++that are new to Exim. Chapter 5 documents all Exim's command line options. This ++information is automatically made into the man page that forms part of the Exim ++distribution. ++ ++Control of messages on the queue can be done via certain privileged command ++line options. There is also an optional monitor program called eximon, which ++displays current information in an X window, and which contains a menu ++interface to Exim's command line administration options. ++ ++ ++1.10 Terminology ++---------------- ++ ++The body of a message is the actual data that the sender wants to transmit. It ++is the last part of a message, and is separated from the header (see below) by ++a blank line. ++ ++When a message cannot be delivered, it is normally returned to the sender in a ++delivery failure message or a "non-delivery report" (NDR). The term bounce is ++commonly used for this action, and the error reports are often called bounce ++messages. This is a convenient shorthand for "delivery failure error report". ++Such messages have an empty sender address in the message's envelope (see ++below) to ensure that they cannot themselves give rise to further bounce ++messages. ++ ++The term default appears frequently in this manual. It is used to qualify a ++value which is used in the absence of any setting in the configuration. It may ++also qualify an action which is taken unless a configuration setting specifies ++otherwise. ++ ++The term defer is used when the delivery of a message to a specific destination ++cannot immediately take place for some reason (a remote host may be down, or a ++user's local mailbox may be full). Such deliveries are deferred until a later ++time. ++ ++The word domain is sometimes used to mean all but the first component of a ++host's name. It is not used in that sense here, where it normally refers to the ++part of an email address following the @ sign. ++ ++A message in transit has an associated envelope, as well as a header and a ++body. The envelope contains a sender address (to which bounce messages should ++be delivered), and any number of recipient addresses. References to the sender ++or the recipients of a message usually mean the addresses in the envelope. An ++MTA uses these addresses for delivery, and for returning bounce messages, not ++the addresses that appear in the header lines. ++ ++The header of a message is the first part of a message's text, consisting of a ++number of lines, each of which has a name such as From:, To:, Subject:, etc. ++Long header lines can be split over several text lines by indenting the ++continuations. The header is separated from the body by a blank line. ++ ++The term local part, which is taken from RFC 2822, is used to refer to that ++part of an email address that precedes the @ sign. The part that follows the @ ++sign is called the domain or mail domain. ++ ++The terms local delivery and remote delivery are used to distinguish delivery ++to a file or a pipe on the local host from delivery by SMTP over TCP/IP to ++another host. As far as Exim is concerned, all hosts other than the host it is ++running on are remote. ++ ++Return path is another name that is used for the sender address in a message's ++envelope. ++ ++The term queue is used to refer to the set of messages awaiting delivery, ++because this term is in widespread use in the context of MTAs. However, in ++Exim's case the reality is more like a pool than a queue, because there is ++normally no ordering of waiting messages. ++ ++The term queue runner is used to describe a process that scans the queue and ++attempts to deliver those messages whose retry times have come. This term is ++used by other MTAs, and also relates to the command runq, but in Exim the ++waiting messages are normally processed in an unpredictable order. ++ ++The term spool directory is used for a directory in which Exim keeps the ++messages on its queue - that is, those that it is in the process of delivering. ++This should not be confused with the directory in which local mailboxes are ++stored, which is called a "spool directory" by some people. In the Exim ++documentation, "spool" is always used in the first sense. ++ ++ ++ ++=============================================================================== ++2. INCORPORATED CODE ++ ++A number of pieces of external code are included in the Exim distribution. ++ ++ * Regular expressions are supported in the main Exim program and in the Exim ++ monitor using the freely-distributable PCRE library, copyright (c) ++ University of Cambridge. The source to PCRE is no longer shipped with Exim, ++ so you will need to use the version of PCRE shipped with your system, or ++ obtain and install the full version of the library from ftp:// ++ ftp.csx.cam.ac.uk/pub/software/programming/pcre. ++ ++ * Support for the cdb (Constant DataBase) lookup method is provided by code ++ contributed by Nigel Metheringham of (at the time he contributed it) Planet ++ Online Ltd. The implementation is completely contained within the code of ++ Exim. It does not link against an external cdb library. The code contains ++ the following statements: ++ ++ Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd ++ ++ This program is free software; you can redistribute it and/or modify it ++ under the terms of the GNU General Public License as published by the ++ Free Software Foundation; either version 2 of the License, or (at your ++ option) any later version. This code implements Dan Bernstein's ++ Constant DataBase (cdb) spec. Information, the spec and sample code for ++ cdb can be obtained from http://www.pobox.com/~djb/cdb.html. This ++ implementation borrows some code from Dan Bernstein's implementation ++ (which has no license restrictions applied to it). ++ ++ * Client support for Microsoft's Secure Password Authentication is provided ++ by code contributed by Marc Prud'hommeaux. Server support was contributed ++ by Tom Kistner. This includes code taken from the Samba project, which is ++ released under the Gnu GPL. ++ ++ * Support for calling the Cyrus pwcheck and saslauthd daemons is provided by ++ code taken from the Cyrus-SASL library and adapted by Alexander S. ++ Sabourenkov. The permission notice appears below, in accordance with the ++ conditions expressed therein. ++ ++ Copyright (c) 2001 Carnegie Mellon University. All rights reserved. ++ ++ Redistribution and use in source and binary forms, with or without ++ modification, are permitted provided that the following conditions are ++ met: ++ ++ 1. Redistributions of source code must retain the above copyright ++ notice, this list of conditions and the following disclaimer. ++ ++ 2. Redistributions in binary form must reproduce the above copyright ++ notice, this list of conditions and the following disclaimer in the ++ documentation and/or other materials provided with the ++ distribution. ++ ++ 3. The name "Carnegie Mellon University" must not be used to endorse ++ or promote products derived from this software without prior ++ written permission. For permission or any other legal details, ++ please contact ++ ++ Office of Technology Transfer ++ Carnegie Mellon University ++ 5000 Forbes Avenue ++ Pittsburgh, PA 15213-3890 ++ (412) 268-4387, fax: (412) 268-7395 ++ tech-transfer@andrew.cmu.edu ++ ++ 4. Redistributions of any form whatsoever must retain the following ++ acknowledgment: ++ ++ "This product includes software developed by Computing Services at ++ Carnegie Mellon University (http://www.cmu.edu/computing/." ++ ++ CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO ++ THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY ++ AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE ++ FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES ++ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN ++ AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING ++ OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS ++ SOFTWARE. ++ ++ * The Exim Monitor program, which is an X-Window application, includes ++ modified versions of the Athena StripChart and TextPop widgets. This code ++ is copyright by DEC and MIT, and their permission notice appears below, in ++ accordance with the conditions expressed therein. ++ ++ Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, ++ Massachusetts, and the Massachusetts Institute of Technology, ++ Cambridge, Massachusetts. ++ ++ All Rights Reserved ++ ++ Permission to use, copy, modify, and distribute this software and its ++ documentation for any purpose and without fee is hereby granted, ++ provided that the above copyright notice appear in all copies and that ++ both that copyright notice and this permission notice appear in ++ supporting documentation, and that the names of Digital or MIT not be ++ used in advertising or publicity pertaining to distribution of the ++ software without specific, written prior permission. ++ ++ DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, ++ INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO ++ EVENT SHALL DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR ++ CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF ++ USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR ++ OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR ++ PERFORMANCE OF THIS SOFTWARE. ++ ++ * The DMARC implementation uses the OpenDMARC library which is Copyrighted by ++ The Trusted Domain Project. Portions of Exim source which use OpenDMARC ++ derived code are indicated in the respective source files. The full ++ OpenDMARC license is provided in the LICENSE.opendmarc file contained in ++ the distributed source code. ++ ++ * Many people have contributed code fragments, some large, some small, that ++ were not covered by any specific licence requirements. It is assumed that ++ the contributors are happy to see their code incorporated into Exim under ++ the GPL. ++ ++ ++ ++=============================================================================== ++3. HOW EXIM RECEIVES AND DELIVERS MAIL ++ ++ ++3.1 Overall philosophy ++---------------------- ++ ++Exim is designed to work efficiently on systems that are permanently connected ++to the Internet and are handling a general mix of mail. In such circumstances, ++most messages can be delivered immediately. Consequently, Exim does not ++maintain independent queues of messages for specific domains or hosts, though ++it does try to send several messages in a single SMTP connection after a host ++has been down, and it also maintains per-host retry information. ++ ++ ++3.2 Policy control ++------------------ ++ ++Policy controls are now an important feature of MTAs that are connected to the ++Internet. Perhaps their most important job is to stop MTAs being abused as ++"open relays" by misguided individuals who send out vast amounts of unsolicited ++junk, and want to disguise its source. Exim provides flexible facilities for ++specifying policy controls on incoming mail: ++ ++ * Exim 4 (unlike previous versions of Exim) implements policy controls on ++ incoming mail by means of Access Control Lists (ACLs). Each list is a ++ series of statements that may either grant or deny access. ACLs can be used ++ at several places in the SMTP dialogue while receiving a message from a ++ remote host. However, the most common places are after each RCPT command, ++ and at the very end of the message. The sysadmin can specify conditions for ++ accepting or rejecting individual recipients or the entire message, ++ respectively, at these two points (see chapter 42). Denial of access ++ results in an SMTP error code. ++ ++ * An ACL is also available for locally generated, non-SMTP messages. In this ++ case, the only available actions are to accept or deny the entire message. ++ ++ * When Exim is compiled with the content-scanning extension, facilities are ++ provided in the ACL mechanism for passing the message to external virus and ++ /or spam scanning software. The result of such a scan is passed back to the ++ ACL, which can then use it to decide what to do with the message. ++ ++ * When a message has been received, either from a remote host or from the ++ local host, but before the final acknowledgment has been sent, a locally ++ supplied C function called local_scan() can be run to inspect the message ++ and decide whether to accept it or not (see chapter 44). If the message is ++ accepted, the list of recipients can be modified by the function. ++ ++ * Using the local_scan() mechanism is another way of calling external scanner ++ software. The SA-Exim add-on package works this way. It does not require ++ Exim to be compiled with the content-scanning extension. ++ ++ * After a message has been accepted, a further checking mechanism is ++ available in the form of the system filter (see chapter 45). This runs at ++ the start of every delivery process. ++ ++ ++3.3 User filters ++---------------- ++ ++In a conventional Exim configuration, users are able to run private filters by ++setting up appropriate .forward files in their home directories. See chapter 22 ++(about the redirect router) for the configuration needed to support this, and ++the separate document entitled Exim's interfaces to mail filtering for user ++details. Two different kinds of filtering are available: ++ ++ * Sieve filters are written in the standard filtering language that is ++ defined by RFC 3028. ++ ++ * Exim filters are written in a syntax that is unique to Exim, but which is ++ more powerful than Sieve, which it pre-dates. ++ ++User filters are run as part of the routing process, described below. ++ ++ ++3.4 Message identification ++-------------------------- ++ ++Every message handled by Exim is given a message id which is sixteen characters ++long. It is divided into three parts, separated by hyphens, for example ++"16VDhn-0001bo-D3". Each part is a sequence of letters and digits, normally ++encoding numbers in base 62. However, in the Darwin operating system (Mac OS X) ++and when Exim is compiled to run under Cygwin, base 36 (avoiding the use of ++lower case letters) is used instead, because the message id is used to ++construct file names, and the names of files in those systems are not always ++case-sensitive. ++ ++The detail of the contents of the message id have changed as Exim has evolved. ++Earlier versions relied on the operating system not re-using a process id (pid) ++within one second. On modern operating systems, this assumption can no longer ++be made, so the algorithm had to be changed. To retain backward compatibility, ++the format of the message id was retained, which is why the following rules are ++somewhat eccentric: ++ ++ * The first six characters of the message id are the time at which the ++ message started to be received, to a granularity of one second. That is, ++ this field contains the number of seconds since the start of the epoch (the ++ normal Unix way of representing the date and time of day). ++ ++ * After the first hyphen, the next six characters are the id of the process ++ that received the message. ++ ++ * There are two different possibilities for the final two characters: ++ ++ 1. If localhost_number is not set, this value is the fractional part of ++ the time of reception, normally in units of 1/2000 of a second, but for ++ systems that must use base 36 instead of base 62 (because of ++ case-insensitive file systems), the units are 1/1000 of a second. ++ ++ 2. If localhost_number is set, it is multiplied by 200 (100) and added to ++ the fractional part of the time, which in this case is in units of 1/ ++ 200 (1/100) of a second. ++ ++After a message has been received, Exim waits for the clock to tick at the ++appropriate resolution before proceeding, so that if another message is ++received by the same process, or by another process with the same (re-used) ++pid, it is guaranteed that the time will be different. In most cases, the clock ++will already have ticked while the message was being received. ++ ++ ++3.5 Receiving mail ++------------------ ++ ++The only way Exim can receive mail from another host is using SMTP over TCP/IP, ++in which case the sender and recipient addresses are transferred using SMTP ++commands. However, from a locally running process (such as a user's MUA), there ++are several possibilities: ++ ++ * If the process runs Exim with the -bm option, the message is read ++ non-interactively (usually via a pipe), with the recipients taken from the ++ command line, or from the body of the message if -t is also used. ++ ++ * If the process runs Exim with the -bS option, the message is also read ++ non-interactively, but in this case the recipients are listed at the start ++ of the message in a series of SMTP RCPT commands, terminated by a DATA ++ command. This is so-called "batch SMTP" format, but it isn't really SMTP. ++ The SMTP commands are just another way of passing envelope addresses in a ++ non-interactive submission. ++ ++ * If the process runs Exim with the -bs option, the message is read ++ interactively, using the SMTP protocol. A two-way pipe is normally used for ++ passing data between the local process and the Exim process. This is "real" ++ SMTP and is handled in the same way as SMTP over TCP/IP. For example, the ++ ACLs for SMTP commands are used for this form of submission. ++ ++ * A local process may also make a TCP/IP call to the host's loopback address ++ (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim ++ does not treat the loopback address specially. It treats all such ++ connections in the same way as connections from other hosts. ++ ++In the three cases that do not involve TCP/IP, the sender address is ++constructed from the login name of the user that called Exim and a default ++qualification domain (which can be set by the qualify_domain configuration ++option). For local or batch SMTP, a sender address that is passed using the ++SMTP MAIL command is ignored. However, the system administrator may allow ++certain users ("trusted users") to specify a different sender address ++unconditionally, or all users to specify certain forms of different sender ++address. The -f option or the SMTP MAIL command is used to specify these ++different addresses. See section 5.2 for details of trusted users, and the ++untrusted_set_sender option for a way of allowing untrusted users to change ++sender addresses. ++ ++Messages received by either of the non-interactive mechanisms are subject to ++checking by the non-SMTP ACL, if one is defined. Messages received using SMTP ++(either over TCP/IP, or interacting with a local process) can be checked by a ++number of ACLs that operate at different times during the SMTP session. Either ++individual recipients, or the entire message, can be rejected if local policy ++requirements are not met. The local_scan() function (see chapter 44) is run for ++all incoming messages. ++ ++Exim can be configured not to start a delivery process when a message is ++received; this can be unconditional, or depend on the number of incoming SMTP ++connections or the system load. In these situations, new messages wait on the ++queue until a queue runner process picks them up. However, in standard ++configurations under normal conditions, delivery is started as soon as a ++message is received. ++ ++ ++3.6 Handling an incoming message ++-------------------------------- ++ ++When Exim accepts a message, it writes two files in its spool directory. The ++first contains the envelope information, the current status of the message, and ++the header lines, and the second contains the body of the message. The names of ++the two spool files consist of the message id, followed by "-H" for the file ++containing the envelope and header, and "-D" for the data file. ++ ++By default all these message files are held in a single directory called input ++inside the general Exim spool directory. Some operating systems do not perform ++very well if the number of files in a directory gets large; to improve ++performance in such cases, the split_spool_directory option can be used. This ++causes Exim to split up the input files into 62 sub-directories whose names are ++single letters or digits. When this is done, the queue is processed one ++sub-directory at a time instead of all at once, which can improve overall ++performance even when there are not enough files in each directory to affect ++file system performance. ++ ++The envelope information consists of the address of the message's sender and ++the addresses of the recipients. This information is entirely separate from any ++addresses contained in the header lines. The status of the message includes a ++list of recipients who have already received the message. The format of the ++first spool file is described in chapter 55. ++ ++Address rewriting that is specified in the rewrite section of the configuration ++(see chapter 31) is done once and for all on incoming addresses, both in the ++header lines and the envelope, at the time the message is accepted. If during ++the course of delivery additional addresses are generated (for example, via ++aliasing), these new addresses are rewritten as soon as they are generated. At ++the time a message is actually delivered (transported) further rewriting can ++take place; because this is a transport option, it can be different for ++different forms of delivery. It is also possible to specify the addition or ++removal of certain header lines at the time the message is delivered (see ++chapters 15 and 24). ++ ++ ++3.7 Life of a message ++--------------------- ++ ++A message remains in the spool directory until it is completely delivered to ++its recipients or to an error address, or until it is deleted by an ++administrator or by the user who originally created it. In cases when delivery ++cannot proceed - for example, when a message can neither be delivered to its ++recipients nor returned to its sender, the message is marked "frozen" on the ++spool, and no more deliveries are attempted. ++ ++An administrator can "thaw" such messages when the problem has been corrected, ++and can also freeze individual messages by hand if necessary. In addition, an ++administrator can force a delivery error, causing a bounce message to be sent. ++ ++There are options called ignore_bounce_errors_after and timeout_frozen_after, ++which discard frozen messages after a certain time. The first applies only to ++frozen bounces, the second to any frozen messages. ++ ++While Exim is working on a message, it writes information about each delivery ++attempt to its main log file. This includes successful, unsuccessful, and ++delayed deliveries for each recipient (see chapter 51). The log lines are also ++written to a separate message log file for each message. These logs are solely ++for the benefit of the administrator, and are normally deleted along with the ++spool files when processing of a message is complete. The use of individual ++message logs can be disabled by setting no_message_logs; this might give an ++improvement in performance on very busy systems. ++ ++All the information Exim itself needs to set up a delivery is kept in the first ++spool file, along with the header lines. When a successful delivery occurs, the ++address is immediately written at the end of a journal file, whose name is the ++message id followed by "-J". At the end of a delivery run, if there are some ++addresses left to be tried again later, the first spool file (the "-H" file) is ++updated to indicate which these are, and the journal file is then deleted. ++Updating the spool file is done by writing a new file and renaming it, to ++minimize the possibility of data loss. ++ ++Should the system or the program crash after a successful delivery but before ++the spool file has been updated, the journal is left lying around. The next ++time Exim attempts to deliver the message, it reads the journal file and ++updates the spool file before proceeding. This minimizes the chances of double ++deliveries caused by crashes. ++ ++ ++3.8 Processing an address for delivery ++-------------------------------------- ++ ++The main delivery processing elements of Exim are called routers and transports ++, and collectively these are known as drivers. Code for a number of them is ++provided in the source distribution, and compile-time options specify which ++ones are included in the binary. Run time options specify which ones are ++actually used for delivering messages. ++ ++Each driver that is specified in the run time configuration is an instance of ++that particular driver type. Multiple instances are allowed; for example, you ++can set up several different smtp transports, each with different option values ++that might specify different ports or different timeouts. Each instance has its ++own identifying name. In what follows we will normally use the instance name ++when discussing one particular instance (that is, one specific configuration of ++the driver), and the generic driver name when discussing the driver's features ++in general. ++ ++A router is a driver that operates on an address, either determining how its ++delivery should happen, by assigning it to a specific transport, or converting ++the address into one or more new addresses (for example, via an alias file). A ++router may also explicitly choose to fail an address, causing it to be bounced. ++ ++A transport is a driver that transmits a copy of the message from Exim's spool ++to some destination. There are two kinds of transport: for a local transport, ++the destination is a file or a pipe on the local host, whereas for a remote ++transport the destination is some other host. A message is passed to a specific ++transport as a result of successful routing. If a message has several ++recipients, it may be passed to a number of different transports. ++ ++An address is processed by passing it to each configured router instance in ++turn, subject to certain preconditions, until a router accepts the address or ++specifies that it should be bounced. We will describe this process in more ++detail shortly. First, as a simple example, we consider how each recipient ++address in a message is processed in a small configuration of three routers. ++ ++To make this a more concrete example, it is described in terms of some actual ++routers, but remember, this is only an example. You can configure Exim's ++routers in many different ways, and there may be any number of routers in a ++configuration. ++ ++The first router that is specified in a configuration is often one that handles ++addresses in domains that are not recognized specially by the local host. These ++are typically addresses for arbitrary domains on the Internet. A precondition ++is set up which looks for the special domains known to the host (for example, ++its own domain name), and the router is run for addresses that do not match. ++Typically, this is a router that looks up domains in the DNS in order to find ++the hosts to which this address routes. If it succeeds, the address is assigned ++to a suitable SMTP transport; if it does not succeed, the router is configured ++to fail the address. ++ ++The second router is reached only when the domain is recognized as one that ++"belongs" to the local host. This router does redirection - also known as ++aliasing and forwarding. When it generates one or more new addresses from the ++original, each of them is routed independently from the start. Otherwise, the ++router may cause an address to fail, or it may simply decline to handle the ++address, in which case the address is passed to the next router. ++ ++The final router in many configurations is one that checks to see if the ++address belongs to a local mailbox. The precondition may involve a check to see ++if the local part is the name of a login account, or it may look up the local ++part in a file or a database. If its preconditions are not met, or if the ++router declines, we have reached the end of the routers. When this happens, the ++address is bounced. ++ ++ ++3.9 Processing an address for verification ++------------------------------------------ ++ ++As well as being used to decide how to deliver to an address, Exim's routers ++are also used for address verification. Verification can be requested as one of ++the checks to be performed in an ACL for incoming messages, on both sender and ++recipient addresses, and it can be tested using the -bv and -bvs command line ++options. ++ ++When an address is being verified, the routers are run in "verify mode". This ++does not affect the way the routers work, but it is a state that can be ++detected. By this means, a router can be skipped or made to behave differently ++when verifying. A common example is a configuration in which the first router ++sends all messages to a message-scanning program, unless they have been ++previously scanned. Thus, the first router accepts all addresses without any ++checking, making it useless for verifying. Normally, the no_verify option would ++be set for such a router, causing it to be skipped in verify mode. ++ ++ ++3.10 Running an individual router ++--------------------------------- ++ ++As explained in the example above, a number of preconditions are checked before ++running a router. If any are not met, the router is skipped, and the address is ++passed to the next router. When all the preconditions on a router are met, the ++router is run. What happens next depends on the outcome, which is one of the ++following: ++ ++ * accept: The router accepts the address, and either assigns it to a ++ transport, or generates one or more "child" addresses. Processing the ++ original address ceases, unless the unseen option is set on the router. ++ This option can be used to set up multiple deliveries with different ++ routing (for example, for keeping archive copies of messages). When unseen ++ is set, the address is passed to the next router. Normally, however, an ++ accept return marks the end of routing. ++ ++ Any child addresses generated by the router are processed independently, ++ starting with the first router by default. It is possible to change this by ++ setting the redirect_router option to specify which router to start at for ++ child addresses. Unlike pass_router (see below) the router specified by ++ redirect_router may be anywhere in the router configuration. ++ ++ * pass: The router recognizes the address, but cannot handle it itself. It ++ requests that the address be passed to another router. By default the ++ address is passed to the next router, but this can be changed by setting ++ the pass_router option. However, (unlike redirect_router) the named router ++ must be below the current router (to avoid loops). ++ ++ * decline: The router declines to accept the address because it does not ++ recognize it at all. By default, the address is passed to the next router, ++ but this can be prevented by setting the no_more option. When no_more is ++ set, all the remaining routers are skipped. In effect, no_more converts ++ decline into fail. ++ ++ * fail: The router determines that the address should fail, and queues it for ++ the generation of a bounce message. There is no further processing of the ++ original address unless unseen is set on the router. ++ ++ * defer: The router cannot handle the address at the present time. (A ++ database may be offline, or a DNS lookup may have timed out.) No further ++ processing of the address happens in this delivery attempt. It is tried ++ again next time the message is considered for delivery. ++ ++ * error: There is some error in the router (for example, a syntax error in ++ its configuration). The action is as for defer. ++ ++If an address reaches the end of the routers without having been accepted by ++any of them, it is bounced as unrouteable. The default error message in this ++situation is "unrouteable address", but you can set your own message by making ++use of the cannot_route_message option. This can be set for any router; the ++value from the last router that "saw" the address is used. ++ ++Sometimes while routing you want to fail a delivery when some conditions are ++met but others are not, instead of passing the address on for further routing. ++You can do this by having a second router that explicitly fails the delivery ++when the relevant conditions are met. The redirect router has a "fail" facility ++for this purpose. ++ ++ ++3.11 Duplicate addresses ++------------------------ ++ ++Once routing is complete, Exim scans the addresses that are assigned to local ++and remote transports, and discards any duplicates that it finds. During this ++check, local parts are treated as case-sensitive. This happens only when ++actually delivering a message; when testing routers with -bt, all the routed ++addresses are shown. ++ ++ ++3.12 Router preconditions ++------------------------- ++ ++The preconditions that are tested for each router are listed below, in the ++order in which they are tested. The individual configuration options are ++described in more detail in chapter 15. ++ ++ * The local_part_prefix and local_part_suffix options can specify that the ++ local parts handled by the router may or must have certain prefixes and/or ++ suffixes. If a mandatory affix (prefix or suffix) is not present, the ++ router is skipped. These conditions are tested first. When an affix is ++ present, it is removed from the local part before further processing, ++ including the evaluation of any other conditions. ++ ++ * Routers can be designated for use only when not verifying an address, that ++ is, only when routing it for delivery (or testing its delivery routing). If ++ the verify option is set false, the router is skipped when Exim is ++ verifying an address. Setting the verify option actually sets two options, ++ verify_sender and verify_recipient, which independently control the use of ++ the router for sender and recipient verification. You can set these options ++ directly if you want a router to be used for only one type of verification. ++ Note that cutthrough delivery is classed as a recipient verification for ++ this purpose. ++ ++ * If the address_test option is set false, the router is skipped when Exim is ++ run with the -bt option to test an address routing. This can be helpful ++ when the first router sends all new messages to a scanner of some sort; it ++ makes it possible to use -bt to test subsequent delivery routing without ++ having to simulate the effect of the scanner. ++ ++ * Routers can be designated for use only when verifying an address, as ++ opposed to routing it for delivery. The verify_only option controls this. ++ Again, cutthrough delibery counts as a verification. ++ ++ * Individual routers can be explicitly skipped when running the routers to ++ check an address given in the SMTP EXPN command (see the expn option). ++ ++ * If the domains option is set, the domain of the address must be in the set ++ of domains that it defines. ++ ++ * If the local_parts option is set, the local part of the address must be in ++ the set of local parts that it defines. If local_part_prefix or ++ local_part_suffix is in use, the prefix or suffix is removed from the local ++ part before this check. If you want to do precondition tests on local parts ++ that include affixes, you can do so by using a condition option (see below) ++ that uses the variables $local_part, $local_part_prefix, and ++ $local_part_suffix as necessary. ++ ++ * If the check_local_user option is set, the local part must be the name of ++ an account on the local host. If this check succeeds, the uid and gid of ++ the local user are placed in $local_user_uid and $local_user_gid and the ++ user's home directory is placed in $home; these values can be used in the ++ remaining preconditions. ++ ++ * If the router_home_directory option is set, it is expanded at this point, ++ because it overrides the value of $home. If this expansion were left till ++ later, the value of $home as set by check_local_user would be used in ++ subsequent tests. Having two different values of $home in the same router ++ could lead to confusion. ++ ++ * If the senders option is set, the envelope sender address must be in the ++ set of addresses that it defines. ++ ++ * If the require_files option is set, the existence or non-existence of ++ specified files is tested. ++ ++ * If the condition option is set, it is evaluated and tested. This option ++ uses an expanded string to allow you to set up your own custom ++ preconditions. Expanded strings are described in chapter 11. ++ ++Note that require_files comes near the end of the list, so you cannot use it to ++check for the existence of a file in which to lookup up a domain, local part, ++or sender. However, as these options are all expanded, you can use the exists ++expansion condition to make such tests within each condition. The require_files ++option is intended for checking files that the router may be going to use ++internally, or which are needed by a specific transport (for example, ++.procmailrc). ++ ++ ++3.13 Delivery in detail ++----------------------- ++ ++When a message is to be delivered, the sequence of events is as follows: ++ ++ * If a system-wide filter file is specified, the message is passed to it. The ++ filter may add recipients to the message, replace the recipients, discard ++ the message, cause a new message to be generated, or cause the message ++ delivery to fail. The format of the system filter file is the same as for ++ Exim user filter files, described in the separate document entitled Exim's ++ interfaces to mail filtering. (Note: Sieve cannot be used for system filter ++ files.) ++ ++ Some additional features are available in system filters - see chapter 45 ++ for details. Note that a message is passed to the system filter only once ++ per delivery attempt, however many recipients it has. However, if there are ++ several delivery attempts because one or more addresses could not be ++ immediately delivered, the system filter is run each time. The filter ++ condition first_delivery can be used to detect the first run of the system ++ filter. ++ ++ * Each recipient address is offered to each configured router in turn, ++ subject to its preconditions, until one is able to handle it. If no router ++ can handle the address, that is, if they all decline, the address is ++ failed. Because routers can be targeted at particular domains, several ++ locally handled domains can be processed entirely independently of each ++ other. ++ ++ * A router that accepts an address may assign it to a local or a remote ++ transport. However, the transport is not run at this time. Instead, the ++ address is placed on a list for the particular transport, which will be run ++ later. Alternatively, the router may generate one or more new addresses ++ (typically from alias, forward, or filter files). New addresses are fed ++ back into this process from the top, but in order to avoid loops, a router ++ ignores any address which has an identically-named ancestor that was ++ processed by itself. ++ ++ * When all the routing has been done, addresses that have been successfully ++ handled are passed to their assigned transports. When local transports are ++ doing real local deliveries, they handle only one address at a time, but if ++ a local transport is being used as a pseudo-remote transport (for example, ++ to collect batched SMTP messages for transmission by some other means) ++ multiple addresses can be handled. Remote transports can always handle more ++ than one address at a time, but can be configured not to do so, or to ++ restrict multiple addresses to the same domain. ++ ++ * Each local delivery to a file or a pipe runs in a separate process under a ++ non-privileged uid, and these deliveries are run one at a time. Remote ++ deliveries also run in separate processes, normally under a uid that is ++ private to Exim ("the Exim user"), but in this case, several remote ++ deliveries can be run in parallel. The maximum number of simultaneous ++ remote deliveries for any one message is set by the remote_max_parallel ++ option. The order in which deliveries are done is not defined, except that ++ all local deliveries happen before any remote deliveries. ++ ++ * When it encounters a local delivery during a queue run, Exim checks its ++ retry database to see if there has been a previous temporary delivery ++ failure for the address before running the local transport. If there was a ++ previous failure, Exim does not attempt a new delivery until the retry time ++ for the address is reached. However, this happens only for delivery ++ attempts that are part of a queue run. Local deliveries are always ++ attempted when delivery immediately follows message reception, even if ++ retry times are set for them. This makes for better behaviour if one ++ particular message is causing problems (for example, causing quota ++ overflow, or provoking an error in a filter file). ++ ++ * Remote transports do their own retry handling, since an address may be ++ deliverable to one of a number of hosts, each of which may have a different ++ retry time. If there have been previous temporary failures and no host has ++ reached its retry time, no delivery is attempted, whether in a queue run or ++ not. See chapter 32 for details of retry strategies. ++ ++ * If there were any permanent errors, a bounce message is returned to an ++ appropriate address (the sender in the common case), with details of the ++ error for each failing address. Exim can be configured to send copies of ++ bounce messages to other addresses. ++ ++ * If one or more addresses suffered a temporary failure, the message is left ++ on the queue, to be tried again later. Delivery of these addresses is said ++ to be deferred. ++ ++ * When all the recipient addresses have either been delivered or bounced, ++ handling of the message is complete. The spool files and message log are ++ deleted, though the message log can optionally be preserved if required. ++ ++ ++3.14 Retry mechanism ++-------------------- ++ ++Exim's mechanism for retrying messages that fail to get delivered at the first ++attempt is the queue runner process. You must either run an Exim daemon that ++uses the -q option with a time interval to start queue runners at regular ++intervals, or use some other means (such as cron) to start them. If you do not ++arrange for queue runners to be run, messages that fail temporarily at the ++first attempt will remain on your queue for ever. A queue runner process works ++its way through the queue, one message at a time, trying each delivery that has ++passed its retry time. You can run several queue runners at once. ++ ++Exim uses a set of configured rules to determine when next to retry the failing ++address (see chapter 32). These rules also specify when Exim should give up ++trying to deliver to the address, at which point it generates a bounce message. ++If no retry rules are set for a particular host, address, and error ++combination, no retries are attempted, and temporary errors are treated as ++permanent. ++ ++ ++3.15 Temporary delivery failure ++------------------------------- ++ ++There are many reasons why a message may not be immediately deliverable to a ++particular address. Failure to connect to a remote machine (because it, or the ++connection to it, is down) is one of the most common. Temporary failures may be ++detected during routing as well as during the transport stage of delivery. ++Local deliveries may be delayed if NFS files are unavailable, or if a mailbox ++is on a file system where the user is over quota. Exim can be configured to ++impose its own quotas on local mailboxes; where system quotas are set they will ++also apply. ++ ++If a host is unreachable for a period of time, a number of messages may be ++waiting for it by the time it recovers, and sending them in a single SMTP ++connection is clearly beneficial. Whenever a delivery to a remote host is ++deferred, Exim makes a note in its hints database, and whenever a successful ++SMTP delivery has happened, it looks to see if any other messages are waiting ++for the same host. If any are found, they are sent over the same SMTP ++connection, subject to a configuration limit as to the maximum number in any ++one connection. ++ ++ ++3.16 Permanent delivery failure ++------------------------------- ++ ++When a message cannot be delivered to some or all of its intended recipients, a ++bounce message is generated. Temporary delivery failures turn into permanent ++errors when their timeout expires. All the addresses that fail in a given ++delivery attempt are listed in a single message. If the original message has ++many recipients, it is possible for some addresses to fail in one delivery ++attempt and others to fail subsequently, giving rise to more than one bounce ++message. The wording of bounce messages can be customized by the administrator. ++See chapter 48 for details. ++ ++Bounce messages contain an X-Failed-Recipients: header line that lists the ++failed addresses, for the benefit of programs that try to analyse such messages ++automatically. ++ ++A bounce message is normally sent to the sender of the original message, as ++obtained from the message's envelope. For incoming SMTP messages, this is the ++address given in the MAIL command. However, when an address is expanded via a ++forward or alias file, an alternative address can be specified for delivery ++failures of the generated addresses. For a mailing list expansion (see section ++49.2) it is common to direct bounce messages to the manager of the list. ++ ++ ++3.17 Failures to deliver bounce messages ++---------------------------------------- ++ ++If a bounce message (either locally generated or received from a remote host) ++itself suffers a permanent delivery failure, the message is left on the queue, ++but it is frozen, awaiting the attention of an administrator. There are options ++that can be used to make Exim discard such failed messages, or to keep them for ++only a short time (see timeout_frozen_after and ignore_bounce_errors_after). ++ ++ ++ ++=============================================================================== ++4. BUILDING AND INSTALLING EXIM ++ ++ ++4.1 Unpacking ++------------- ++ ++Exim is distributed as a gzipped or bzipped tar file which, when unpacked, ++creates a directory with the name of the current release (for example, ++exim-4.82) into which the following files are placed: ++ ++ ACKNOWLEDGMENTS contains some acknowledgments ++ CHANGES contains a reference to where changes are documented ++ LICENCE the GNU General Public Licence ++ Makefile top-level make file ++ NOTICE conditions for the use of Exim ++ README list of files, directories and simple build instructions ++ ++Other files whose names begin with README may also be present. The following ++subdirectories are created: ++ ++ Local an empty directory for local configuration files ++ OS OS-specific files ++ doc documentation files ++ exim_monitor source files for the Exim monitor ++ scripts scripts used in the build process ++ src remaining source files ++ util independent utilities ++ ++The main utility programs are contained in the src directory, and are built ++with the Exim binary. The util directory contains a few optional scripts that ++may be useful to some sites. ++ ++ ++4.2 Multiple machine architectures and operating systems ++-------------------------------------------------------- ++ ++The building process for Exim is arranged to make it easy to build binaries for ++a number of different architectures and operating systems from the same set of ++source files. Compilation does not take place in the src directory. Instead, a ++build directory is created for each architecture and operating system. Symbolic ++links to the sources are installed in this directory, which is where the actual ++building takes place. In most cases, Exim can discover the machine architecture ++and operating system for itself, but the defaults can be overridden if ++necessary. ++ ++ ++4.3 PCRE library ++---------------- ++ ++Exim no longer has an embedded PCRE library as the vast majority of modern ++systems include PCRE as a system library, although you may need to install the ++PCRE or PCRE development package for your operating system. If your system has ++a normal PCRE installation the Exim build process will need no further ++configuration. If the library or the headers are in an unusual location you ++will need to either set the PCRE_LIBS and INCLUDE directives appropriately, or ++set PCRE_CONFIG=yes to use the installed pcre-config command. If your operating ++system has no PCRE support then you will need to obtain and build the current ++PCRE from ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/. More ++information on PCRE is available at http://www.pcre.org/. ++ ++ ++4.4 DBM libraries ++----------------- ++ ++Even if you do not use any DBM files in your configuration, Exim still needs a ++DBM library in order to operate, because it uses indexed files for its hints ++databases. Unfortunately, there are a number of DBM libraries in existence, and ++different operating systems often have different ones installed. ++ ++If you are using Solaris, IRIX, one of the modern BSD systems, or a modern ++Linux distribution, the DBM configuration should happen automatically, and you ++may be able to ignore this section. Otherwise, you may have to learn more than ++you would like about DBM libraries from what follows. ++ ++Licensed versions of Unix normally contain a library of DBM functions operating ++via the ndbm interface, and this is what Exim expects by default. Free versions ++of Unix seem to vary in what they contain as standard. In particular, some ++early versions of Linux have no default DBM library, and different distributors ++have chosen to bundle different libraries with their packaged versions. ++However, the more recent releases seem to have standardized on the Berkeley DB ++library. ++ ++Different DBM libraries have different conventions for naming the files they ++use. When a program opens a file called dbmfile, there are several ++possibilities: ++ ++ 1. A traditional ndbm implementation, such as that supplied as part of ++ Solaris, operates on two files called dbmfile.dir and dbmfile.pag. ++ ++ 2. The GNU library, gdbm, operates on a single file. If used via its ndbm ++ compatibility interface it makes two different hard links to it with names ++ dbmfile.dir and dbmfile.pag, but if used via its native interface, the file ++ name is used unmodified. ++ ++ 3. The Berkeley DB package, if called via its ndbm compatibility interface, ++ operates on a single file called dbmfile.db, but otherwise looks to the ++ programmer exactly the same as the traditional ndbm implementation. ++ ++ 4. If the Berkeley package is used in its native mode, it operates on a single ++ file called dbmfile; the programmer's interface is somewhat different to ++ the traditional ndbm interface. ++ ++ 5. To complicate things further, there are several very different versions of ++ the Berkeley DB package. Version 1.85 was stable for a very long time, ++ releases 2.x and 3.x were current for a while, but the latest versions are ++ now numbered 4.x. Maintenance of some of the earlier releases has ceased. ++ All versions of Berkeley DB can be obtained from http://www.sleepycat.com/. ++ ++ 6. Yet another DBM library, called tdb, is available from http:// ++ download.sourceforge.net/tdb. It has its own interface, and also operates ++ on a single file. ++ ++Exim and its utilities can be compiled to use any of these interfaces. In order ++to use any version of the Berkeley DB package in native mode, you must set ++USE_DB in an appropriate configuration file (typically Local/Makefile). For ++example: ++ ++USE_DB=yes ++ ++Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An error is ++diagnosed if you set more than one of these. ++ ++At the lowest level, the build-time configuration sets none of these options, ++thereby assuming an interface of type (1). However, some operating system ++configuration files (for example, those for the BSD operating systems and ++Linux) assume type (4) by setting USE_DB as their default, and the ++configuration files for Cygwin set USE_GDBM. Anything you set in Local/Makefile ++, however, overrides these system defaults. ++ ++As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be necessary to ++set DBMLIB, to cause inclusion of the appropriate library, as in one of these ++lines: ++ ++DBMLIB = -ldb ++DBMLIB = -ltdb ++ ++Settings like that will work if the DBM library is installed in the standard ++place. Sometimes it is not, and the library's header file may also not be in ++the default path. You may need to set INCLUDE to specify where the header file ++is, and to specify the path to the library more fully in DBMLIB, as in this ++example: ++ ++INCLUDE=-I/usr/local/include/db-4.1 ++DBMLIB=/usr/local/lib/db-4.1/libdb.a ++ ++There is further detailed discussion about the various DBM libraries in the ++file doc/dbm.discuss.txt in the Exim distribution. ++ ++ ++4.5 Pre-building configuration ++------------------------------ ++ ++Before building Exim, a local configuration file that specifies options ++independent of any operating system has to be created with the name Local/ ++Makefile. A template for this file is supplied as the file src/EDITME, and it ++contains full descriptions of all the option settings therein. These ++descriptions are therefore not repeated here. If you are building Exim for the ++first time, the simplest thing to do is to copy src/EDITME to Local/Makefile, ++then read it and edit it appropriately. ++ ++There are three settings that you must supply, because Exim will not build ++without them. They are the location of the run time configuration file ++(CONFIGURE_FILE), the directory in which Exim binaries will be installed ++(BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and maybe ++EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be a ++colon-separated list of file names; Exim uses the first of them that exists. ++ ++There are a few other parameters that can be specified either at build time or ++at run time, to enable the same binary to be used on a number of different ++machines. However, if the locations of Exim's spool directory and log file ++directory (if not within the spool directory) are fixed, it is recommended that ++you specify them in Local/Makefile instead of at run time, so that errors ++detected early in Exim's execution (such as a malformed configuration file) can ++be logged. ++ ++Exim's interfaces for calling virus and spam scanning software directly from ++access control lists are not compiled by default. If you want to include these ++facilities, you need to set ++ ++WITH_CONTENT_SCAN=yes ++ ++in your Local/Makefile. For details of the facilities themselves, see chapter ++43. ++ ++If you are going to build the Exim monitor, a similar configuration process is ++required. The file exim_monitor/EDITME must be edited appropriately for your ++installation and saved under the name Local/eximon.conf. If you are happy with ++the default settings described in exim_monitor/EDITME, Local/eximon.conf can be ++empty, but it must exist. ++ ++This is all the configuration that is needed in straightforward cases for known ++operating systems. However, the building process is set up so that it is easy ++to override options that are set by default or by operating-system-specific ++configuration files, for example to change the name of the C compiler, which ++defaults to gcc. See section 4.13 below for details of how to do this. ++ ++ ++4.6 Support for iconv() ++----------------------- ++ ++The contents of header lines in messages may be encoded according to the rules ++described RFC 2047. This makes it possible to transmit characters that are not ++in the ASCII character set, and to label them as being in a particular ++character set. When Exim is inspecting header lines by means of the $h_ ++mechanism, it decodes them, and translates them into a specified character set ++(default ISO-8859-1). The translation is possible only if the operating system ++supports the iconv() function. ++ ++However, some of the operating systems that supply iconv() do not support very ++many conversions. The GNU libiconv library (available from http://www.gnu.org/ ++software/libiconv/) can be installed on such systems to remedy this deficiency, ++as well as on systems that do not supply iconv() at all. After installing ++libiconv, you should add ++ ++HAVE_ICONV=yes ++ ++to your Local/Makefile and rebuild Exim. ++ ++ ++4.7 Including TLS/SSL encryption support ++---------------------------------------- ++ ++Exim can be built to support encrypted SMTP connections, using the STARTTLS ++command as per RFC 2487. It can also support legacy clients that expect to ++start a TLS session immediately on connection to a non-standard port (see the ++tls_on_connect_ports runtime option and the -tls-on-connect command line ++option). ++ ++If you want to build Exim with TLS support, you must first install either the ++OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for ++implementing SSL. ++ ++If OpenSSL is installed, you should set ++ ++SUPPORT_TLS=yes ++TLS_LIBS=-lssl -lcrypto ++ ++in Local/Makefile. You may also need to specify the locations of the OpenSSL ++library and include files. For example: ++ ++SUPPORT_TLS=yes ++TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto ++TLS_INCLUDE=-I/usr/local/openssl/include/ ++ ++If you have pkg-config available, then instead you can just use: ++ ++SUPPORT_TLS=yes ++USE_OPENSSL_PC=openssl ++ ++If GnuTLS is installed, you should set ++ ++SUPPORT_TLS=yes ++USE_GNUTLS=yes ++TLS_LIBS=-lgnutls -ltasn1 -lgcrypt ++ ++in Local/Makefile, and again you may need to specify the locations of the ++library and include files. For example: ++ ++SUPPORT_TLS=yes ++USE_GNUTLS=yes ++TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt ++TLS_INCLUDE=-I/usr/gnu/include ++ ++If you have pkg-config available, then instead you can just use: ++ ++SUPPORT_TLS=yes ++USE_GNUTLS=yes ++USE_GNUTLS_PC=gnutls ++ ++You do not need to set TLS_INCLUDE if the relevant directory is already ++specified in INCLUDE. Details of how to configure Exim to make use of TLS are ++given in chapter 41. ++ ++ ++4.8 Use of tcpwrappers ++---------------------- ++ ++Exim can be linked with the tcpwrappers library in order to check incoming SMTP ++calls using the tcpwrappers control files. This may be a convenient alternative ++to Exim's own checking facilities for installations that are already making use ++of tcpwrappers for other purposes. To do this, you should set USE_TCP_WRAPPERS ++in Local/Makefile, arrange for the file tcpd.h to be available at compile time, ++and also ensure that the library libwrap.a is available at link time, typically ++by including -lwrap in EXTRALIBS_EXIM. For example, if tcpwrappers is installed ++in /usr/local, you might have ++ ++USE_TCP_WRAPPERS=yes ++CFLAGS=-O -I/usr/local/include ++EXTRALIBS_EXIM=-L/usr/local/lib -lwrap ++ ++in Local/Makefile. The daemon name to use in the tcpwrappers control files is ++"exim". For example, the line ++ ++exim : LOCAL 192.168.1. .friendly.domain.example ++ ++in your /etc/hosts.allow file allows connections from the local host, from the ++subnet 192.168.1.0/24, and from all hosts in friendly.domain.example. All other ++connections are denied. The daemon name used by tcpwrappers can be changed at ++build time by setting TCP_WRAPPERS_DAEMON_NAME in Local/Makefile, or by setting ++tcp_wrappers_daemon_name in the configure file. Consult the tcpwrappers ++documentation for further details. ++ ++ ++4.9 Including support for IPv6 ++------------------------------ ++ ++Exim contains code for use on systems that have IPv6 support. Setting ++"HAVE_IPV6=YES" in Local/Makefile causes the IPv6 code to be included; it may ++also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems where the IPv6 ++support is not fully integrated into the normal include and library files. ++ ++Two different types of DNS record for handling IPv6 addresses have been ++defined. AAAA records (analogous to A records for IPv4) are in use, and are ++currently seen as the mainstream. Another record type called A6 was proposed as ++better than AAAA because it had more flexibility. However, it was felt to be ++over-complex, and its status was reduced to "experimental". It is not known if ++anyone is actually using A6 records. Exim has support for A6 records, but this ++is included only if you set "SUPPORT_A6=YES" in Local/Makefile. The support has ++not been tested for some time. ++ ++ ++4.10 Dynamically loaded lookup module support ++--------------------------------------------- ++ ++On some platforms, Exim supports not compiling all lookup types directly into ++the main binary, instead putting some into external modules which can be loaded ++on demand. This permits packagers to build Exim with support for lookups with ++extensive library dependencies without requiring all users to install all of ++those dependencies. Most, but not all, lookup types can be built this way. ++ ++Set "LOOKUP_MODULE_DIR" to the directory into which the modules will be ++installed; Exim will only load modules from that directory, as a security ++measure. You will need to set "CFLAGS_DYNAMIC" if not already defined for your ++OS; see OS/Makefile-Linux for an example. Some other requirements for adjusting ++"EXTRALIBS" may also be necessary, see src/EDITME for details. ++ ++Then, for each module to be loaded dynamically, define the relevant "LOOKUP_"< ++lookup_type> flags to have the value "2" instead of "yes". For example, this ++will build in lsearch but load sqlite and mysql support on demand: ++ ++LOOKUP_LSEARCH=yes ++LOOKUP_SQLITE=2 ++LOOKUP_MYSQL=2 ++ ++ ++4.11 The building process ++------------------------- ++ ++Once Local/Makefile (and Local/eximon.conf, if required) have been created, run ++make at the top level. It determines the architecture and operating system ++types, and creates a build directory if one does not exist. For example, on a ++Sun system running Solaris 8, the directory build-SunOS5-5.8-sparc is created. ++Symbolic links to relevant source files are installed in the build directory. ++ ++Warning: The -j (parallel) flag must not be used with make; the building ++process fails if it is set. ++ ++If this is the first time make has been run, it calls a script that builds a ++make file inside the build directory, using the configuration files from the ++Local directory. The new make file is then passed to another instance of make. ++This does the real work, building a number of utility scripts, and then ++compiling and linking the binaries for the Exim monitor (if configured), a ++number of utility programs, and finally Exim itself. The command "make ++makefile" can be used to force a rebuild of the make file in the build ++directory, should this ever be necessary. ++ ++If you have problems building Exim, check for any comments there may be in the ++README file concerning your operating system, and also take a look at the FAQ, ++where some common problems are covered. ++ ++ ++4.12 Output from "make" ++----------------------- ++ ++The output produced by the make process for compile lines is often very ++unreadable, because these lines can be very long. For this reason, the normal ++output is suppressed by default, and instead output similar to that which ++appears when compiling the 2.6 Linux kernel is generated: just a short line for ++each module that is being compiled or linked. However, it is still possible to ++get the full output, by calling make like this: ++ ++FULLECHO='' make -e ++ ++The value of FULLECHO defaults to "@", the flag character that suppresses ++command reflection in make. When you ask for the full output, it is given in ++addition to the short output. ++ ++ ++4.13 Overriding build-time options for Exim ++------------------------------------------- ++ ++The main make file that is created at the beginning of the building process ++consists of the concatenation of a number of files which set configuration ++values, followed by a fixed set of make instructions. If a value is set more ++than once, the last setting overrides any previous ones. This provides a ++convenient way of overriding defaults. The files that are concatenated are, in ++order: ++ ++OS/Makefile-Default ++OS/Makefile-<ostype> ++Local/Makefile ++Local/Makefile-<ostype> ++Local/Makefile-<archtype> ++Local/Makefile-<ostype>-<archtype> ++OS/Makefile-Base ++ ++where <ostype> is the operating system type and <archtype> is the architecture ++type. Local/Makefile is required to exist, and the building process fails if it ++is absent. The other three Local files are optional, and are often not needed. ++ ++The values used for <ostype> and <archtype> are obtained from scripts called ++scripts/os-type and scripts/arch-type respectively. If either of the ++environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their values are ++used, thereby providing a means of forcing particular settings. Otherwise, the ++scripts try to get values from the uname command. If this fails, the shell ++variables OSTYPE and ARCHTYPE are inspected. A number of ad hoc transformations ++are then applied, to produce the standard names that Exim expects. You can run ++these scripts directly from the shell in order to find out what values are ++being used on your system. ++ ++OS/Makefile-Default contains comments about the variables that are set therein. ++Some (but not all) are mentioned below. If there is something that needs ++changing, review the contents of this file and the contents of the make file ++for your operating system (OS/Makefile-<ostype>) to see what the default values ++are. ++ ++If you need to change any of the values that are set in OS/Makefile-Default or ++in OS/Makefile-<ostype>, or to add any new definitions, you do not need to ++change the original files. Instead, you should make the changes by putting the ++new values in an appropriate Local file. For example, when building Exim in ++many releases of the Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1) ++operating system, it is necessary to specify that the C compiler is called cc ++rather than gcc. Also, the compiler must be called with the option -std1, to ++make it recognize some of the features of Standard C that Exim uses. (Most ++other compilers recognize Standard C by default.) To do this, you should create ++a file called Local/Makefile-OSF1 containing the lines ++ ++CC=cc ++CFLAGS=-std1 ++ ++If you are compiling for just one operating system, it may be easier to put ++these lines directly into Local/Makefile. ++ ++Keeping all your local configuration settings separate from the distributed ++files makes it easy to transfer them to new versions of Exim simply by copying ++the contents of the Local directory. ++ ++Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file ++lookup, but not all systems have these components installed, so the default is ++not to include the relevant code in the binary. All the different kinds of file ++and database lookup that Exim supports are implemented as separate code modules ++which are included only if the relevant compile-time options are set. In the ++case of LDAP, NIS, and NIS+, the settings for Local/Makefile are: ++ ++LOOKUP_LDAP=yes ++LOOKUP_NIS=yes ++LOOKUP_NISPLUS=yes ++ ++and similar settings apply to the other lookup types. They are all listed in ++src/EDITME. In many cases the relevant include files and interface libraries ++need to be installed before compiling Exim. However, there are some optional ++lookup types (such as cdb) for which the code is entirely contained within ++Exim, and no external include files or libraries are required. When a lookup ++type is not included in the binary, attempts to configure Exim to use it cause ++run time configuration errors. ++ ++Many systems now use a tool called pkg-config to encapsulate information about ++how to compile against a library; Exim has some initial support for being able ++to use pkg-config for lookups and authenticators. For any given makefile ++variable which starts "LOOKUP_" or "AUTH_", you can add a new variable with the ++"_PC" suffix in the name and assign as the value the name of the package to be ++queried. The results of querying via the pkg-config command will be added to ++the appropriate Makefile variables with "+=" directives, so your version of ++make will need to support that syntax. For instance: ++ ++LOOKUP_SQLITE=yes ++LOOKUP_SQLITE_PC=sqlite3 ++AUTH_GSASL=yes ++AUTH_GSASL_PC=libgsasl ++AUTH_HEIMDAL_GSSAPI=yes ++AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi ++ ++Exim can be linked with an embedded Perl interpreter, allowing Perl subroutines ++to be called during string expansion. To enable this facility, ++ ++EXIM_PERL=perl.o ++ ++must be defined in Local/Makefile. Details of this facility are given in ++chapter 12. ++ ++The location of the X11 libraries is something that varies a lot between ++operating systems, and there may be different versions of X11 to cope with. ++Exim itself makes no use of X11, but if you are compiling the Exim monitor, the ++X11 libraries must be available. The following three variables are set in OS/ ++Makefile-Default: ++ ++X11=/usr/X11R6 ++XINCLUDE=-I$(X11)/include ++XLFLAGS=-L$(X11)/lib ++ ++These are overridden in some of the operating-system configuration files. For ++example, in OS/Makefile-SunOS5 there is ++ ++X11=/usr/openwin ++XINCLUDE=-I$(X11)/include ++XLFLAGS=-L$(X11)/lib -R$(X11)/lib ++ ++If you need to override the default setting for your operating system, place a ++definition of all three of these variables into your Local/Makefile-<ostype> ++file. ++ ++If you need to add any extra libraries to the link steps, these can be put in a ++variable called EXTRALIBS, which appears in all the link commands, but by ++default is not defined. In contrast, EXTRALIBS_EXIM is used only on the command ++for linking the main Exim binary, and not for any associated utilities. ++ ++There is also DBMLIB, which appears in the link commands for binaries that use ++DBM functions (see also section 4.4). Finally, there is EXTRALIBS_EXIMON, which ++appears only in the link step for the Exim monitor binary, and which can be ++used, for example, to include additional X11 libraries. ++ ++The make file copes with rebuilding Exim correctly if any of the configuration ++files are edited. However, if an optional configuration file is deleted, it is ++necessary to touch the associated non-optional file (that is, Local/Makefile or ++Local/eximon.conf) before rebuilding. ++ ++ ++4.14 OS-specific header files ++----------------------------- ++ ++The OS directory contains a number of files with names of the form os.h- ++<ostype>. These are system-specific C header files that should not normally ++need to be changed. There is a list of macro settings that are recognized in ++the file OS/os.configuring, which should be consulted if you are porting Exim ++to a new operating system. ++ ++ ++4.15 Overriding build-time options for the monitor ++-------------------------------------------------- ++ ++A similar process is used for overriding things when building the Exim monitor, ++where the files that are involved are ++ ++OS/eximon.conf-Default ++OS/eximon.conf-<ostype> ++Local/eximon.conf ++Local/eximon.conf-<ostype> ++Local/eximon.conf-<archtype> ++Local/eximon.conf-<ostype>-<archtype> ++ ++As with Exim itself, the final three files need not exist, and in this case the ++OS/eximon.conf-<ostype> file is also optional. The default values in OS/ ++eximon.conf-Default can be overridden dynamically by setting environment ++variables of the same name, preceded by EXIMON_. For example, setting ++EXIMON_LOG_DEPTH in the environment overrides the value of LOG_DEPTH at run ++time. ++ ++ ++4.16 Installing Exim binaries and scripts ++----------------------------------------- ++ ++The command "make install" runs the exim_install script with no arguments. The ++script copies binaries and utility scripts into the directory whose name is ++specified by the BIN_DIRECTORY setting in Local/Makefile. The install script ++copies files only if they are newer than the files they are going to replace. ++The Exim binary is required to be owned by root and have the setuid bit set, ++for normal configurations. Therefore, you must run "make install" as root so ++that it can set up the Exim binary in this way. However, in some special ++situations (for example, if a host is doing no local deliveries) it may be ++possible to run Exim without making the binary setuid root (see chapter 54 for ++details). ++ ++Exim's run time configuration file is named by the CONFIGURE_FILE setting in ++Local/Makefile. If this names a single file, and the file does not exist, the ++default configuration file src/configure.default is copied there by the ++installation script. If a run time configuration file already exists, it is ++left alone. If CONFIGURE_FILE is a colon-separated list, naming several ++alternative files, no default is installed. ++ ++One change is made to the default configuration file when it is installed: the ++default configuration contains a router that references a system aliases file. ++The path to this file is set to the value specified by SYSTEM_ALIASES_FILE in ++Local/Makefile (/etc/aliases by default). If the system aliases file does not ++exist, the installation script creates it, and outputs a comment to the user. ++ ++The created file contains no aliases, but it does contain comments about the ++aliases a site should normally have. Mail aliases have traditionally been kept ++in /etc/aliases. However, some operating systems are now using /etc/mail/ ++aliases. You should check if yours is one of these, and change Exim's ++configuration if necessary. ++ ++The default configuration uses the local host's name as the only local domain, ++and is set up to do local deliveries into the shared directory /var/mail, ++running as the local user. System aliases and .forward files in users' home ++directories are supported, but no NIS or NIS+ support is configured. Domains ++other than the name of the local host are routed using the DNS, with delivery ++over SMTP. ++ ++It is possible to install Exim for special purposes (such as building a binary ++distribution) in a private part of the file system. You can do this by a ++command such as ++ ++make DESTDIR=/some/directory/ install ++ ++This has the effect of pre-pending the specified directory to all the file ++paths, except the name of the system aliases file that appears in the default ++configuration. (If a default alias file is created, its name is modified.) For ++backwards compatibility, ROOT is used if DESTDIR is not set, but this usage is ++deprecated. ++ ++Running make install does not copy the Exim 4 conversion script convert4r4. You ++will probably run this only once if you are upgrading from Exim 3. None of the ++documentation files in the doc directory are copied, except for the info files ++when you have set INFO_DIRECTORY, as described in section 4.17 below. ++ ++For the utility programs, old versions are renamed by adding the suffix .O to ++their names. The Exim binary itself, however, is handled differently. It is ++installed under a name that includes the version number and the compile number, ++for example exim-4.82-1. The script then arranges for a symbolic link called ++exim to point to the binary. If you are updating a previous version of Exim, ++the script takes care to ensure that the name exim is never absent from the ++directory (as seen by other processes). ++ ++If you want to see what the make install will do before running it for real, ++you can pass the -n option to the installation script by this command: ++ ++make INSTALL_ARG=-n install ++ ++The contents of the variable INSTALL_ARG are passed to the installation script. ++You do not need to be root to run this test. Alternatively, you can run the ++installation script directly, but this must be from within the build directory. ++For example, from the top-level Exim directory you could use this command: ++ ++(cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n) ++ ++There are two other options that can be supplied to the installation script. ++ ++ * -no_chown bypasses the call to change the owner of the installed binary to ++ root, and the call to make it a setuid binary. ++ ++ * -no_symlink bypasses the setting up of the symbolic link exim to the ++ installed binary. ++ ++INSTALL_ARG can be used to pass these options to the script. For example: ++ ++make INSTALL_ARG=-no_symlink install ++ ++The installation script can also be given arguments specifying which files are ++to be copied. For example, to install just the Exim binary, and nothing else, ++without creating the symbolic link, you could use: ++ ++make INSTALL_ARG='-no_symlink exim' install ++ ++ ++4.17 Installing info documentation ++---------------------------------- ++ ++Not all systems use the GNU info system for documentation, and for this reason, ++the Texinfo source of Exim's documentation is not included in the main ++distribution. Instead it is available separately from the ftp site (see section ++1.6). ++ ++If you have defined INFO_DIRECTORY in Local/Makefile and the Texinfo source of ++the documentation is found in the source tree, running "make install" ++automatically builds the info files and installs them. ++ ++ ++4.18 Setting up the spool directory ++----------------------------------- ++ ++When it starts up, Exim tries to create its spool directory if it does not ++exist. The Exim uid and gid are used for the owner and group of the spool ++directory. Sub-directories are automatically created in the spool directory as ++necessary. ++ ++ ++4.19 Testing ++------------ ++ ++Having installed Exim, you can check that the run time configuration file is ++syntactically valid by running the following command, which assumes that the ++Exim binary directory is within your PATH environment variable: ++ ++exim -bV ++ ++If there are any errors in the configuration file, Exim outputs error messages. ++Otherwise it outputs the version number and build date, the DBM library that is ++being used, and information about which drivers and other optional code modules ++are included in the binary. Some simple routing tests can be done by using the ++address testing option. For example, ++ ++exim -bt <local username> ++ ++should verify that it recognizes a local mailbox, and ++ ++exim -bt <remote address> ++ ++a remote one. Then try getting it to deliver mail, both locally and remotely. ++This can be done by passing messages directly to Exim, without going through a ++user agent. For example: ++ ++exim -v postmaster@your.domain.example ++From: user@your.domain.example ++To: postmaster@your.domain.example ++Subject: Testing Exim ++ ++This is a test message. ++^D ++ ++The -v option causes Exim to output some verification of what it is doing. In ++this case you should see copies of three log lines, one for the message's ++arrival, one for its delivery, and one containing "Completed". ++ ++If you encounter problems, look at Exim's log files (mainlog and paniclog) to ++see if there is any relevant information there. Another source of information ++is running Exim with debugging turned on, by specifying the -d option. If a ++message is stuck on Exim's spool, you can force a delivery with debugging ++turned on by a command of the form ++ ++exim -d -M <exim-message-id> ++ ++You must be root or an "admin user" in order to do this. The -d option produces ++rather a lot of output, but you can cut this down to specific areas. For ++example, if you use -d-all+route only the debugging information relevant to ++routing is included. (See the -d option in chapter 5 for more details.) ++ ++One specific problem that has shown up on some sites is the inability to do ++local deliveries into a shared mailbox directory, because it does not have the ++"sticky bit" set on it. By default, Exim tries to create a lock file before ++writing to a mailbox file, and if it cannot create the lock file, the delivery ++is deferred. You can get round this either by setting the "sticky bit" on the ++directory, or by setting a specific group for local deliveries and allowing ++that group to create files in the directory (see the comments above the ++local_delivery transport in the default configuration file). Another approach ++is to configure Exim not to use lock files, but just to rely on fcntl() locking ++instead. However, you should do this only if all user agents also use fcntl() ++locking. For further discussion of locking issues, see chapter 26. ++ ++One thing that cannot be tested on a system that is already running an MTA is ++the receipt of incoming SMTP mail on the standard SMTP port. However, the -oX ++option can be used to run an Exim daemon that listens on some other port, or ++inetd can be used to do this. The -bh option and the exim_checkaccess utility ++can be used to check out policy controls on incoming SMTP mail. ++ ++Testing a new version on a system that is already running Exim can most easily ++be done by building a binary with a different CONFIGURE_FILE setting. From ++within the run time configuration, all other file and directory names that Exim ++uses can be altered, in order to keep it entirely clear of the production ++version. ++ ++ ++4.20 Replacing another MTA with Exim ++------------------------------------ ++ ++Building and installing Exim for the first time does not of itself put it in ++general use. The name by which the system's MTA is called by mail user agents ++is either /usr/sbin/sendmail, or /usr/lib/sendmail (depending on the operating ++system), and it is necessary to make this name point to the exim binary in ++order to get the user agents to pass messages to Exim. This is normally done by ++renaming any existing file and making /usr/sbin/sendmail or /usr/lib/sendmail a ++symbolic link to the exim binary. It is a good idea to remove any setuid ++privilege and executable status from the old MTA. It is then necessary to stop ++and restart the mailer daemon, if one is running. ++ ++Some operating systems have introduced alternative ways of switching MTAs. For ++example, if you are running FreeBSD, you need to edit the file /etc/mail/ ++mailer.conf instead of setting up a symbolic link as just described. A typical ++example of the contents of this file for running Exim is as follows: ++ ++sendmail /usr/exim/bin/exim ++send-mail /usr/exim/bin/exim ++mailq /usr/exim/bin/exim -bp ++newaliases /usr/bin/true ++ ++Once you have set up the symbolic link, or edited /etc/mail/mailer.conf, your ++Exim installation is "live". Check it by sending a message from your favourite ++user agent. ++ ++You should consider what to tell your users about the change of MTA. Exim may ++have different capabilities to what was previously running, and there are ++various operational differences such as the text of messages produced by ++command line options and in bounce messages. If you allow your users to make ++use of Exim's filtering capabilities, you should make the document entitled ++Exim's interface to mail filtering available to them. ++ ++ ++4.21 Upgrading Exim ++------------------- ++ ++If you are already running Exim on your host, building and installing a new ++version automatically makes it available to MUAs, or any other programs that ++call the MTA directly. However, if you are running an Exim daemon, you do need ++to send it a HUP signal, to make it re-execute itself, and thereby pick up the ++new binary. You do not need to stop processing mail in order to install a new ++version of Exim. The install script does not modify an existing runtime ++configuration file. ++ ++ ++4.22 Stopping the Exim daemon on Solaris ++---------------------------------------- ++ ++The standard command for stopping the mailer daemon on Solaris is ++ ++/etc/init.d/sendmail stop ++ ++If /usr/lib/sendmail has been turned into a symbolic link, this script fails to ++stop Exim because it uses the command ps -e and greps the output for the text ++"sendmail"; this is not present because the actual program name (that is, ++"exim") is given by the ps command with these options. A solution is to replace ++the line that finds the process id with something like ++ ++pid=`cat /var/spool/exim/exim-daemon.pid` ++ ++to obtain the daemon's pid directly from the file that Exim saves it in. ++ ++Note, however, that stopping the daemon does not "stop Exim". Messages can ++still be received from local processes, and if automatic delivery is configured ++(the normal case), deliveries will still occur. ++ ++ ++ ++=============================================================================== ++5. THE EXIM COMMAND LINE ++ ++Exim's command line takes the standard Unix form of a sequence of options, each ++starting with a hyphen character, followed by a number of arguments. The ++options are compatible with the main options of Sendmail, and there are also ++some additional options, some of which are compatible with Smail 3. Certain ++combinations of options do not make sense, and provoke an error if used. The ++form of the arguments depends on which options are set. ++ ++ ++5.1 Setting options by program name ++----------------------------------- ++ ++If Exim is called under the name mailq, it behaves as if the option -bp were ++present before any other options. The -bp option requests a listing of the ++contents of the mail queue on the standard output. This feature is for ++compatibility with some systems that contain a command of that name in one of ++the standard libraries, symbolically linked to /usr/sbin/sendmail or /usr/lib/ ++sendmail. ++ ++If Exim is called under the name rsmtp it behaves as if the option -bS were ++present before any other options, for compatibility with Smail. The -bS option ++is used for reading in a number of messages in batched SMTP format. ++ ++If Exim is called under the name rmail it behaves as if the -i and -oee options ++were present before any other options, for compatibility with Smail. The name ++rmail is used as an interface by some UUCP systems. ++ ++If Exim is called under the name runq it behaves as if the option -q were ++present before any other options, for compatibility with Smail. The -q option ++causes a single queue runner process to be started. ++ ++If Exim is called under the name newaliases it behaves as if the option -bi ++were present before any other options, for compatibility with Sendmail. This ++option is used for rebuilding Sendmail's alias file. Exim does not have the ++concept of a single alias file, but can be configured to run a given command if ++called with the -bi option. ++ ++ ++5.2 Trusted and admin users ++--------------------------- ++ ++Some Exim options are available only to trusted users and others are available ++only to admin users. In the description below, the phrases "Exim user" and ++"Exim group" mean the user and group defined by EXIM_USER and EXIM_GROUP in ++Local/Makefile or set by the exim_user and exim_group options. These do not ++necessarily have to use the name "exim". ++ ++ * The trusted users are root, the Exim user, any user listed in the ++ trusted_users configuration option, and any user whose current group or any ++ supplementary group is one of those listed in the trusted_groups ++ configuration option. Note that the Exim group is not automatically ++ trusted. ++ ++ Trusted users are always permitted to use the -f option or a leading ++ "From " line to specify the envelope sender of a message that is passed to ++ Exim through the local interface (see the -bm and -f options below). See ++ the untrusted_set_sender option for a way of permitting non-trusted users ++ to set envelope senders. ++ ++ For a trusted user, there is never any check on the contents of the From: ++ header line, and a Sender: line is never added. Furthermore, any existing ++ Sender: line in incoming local (non-TCP/IP) messages is not removed. ++ ++ Trusted users may also specify a host name, host address, interface ++ address, protocol name, ident value, and authentication data when ++ submitting a message locally. Thus, they are able to insert messages into ++ Exim's queue locally that have the characteristics of messages received ++ from a remote host. Untrusted users may in some circumstances use -f, but ++ can never set the other values that are available to trusted users. ++ ++ * The admin users are root, the Exim user, and any user that is a member of ++ the Exim group or of any group listed in the admin_groups configuration ++ option. The current group does not have to be one of these groups. ++ ++ Admin users are permitted to list the queue, and to carry out certain ++ operations on messages, for example, to force delivery failures. It is also ++ necessary to be an admin user in order to see the full information provided ++ by the Exim monitor, and full debugging output. ++ ++ By default, the use of the -M, -q, -R, and -S options to cause Exim to ++ attempt delivery of messages on its queue is restricted to admin users. ++ However, this restriction can be relaxed by setting the prod_requires_admin ++ option false (that is, specifying no_prod_requires_admin). ++ ++ Similarly, the use of the -bp option to list all the messages in the queue ++ is restricted to admin users unless queue_list_requires_admin is set false. ++ ++Warning: If you configure your system so that admin users are able to edit ++Exim's configuration file, you are giving those users an easy way of getting ++root. There is further discussion of this issue at the start of chapter 6. ++ ++ ++5.3 Command line options ++------------------------ ++ ++Exim's command line options are described in alphabetical order below. If none ++of the options that specifies a specific action (such as starting the daemon or ++a queue runner, or testing an address, or receiving a message in a specific ++format, or listing the queue) are present, and there is at least one argument ++on the command line, -bm (accept a local message on the standard input, with ++the arguments specifying the recipients) is assumed. Otherwise, Exim outputs a ++brief message about itself and exits. ++ ++-- ++ ++ This is a pseudo-option whose only purpose is to terminate the options and ++ therefore to cause subsequent command line items to be treated as arguments ++ rather than options, even if they begin with hyphens. ++ ++--help ++ ++ This option causes Exim to output a few sentences stating what it is. The ++ same output is generated if the Exim binary is called with no options and ++ no arguments. ++ ++--version ++ ++ This option is an alias for -bV and causes version information to be ++ displayed. ++ ++-Ac, -Am ++ ++ These options are used by Sendmail for selecting configuration files and ++ are ignored by Exim. ++ ++-B<type> ++ ++ This is a Sendmail option for selecting 7 or 8 bit processing. Exim is ++ 8-bit clean; it ignores this option. ++ ++-bd ++ ++ This option runs Exim as a daemon, awaiting incoming SMTP connections. ++ Usually the -bd option is combined with the -q<time> option, to specify ++ that the daemon should also initiate periodic queue runs. ++ ++ The -bd option can be used only by an admin user. If either of the -d ++ (debugging) or -v (verifying) options are set, the daemon does not ++ disconnect from the controlling terminal. When running this way, it can be ++ stopped by pressing ctrl-C. ++ ++ By default, Exim listens for incoming connections to the standard SMTP port ++ on all the host's running interfaces. However, it is possible to listen on ++ other ports, on multiple ports, and only on specific interfaces. Chapter 13 ++ contains a description of the options that control this. ++ ++ When a listening daemon is started without the use of -oX (that is, without ++ overriding the normal configuration), it writes its process id to a file ++ called exim-daemon.pid in Exim's spool directory. This location can be ++ overridden by setting PID_FILE_PATH in Local/Makefile. The file is written ++ while Exim is still running as root. ++ ++ When -oX is used on the command line to start a listening daemon, the ++ process id is not written to the normal pid file path. However, -oP can be ++ used to specify a path on the command line if a pid file is required. ++ ++ The SIGHUP signal can be used to cause the daemon to re-execute itself. ++ This should be done whenever Exim's configuration file, or any file that is ++ incorporated into it by means of the .include facility, is changed, and ++ also whenever a new version of Exim is installed. It is not necessary to do ++ this when other files that are referenced from the configuration (for ++ example, alias files) are changed, because these are reread each time they ++ are used. ++ ++-bdf ++ ++ This option has the same effect as -bd except that it never disconnects ++ from the controlling terminal, even when no debugging is specified. ++ ++-be ++ ++ Run Exim in expansion testing mode. Exim discards its root privilege, to ++ prevent ordinary users from using this mode to read otherwise inaccessible ++ files. If no arguments are given, Exim runs interactively, prompting for ++ lines of data. Otherwise, it processes each argument in turn. ++ ++ If Exim was built with USE_READLINE=yes in Local/Makefile, it tries to load ++ the libreadline library dynamically whenever the -be option is used without ++ command line arguments. If successful, it uses the readline() function, ++ which provides extensive line-editing facilities, for reading the test ++ data. A line history is supported. ++ ++ Long expansion expressions can be split over several lines by using ++ backslash continuations. As in Exim's run time configuration, white space ++ at the start of continuation lines is ignored. Each argument or data line ++ is passed through the string expansion mechanism, and the result is output. ++ Variable values from the configuration file (for example, $qualify_domain) ++ are available, but no message-specific values (such as $sender_domain) are ++ set, because no message is being processed (but see -bem and -Mset). ++ ++ Note: If you use this mechanism to test lookups, and you change the data ++ files or databases you are using, you must exit and restart Exim before ++ trying the same lookup again. Otherwise, because each Exim process caches ++ the results of lookups, you will just get the same result as before. ++ ++-bem <filename> ++ ++ This option operates like -be except that it must be followed by the name ++ of a file. For example: ++ ++ exim -bem /tmp/testmessage ++ ++ The file is read as a message (as if receiving a locally-submitted non-SMTP ++ message) before any of the test expansions are done. Thus, message-specific ++ variables such as $message_size and $header_from: are available. However, ++ no Received: header is added to the message. If the -t option is set, ++ recipients are read from the headers in the normal way, and are shown in ++ the $recipients variable. Note that recipients cannot be given on the ++ command line, because further arguments are taken as strings to expand ++ (just like -be). ++ ++-bF <filename> ++ ++ This option is the same as -bf except that it assumes that the filter being ++ tested is a system filter. The additional commands that are available only ++ in system filters are recognized. ++ ++-bf <filename> ++ ++ This option runs Exim in user filter testing mode; the file is the filter ++ file to be tested, and a test message must be supplied on the standard ++ input. If there are no message-dependent tests in the filter, an empty file ++ can be supplied. ++ ++ If you want to test a system filter file, use -bF instead of -bf. You can ++ use both -bF and -bf on the same command, in order to test a system filter ++ and a user filter in the same run. For example: ++ ++ exim -bF /system/filter -bf /user/filter </test/message ++ ++ This is helpful when the system filter adds header lines or sets filter ++ variables that are used by the user filter. ++ ++ If the test filter file does not begin with one of the special lines ++ ++ # Exim filter ++ # Sieve filter ++ ++ it is taken to be a normal .forward file, and is tested for validity under ++ that interpretation. See sections 22.4 to 22.6 for a description of the ++ possible contents of non-filter redirection lists. ++ ++ The result of an Exim command that uses -bf, provided no errors are ++ detected, is a list of the actions that Exim would try to take if presented ++ with the message for real. More details of filter testing are given in the ++ separate document entitled Exim's interfaces to mail filtering. ++ ++ When testing a filter file, the envelope sender can be set by the -f ++ option, or by a "From " line at the start of the test message. Various ++ parameters that would normally be taken from the envelope recipient address ++ of the message can be set by means of additional command line options (see ++ the next four options). ++ ++-bfd <domain> ++ ++ This sets the domain of the recipient address when a filter file is being ++ tested by means of the -bf option. The default is the value of ++ $qualify_domain. ++ ++-bfl <local part> ++ ++ This sets the local part of the recipient address when a filter file is ++ being tested by means of the -bf option. The default is the username of the ++ process that calls Exim. A local part should be specified with any prefix ++ or suffix stripped, because that is how it appears to the filter when a ++ message is actually being delivered. ++ ++-bfp <prefix> ++ ++ This sets the prefix of the local part of the recipient address when a ++ filter file is being tested by means of the -bf option. The default is an ++ empty prefix. ++ ++-bfs <suffix> ++ ++ This sets the suffix of the local part of the recipient address when a ++ filter file is being tested by means of the -bf option. The default is an ++ empty suffix. ++ ++-bh <IP address> ++ ++ This option runs a fake SMTP session as if from the given IP address, using ++ the standard input and output. The IP address may include a port number at ++ the end, after a full stop. For example: ++ ++ exim -bh 10.9.8.7.1234 ++ exim -bh fe80::a00:20ff:fe86:a061.5678 ++ ++ When an IPv6 address is given, it is converted into canonical form. In the ++ case of the second example above, the value of $sender_host_address after ++ conversion to the canonical form is ++ "fe80:0000:0000:0a00:20ff:fe86:a061.5678". ++ ++ Comments as to what is going on are written to the standard error file. ++ These include lines beginning with "LOG" for anything that would have been ++ logged. This facility is provided for testing configuration options for ++ incoming messages, to make sure they implement the required policy. For ++ example, you can test your relay controls using -bh. ++ ++ Warning 1: You can test features of the configuration that rely on ident ++ (RFC 1413) information by using the -oMt option. However, Exim cannot ++ actually perform an ident callout when testing using -bh because there is ++ no incoming SMTP connection. ++ ++ Warning 2: Address verification callouts (see section 42.44) are also ++ skipped when testing using -bh. If you want these callouts to occur, use ++ -bhc instead. ++ ++ Messages supplied during the testing session are discarded, and nothing is ++ written to any of the real log files. There may be pauses when DNS (and ++ other) lookups are taking place, and of course these may time out. The -oMi ++ option can be used to specify a specific IP interface and port if this is ++ important, and -oMaa and -oMai can be used to set parameters as if the SMTP ++ session were authenticated. ++ ++ The exim_checkaccess utility is a "packaged" version of -bh whose output ++ just states whether a given recipient address from a given host is ++ acceptable or not. See section 52.8. ++ ++ Features such as authentication and encryption, where the client input is ++ not plain text, cannot easily be tested with -bh. Instead, you should use a ++ specialized SMTP test program such as swaks. ++ ++-bhc <IP address> ++ ++ This option operates in the same way as -bh, except that address ++ verification callouts are performed if required. This includes consulting ++ and updating the callout cache database. ++ ++-bi ++ ++ Sendmail interprets the -bi option as a request to rebuild its alias file. ++ Exim does not have the concept of a single alias file, and so it cannot ++ mimic this behaviour. However, calls to /usr/lib/sendmail with the -bi ++ option tend to appear in various scripts such as NIS make files, so the ++ option must be recognized. ++ ++ If -bi is encountered, the command specified by the bi_command ++ configuration option is run, under the uid and gid of the caller of Exim. ++ If the -oA option is used, its value is passed to the command as an ++ argument. The command set by bi_command may not contain arguments. The ++ command can use the exim_dbmbuild utility, or some other means, to rebuild ++ alias files if this is required. If the bi_command option is not set, ++ calling Exim with -bi is a no-op. ++ ++-bI:help ++ ++ We shall provide various options starting "-bI:" for querying Exim for ++ information. The output of many of these will be intended for machine ++ consumption. This one is not. The -bI:help option asks Exim for a synopsis ++ of supported options beginning "-bI:". Use of any of these options shall ++ cause Exim to exit after producing the requested output. ++ ++-bI:dscp ++ ++ This option causes Exim to emit an alphabetically sorted list of all ++ recognised DSCP names. ++ ++-bI:sieve ++ ++ This option causes Exim to emit an alphabetically sorted list of all ++ supported Sieve protocol extensions on stdout, one per line. This is ++ anticipated to be useful for ManageSieve (RFC 5804) implementations, in ++ providing that protocol's "SIEVE" capability response line. As the precise ++ list may depend upon compile-time build options, which this option will ++ adapt to, this is the only way to guarantee a correct response. ++ ++-bm ++ ++ This option runs an Exim receiving process that accepts an incoming, ++ locally-generated message on the standard input. The recipients are given ++ as the command arguments (except when -t is also present - see below). Each ++ argument can be a comma-separated list of RFC 2822 addresses. This is the ++ default option for selecting the overall action of an Exim call; it is ++ assumed if no other conflicting option is present. ++ ++ If any addresses in the message are unqualified (have no domain), they are ++ qualified by the values of the qualify_domain or qualify_recipient options, ++ as appropriate. The -bnq option (see below) provides a way of suppressing ++ this for special cases. ++ ++ Policy checks on the contents of local messages can be enforced by means of ++ the non-SMTP ACL. See chapter 42 for details. ++ ++ The return code is zero if the message is successfully accepted. Otherwise, ++ the action is controlled by the -oex option setting - see below. ++ ++ The format of the message must be as defined in RFC 2822, except that, for ++ compatibility with Sendmail and Smail, a line in one of the forms ++ ++ From sender Fri Jan 5 12:55 GMT 1997 ++ From sender Fri, 5 Jan 97 12:55:01 ++ ++ (with the weekday optional, and possibly with additional text after the ++ date) is permitted to appear at the start of the message. There appears to ++ be no authoritative specification of the format of this line. Exim ++ recognizes it by matching against the regular expression defined by the ++ uucp_from_pattern option, which can be changed if necessary. ++ ++ The specified sender is treated as if it were given as the argument to the ++ -f option, but if a -f option is also present, its argument is used in ++ preference to the address taken from the message. The caller of Exim must ++ be a trusted user for the sender of a message to be set in this way. ++ ++-bmalware <filename> ++ ++ This debugging option causes Exim to scan the given file, using the malware ++ scanning framework. The option of av_scanner influences this option, so if ++ av_scanner's value is dependent upon an expansion then the expansion should ++ have defaults which apply to this invocation. ACLs are not invoked, so if ++ av_scanner references an ACL variable then that variable will never be ++ populated and -bmalware will fail. ++ ++ Exim will have changed working directory before resolving the filename, so ++ using fully qualified pathnames is advisable. Exim will be running as the ++ Exim user when it tries to open the file, rather than as the invoking user. ++ This option requires admin privileges. ++ ++ The -bmalware option will not be extended to be more generally useful, ++ there are better tools for file-scanning. This option exists to help ++ administrators verify their Exim and AV scanner configuration. ++ ++-bnq ++ ++ By default, Exim automatically qualifies unqualified addresses (those ++ without domains) that appear in messages that are submitted locally (that ++ is, not over TCP/IP). This qualification applies both to addresses in ++ envelopes, and addresses in header lines. Sender addresses are qualified ++ using qualify_domain, and recipient addresses using qualify_recipient ++ (which defaults to the value of qualify_domain). ++ ++ Sometimes, qualification is not wanted. For example, if -bS (batch SMTP) is ++ being used to re-submit messages that originally came from remote hosts ++ after content scanning, you probably do not want to qualify unqualified ++ addresses in header lines. (Such lines will be present only if you have not ++ enabled a header syntax check in the appropriate ACL.) ++ ++ The -bnq option suppresses all qualification of unqualified addresses in ++ messages that originate on the local host. When this is used, unqualified ++ addresses in the envelope provoke errors (causing message rejection) and ++ unqualified addresses in header lines are left alone. ++ ++-bP ++ ++ If this option is given with no arguments, it causes the values of all ++ Exim's main configuration options to be written to the standard output. The ++ values of one or more specific options can be requested by giving their ++ names as arguments, for example: ++ ++ exim -bP qualify_domain hold_domains ++ ++ However, any option setting that is preceded by the word "hide" in the ++ configuration file is not shown in full, except to an admin user. For other ++ users, the output is as in this example: ++ ++ mysql_servers = <value not displayable> ++ ++ If configure_file is given as an argument, the name of the run time ++ configuration file is output. If a list of configuration files was ++ supplied, the value that is output here is the name of the file that was ++ actually used. ++ ++ If the -n flag is given, then for most modes of -bP operation the name will ++ not be output. ++ ++ If log_file_path or pid_file_path are given, the names of the directories ++ where log files and daemon pid files are written are output, respectively. ++ If these values are unset, log files are written in a sub-directory of the ++ spool directory called log, and the pid file is written directly into the ++ spool directory. ++ ++ If -bP is followed by a name preceded by "+", for example, ++ ++ exim -bP +local_domains ++ ++ it searches for a matching named list of any type (domain, host, address, ++ or local part) and outputs what it finds. ++ ++ If one of the words router, transport, or authenticator is given, followed ++ by the name of an appropriate driver instance, the option settings for that ++ driver are output. For example: ++ ++ exim -bP transport local_delivery ++ ++ The generic driver options are output first, followed by the driver's ++ private options. A list of the names of drivers of a particular type can be ++ obtained by using one of the words router_list, transport_list, or ++ authenticator_list, and a complete list of all drivers with their option ++ settings can be obtained by using routers, transports, or authenticators. ++ ++ If invoked by an admin user, then macro, macro_list and macros are ++ available, similarly to the drivers. Because macros are sometimes used for ++ storing passwords, this option is restricted. The output format is one item ++ per line. ++ ++-bp ++ ++ This option requests a listing of the contents of the mail queue on the ++ standard output. If the -bp option is followed by a list of message ids, ++ just those messages are listed. By default, this option can be used only by ++ an admin user. However, the queue_list_requires_admin option can be set ++ false to allow any user to see the queue. ++ ++ Each message on the queue is displayed as in the following example: ++ ++ 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example> ++ red.king@looking-glass.fict.example ++ <other addresses> ++ ++ The first line contains the length of time the message has been on the ++ queue (in this case 25 minutes), the size of the message (2.9K), the unique ++ local identifier for the message, and the message sender, as contained in ++ the envelope. For bounce messages, the sender address is empty, and appears ++ as "<>". If the message was submitted locally by an untrusted user who ++ overrode the default sender address, the user's login name is shown in ++ parentheses before the sender address. ++ ++ If the message is frozen (attempts to deliver it are suspended) then the ++ text "*** frozen ***" is displayed at the end of this line. ++ ++ The recipients of the message (taken from the envelope, not the headers) ++ are displayed on subsequent lines. Those addresses to which the message has ++ already been delivered are marked with the letter D. If an original address ++ gets expanded into several addresses via an alias or forward file, the ++ original is displayed with a D only when deliveries for all of its child ++ addresses are complete. ++ ++-bpa ++ ++ This option operates like -bp, but in addition it shows delivered addresses ++ that were generated from the original top level address(es) in each message ++ by alias or forwarding operations. These addresses are flagged with "+D" ++ instead of just "D". ++ ++-bpc ++ ++ This option counts the number of messages on the queue, and writes the ++ total to the standard output. It is restricted to admin users, unless ++ queue_list_requires_admin is set false. ++ ++-bpr ++ ++ This option operates like -bp, but the output is not sorted into ++ chronological order of message arrival. This can speed it up when there are ++ lots of messages on the queue, and is particularly useful if the output is ++ going to be post-processed in a way that doesn't need the sorting. ++ ++-bpra ++ ++ This option is a combination of -bpr and -bpa. ++ ++-bpru ++ ++ This option is a combination of -bpr and -bpu. ++ ++-bpu ++ ++ This option operates like -bp but shows only undelivered top-level ++ addresses for each message displayed. Addresses generated by aliasing or ++ forwarding are not shown, unless the message was deferred after processing ++ by a router with the one_time option set. ++ ++-brt ++ ++ This option is for testing retry rules, and it must be followed by up to ++ three arguments. It causes Exim to look for a retry rule that matches the ++ values and to write it to the standard output. For example: ++ ++ exim -brt bach.comp.mus.example ++ Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m; ++ ++ See chapter 32 for a description of Exim's retry rules. The first argument, ++ which is required, can be a complete address in the form local_part@domain, ++ or it can be just a domain name. If the second argument contains a dot, it ++ is interpreted as an optional second domain name; if no retry rule is found ++ for the first argument, the second is tried. This ties in with Exim's ++ behaviour when looking for retry rules for remote hosts - if no rule is ++ found that matches the host, one that matches the mail domain is sought. ++ Finally, an argument that is the name of a specific delivery error, as used ++ in setting up retry rules, can be given. For example: ++ ++ exim -brt haydn.comp.mus.example quota_3d ++ Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m ++ ++-brw ++ ++ This option is for testing address rewriting rules, and it must be followed ++ by a single argument, consisting of either a local part without a domain, ++ or a complete address with a fully qualified domain. Exim outputs how this ++ address would be rewritten for each possible place it might appear. See ++ chapter 31 for further details. ++ ++-bS ++ ++ This option is used for batched SMTP input, which is an alternative ++ interface for non-interactive local message submission. A number of ++ messages can be submitted in a single run. However, despite its name, this ++ is not really SMTP input. Exim reads each message's envelope from SMTP ++ commands on the standard input, but generates no responses. If the caller ++ is trusted, or untrusted_set_sender is set, the senders in the SMTP MAIL ++ commands are believed; otherwise the sender is always the caller of Exim. ++ ++ The message itself is read from the standard input, in SMTP format (leading ++ dots doubled), terminated by a line containing just a single dot. An error ++ is provoked if the terminating dot is missing. A further message may then ++ follow. ++ ++ As for other local message submissions, the contents of incoming batch SMTP ++ messages can be checked using the non-SMTP ACL (see chapter 42). ++ Unqualified addresses are automatically qualified using qualify_domain and ++ qualify_recipient, as appropriate, unless the -bnq option is used. ++ ++ Some other SMTP commands are recognized in the input. HELO and EHLO act as ++ RSET; VRFY, EXPN, ETRN, and HELP act as NOOP; QUIT quits, ignoring the rest ++ of the standard input. ++ ++ If any error is encountered, reports are written to the standard output and ++ error streams, and Exim gives up immediately. The return code is 0 if no ++ error was detected; it is 1 if one or more messages were accepted before ++ the error was detected; otherwise it is 2. ++ ++ More details of input using batched SMTP are given in section 47.11. ++ ++-bs ++ ++ This option causes Exim to accept one or more messages by reading SMTP ++ commands on the standard input, and producing SMTP replies on the standard ++ output. SMTP policy controls, as defined in ACLs (see chapter 42) are ++ applied. Some user agents use this interface as a way of passing ++ locally-generated messages to the MTA. ++ ++ In this usage, if the caller of Exim is trusted, or untrusted_set_sender is ++ set, the senders of messages are taken from the SMTP MAIL commands. ++ Otherwise the content of these commands is ignored and the sender is set up ++ as the calling user. Unqualified addresses are automatically qualified ++ using qualify_domain and qualify_recipient, as appropriate, unless the -bnq ++ option is used. ++ ++ The -bs option is also used to run Exim from inetd, as an alternative to ++ using a listening daemon. Exim can distinguish the two cases by checking ++ whether the standard input is a TCP/IP socket. When Exim is called from ++ inetd, the source of the mail is assumed to be remote, and the comments ++ above concerning senders and qualification do not apply. In this situation, ++ Exim behaves in exactly the same way as it does when receiving a message ++ via the listening daemon. ++ ++-bt ++ ++ This option runs Exim in address testing mode, in which each argument is ++ taken as a recipient address to be tested for deliverability. The results ++ are written to the standard output. If a test fails, and the caller is not ++ an admin user, no details of the failure are output, because these might ++ contain sensitive information such as usernames and passwords for database ++ lookups. ++ ++ If no arguments are given, Exim runs in an interactive manner, prompting ++ with a right angle bracket for addresses to be tested. ++ ++ Unlike the -be test option, you cannot arrange for Exim to use the readline ++ () function, because it is running as root and there are security issues. ++ ++ Each address is handled as if it were the recipient address of a message ++ (compare the -bv option). It is passed to the routers and the result is ++ written to the standard output. However, any router that has ++ no_address_test set is bypassed. This can make -bt easier to use for ++ genuine routing tests if your first router passes everything to a scanner ++ program. ++ ++ The return code is 2 if any address failed outright; it is 1 if no address ++ failed outright but at least one could not be resolved for some reason. ++ Return code 0 is given only when all addresses succeed. ++ ++ Note: When actually delivering a message, Exim removes duplicate recipient ++ addresses after routing is complete, so that only one delivery takes place. ++ This does not happen when testing with -bt; the full results of routing are ++ always shown. ++ ++ Warning: -bt can only do relatively simple testing. If any of the routers ++ in the configuration makes any tests on the sender address of a message, ++ you can use the -f option to set an appropriate sender when running -bt ++ tests. Without it, the sender is assumed to be the calling user at the ++ default qualifying domain. However, if you have set up (for example) ++ routers whose behaviour depends on the contents of an incoming message, you ++ cannot test those conditions using -bt. The -N option provides a possible ++ way of doing such tests. ++ ++-bV ++ ++ This option causes Exim to write the current version number, compilation ++ number, and compilation date of the exim binary to the standard output. It ++ also lists the DBM library that is being used, the optional modules (such ++ as specific lookup types), the drivers that are included in the binary, and ++ the name of the run time configuration file that is in use. ++ ++ As part of its operation, -bV causes Exim to read and syntax check its ++ configuration file. However, this is a static check only. It cannot check ++ values that are to be expanded. For example, although a misspelt ACL verb ++ is detected, an error in the verb's arguments is not. You cannot rely on ++ -bV alone to discover (for example) all the typos in the configuration; ++ some realistic testing is needed. The -bh and -N options provide more ++ dynamic testing facilities. ++ ++-bv ++ ++ This option runs Exim in address verification mode, in which each argument ++ is taken as a recipient address to be verified by the routers. (This does ++ not involve any verification callouts). During normal operation, ++ verification happens mostly as a consequence processing a verify condition ++ in an ACL (see chapter 42). If you want to test an entire ACL, possibly ++ including callouts, see the -bh and -bhc options. ++ ++ If verification fails, and the caller is not an admin user, no details of ++ the failure are output, because these might contain sensitive information ++ such as usernames and passwords for database lookups. ++ ++ If no arguments are given, Exim runs in an interactive manner, prompting ++ with a right angle bracket for addresses to be verified. ++ ++ Unlike the -be test option, you cannot arrange for Exim to use the readline ++ () function, because it is running as exim and there are security issues. ++ ++ Verification differs from address testing (the -bt option) in that routers ++ that have no_verify set are skipped, and if the address is accepted by a ++ router that has fail_verify set, verification fails. The address is ++ verified as a recipient if -bv is used; to test verification for a sender ++ address, -bvs should be used. ++ ++ If the -v option is not set, the output consists of a single line for each ++ address, stating whether it was verified or not, and giving a reason in the ++ latter case. Without -v, generating more than one address by redirection ++ causes verification to end successfully, without considering the generated ++ addresses. However, if just one address is generated, processing continues, ++ and the generated address must verify successfully for the overall ++ verification to succeed. ++ ++ When -v is set, more details are given of how the address has been handled, ++ and in the case of address redirection, all the generated addresses are ++ also considered. Verification may succeed for some and fail for others. ++ ++ The return code is 2 if any address failed outright; it is 1 if no address ++ failed outright but at least one could not be resolved for some reason. ++ Return code 0 is given only when all addresses succeed. ++ ++ If any of the routers in the configuration makes any tests on the sender ++ address of a message, you should use the -f option to set an appropriate ++ sender when running -bv tests. Without it, the sender is assumed to be the ++ calling user at the default qualifying domain. ++ ++-bvs ++ ++ This option acts like -bv, but verifies the address as a sender rather than ++ a recipient address. This affects any rewriting and qualification that ++ might happen. ++ ++-bw ++ ++ This option runs Exim as a daemon, awaiting incoming SMTP connections, ++ similarly to the -bd option. All port specifications on the command-line ++ and in the configuration file are ignored. Queue-running may not be ++ specified. ++ ++ In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is ++ listening for connections. This permits the system to start up and have ++ inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for ++ each port only when the first connection is received. ++ ++ If the option is given as -bw<time> then the time is a timeout, after which ++ the daemon will exit, which should cause inetd to listen once more. ++ ++-C <filelist> ++ ++ This option causes Exim to find the run time configuration file from the ++ given list instead of from the list specified by the CONFIGURE_FILE ++ compile-time setting. Usually, the list will consist of just a single file ++ name, but it can be a colon-separated list of names. In this case, the ++ first file that exists is used. Failure to open an existing file stops Exim ++ from proceeding any further along the list, and an error is generated. ++ ++ When this option is used by a caller other than root, and the list is ++ different from the compiled-in list, Exim gives up its root privilege ++ immediately, and runs with the real and effective uid and gid set to those ++ of the caller. However, if a TRUSTED_CONFIG_LIST file is defined in Local/ ++ Makefile, that file contains a list of full pathnames, one per line, for ++ configuration files which are trusted. Root privilege is retained for any ++ configuration file so listed, as long as the caller is the Exim user (or ++ the user specified in the CONFIGURE_OWNER option, if any), and as long as ++ the configuration file is not writeable by inappropriate users or groups. ++ ++ Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a ++ configuration using -C right through message reception and delivery, even ++ if the caller is root. The reception works, but by that time, Exim is ++ running as the Exim user, so when it re-executes to regain privilege for ++ the delivery, the use of -C causes privilege to be lost. However, root can ++ test reception and delivery using two separate commands (one to put a ++ message on the queue, using -odq, and another to do the delivery, using -M ++ ). ++ ++ If ALT_CONFIG_PREFIX is defined in Local/Makefile, it specifies a prefix ++ string with which any file named in a -C command line option must start. In ++ addition, the file name must not contain the sequence "/../". However, if ++ the value of the -C option is identical to the value of CONFIGURE_FILE in ++ Local/Makefile, Exim ignores -C and proceeds as usual. There is no default ++ setting for ALT_CONFIG_PREFIX; when it is unset, any file name can be used ++ with -C. ++ ++ ALT_CONFIG_PREFIX can be used to confine alternative configuration files to ++ a directory to which only root has access. This prevents someone who has ++ broken into the Exim account from running a privileged Exim with an ++ arbitrary configuration file. ++ ++ The -C facility is useful for ensuring that configuration files are ++ syntactically correct, but cannot be used for test deliveries, unless the ++ caller is privileged, or unless it is an exotic configuration that does not ++ require privilege. No check is made on the owner or group of the files ++ specified by this option. ++ ++-D<macro>=<value> ++ ++ This option can be used to override macro definitions in the configuration ++ file (see section 6.4). However, like -C, if it is used by an unprivileged ++ caller, it causes Exim to give up its root privilege. If DISABLE_D_OPTION ++ is defined in Local/Makefile, the use of -D is completely disabled, and its ++ use causes an immediate error exit. ++ ++ If WHITELIST_D_MACROS is defined in Local/Makefile then it should be a ++ colon-separated list of macros which are considered safe and, if -D only ++ supplies macros from this list, and the values are acceptable, then Exim ++ will not give up root privilege if the caller is root, the Exim run-time ++ user, or the CONFIGURE_OWNER, if set. This is a transition mechanism and is ++ expected to be removed in the future. Acceptable values for the macros ++ satisfy the regexp: "^[A-Za-z0-9_/.-]*$" ++ ++ The entire option (including equals sign if present) must all be within one ++ command line item. -D can be used to set the value of a macro to the empty ++ string, in which case the equals sign is optional. These two commands are ++ synonymous: ++ ++ exim -DABC ... ++ exim -DABC= ... ++ ++ To include spaces in a macro definition item, quotes must be used. If you ++ use quotes, spaces are permitted around the macro name and the equals sign. ++ For example: ++ ++ exim '-D ABC = something' ... ++ ++ -D may be repeated up to 10 times on a command line. ++ ++-d<debug options> ++ ++ This option causes debugging information to be written to the standard ++ error stream. It is restricted to admin users because debugging output may ++ show database queries that contain password information. Also, the details ++ of users' filter files should be protected. If a non-admin user uses -d, ++ Exim writes an error message to the standard error stream and exits with a ++ non-zero return code. ++ ++ When -d is used, -v is assumed. If -d is given on its own, a lot of ++ standard debugging data is output. This can be reduced, or increased to ++ include some more rarely needed information, by directly following -d with ++ a string made up of names preceded by plus or minus characters. These add ++ or remove sets of debugging data, respectively. For example, -d+filter adds ++ filter debugging, whereas -d-all+filter selects only filter debugging. Note ++ that no spaces are allowed in the debug setting. The available debugging ++ categories are: ++ ++ acl ACL interpretation ++ auth authenticators ++ deliver general delivery logic ++ dns DNS lookups (see also resolver) ++ dnsbl DNS black list (aka RBL) code ++ exec arguments for execv() calls ++ expand detailed debugging for string expansions ++ filter filter handling ++ hints_lookup hints data lookups ++ host_lookup all types of name-to-IP address handling ++ ident ident lookup ++ interface lists of local interfaces ++ lists matching things in lists ++ load system load checks ++ local_scan can be used by local_scan() (see chapter 44) ++ lookup general lookup code and all lookups ++ memory memory handling ++ pid add pid to debug output lines ++ process_info setting info for the process log ++ queue_run queue runs ++ receive general message reception logic ++ resolver turn on the DNS resolver's debugging output ++ retry retry handling ++ rewrite address rewriting ++ route address routing ++ timestamp add timestamp to debug output lines ++ tls TLS logic ++ transport transports ++ uid changes of uid/gid and looking up uid/gid ++ verify address verification logic ++ all almost all of the above (see below), and also -v ++ ++ The "all" option excludes "memory" when used as "+all", but includes it for ++ "-all". The reason for this is that "+all" is something that people tend to ++ use when generating debug output for Exim maintainers. If "+memory" is ++ included, an awful lot of output that is very rarely of interest is ++ generated, so it now has to be explicitly requested. However, "-all" does ++ turn everything off. ++ ++ The "resolver" option produces output only if the DNS resolver was compiled ++ with DEBUG enabled. This is not the case in some operating systems. Also, ++ unfortunately, debugging output from the DNS resolver is written to stdout ++ rather than stderr. ++ ++ The default (-d with no argument) omits "expand", "filter", "interface", ++ "load", "memory", "pid", "resolver", and "timestamp". However, the "pid" ++ selector is forced when debugging is turned on for a daemon, which then ++ passes it on to any re-executed Exims. Exim also automatically adds the pid ++ to debug lines when several remote deliveries are run in parallel. ++ ++ The "timestamp" selector causes the current time to be inserted at the ++ start of all debug output lines. This can be useful when trying to track ++ down delays in processing. ++ ++ If the debug_print option is set in any driver, it produces output whenever ++ any debugging is selected, or if -v is used. ++ ++-dd<debug options> ++ ++ This option behaves exactly like -d except when used on a command that ++ starts a daemon process. In that case, debugging is turned off for the ++ subprocesses that the daemon creates. Thus, it is useful for monitoring the ++ behaviour of the daemon without creating as much output as full debugging ++ does. ++ ++-dropcr ++ ++ This is an obsolete option that is now a no-op. It used to affect the way ++ Exim handled CR and LF characters in incoming messages. What happens now is ++ described in section 46.2. ++ ++-E ++ ++ This option specifies that an incoming message is a locally-generated ++ delivery failure report. It is used internally by Exim when handling ++ delivery failures and is not intended for external use. Its only effect is ++ to stop Exim generating certain messages to the postmaster, as otherwise ++ message cascades could occur in some situations. As part of the same ++ option, a message id may follow the characters -E. If it does, the log ++ entry for the receipt of the new message contains the id, following "R=", ++ as a cross-reference. ++ ++-ex ++ ++ There are a number of Sendmail options starting with -oe which seem to be ++ called by various programs without the leading o in the option. For ++ example, the vacation program uses -eq. Exim treats all options of the form ++ -ex as synonymous with the corresponding -oex options. ++ ++-F <string> ++ ++ This option sets the sender's full name for use when a locally-generated ++ message is being accepted. In the absence of this option, the user's gecos ++ entry from the password data is used. As users are generally permitted to ++ alter their gecos entries, no security considerations are involved. White ++ space between -F and the <string> is optional. ++ ++-f <address> ++ ++ This option sets the address of the envelope sender of a locally-generated ++ message (also known as the return path). The option can normally be used ++ only by a trusted user, but untrusted_set_sender can be set to allow ++ untrusted users to use it. ++ ++ Processes running as root or the Exim user are always trusted. Other ++ trusted users are defined by the trusted_users or trusted_groups options. ++ In the absence of -f, or if the caller is not trusted, the sender of a ++ local message is set to the caller's login name at the default qualify ++ domain. ++ ++ There is one exception to the restriction on the use of -f: an empty sender ++ can be specified by any user, trusted or not, to create a message that can ++ never provoke a bounce. An empty sender can be specified either as an empty ++ string, or as a pair of angle brackets with nothing between them, as in ++ these examples of shell commands: ++ ++ exim -f '<>' user@domain ++ exim -f "" user@domain ++ ++ In addition, the use of -f is not restricted when testing a filter file ++ with -bf or when testing or verifying addresses using the -bt or -bv ++ options. ++ ++ Allowing untrusted users to change the sender address does not of itself ++ make it possible to send anonymous mail. Exim still checks that the From: ++ header refers to the local user, and if it does not, it adds a Sender: ++ header, though this can be overridden by setting no_local_from_check. ++ ++ White space between -f and the <address> is optional (that is, they can be ++ given as two arguments or one combined argument). The sender of a ++ locally-generated message can also be set (when permitted) by an initial ++ "From " line in the message - see the description of -bm above - but if -f ++ is also present, it overrides "From ". ++ ++-G ++ ++ This option is equivalent to an ACL applying: ++ ++ control = suppress_local_fixups ++ ++ for every message received. Note that Sendmail will complain about such bad ++ formatting, where Exim silently just does not fix it up. This may change in ++ future. ++ ++ As this affects audit information, the caller must be a trusted user to use ++ this option. ++ ++-h <number> ++ ++ This option is accepted for compatibility with Sendmail, but has no effect. ++ (In Sendmail it overrides the "hop count" obtained by counting Received: ++ headers.) ++ ++-i ++ ++ This option, which has the same effect as -oi, specifies that a dot on a ++ line by itself should not terminate an incoming, non-SMTP message. I can ++ find no documentation for this option in Solaris 2.4 Sendmail, but the ++ mailx command in Solaris 2.4 uses it. See also -ti. ++ ++-L <tag> ++ ++ This option is equivalent to setting syslog_processname in the config file ++ and setting log_file_path to "syslog". Its use is restricted to ++ administrators. The configuration file has to be read and parsed, to ++ determine access rights, before this is set and takes effect, so early ++ configuration file errors will not honour this flag. ++ ++ The tag should not be longer than 32 characters. ++ ++-M <message id> <message id> ... ++ ++ This option requests Exim to run a delivery attempt on each message in ++ turn. If any of the messages are frozen, they are automatically thawed ++ before the delivery attempt. The settings of queue_domains, ++ queue_smtp_domains, and hold_domains are ignored. ++ ++ Retry hints for any of the addresses are overridden - Exim tries to deliver ++ even if the normal retry time has not yet been reached. This option ++ requires the caller to be an admin user. However, there is an option called ++ prod_requires_admin which can be set false to relax this restriction (and ++ also the same requirement for the -q, -R, and -S options). ++ ++ The deliveries happen synchronously, that is, the original Exim process ++ does not terminate until all the delivery attempts have finished. No output ++ is produced unless there is a serious error. If you want to see what is ++ happening, use the -v option as well, or inspect Exim's main log. ++ ++-Mar <message id> <address> <address> ... ++ ++ This option requests Exim to add the addresses to the list of recipients of ++ the message ("ar" for "add recipients"). The first argument must be a ++ message id, and the remaining ones must be email addresses. However, if the ++ message is active (in the middle of a delivery attempt), it is not altered. ++ This option can be used only by an admin user. ++ ++-MC <transport> <hostname> <sequence number> <message id> ++ ++ This option is not intended for use by external callers. It is used ++ internally by Exim to invoke another instance of itself to deliver a ++ waiting message using an existing SMTP connection, which is passed as the ++ standard input. Details are given in chapter 47. This must be the final ++ option, and the caller must be root or the Exim user in order to use it. ++ ++-MCA ++ ++ This option is not intended for use by external callers. It is used ++ internally by Exim in conjunction with the -MC option. It signifies that ++ the connection to the remote host has been authenticated. ++ ++-MCP ++ ++ This option is not intended for use by external callers. It is used ++ internally by Exim in conjunction with the -MC option. It signifies that ++ the server to which Exim is connected supports pipelining. ++ ++-MCQ <process id> <pipe fd> ++ ++ This option is not intended for use by external callers. It is used ++ internally by Exim in conjunction with the -MC option when the original ++ delivery was started by a queue runner. It passes on the process id of the ++ queue runner, together with the file descriptor number of an open pipe. ++ Closure of the pipe signals the final completion of the sequence of ++ processes that are passing messages through the same SMTP connection. ++ ++-MCS ++ ++ This option is not intended for use by external callers. It is used ++ internally by Exim in conjunction with the -MC option, and passes on the ++ fact that the SMTP SIZE option should be used on messages delivered down ++ the existing connection. ++ ++-MCT ++ ++ This option is not intended for use by external callers. It is used ++ internally by Exim in conjunction with the -MC option, and passes on the ++ fact that the host to which Exim is connected supports TLS encryption. ++ ++-Mc <message id> <message id> ... ++ ++ This option requests Exim to run a delivery attempt on each message in ++ turn, but unlike the -M option, it does check for retry hints, and respects ++ any that are found. This option is not very useful to external callers. It ++ is provided mainly for internal use by Exim when it needs to re-invoke ++ itself in order to regain root privilege for a delivery (see chapter 54). ++ However, -Mc can be useful when testing, in order to run a delivery that ++ respects retry times and other options such as hold_domains that are ++ overridden when -M is used. Such a delivery does not count as a queue run. ++ If you want to run a specific delivery as if in a queue run, you should use ++ -q with a message id argument. A distinction between queue run deliveries ++ and other deliveries is made in one or two places. ++ ++-Mes <message id> <address> ++ ++ This option requests Exim to change the sender address in the message to ++ the given address, which must be a fully qualified address or "<>" ("es" ++ for "edit sender"). There must be exactly two arguments. The first argument ++ must be a message id, and the second one an email address. However, if the ++ message is active (in the middle of a delivery attempt), its status is not ++ altered. This option can be used only by an admin user. ++ ++-Mf <message id> <message id> ... ++ ++ This option requests Exim to mark each listed message as "frozen". This ++ prevents any delivery attempts taking place until the message is "thawed", ++ either manually or as a result of the auto_thaw configuration option. ++ However, if any of the messages are active (in the middle of a delivery ++ attempt), their status is not altered. This option can be used only by an ++ admin user. ++ ++-Mg <message id> <message id> ... ++ ++ This option requests Exim to give up trying to deliver the listed messages, ++ including any that are frozen. However, if any of the messages are active, ++ their status is not altered. For non-bounce messages, a delivery error ++ message is sent to the sender, containing the text "cancelled by ++ administrator". Bounce messages are just discarded. This option can be used ++ only by an admin user. ++ ++-Mmad <message id> <message id> ... ++ ++ This option requests Exim to mark all the recipient addresses in the ++ messages as already delivered ("mad" for "mark all delivered"). However, if ++ any message is active (in the middle of a delivery attempt), its status is ++ not altered. This option can be used only by an admin user. ++ ++-Mmd <message id> <address> <address> ... ++ ++ This option requests Exim to mark the given addresses as already delivered ++ ("md" for "mark delivered"). The first argument must be a message id, and ++ the remaining ones must be email addresses. These are matched to recipient ++ addresses in the message in a case-sensitive manner. If the message is ++ active (in the middle of a delivery attempt), its status is not altered. ++ This option can be used only by an admin user. ++ ++-Mrm <message id> <message id> ... ++ ++ This option requests Exim to remove the given messages from the queue. No ++ bounce messages are sent; each message is simply forgotten. However, if any ++ of the messages are active, their status is not altered. This option can be ++ used only by an admin user or by the user who originally caused the message ++ to be placed on the queue. ++ ++-Mset <message id> ++ ++ This option is useful only in conjunction with -be (that is, when testing ++ string expansions). Exim loads the given message from its spool before ++ doing the test expansions, thus setting message-specific variables such as ++ $message_size and the header variables. The $recipients variable is made ++ available. This feature is provided to make it easier to test expansions ++ that make use of these variables. However, this option can be used only by ++ an admin user. See also -bem. ++ ++-Mt <message id> <message id> ... ++ ++ This option requests Exim to "thaw" any of the listed messages that are ++ "frozen", so that delivery attempts can resume. However, if any of the ++ messages are active, their status is not altered. This option can be used ++ only by an admin user. ++ ++-Mvb <message id> ++ ++ This option causes the contents of the message body (-D) spool file to be ++ written to the standard output. This option can be used only by an admin ++ user. ++ ++-Mvc <message id> ++ ++ This option causes a copy of the complete message (header lines plus body) ++ to be written to the standard output in RFC 2822 format. This option can be ++ used only by an admin user. ++ ++-Mvh <message id> ++ ++ This option causes the contents of the message headers (-H) spool file to ++ be written to the standard output. This option can be used only by an admin ++ user. ++ ++-Mvl <message id> ++ ++ This option causes the contents of the message log spool file to be written ++ to the standard output. This option can be used only by an admin user. ++ ++-m ++ ++ This is apparently a synonym for -om that is accepted by Sendmail, so Exim ++ treats it that way too. ++ ++-N ++ ++ This is a debugging option that inhibits delivery of a message at the ++ transport level. It implies -v. Exim goes through many of the motions of ++ delivery - it just doesn't actually transport the message, but instead ++ behaves as if it had successfully done so. However, it does not make any ++ updates to the retry database, and the log entries for deliveries are ++ flagged with "*>" rather than "=>". ++ ++ Because -N discards any message to which it applies, only root or the Exim ++ user are allowed to use it with -bd, -q, -R or -M. In other words, an ++ ordinary user can use it only when supplying an incoming message to which ++ it will apply. Although transportation never fails when -N is set, an ++ address may be deferred because of a configuration problem on a transport, ++ or a routing problem. Once -N has been used for a delivery attempt, it ++ sticks to the message, and applies to any subsequent delivery attempts that ++ may happen for that message. ++ ++-n ++ ++ This option is interpreted by Sendmail to mean "no aliasing". For normal ++ modes of operation, it is ignored by Exim. When combined with -bP it ++ suppresses the name of an option from being output. ++ ++-O <data> ++ ++ This option is interpreted by Sendmail to mean "set option". It is ignored ++ by Exim. ++ ++-oA <file name> ++ ++ This option is used by Sendmail in conjunction with -bi to specify an ++ alternative alias file name. Exim handles -bi differently; see the ++ description above. ++ ++-oB <n> ++ ++ This is a debugging option which limits the maximum number of messages that ++ can be delivered down one SMTP connection, overriding the value set in any ++ smtp transport. If <n> is omitted, the limit is set to 1. ++ ++-odb ++ ++ This option applies to all modes in which Exim accepts incoming messages, ++ including the listening daemon. It requests "background" delivery of such ++ messages, which means that the accepting process automatically starts a ++ delivery process for each message received, but does not wait for the ++ delivery processes to finish. ++ ++ When all the messages have been received, the reception process exits, ++ leaving the delivery processes to finish in their own time. The standard ++ output and error streams are closed at the start of each delivery process. ++ This is the default action if none of the -od options are present. ++ ++ If one of the queueing options in the configuration file (queue_only or ++ queue_only_file, for example) is in effect, -odb overrides it if ++ queue_only_override is set true, which is the default setting. If ++ queue_only_override is set false, -odb has no effect. ++ ++-odf ++ ++ This option requests "foreground" (synchronous) delivery when Exim has ++ accepted a locally-generated message. (For the daemon it is exactly the ++ same as -odb.) A delivery process is automatically started to deliver the ++ message, and Exim waits for it to complete before proceeding. ++ ++ The original Exim reception process does not finish until the delivery ++ process for the final message has ended. The standard error stream is left ++ open during deliveries. ++ ++ However, like -odb, this option has no effect if queue_only_override is ++ false and one of the queueing options in the configuration file is in ++ effect. ++ ++ If there is a temporary delivery error during foreground delivery, the ++ message is left on the queue for later delivery, and the original reception ++ process exits. See chapter 50 for a way of setting up a restricted ++ configuration that never queues messages. ++ ++-odi ++ ++ This option is synonymous with -odf. It is provided for compatibility with ++ Sendmail. ++ ++-odq ++ ++ This option applies to all modes in which Exim accepts incoming messages, ++ including the listening daemon. It specifies that the accepting process ++ should not automatically start a delivery process for each message ++ received. Messages are placed on the queue, and remain there until a ++ subsequent queue runner process encounters them. There are several ++ configuration options (such as queue_only) that can be used to queue ++ incoming messages under certain conditions. This option overrides all of ++ them and also -odqs. It always forces queueing. ++ ++-odqs ++ ++ This option is a hybrid between -odb/-odi and -odq. However, like -odb and ++ -odi, this option has no effect if queue_only_override is false and one of ++ the queueing options in the configuration file is in effect. ++ ++ When -odqs does operate, a delivery process is started for each incoming ++ message, in the background by default, but in the foreground if -odi is ++ also present. The recipient addresses are routed, and local deliveries are ++ done in the normal way. However, if any SMTP deliveries are required, they ++ are not done at this time, so the message remains on the queue until a ++ subsequent queue runner process encounters it. Because routing was done, ++ Exim knows which messages are waiting for which hosts, and so a number of ++ messages for the same host can be sent in a single SMTP connection. The ++ queue_smtp_domains configuration option has the same effect for specific ++ domains. See also the -qq option. ++ ++-oee ++ ++ If an error is detected while a non-SMTP message is being received (for ++ example, a malformed address), the error is reported to the sender in a ++ mail message. ++ ++ Provided this error message is successfully sent, the Exim receiving ++ process exits with a return code of zero. If not, the return code is 2 if ++ the problem is that the original message has no recipients, or 1 for any ++ other error. This is the default -oex option if Exim is called as rmail. ++ ++-oem ++ ++ This is the same as -oee, except that Exim always exits with a non-zero ++ return code, whether or not the error message was successfully sent. This ++ is the default -oex option, unless Exim is called as rmail. ++ ++-oep ++ ++ If an error is detected while a non-SMTP message is being received, the ++ error is reported by writing a message to the standard error file (stderr). ++ The return code is 1 for all errors. ++ ++-oeq ++ ++ This option is supported for compatibility with Sendmail, but has the same ++ effect as -oep. ++ ++-oew ++ ++ This option is supported for compatibility with Sendmail, but has the same ++ effect as -oem. ++ ++-oi ++ ++ This option, which has the same effect as -i, specifies that a dot on a ++ line by itself should not terminate an incoming, non-SMTP message. ++ Otherwise, a single dot does terminate, though Exim does no special ++ processing for other lines that start with a dot. This option is set by ++ default if Exim is called as rmail. See also -ti. ++ ++-oitrue ++ ++ This option is treated as synonymous with -oi. ++ ++-oMa <host address> ++ ++ A number of options starting with -oM can be used to set values associated ++ with remote hosts on locally-submitted messages (that is, messages not ++ received over TCP/IP). These options can be used by any caller in ++ conjunction with the -bh, -be, -bf, -bF, -bt, or -bv testing options. In ++ other circumstances, they are ignored unless the caller is trusted. ++ ++ The -oMa option sets the sender host address. This may include a port ++ number at the end, after a full stop (period). For example: ++ ++ exim -bs -oMa 10.9.8.7.1234 ++ ++ An alternative syntax is to enclose the IP address in square brackets, ++ followed by a colon and the port number: ++ ++ exim -bs -oMa [10.9.8.7]:1234 ++ ++ The IP address is placed in the $sender_host_address variable, and the ++ port, if present, in $sender_host_port. If both -oMa and -bh are present on ++ the command line, the sender host IP address is taken from whichever one is ++ last. ++ ++-oMaa <name> ++ ++ See -oMa above for general remarks about the -oM options. The -oMaa option ++ sets the value of $sender_host_authenticated (the authenticator name). See ++ chapter 33 for a discussion of SMTP authentication. This option can be used ++ with -bh and -bs to set up an authenticated SMTP session without actually ++ using the SMTP AUTH command. ++ ++-oMai <string> ++ ++ See -oMa above for general remarks about the -oM options. The -oMai option ++ sets the value of $authenticated_id (the id that was authenticated). This ++ overrides the default value (the caller's login id, except with -bh, where ++ there is no default) for messages from local sources. See chapter 33 for a ++ discussion of authenticated ids. ++ ++-oMas <address> ++ ++ See -oMa above for general remarks about the -oM options. The -oMas option ++ sets the authenticated sender value in $authenticated_sender. It overrides ++ the sender address that is created from the caller's login id for messages ++ from local sources, except when -bh is used, when there is no default. For ++ both -bh and -bs, an authenticated sender that is specified on a MAIL ++ command overrides this value. See chapter 33 for a discussion of ++ authenticated senders. ++ ++-oMi <interface address> ++ ++ See -oMa above for general remarks about the -oM options. The -oMi option ++ sets the IP interface address value. A port number may be included, using ++ the same syntax as for -oMa. The interface address is placed in ++ $received_ip_address and the port number, if present, in $received_port. ++ ++-oMr <protocol name> ++ ++ See -oMa above for general remarks about the -oM options. The -oMr option ++ sets the received protocol value that is stored in $received_protocol. ++ However, it does not apply (and is ignored) when -bh or -bs is used. For ++ -bh, the protocol is forced to one of the standard SMTP protocol names (see ++ the description of $received_protocol in section 11.9). For -bs, the ++ protocol is always "local-" followed by one of those same names. For -bS ++ (batched SMTP) however, the protocol can be set by -oMr. ++ ++-oMs <host name> ++ ++ See -oMa above for general remarks about the -oM options. The -oMs option ++ sets the sender host name in $sender_host_name. When this option is ++ present, Exim does not attempt to look up a host name from an IP address; ++ it uses the name it is given. ++ ++-oMt <ident string> ++ ++ See -oMa above for general remarks about the -oM options. The -oMt option ++ sets the sender ident value in $sender_ident. The default setting for local ++ callers is the login id of the calling process, except when -bh is used, ++ when there is no default. ++ ++-om ++ ++ In Sendmail, this option means "me too", indicating that the sender of a ++ message should receive a copy of the message if the sender appears in an ++ alias expansion. Exim always does this, so the option does nothing. ++ ++-oo ++ ++ This option is ignored. In Sendmail it specifies "old style headers", ++ whatever that means. ++ ++-oP <path> ++ ++ This option is useful only in conjunction with -bd or -q with a time value. ++ The option specifies the file to which the process id of the daemon is ++ written. When -oX is used with -bd, or when -q with a time is used without ++ -bd, this is the only way of causing Exim to write a pid file, because in ++ those cases, the normal pid file is not used. ++ ++-or <time> ++ ++ This option sets a timeout value for incoming non-SMTP messages. If it is ++ not set, Exim will wait forever for the standard input. The value can also ++ be set by the receive_timeout option. The format used for specifying times ++ is described in section 6.15. ++ ++-os <time> ++ ++ This option sets a timeout value for incoming SMTP messages. The timeout ++ applies to each SMTP command and block of data. The value can also be set ++ by the smtp_receive_timeout option; it defaults to 5 minutes. The format ++ used for specifying times is described in section 6.15. ++ ++-ov ++ ++ This option has exactly the same effect as -v. ++ ++-oX <number or string> ++ ++ This option is relevant only when the -bd (start listening daemon) option ++ is also given. It controls which ports and interfaces the daemon uses. ++ Details of the syntax, and how it interacts with configuration file ++ options, are given in chapter 13. When -oX is used to start a daemon, no ++ pid file is written unless -oP is also present to specify a pid file name. ++ ++-pd ++ ++ This option applies when an embedded Perl interpreter is linked with Exim ++ (see chapter 12). It overrides the setting of the perl_at_start option, ++ forcing the starting of the interpreter to be delayed until it is needed. ++ ++-ps ++ ++ This option applies when an embedded Perl interpreter is linked with Exim ++ (see chapter 12). It overrides the setting of the perl_at_start option, ++ forcing the starting of the interpreter to occur as soon as Exim is ++ started. ++ ++-p<rval>:<sval> ++ ++ For compatibility with Sendmail, this option is equivalent to ++ ++ -oMr <rval> -oMs <sval> ++ ++ It sets the incoming protocol and host name (for trusted callers). The host ++ name and its colon can be omitted when only the protocol is to be set. Note ++ the Exim already has two private options, -pd and -ps, that refer to ++ embedded Perl. It is therefore impossible to set a protocol value of "d" or ++ "s" using this option (but that does not seem a real limitation). ++ ++-q ++ ++ This option is normally restricted to admin users. However, there is a ++ configuration option called prod_requires_admin which can be set false to ++ relax this restriction (and also the same requirement for the -M, -R, and ++ -S options). ++ ++ The -q option starts one queue runner process. This scans the queue of ++ waiting messages, and runs a delivery process for each one in turn. It ++ waits for each delivery process to finish before starting the next one. A ++ delivery process may not actually do any deliveries if the retry times for ++ the addresses have not been reached. Use -qf (see below) if you want to ++ override this. ++ ++ If the delivery process spawns other processes to deliver other messages ++ down passed SMTP connections, the queue runner waits for these to finish ++ before proceeding. ++ ++ When all the queued messages have been considered, the original queue ++ runner process terminates. In other words, a single pass is made over the ++ waiting mail, one message at a time. Use -q with a time (see below) if you ++ want this to be repeated periodically. ++ ++ Exim processes the waiting messages in an unpredictable order. It isn't ++ very random, but it is likely to be different each time, which is all that ++ matters. If one particular message screws up a remote MTA, other messages ++ to the same MTA have a chance of getting through if they get tried first. ++ ++ It is possible to cause the messages to be processed in lexical message id ++ order, which is essentially the order in which they arrived, by setting the ++ queue_run_in_order option, but this is not recommended for normal use. ++ ++-q<qflags> ++ ++ The -q option may be followed by one or more flag letters that change its ++ behaviour. They are all optional, but if more than one is present, they ++ must appear in the correct order. Each flag is described in a separate item ++ below. ++ ++-qq... ++ ++ An option starting with -qq requests a two-stage queue run. In the first ++ stage, the queue is scanned as if the queue_smtp_domains option matched ++ every domain. Addresses are routed, local deliveries happen, but no remote ++ transports are run. ++ ++ The hints database that remembers which messages are waiting for specific ++ hosts is updated, as if delivery to those hosts had been deferred. After ++ this is complete, a second, normal queue scan happens, with routing and ++ delivery taking place as normal. Messages that are routed to the same host ++ should mostly be delivered down a single SMTP connection because of the ++ hints that were set up during the first queue scan. This option may be ++ useful for hosts that are connected to the Internet intermittently. ++ ++-q[q]i... ++ ++ If the i flag is present, the queue runner runs delivery processes only for ++ those messages that haven't previously been tried. (i stands for "initial ++ delivery".) This can be helpful if you are putting messages on the queue ++ using -odq and want a queue runner just to process the new messages. ++ ++-q[q][i]f... ++ ++ If one f flag is present, a delivery attempt is forced for each non-frozen ++ message, whereas without f only those non-frozen addresses that have passed ++ their retry times are tried. ++ ++-q[q][i]ff... ++ ++ If ff is present, a delivery attempt is forced for every message, whether ++ frozen or not. ++ ++-q[q][i][f[f]]l ++ ++ The l (the letter "ell") flag specifies that only local deliveries are to ++ be done. If a message requires any remote deliveries, it remains on the ++ queue for later delivery. ++ ++-q<qflags> <start id> <end id> ++ ++ When scanning the queue, Exim can be made to skip over messages whose ids ++ are lexically less than a given value by following the -q option with a ++ starting message id. For example: ++ ++ exim -q 0t5C6f-0000c8-00 ++ ++ Messages that arrived earlier than "0t5C6f-0000c8-00" are not inspected. If ++ a second message id is given, messages whose ids are lexically greater than ++ it are also skipped. If the same id is given twice, for example, ++ ++ exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00 ++ ++ just one delivery process is started, for that message. This differs from ++ -M in that retry data is respected, and it also differs from -Mc in that it ++ counts as a delivery from a queue run. Note that the selection mechanism ++ does not affect the order in which the messages are scanned. There are also ++ other ways of selecting specific sets of messages for delivery in a queue ++ run - see -R and -S. ++ ++-q<qflags><time> ++ ++ When a time value is present, the -q option causes Exim to run as a daemon, ++ starting a queue runner process at intervals specified by the given time ++ value (whose format is described in section 6.15). This form of the -q ++ option is commonly combined with the -bd option, in which case a single ++ daemon process handles both functions. A common way of starting up a ++ combined daemon at system boot time is to use a command such as ++ ++ /usr/exim/bin/exim -bd -q30m ++ ++ Such a daemon listens for incoming SMTP calls, and also starts a queue ++ runner process every 30 minutes. ++ ++ When a daemon is started by -q with a time value, but without -bd, no pid ++ file is written unless one is explicitly requested by the -oP option. ++ ++-qR<rsflags> <string> ++ ++ This option is synonymous with -R. It is provided for Sendmail ++ compatibility. ++ ++-qS<rsflags> <string> ++ ++ This option is synonymous with -S. ++ ++-R<rsflags> <string> ++ ++ The <rsflags> may be empty, in which case the white space before the string ++ is optional, unless the string is f, ff, r, rf, or rff, which are the ++ possible values for <rsflags>. White space is required if <rsflags> is not ++ empty. ++ ++ This option is similar to -q with no time value, that is, it causes Exim to ++ perform a single queue run, except that, when scanning the messages on the ++ queue, Exim processes only those that have at least one undelivered ++ recipient address containing the given string, which is checked in a ++ case-independent way. If the <rsflags> start with r, <string> is ++ interpreted as a regular expression; otherwise it is a literal string. ++ ++ If you want to do periodic queue runs for messages with specific ++ recipients, you can combine -R with -q and a time value. For example: ++ ++ exim -q25m -R @special.domain.example ++ ++ This example does a queue run for messages with recipients in the given ++ domain every 25 minutes. Any additional flags that are specified with -q ++ are applied to each queue run. ++ ++ Once a message is selected for delivery by this mechanism, all its ++ addresses are processed. For the first selected message, Exim overrides any ++ retry information and forces a delivery attempt for each undelivered ++ address. This means that if delivery of any address in the first message is ++ successful, any existing retry information is deleted, and so delivery ++ attempts for that address in subsequently selected messages (which are ++ processed without forcing) will run. However, if delivery of any address ++ does not succeed, the retry information is updated, and in subsequently ++ selected messages, the failing address will be skipped. ++ ++ If the <rsflags> contain f or ff, the delivery forcing applies to all ++ selected messages, not just the first; frozen messages are included when ff ++ is present. ++ ++ The -R option makes it straightforward to initiate delivery of all messages ++ to a given domain after a host has been down for some time. When the SMTP ++ command ETRN is accepted by its ACL (see chapter 42), its default effect is ++ to run Exim with the -R option, but it can be configured to run an ++ arbitrary command instead. ++ ++-r ++ ++ This is a documented (for Sendmail) obsolete alternative name for -f. ++ ++-S<rsflags> <string> ++ ++ This option acts like -R except that it checks the string against each ++ message's sender instead of against the recipients. If -R is also set, both ++ conditions must be met for a message to be selected. If either of the ++ options has f or ff in its flags, the associated action is taken. ++ ++-Tqt <times> ++ ++ This is an option that is exclusively for use by the Exim testing suite. It ++ is not recognized when Exim is run normally. It allows for the setting up ++ of explicit "queue times" so that various warning/retry features can be ++ tested. ++ ++-t ++ ++ When Exim is receiving a locally-generated, non-SMTP message on its ++ standard input, the -t option causes the recipients of the message to be ++ obtained from the To:, Cc:, and Bcc: header lines in the message instead of ++ from the command arguments. The addresses are extracted before any ++ rewriting takes place and the Bcc: header line, if present, is then ++ removed. ++ ++ If the command has any arguments, they specify addresses to which the ++ message is not to be delivered. That is, the argument addresses are removed ++ from the recipients list obtained from the headers. This is compatible with ++ Smail 3 and in accordance with the documented behaviour of several versions ++ of Sendmail, as described in man pages on a number of operating systems ++ (e.g. Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail ++ add argument addresses to those obtained from the headers, and the O'Reilly ++ Sendmail book documents it that way. Exim can be made to add argument ++ addresses instead of subtracting them by setting the option ++ extract_addresses_remove_arguments false. ++ ++ If there are any Resent- header lines in the message, Exim extracts ++ recipients from all Resent-To:, Resent-Cc:, and Resent-Bcc: header lines ++ instead of from To:, Cc:, and Bcc:. This is for compatibility with Sendmail ++ and other MTAs. (Prior to release 4.20, Exim gave an error if -t was used ++ in conjunction with Resent- header lines.) ++ ++ RFC 2822 talks about different sets of Resent- header lines (for when a ++ message is resent several times). The RFC also specifies that they should ++ be added at the front of the message, and separated by Received: lines. It ++ is not at all clear how -t should operate in the present of multiple sets, ++ nor indeed exactly what constitutes a "set". In practice, it seems that ++ MUAs do not follow the RFC. The Resent- lines are often added at the end of ++ the header, and if a message is resent more than once, it is common for the ++ original set of Resent- headers to be renamed as X-Resent- when a new set ++ is added. This removes any possible ambiguity. ++ ++-ti ++ ++ This option is exactly equivalent to -t -i. It is provided for ++ compatibility with Sendmail. ++ ++-tls-on-connect ++ ++ This option is available when Exim is compiled with TLS support. It forces ++ all incoming SMTP connections to behave as if the incoming port is listed ++ in the tls_on_connect_ports option. See section 13.4 and chapter 41 for ++ further details. ++ ++-U ++ ++ Sendmail uses this option for "initial message submission", and its ++ documentation states that in future releases, it may complain about ++ syntactically invalid messages rather than fixing them when this flag is ++ not set. Exim ignores this option. ++ ++-v ++ ++ This option causes Exim to write information to the standard error stream, ++ describing what it is doing. In particular, it shows the log lines for ++ receiving and delivering a message, and if an SMTP connection is made, the ++ SMTP dialogue is shown. Some of the log lines shown may not actually be ++ written to the log if the setting of log_selector discards them. Any ++ relevant selectors are shown with each log line. If none are shown, the ++ logging is unconditional. ++ ++-x ++ ++ AIX uses -x for a private purpose ("mail from a local mail program has ++ National Language Support extended characters in the body of the mail ++ item"). It sets -x when calling the MTA from its mail command. Exim ignores ++ this option. ++ ++-X <logfile> ++ ++ This option is interpreted by Sendmail to cause debug information to be ++ sent to the named file. It is ignored by Exim. ++ ++ ++ ++=============================================================================== ++6. THE EXIM RUN TIME CONFIGURATION FILE ++ ++Exim uses a single run time configuration file that is read whenever an Exim ++binary is executed. Note that in normal operation, this happens frequently, ++because Exim is designed to operate in a distributed manner, without central ++control. ++ ++If a syntax error is detected while reading the configuration file, Exim writes ++a message on the standard error, and exits with a non-zero return code. The ++message is also written to the panic log. Note: Only simple syntax errors can ++be detected at this time. The values of any expanded options are not checked ++until the expansion happens, even when the expansion does not actually alter ++the string. ++ ++The name of the configuration file is compiled into the binary for security ++reasons, and is specified by the CONFIGURE_FILE compilation option. In most ++configurations, this specifies a single file. However, it is permitted to give ++a colon-separated list of file names, in which case Exim uses the first ++existing file in the list. ++ ++The run time configuration file must be owned by root or by the user that is ++specified at compile time by the CONFIGURE_OWNER option (if set). The ++configuration file must not be world-writeable, or group-writeable unless its ++group is the root group or the one specified at compile time by the ++CONFIGURE_GROUP option. ++ ++Warning: In a conventional configuration, where the Exim binary is setuid to ++root, anybody who is able to edit the run time configuration file has an easy ++way to run commands as root. If you specify a user or group in the ++CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users who ++are members of that group will trivially be able to obtain root privileges. ++ ++Up to Exim version 4.72, the run time configuration file was also permitted to ++be writeable by the Exim user and/or group. That has been changed in Exim 4.73 ++since it offered a simple privilege escalation for any attacker who managed to ++compromise the Exim user account. ++ ++A default configuration file, which will work correctly in simple situations, ++is provided in the file src/configure.default. If CONFIGURE_FILE defines just ++one file name, the installation process copies the default configuration to a ++new file of that name if it did not previously exist. If CONFIGURE_FILE is a ++list, no default is automatically installed. Chapter 7 is a "walk-through" ++discussion of the default configuration. ++ ++ ++6.1 Using a different configuration file ++---------------------------------------- ++ ++A one-off alternate configuration can be specified by the -C command line ++option, which may specify a single file or a list of files. However, when -C is ++used, Exim gives up its root privilege, unless called by root (or unless the ++argument for -C is identical to the built-in value from CONFIGURE_FILE), or is ++listed in the TRUSTED_CONFIG_LIST file and the caller is the Exim user or the ++user specified in the CONFIGURE_OWNER setting. -C is useful mainly for checking ++the syntax of configuration files before installing them. No owner or group ++checks are done on a configuration file specified by -C, if root privilege has ++been dropped. ++ ++Even the Exim user is not trusted to specify an arbitrary configuration file ++with the -C option to be used with root privileges, unless that file is listed ++in the TRUSTED_CONFIG_LIST file. This locks out the possibility of testing a ++configuration using -C right through message reception and delivery, even if ++the caller is root. The reception works, but by that time, Exim is running as ++the Exim user, so when it re-execs to regain privilege for the delivery, the ++use of -C causes privilege to be lost. However, root can test reception and ++delivery using two separate commands (one to put a message on the queue, using ++-odq, and another to do the delivery, using -M). ++ ++If ALT_CONFIG_PREFIX is defined in Local/Makefile, it specifies a prefix string ++with which any file named in a -C command line option must start. In addition, ++the file name must not contain the sequence "/../". There is no default setting ++for ALT_CONFIG_PREFIX; when it is unset, any file name can be used with -C. ++ ++One-off changes to a configuration can be specified by the -D command line ++option, which defines and overrides values for macros used inside the ++configuration file. However, like -C, the use of this option by a ++non-privileged user causes Exim to discard its root privilege. If ++DISABLE_D_OPTION is defined in Local/Makefile, the use of -D is completely ++disabled, and its use causes an immediate error exit. ++ ++The WHITELIST_D_MACROS option in Local/Makefile permits the binary builder to ++declare certain macro names trusted, such that root privilege will not ++necessarily be discarded. WHITELIST_D_MACROS defines a colon-separated list of ++macros which are considered safe and, if -D only supplies macros from this ++list, and the values are acceptable, then Exim will not give up root privilege ++if the caller is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. ++This is a transition mechanism and is expected to be removed in the future. ++Acceptable values for the macros satisfy the regexp: "^[A-Za-z0-9_/.-]*$" ++ ++Some sites may wish to use the same Exim binary on different machines that ++share a file system, but to use different configuration files on each machine. ++If CONFIGURE_FILE_USE_NODE is defined in Local/Makefile, Exim first looks for a ++file whose name is the configuration file name followed by a dot and the ++machine's node name, as obtained from the uname() function. If this file does ++not exist, the standard name is tried. This processing occurs for each file ++name in the list given by CONFIGURE_FILE or -C. ++ ++In some esoteric situations different versions of Exim may be run under ++different effective uids and the CONFIGURE_FILE_USE_EUID is defined to help ++with this. See the comments in src/EDITME for details. ++ ++ ++6.2 Configuration file format ++----------------------------- ++ ++Exim's configuration file is divided into a number of different parts. General ++option settings must always appear at the start of the file. The other parts ++are all optional, and may appear in any order. Each part other than the first ++is introduced by the word "begin" followed by the name of the part. The ++optional parts are: ++ ++ * ACL: Access control lists for controlling incoming SMTP mail (see chapter ++ 42). ++ ++ * authenticators: Configuration settings for the authenticator drivers. These ++ are concerned with the SMTP AUTH command (see chapter 33). ++ ++ * routers: Configuration settings for the router drivers. Routers process ++ addresses and determine how the message is to be delivered (see chapters 15 ++ -22). ++ ++ * transports: Configuration settings for the transport drivers. Transports ++ define mechanisms for copying messages to destinations (see chapters 24-30 ++ ). ++ ++ * retry: Retry rules, for use when a message cannot be delivered immediately. ++ If there is no retry section, or if it is empty (that is, no retry rules ++ are defined), Exim will not retry deliveries. In this situation, temporary ++ errors are treated the same as permanent errors. Retry rules are discussed ++ in chapter 32. ++ ++ * rewrite: Global address rewriting rules, for use when a message arrives and ++ when new addresses are generated during delivery. Rewriting is discussed in ++ chapter 31. ++ ++ * local_scan: Private options for the local_scan() function. If you want to ++ use this feature, you must set ++ ++ LOCAL_SCAN_HAS_OPTIONS=yes ++ ++ in Local/Makefile before building Exim. Details of the local_scan() ++ facility are given in chapter 44. ++ ++Leading and trailing white space in configuration lines is always ignored. ++ ++Blank lines in the file, and lines starting with a # character (ignoring ++leading white space) are treated as comments and are ignored. Note: A # ++character other than at the beginning of a line is not treated specially, and ++does not introduce a comment. ++ ++Any non-comment line can be continued by ending it with a backslash. Note that ++the general rule for white space means that trailing white space after the ++backslash and leading white space at the start of continuation lines is ++ignored. Comment lines beginning with # (but not empty lines) may appear in the ++middle of a sequence of continuation lines. ++ ++A convenient way to create a configuration file is to start from the default, ++which is supplied in src/configure.default, and add, delete, or change settings ++as required. ++ ++The ACLs, retry rules, and rewriting rules have their own syntax which is ++described in chapters 42, 32, and 31, respectively. The other parts of the ++configuration file have some syntactic items in common, and these are described ++below, from section 6.10 onwards. Before that, the inclusion, macro, and ++conditional facilities are described. ++ ++ ++6.3 File inclusions in the configuration file ++--------------------------------------------- ++ ++You can include other files inside Exim's run time configuration file by using ++this syntax: ++ ++.include <file name> ++.include_if_exists <file name> ++ ++on a line by itself. Double quotes round the file name are optional. If you use ++the first form, a configuration error occurs if the file does not exist; the ++second form does nothing for non-existent files. In all cases, an absolute file ++name is required. ++ ++Includes may be nested to any depth, but remember that Exim reads its ++configuration file often, so it is a good idea to keep them to a minimum. If ++you change the contents of an included file, you must HUP the daemon, because ++an included file is read only when the configuration itself is read. ++ ++The processing of inclusions happens early, at a physical line level, so, like ++comment lines, an inclusion can be used in the middle of an option setting, for ++example: ++ ++hosts_lookup = a.b.c \ ++ .include /some/file ++ ++Include processing happens after macro processing (see below). Its effect is to ++process the lines of the included file as if they occurred inline where the ++inclusion appears. ++ ++ ++6.4 Macros in the configuration file ++------------------------------------ ++ ++If a line in the main part of the configuration (that is, before the first ++"begin" line) begins with an upper case letter, it is taken as a macro ++definition, and must be of the form ++ ++<name> = <rest of line> ++ ++The name must consist of letters, digits, and underscores, and need not all be ++in upper case, though that is recommended. The rest of the line, including any ++continuations, is the replacement text, and has leading and trailing white ++space removed. Quotes are not removed. The replacement text can never end with ++a backslash character, but this doesn't seem to be a serious limitation. ++ ++Macros may also be defined between router, transport, authenticator, or ACL ++definitions. They may not, however, be defined within an individual driver or ++ACL, or in the local_scan, retry, or rewrite sections of the configuration. ++ ++ ++6.5 Macro substitution ++---------------------- ++ ++Once a macro is defined, all subsequent lines in the file (and any included ++files) are scanned for the macro name; if there are several macros, the line is ++scanned for each in turn, in the order in which the macros are defined. The ++replacement text is not re-scanned for the current macro, though it is scanned ++for subsequently defined macros. For this reason, a macro name may not contain ++the name of a previously defined macro as a substring. You could, for example, ++define ++ ++ABCD_XYZ = <something> ++ABCD = <something else> ++ ++but putting the definitions in the opposite order would provoke a configuration ++error. Macro expansion is applied to individual physical lines from the file, ++before checking for line continuation or file inclusion (see above). If a line ++consists solely of a macro name, and the expansion of the macro is empty, the ++line is ignored. A macro at the start of a line may turn the line into a ++comment line or a ".include" line. ++ ++ ++6.6 Redefining macros ++--------------------- ++ ++Once defined, the value of a macro can be redefined later in the configuration ++(or in an included file). Redefinition is specified by using == instead of =. ++For example: ++ ++MAC = initial value ++... ++MAC == updated value ++ ++Redefinition does not alter the order in which the macros are applied to the ++subsequent lines of the configuration file. It is still the same order in which ++the macros were originally defined. All that changes is the macro's value. ++Redefinition makes it possible to accumulate values. For example: ++ ++MAC = initial value ++... ++MAC == MAC and something added ++ ++This can be helpful in situations where the configuration file is built from a ++number of other files. ++ ++ ++6.7 Overriding macro values ++--------------------------- ++ ++The values set for macros in the configuration file can be overridden by the -D ++command line option, but Exim gives up its root privilege when -D is used, ++unless called by root or the Exim user. A definition on the command line using ++the -D option causes all definitions and redefinitions within the file to be ++ignored. ++ ++ ++6.8 Example of macro usage ++-------------------------- ++ ++As an example of macro usage, consider a configuration where aliases are looked ++up in a MySQL database. It helps to keep the file less cluttered if long ++strings such as SQL statements are defined separately as macros, for example: ++ ++ALIAS_QUERY = select mailbox from user where \ ++ login='${quote_mysql:$local_part}'; ++ ++This can then be used in a redirect router setting like this: ++ ++data = ${lookup mysql{ALIAS_QUERY}} ++ ++In earlier versions of Exim macros were sometimes used for domain, host, or ++address lists. In Exim 4 these are handled better by named lists - see section ++10.5. ++ ++ ++6.9 Conditional skips in the configuration file ++----------------------------------------------- ++ ++You can use the directives ".ifdef", ".ifndef", ".elifdef", ".elifndef", ++".else", and ".endif" to dynamically include or exclude portions of the ++configuration file. The processing happens whenever the file is read (that is, ++when an Exim binary starts to run). ++ ++The implementation is very simple. Instances of the first four directives must ++be followed by text that includes the names of one or macros. The condition ++that is tested is whether or not any macro substitution has taken place in the ++line. Thus: ++ ++.ifdef AAA ++message_size_limit = 50M ++.else ++message_size_limit = 100M ++.endif ++ ++sets a message size limit of 50M if the macro "AAA" is defined, and 100M ++otherwise. If there is more than one macro named on the line, the condition is ++true if any of them are defined. That is, it is an "or" condition. To obtain an ++"and" condition, you need to use nested ".ifdef"s. ++ ++Although you can use a macro expansion to generate one of these directives, it ++is not very useful, because the condition "there was a macro substitution in ++this line" will always be true. ++ ++Text following ".else" and ".endif" is ignored, and can be used as comment to ++clarify complicated nestings. ++ ++ ++6.10 Common option syntax ++------------------------- ++ ++For the main set of options, driver options, and local_scan() options, each ++setting is on a line by itself, and starts with a name consisting of lower-case ++letters and underscores. Many options require a data value, and in these cases ++the name must be followed by an equals sign (with optional white space) and ++then the value. For example: ++ ++qualify_domain = mydomain.example.com ++ ++Some option settings may contain sensitive data, for example, passwords for ++accessing databases. To stop non-admin users from using the -bP command line ++option to read these values, you can precede the option settings with the word ++"hide". For example: ++ ++hide mysql_servers = localhost/users/admin/secret-password ++ ++For non-admin users, such options are displayed like this: ++ ++mysql_servers = <value not displayable> ++ ++If "hide" is used on a driver option, it hides the value of that option on all ++instances of the same driver. ++ ++The following sections describe the syntax used for the different data types ++that are found in option settings. ++ ++ ++6.11 Boolean options ++-------------------- ++ ++Options whose type is given as boolean are on/off switches. There are two ++different ways of specifying such options: with and without a data value. If ++the option name is specified on its own without data, the switch is turned on; ++if it is preceded by "no_" or "not_" the switch is turned off. However, boolean ++options may be followed by an equals sign and one of the words "true", "false", ++"yes", or "no", as an alternative syntax. For example, the following two ++settings have exactly the same effect: ++ ++queue_only ++queue_only = true ++ ++The following two lines also have the same (opposite) effect: ++ ++no_queue_only ++queue_only = false ++ ++You can use whichever syntax you prefer. ++ ++ ++6.12 Integer values ++------------------- ++ ++If an option's type is given as "integer", the value can be given in decimal, ++hexadecimal, or octal. If it starts with a digit greater than zero, a decimal ++number is assumed. Otherwise, it is treated as an octal number unless it starts ++with the characters "0x", in which case the remainder is interpreted as a ++hexadecimal number. ++ ++If an integer value is followed by the letter K, it is multiplied by 1024; if ++it is followed by the letter M, it is multiplied by 1024x1024. When the values ++of integer option settings are output, values which are an exact multiple of ++1024 or 1024x1024 are sometimes, but not always, printed using the letters K ++and M. The printing style is independent of the actual input format that was ++used. ++ ++ ++6.13 Octal integer values ++------------------------- ++ ++If an option's type is given as "octal integer", its value is always ++interpreted as an octal number, whether or not it starts with the digit zero. ++Such options are always output in octal. ++ ++ ++6.14 Fixed point numbers ++------------------------ ++ ++If an option's type is given as "fixed-point", its value must be a decimal ++integer, optionally followed by a decimal point and up to three further digits. ++ ++ ++6.15 Time intervals ++------------------- ++ ++A time interval is specified as a sequence of numbers, each followed by one of ++the following letters, with no intervening white space: ++ ++ s seconds ++ m minutes ++ h hours ++ d days ++ w weeks ++ ++For example, "3h50m" specifies 3 hours and 50 minutes. The values of time ++intervals are output in the same format. Exim does not restrict the values; it ++is perfectly acceptable, for example, to specify "90m" instead of "1h30m". ++ ++ ++6.16 String values ++------------------ ++ ++If an option's type is specified as "string", the value can be specified with ++or without double-quotes. If it does not start with a double-quote, the value ++consists of the remainder of the line plus any continuation lines, starting at ++the first character after any leading white space, with trailing white space ++removed, and with no interpretation of the characters in the string. Because ++Exim removes comment lines (those beginning with #) at an early stage, they can ++appear in the middle of a multi-line string. The following two settings are ++therefore equivalent: ++ ++trusted_users = uucp:mail ++trusted_users = uucp:\ ++ # This comment line is ignored ++ mail ++ ++If a string does start with a double-quote, it must end with a closing ++double-quote, and any backslash characters other than those used for line ++continuation are interpreted as escape characters, as follows: ++ ++ "\\" single backslash ++ "\n" newline ++ "\r" carriage return ++ "\t" tab ++ "\"<octal digits> up to 3 octal digits specify one character ++ "\x"<hex digits> up to 2 hexadecimal digits specify one character ++ ++If a backslash is followed by some other character, including a double-quote ++character, that character replaces the pair. ++ ++Quoting is necessary only if you want to make use of the backslash escapes to ++insert special characters, or if you need to specify a value with leading or ++trailing spaces. These cases are rare, so quoting is almost never needed in ++current versions of Exim. In versions of Exim before 3.14, quoting was required ++in order to continue lines, so you may come across older configuration files ++and examples that apparently quote unnecessarily. ++ ++ ++6.17 Expanded strings ++--------------------- ++ ++Some strings in the configuration file are subjected to string expansion, by ++which means various parts of the string may be changed according to the ++circumstances (see chapter 11). The input syntax for such strings is as just ++described; in particular, the handling of backslashes in quoted strings is done ++as part of the input process, before expansion takes place. However, backslash ++is also an escape character for the expander, so any backslashes that are ++required for that reason must be doubled if they are within a quoted ++configuration string. ++ ++ ++6.18 User and group names ++------------------------- ++ ++User and group names are specified as strings, using the syntax described ++above, but the strings are interpreted specially. A user or group name must ++either consist entirely of digits, or be a name that can be looked up using the ++getpwnam() or getgrnam() function, as appropriate. ++ ++ ++6.19 List construction ++---------------------- ++ ++The data for some configuration options is a list of items, with colon as the ++default separator. Many of these options are shown with type "string list" in ++the descriptions later in this document. Others are listed as "domain list", ++"host list", "address list", or "local part list". Syntactically, they are all ++the same; however, those other than "string list" are subject to particular ++kinds of interpretation, as described in chapter 10. ++ ++In all these cases, the entire list is treated as a single string as far as the ++input syntax is concerned. The trusted_users setting in section 6.16 above is ++an example. If a colon is actually needed in an item in a list, it must be ++entered as two colons. Leading and trailing white space on each item in a list ++is ignored. This makes it possible to include items that start with a colon, ++and in particular, certain forms of IPv6 address. For example, the list ++ ++local_interfaces = 127.0.0.1 : ::::1 ++ ++contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1. ++ ++Note: Although leading and trailing white space is ignored in individual list ++items, it is not ignored when parsing the list. The space after the first colon ++in the example above is necessary. If it were not there, the list would be ++interpreted as the two items 127.0.0.1:: and 1. ++ ++ ++6.20 Changing list separators ++----------------------------- ++ ++Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was ++introduced to allow the separator character to be changed. If a list begins ++with a left angle bracket, followed by any punctuation character, that ++character is used instead of colon as the list separator. For example, the list ++above can be rewritten to use a semicolon separator like this: ++ ++local_interfaces = <; 127.0.0.1 ; ::1 ++ ++This facility applies to all lists, with the exception of the list in ++log_file_path. It is recommended that the use of non-colon separators be ++confined to circumstances where they really are needed. ++ ++It is also possible to use newline and other control characters (those with ++code values less than 32, plus DEL) as separators in lists. Such separators ++must be provided literally at the time the list is processed. For options that ++are string-expanded, you can write the separator using a normal escape ++sequence. This will be processed by the expander before the string is ++interpreted as a list. For example, if a newline-separated list of domains is ++generated by a lookup, you can process it directly by a line such as this: ++ ++domains = <\n ${lookup mysql{.....}} ++ ++This avoids having to change the list separator in such data. You are unlikely ++to want to use a control character as a separator in an option that is not ++expanded, because the value is literal text. However, it can be done by giving ++the value in quotes. For example: ++ ++local_interfaces = "<\n 127.0.0.1 \n ::1" ++ ++Unlike printing character separators, which can be included in list items by ++doubling, it is not possible to include a control character as data when it is ++set as the separator. Two such characters in succession are interpreted as ++enclosing an empty list item. ++ ++ ++6.21 Empty items in lists ++------------------------- ++ ++An empty item at the end of a list is always ignored. In other words, trailing ++separator characters are ignored. Thus, the list in ++ ++senders = user@domain : ++ ++contains only a single item. If you want to include an empty string as one item ++in a list, it must not be the last item. For example, this list contains three ++items, the second of which is empty: ++ ++senders = user1@domain : : user2@domain ++ ++Note: There must be white space between the two colons, as otherwise they are ++interpreted as representing a single colon data character (and the list would ++then contain just one item). If you want to specify a list that contains just ++one, empty item, you can do it as in this example: ++ ++senders = : ++ ++In this case, the first item is empty, and the second is discarded because it ++is at the end of the list. ++ ++ ++6.22 Format of driver configurations ++------------------------------------ ++ ++There are separate parts in the configuration for defining routers, transports, ++and authenticators. In each part, you are defining a number of driver ++instances, each with its own set of options. Each driver instance is defined by ++a sequence of lines like this: ++ ++<instance name>: ++ <option> ++ ... ++ <option> ++ ++In the following example, the instance name is localuser, and it is followed by ++three options settings: ++ ++localuser: ++ driver = accept ++ check_local_user ++ transport = local_delivery ++ ++For each driver instance, you specify which Exim code module it uses - by the ++setting of the driver option - and (optionally) some configuration settings. ++For example, in the case of transports, if you want a transport to deliver with ++SMTP you would use the smtp driver; if you want to deliver to a local file you ++would use the appendfile driver. Each of the drivers is described in detail in ++its own separate chapter later in this manual. ++ ++You can have several routers, transports, or authenticators that are based on ++the same underlying driver (each must have a different instance name). ++ ++The order in which routers are defined is important, because addresses are ++passed to individual routers one by one, in order. The order in which ++transports are defined does not matter at all. The order in which ++authenticators are defined is used only when Exim, as a client, is searching ++them to find one that matches an authentication mechanism offered by the ++server. ++ ++Within a driver instance definition, there are two kinds of option: generic and ++private. The generic options are those that apply to all drivers of the same ++type (that is, all routers, all transports or all authenticators). The driver ++option is a generic option that must appear in every definition. The private ++options are special for each driver, and none need appear, because they all ++have default values. ++ ++The options may appear in any order, except that the driver option must precede ++any private options, since these depend on the particular driver. For this ++reason, it is recommended that driver always be the first option. ++ ++Driver instance names, which are used for reference in log entries and ++elsewhere, can be any sequence of letters, digits, and underscores (starting ++with a letter) and must be unique among drivers of the same type. A router and ++a transport (for example) can each have the same name, but no two router ++instances can have the same name. The name of a driver instance should not be ++confused with the name of the underlying driver module. For example, the ++configuration lines: ++ ++remote_smtp: ++ driver = smtp ++ ++create an instance of the smtp transport driver whose name is remote_smtp. The ++same driver code can be used more than once, with different instance names and ++different option settings each time. A second instance of the smtp transport, ++with different options, might be defined thus: ++ ++special_smtp: ++ driver = smtp ++ port = 1234 ++ command_timeout = 10s ++ ++The names remote_smtp and special_smtp would be used to reference these ++transport instances from routers, and these names would appear in log lines. ++ ++Comment lines may be present in the middle of driver specifications. The full ++list of option settings for any particular driver instance, including all the ++defaulted values, can be extracted by making use of the -bP command line ++option. ++ ++ ++ ++=============================================================================== ++7. THE DEFAULT CONFIGURATION FILE ++ ++The default configuration file supplied with Exim as src/configure.default is ++sufficient for a host with simple mail requirements. As an introduction to the ++way Exim is configured, this chapter "walks through" the default configuration, ++giving brief explanations of the settings. Detailed descriptions of the options ++are given in subsequent chapters. The default configuration file itself ++contains extensive comments about ways you might want to modify the initial ++settings. However, note that there are many options that are not mentioned at ++all in the default configuration. ++ ++ ++7.1 Main configuration settings ++------------------------------- ++ ++The main (global) configuration option settings must always come first in the ++file. The first thing you'll see in the file, after some initial comments, is ++the line ++ ++# primary_hostname = ++ ++This is a commented-out setting of the primary_hostname option. Exim needs to ++know the official, fully qualified name of your host, and this is where you can ++specify it. However, in most cases you do not need to set this option. When it ++is unset, Exim uses the uname() system function to obtain the host name. ++ ++The first three non-comment configuration lines are as follows: ++ ++domainlist local_domains = @ ++domainlist relay_to_domains = ++hostlist relay_from_hosts = 127.0.0.1 ++ ++These are not, in fact, option settings. They are definitions of two named ++domain lists and one named host list. Exim allows you to give names to lists of ++domains, hosts, and email addresses, in order to make it easier to manage the ++configuration file (see section 10.5). ++ ++The first line defines a domain list called local_domains; this is used later ++in the configuration to identify domains that are to be delivered on the local ++host. ++ ++There is just one item in this list, the string "@". This is a special form of ++entry which means "the name of the local host". Thus, if the local host is ++called a.host.example, mail to any.user@a.host.example is expected to be ++delivered locally. Because the local host's name is referenced indirectly, the ++same configuration file can be used on different hosts. ++ ++The second line defines a domain list called relay_to_domains, but the list ++itself is empty. Later in the configuration we will come to the part that ++controls mail relaying through the local host; it allows relaying to any ++domains in this list. By default, therefore, no relaying on the basis of a mail ++domain is permitted. ++ ++The third line defines a host list called relay_from_hosts. This list is used ++later in the configuration to permit relaying from any host or IP address that ++matches the list. The default contains just the IP address of the IPv4 loopback ++interface, which means that processes on the local host are able to submit mail ++for relaying by sending it over TCP/IP to that interface. No other hosts are ++permitted to submit messages for relaying. ++ ++Just to be sure there's no misunderstanding: at this point in the configuration ++we aren't actually setting up any controls. We are just defining some domains ++and hosts that will be used in the controls that are specified later. ++ ++The next two configuration lines are genuine option settings: ++ ++acl_smtp_rcpt = acl_check_rcpt ++acl_smtp_data = acl_check_data ++ ++These options specify Access Control Lists (ACLs) that are to be used during an ++incoming SMTP session for every recipient of a message (every RCPT command), ++and after the contents of the message have been received, respectively. The ++names of the lists are acl_check_rcpt and acl_check_data, and we will come to ++their definitions below, in the ACL section of the configuration. The RCPT ACL ++controls which recipients are accepted for an incoming message - if a ++configuration does not provide an ACL to check recipients, no SMTP mail can be ++accepted. The DATA ACL allows the contents of a message to be checked. ++ ++Two commented-out option settings are next: ++ ++# av_scanner = clamd:/tmp/clamd ++# spamd_address = 127.0.0.1 783 ++ ++These are example settings that can be used when Exim is compiled with the ++content-scanning extension. The first specifies the interface to the virus ++scanner, and the second specifies the interface to SpamAssassin. Further ++details are given in chapter 43. ++ ++Three more commented-out option settings follow: ++ ++# tls_advertise_hosts = * ++# tls_certificate = /etc/ssl/exim.crt ++# tls_privatekey = /etc/ssl/exim.pem ++ ++These are example settings that can be used when Exim is compiled with support ++for TLS (aka SSL) as described in section 4.7. The first one specifies the list ++of clients that are allowed to use TLS when connecting to this server; in this ++case the wildcard means all clients. The other options specify where Exim ++should find its TLS certificate and private key, which together prove the ++server's identity to any clients that connect. More details are given in ++chapter 41. ++ ++Another two commented-out option settings follow: ++ ++# daemon_smtp_ports = 25 : 465 : 587 ++# tls_on_connect_ports = 465 ++ ++These options provide better support for roaming users who wish to use this ++server for message submission. They are not much use unless you have turned on ++TLS (as described in the previous paragraph) and authentication (about which ++more in section 7.7). The usual SMTP port 25 is often blocked on end-user ++networks, so RFC 4409 specifies that message submission should use port 587 ++instead. However some software (notably Microsoft Outlook) cannot be configured ++to use port 587 correctly, so these settings also enable the non-standard ++"smtps" (aka "ssmtp") port 465 (see section 13.4). ++ ++Two more commented-out options settings follow: ++ ++# qualify_domain = ++# qualify_recipient = ++ ++The first of these specifies a domain that Exim uses when it constructs a ++complete email address from a local login name. This is often needed when Exim ++receives a message from a local process. If you do not set qualify_domain, the ++value of primary_hostname is used. If you set both of these options, you can ++have different qualification domains for sender and recipient addresses. If you ++set only the first one, its value is used in both cases. ++ ++The following line must be uncommented if you want Exim to recognize addresses ++of the form user@[10.11.12.13] that is, with a "domain literal" (an IP address ++within square brackets) instead of a named domain. ++ ++# allow_domain_literals ++ ++The RFCs still require this form, but many people think that in the modern ++Internet it makes little sense to permit mail to be sent to specific hosts by ++quoting their IP addresses. This ancient format has been used by people who try ++to abuse hosts by using them for unwanted relaying. However, some people ++believe there are circumstances (for example, messages addressed to postmaster) ++where domain literals are still useful. ++ ++The next configuration line is a kind of trigger guard: ++ ++never_users = root ++ ++It specifies that no delivery must ever be run as the root user. The normal ++convention is to set up root as an alias for the system administrator. This ++setting is a guard against slips in the configuration. The list of users ++specified by never_users is not, however, the complete list; the build-time ++configuration in Local/Makefile has an option called FIXED_NEVER_USERS ++specifying a list that cannot be overridden. The contents of never_users are ++added to this list. By default FIXED_NEVER_USERS also specifies root. ++ ++When a remote host connects to Exim in order to send mail, the only information ++Exim has about the host's identity is its IP address. The next configuration ++line, ++ ++host_lookup = * ++ ++specifies that Exim should do a reverse DNS lookup on all incoming connections, ++in order to get a host name. This improves the quality of the logging ++information, but if you feel it is too expensive, you can remove it entirely, ++or restrict the lookup to hosts on "nearby" networks. Note that it is not ++always possible to find a host name from an IP address, because not all DNS ++reverse zones are maintained, and sometimes DNS servers are unreachable. ++ ++The next two lines are concerned with ident callbacks, as defined by RFC 1413 ++(hence their names): ++ ++rfc1413_hosts = * ++rfc1413_query_timeout = 5s ++ ++These settings cause Exim to make ident callbacks for all incoming SMTP calls. ++You can limit the hosts to which these calls are made, or change the timeout ++that is used. If you set the timeout to zero, all ident calls are disabled. ++Although they are cheap and can provide useful information for tracing problem ++messages, some hosts and firewalls have problems with ident calls. This can ++result in a timeout instead of an immediate refused connection, leading to ++delays on starting up an incoming SMTP session. ++ ++When Exim receives messages over SMTP connections, it expects all addresses to ++be fully qualified with a domain, as required by the SMTP definition. However, ++if you are running a server to which simple clients submit messages, you may ++find that they send unqualified addresses. The two commented-out options: ++ ++# sender_unqualified_hosts = ++# recipient_unqualified_hosts = ++ ++show how you can specify hosts that are permitted to send unqualified sender ++and recipient addresses, respectively. ++ ++The percent_hack_domains option is also commented out: ++ ++# percent_hack_domains = ++ ++It provides a list of domains for which the "percent hack" is to operate. This ++is an almost obsolete form of explicit email routing. If you do not know ++anything about it, you can safely ignore this topic. ++ ++The last two settings in the main part of the default configuration are ++concerned with messages that have been "frozen" on Exim's queue. When a message ++is frozen, Exim no longer continues to try to deliver it. Freezing occurs when ++a bounce message encounters a permanent failure because the sender address of ++the original message that caused the bounce is invalid, so the bounce cannot be ++delivered. This is probably the most common case, but there are also other ++conditions that cause freezing, and frozen messages are not always bounce ++messages. ++ ++ignore_bounce_errors_after = 2d ++timeout_frozen_after = 7d ++ ++The first of these options specifies that failing bounce messages are to be ++discarded after 2 days on the queue. The second specifies that any frozen ++message (whether a bounce message or not) is to be timed out (and discarded) ++after a week. In this configuration, the first setting ensures that no failing ++bounce message ever lasts a week. ++ ++ ++7.2 ACL configuration ++--------------------- ++ ++In the default configuration, the ACL section follows the main configuration. ++It starts with the line ++ ++begin acl ++ ++and it contains the definitions of two ACLs, called acl_check_rcpt and ++acl_check_data, that were referenced in the settings of acl_smtp_rcpt and ++acl_smtp_data above. ++ ++The first ACL is used for every RCPT command in an incoming SMTP message. Each ++RCPT command specifies one of the message's recipients. The ACL statements are ++considered in order, until the recipient address is either accepted or ++rejected. The RCPT command is then accepted or rejected, according to the ++result of the ACL processing. ++ ++acl_check_rcpt: ++ ++This line, consisting of a name terminated by a colon, marks the start of the ++ACL, and names it. ++ ++accept hosts = : ++ ++This ACL statement accepts the recipient if the sending host matches the list. ++But what does that strange list mean? It doesn't actually contain any host ++names or IP addresses. The presence of the colon puts an empty item in the ++list; Exim matches this only if the incoming message did not come from a remote ++host, because in that case, the remote hostname is empty. The colon is ++important. Without it, the list itself is empty, and can never match anything. ++ ++What this statement is doing is to accept unconditionally all recipients in ++messages that are submitted by SMTP from local processes using the standard ++input and output (that is, not using TCP/IP). A number of MUAs operate in this ++manner. ++ ++deny message = Restricted characters in address ++ domains = +local_domains ++ local_parts = ^[.] : ^.*[@%!/|] ++ ++deny message = Restricted characters in address ++ domains = !+local_domains ++ local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./ ++ ++These statements are concerned with local parts that contain any of the ++characters "@", "%", "!", "/", "|", or dots in unusual places. Although these ++characters are entirely legal in local parts (in the case of "@" and leading ++dots, only if correctly quoted), they do not commonly occur in Internet mail ++addresses. ++ ++The first three have in the past been associated with explicitly routed ++addresses (percent is still sometimes used - see the percent_hack_domains ++option). Addresses containing these characters are regularly tried by spammers ++in an attempt to bypass relaying restrictions, and also by open relay testing ++programs. Unless you really need them it is safest to reject these characters ++at this early stage. This configuration is heavy-handed in rejecting these ++characters for all messages it accepts from remote hosts. This is a deliberate ++policy of being as safe as possible. ++ ++The first rule above is stricter, and is applied to messages that are addressed ++to one of the local domains handled by this host. This is implemented by the ++first condition, which restricts it to domains that are listed in the ++local_domains domain list. The "+" character is used to indicate a reference to ++a named list. In this configuration, there is just one domain in local_domains, ++but in general there may be many. ++ ++The second condition on the first statement uses two regular expressions to ++block local parts that begin with a dot or contain "@", "%", "!", "/", or "|". ++If you have local accounts that include these characters, you will have to ++modify this rule. ++ ++Empty components (two dots in a row) are not valid in RFC 2822, but Exim allows ++them because they have been encountered in practice. (Consider the common ++convention of local parts constructed as " ++first-initial.second-initial.family-name" when applied to someone like the ++author of Exim, who has no second initial.) However, a local part starting with ++a dot or containing "/../" can cause trouble if it is used as part of a file ++name (for example, for a mailing list). This is also true for local parts that ++contain slashes. A pipe symbol can also be troublesome if the local part is ++incorporated unthinkingly into a shell command line. ++ ++The second rule above applies to all other domains, and is less strict. This ++allows your own users to send outgoing messages to sites that use slashes and ++vertical bars in their local parts. It blocks local parts that begin with a ++dot, slash, or vertical bar, but allows these characters within the local part. ++However, the sequence "/../" is barred. The use of "@", "%", and "!" is ++blocked, as before. The motivation here is to prevent your users (or your ++users' viruses) from mounting certain kinds of attack on remote sites. ++ ++accept local_parts = postmaster ++ domains = +local_domains ++ ++This statement, which has two conditions, accepts an incoming address if the ++local part is postmaster and the domain is one of those listed in the ++local_domains domain list. The "+" character is used to indicate a reference to ++a named list. In this configuration, there is just one domain in local_domains, ++but in general there may be many. ++ ++The presence of this statement means that mail to postmaster is never blocked ++by any of the subsequent tests. This can be helpful while sorting out problems ++in cases where the subsequent tests are incorrectly denying access. ++ ++require verify = sender ++ ++This statement requires the sender address to be verified before any subsequent ++ACL statement can be used. If verification fails, the incoming recipient ++address is refused. Verification consists of trying to route the address, to ++see if a bounce message could be delivered to it. In the case of remote ++addresses, basic verification checks only the domain, but callouts can be used ++for more verification if required. Section 42.43 discusses the details of ++address verification. ++ ++accept hosts = +relay_from_hosts ++ control = submission ++ ++This statement accepts the address if the message is coming from one of the ++hosts that are defined as being allowed to relay through this host. Recipient ++verification is omitted here, because in many cases the clients are dumb MUAs ++that do not cope well with SMTP error responses. For the same reason, the ++second line specifies "submission mode" for messages that are accepted. This is ++described in detail in section 46.1; it causes Exim to fix messages that are ++deficient in some way, for example, because they lack a Date: header line. If ++you are actually relaying out from MTAs, you should probably add recipient ++verification here, and disable submission mode. ++ ++accept authenticated = * ++ control = submission ++ ++This statement accepts the address if the client host has authenticated itself. ++Submission mode is again specified, on the grounds that such messages are most ++likely to come from MUAs. The default configuration does not define any ++authenticators, though it does include some nearly complete commented-out ++examples described in 7.7. This means that no client can in fact authenticate ++until you complete the authenticator definitions. ++ ++require message = relay not permitted ++ domains = +local_domains : +relay_to_domains ++ ++This statement rejects the address if its domain is neither a local domain nor ++one of the domains for which this host is a relay. ++ ++require verify = recipient ++ ++This statement requires the recipient address to be verified; if verification ++fails, the address is rejected. ++ ++# deny message = rejected because $sender_host_address \ ++# is in a black list at $dnslist_domain\n\ ++# $dnslist_text ++# dnslists = black.list.example ++# ++# warn dnslists = black.list.example ++# add_header = X-Warning: $sender_host_address is in \ ++# a black list at $dnslist_domain ++# log_message = found in $dnslist_domain ++ ++These commented-out lines are examples of how you could configure Exim to check ++sending hosts against a DNS black list. The first statement rejects messages ++from blacklisted hosts, whereas the second just inserts a warning header line. ++ ++# require verify = csa ++ ++This commented-out line is an example of how you could turn on client SMTP ++authorization (CSA) checking. Such checks do DNS lookups for special SRV ++records. ++ ++accept ++ ++The final statement in the first ACL unconditionally accepts any recipient ++address that has successfully passed all the previous tests. ++ ++acl_check_data: ++ ++This line marks the start of the second ACL, and names it. Most of the contents ++of this ACL are commented out: ++ ++# deny malware = * ++# message = This message contains a virus \ ++# ($malware_name). ++ ++These lines are examples of how to arrange for messages to be scanned for ++viruses when Exim has been compiled with the content-scanning extension, and a ++suitable virus scanner is installed. If the message is found to contain a ++virus, it is rejected with the given custom error message. ++ ++# warn spam = nobody ++# message = X-Spam_score: $spam_score\n\ ++# X-Spam_score_int: $spam_score_int\n\ ++# X-Spam_bar: $spam_bar\n\ ++# X-Spam_report: $spam_report ++ ++These lines are an example of how to arrange for messages to be scanned by ++SpamAssassin when Exim has been compiled with the content-scanning extension, ++and SpamAssassin has been installed. The SpamAssassin check is run with ++"nobody" as its user parameter, and the results are added to the message as a ++series of extra header line. In this case, the message is not rejected, ++whatever the spam score. ++ ++accept ++ ++This final line in the DATA ACL accepts the message unconditionally. ++ ++ ++7.3 Router configuration ++------------------------ ++ ++The router configuration comes next in the default configuration, introduced by ++the line ++ ++begin routers ++ ++Routers are the modules in Exim that make decisions about where to send ++messages. An address is passed to each router in turn, until it is either ++accepted, or failed. This means that the order in which you define the routers ++matters. Each router is fully described in its own chapter later in this ++manual. Here we give only brief overviews. ++ ++# domain_literal: ++# driver = ipliteral ++# domains = !+local_domains ++# transport = remote_smtp ++ ++This router is commented out because the majority of sites do not want to ++support domain literal addresses (those of the form user@[10.9.8.7]). If you ++uncomment this router, you also need to uncomment the setting of ++allow_domain_literals in the main part of the configuration. ++ ++dnslookup: ++ driver = dnslookup ++ domains = ! +local_domains ++ transport = remote_smtp ++ ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8 ++ no_more ++ ++The first uncommented router handles addresses that do not involve any local ++domains. This is specified by the line ++ ++domains = ! +local_domains ++ ++The domains option lists the domains to which this router applies, but the ++exclamation mark is a negation sign, so the router is used only for domains ++that are not in the domain list called local_domains (which was defined at the ++start of the configuration). The plus sign before local_domains indicates that ++it is referring to a named list. Addresses in other domains are passed on to ++the following routers. ++ ++The name of the router driver is dnslookup, and is specified by the driver ++option. Do not be confused by the fact that the name of this router instance is ++the same as the name of the driver. The instance name is arbitrary, but the ++name set in the driver option must be one of the driver modules that is in the ++Exim binary. ++ ++The dnslookup router routes addresses by looking up their domains in the DNS in ++order to obtain a list of hosts to which the address is routed. If the router ++succeeds, the address is queued for the remote_smtp transport, as specified by ++the transport option. If the router does not find the domain in the DNS, no ++further routers are tried because of the no_more setting, so the address fails ++and is bounced. ++ ++The ignore_target_hosts option specifies a list of IP addresses that are to be ++entirely ignored. This option is present because a number of cases have been ++encountered where MX records in the DNS point to host names whose IP addresses ++are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1). Completely ignoring ++these IP addresses causes Exim to fail to route the email address, so it ++bounces. Otherwise, Exim would log a routing problem, and continue to try to ++deliver the message periodically until the address timed out. ++ ++system_aliases: ++ driver = redirect ++ allow_fail ++ allow_defer ++ data = ${lookup{$local_part}lsearch{/etc/aliases}} ++# user = exim ++ file_transport = address_file ++ pipe_transport = address_pipe ++ ++Control reaches this and subsequent routers only for addresses in the local ++domains. This router checks to see whether the local part is defined as an ++alias in the /etc/aliases file, and if so, redirects it according to the data ++that it looks up from that file. If no data is found for the local part, the ++value of the data option is empty, causing the address to be passed to the next ++router. ++ ++/etc/aliases is a conventional name for the system aliases file that is often ++used. That is why it is referenced by from the default configuration file. ++However, you can change this by setting SYSTEM_ALIASES_FILE in Local/Makefile ++before building Exim. ++ ++userforward: ++ driver = redirect ++ check_local_user ++# local_part_suffix = +* : -* ++# local_part_suffix_optional ++ file = $home/.forward ++# allow_filter ++ no_verify ++ no_expn ++ check_ancestor ++ file_transport = address_file ++ pipe_transport = address_pipe ++ reply_transport = address_reply ++ ++This is the most complicated router in the default configuration. It is another ++redirection router, but this time it is looking for forwarding data set up by ++individual users. The check_local_user setting specifies a check that the local ++part of the address is the login name of a local user. If it is not, the router ++is skipped. The two commented options that follow check_local_user, namely: ++ ++# local_part_suffix = +* : -* ++# local_part_suffix_optional ++ ++show how you can specify the recognition of local part suffixes. If the first ++is uncommented, a suffix beginning with either a plus or a minus sign, followed ++by any sequence of characters, is removed from the local part and placed in the ++variable $local_part_suffix. The second suffix option specifies that the ++presence of a suffix in the local part is optional. When a suffix is present, ++the check for a local login uses the local part with the suffix removed. ++ ++When a local user account is found, the file called .forward in the user's home ++directory is consulted. If it does not exist, or is empty, the router declines. ++Otherwise, the contents of .forward are interpreted as redirection data (see ++chapter 22 for more details). ++ ++Traditional .forward files contain just a list of addresses, pipes, or files. ++Exim supports this by default. However, if allow_filter is set (it is commented ++out by default), the contents of the file are interpreted as a set of Exim or ++Sieve filtering instructions, provided the file begins with "#Exim filter" or " ++#Sieve filter", respectively. User filtering is discussed in the separate ++document entitled Exim's interfaces to mail filtering. ++ ++The no_verify and no_expn options mean that this router is skipped when ++verifying addresses, or when running as a consequence of an SMTP EXPN command. ++There are two reasons for doing this: ++ ++ 1. Whether or not a local user has a .forward file is not really relevant when ++ checking an address for validity; it makes sense not to waste resources ++ doing unnecessary work. ++ ++ 2. More importantly, when Exim is verifying addresses or handling an EXPN ++ command during an SMTP session, it is running as the Exim user, not as ++ root. The group is the Exim group, and no additional groups are set up. It ++ may therefore not be possible for Exim to read users' .forward files at ++ this time. ++ ++The setting of check_ancestor prevents the router from generating a new address ++that is the same as any previous address that was redirected. (This works round ++a problem concerning a bad interaction between aliasing and forwarding - see ++section 22.5). ++ ++The final three option settings specify the transports that are to be used when ++forwarding generates a direct delivery to a file, or to a pipe, or sets up an ++auto-reply, respectively. For example, if a .forward file contains ++ ++a.nother@elsewhere.example, /home/spqr/archive ++ ++the delivery to /home/spqr/archive is done by running the address_file ++transport. ++ ++localuser: ++ driver = accept ++ check_local_user ++# local_part_suffix = +* : -* ++# local_part_suffix_optional ++ transport = local_delivery ++ ++The final router sets up delivery into local mailboxes, provided that the local ++part is the name of a local login, by accepting the address and assigning it to ++the local_delivery transport. Otherwise, we have reached the end of the ++routers, so the address is bounced. The commented suffix settings fulfil the ++same purpose as they do for the userforward router. ++ ++ ++7.4 Transport configuration ++--------------------------- ++ ++Transports define mechanisms for actually delivering messages. They operate ++only when referenced from routers, so the order in which they are defined does ++not matter. The transports section of the configuration starts with ++ ++begin transports ++ ++One remote transport and four local transports are defined. ++ ++remote_smtp: ++ driver = smtp ++ ++This transport is used for delivering messages over SMTP connections. All its ++options are defaulted. The list of remote hosts comes from the router. ++ ++local_delivery: ++ driver = appendfile ++ file = /var/mail/$local_part ++ delivery_date_add ++ envelope_to_add ++ return_path_add ++# group = mail ++# mode = 0660 ++ ++This appendfile transport is used for local delivery to user mailboxes in ++traditional BSD mailbox format. By default it runs under the uid and gid of the ++local user, which requires the sticky bit to be set on the /var/mail directory. ++Some systems use the alternative approach of running mail deliveries under a ++particular group instead of using the sticky bit. The commented options show ++how this can be done. ++ ++Exim adds three headers to the message as it delivers it: Delivery-date:, ++Envelope-to: and Return-path:. This action is requested by the three ++similarly-named options above. ++ ++address_pipe: ++ driver = pipe ++ return_output ++ ++This transport is used for handling deliveries to pipes that are generated by ++redirection (aliasing or users' .forward files). The return_output option ++specifies that any output generated by the pipe is to be returned to the ++sender. ++ ++address_file: ++ driver = appendfile ++ delivery_date_add ++ envelope_to_add ++ return_path_add ++ ++This transport is used for handling deliveries to files that are generated by ++redirection. The name of the file is not specified in this instance of ++appendfile, because it comes from the redirect router. ++ ++address_reply: ++ driver = autoreply ++ ++This transport is used for handling automatic replies generated by users' ++filter files. ++ ++ ++7.5 Default retry rule ++---------------------- ++ ++The retry section of the configuration file contains rules which affect the way ++Exim retries deliveries that cannot be completed at the first attempt. It is ++introduced by the line ++ ++begin retry ++ ++In the default configuration, there is just one rule, which applies to all ++errors: ++ ++* * F,2h,15m; G,16h,1h,1.5; F,4d,6h ++ ++This causes any temporarily failing address to be retried every 15 minutes for ++2 hours, then at intervals starting at one hour and increasing by a factor of ++1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address ++is not delivered after 4 days of temporary failure, it is bounced. ++ ++If the retry section is removed from the configuration, or is empty (that is, ++if no retry rules are defined), Exim will not retry deliveries. This turns ++temporary errors into permanent errors. ++ ++ ++7.6 Rewriting configuration ++--------------------------- ++ ++The rewriting section of the configuration, introduced by ++ ++begin rewrite ++ ++contains rules for rewriting addresses in messages as they arrive. There are no ++rewriting rules in the default configuration file. ++ ++ ++7.7 Authenticators configuration ++-------------------------------- ++ ++The authenticators section of the configuration, introduced by ++ ++begin authenticators ++ ++defines mechanisms for the use of the SMTP AUTH command. The default ++configuration file contains two commented-out example authenticators which ++support plaintext username/password authentication using the standard PLAIN ++mechanism and the traditional but non-standard LOGIN mechanism, with Exim ++acting as the server. PLAIN and LOGIN are enough to support most MUA software. ++ ++The example PLAIN authenticator looks like this: ++ ++#PLAIN: ++# driver = plaintext ++# server_set_id = $auth2 ++# server_prompts = : ++# server_condition = Authentication is not yet configured ++# server_advertise_condition = ${if def:tls_in_cipher } ++ ++And the example LOGIN authenticator looks like this: ++ ++#LOGIN: ++# driver = plaintext ++# server_set_id = $auth1 ++# server_prompts = <| Username: | Password: ++# server_condition = Authentication is not yet configured ++# server_advertise_condition = ${if def:tls_in_cipher } ++ ++The server_set_id option makes Exim remember the authenticated username in ++$authenticated_id, which can be used later in ACLs or routers. The ++server_prompts option configures the plaintext authenticator so that it ++implements the details of the specific authentication mechanism, i.e. PLAIN or ++LOGIN. The server_advertise_condition setting controls when Exim offers ++authentication to clients; in the examples, this is only when TLS or SSL has ++been started, so to enable the authenticators you also need to add support for ++TLS as described in section 7.1. ++ ++The server_condition setting defines how to verify that the username and ++password are correct. In the examples it just produces an error message. To ++make the authenticators work, you can use a string expansion expression like ++one of the examples in chapter 34. ++ ++Beware that the sequence of the parameters to PLAIN and LOGIN differ; the ++usercode and password are in different positions. Chapter 34 covers both. ++ ++ ++ ++=============================================================================== ++8. REGULAR EXPRESSIONS ++ ++Exim supports the use of regular expressions in many of its options. It uses ++the PCRE regular expression library; this provides regular expression matching ++that is compatible with Perl 5. The syntax and semantics of regular expressions ++is discussed in many Perl reference books, and also in Jeffrey Friedl's ++Mastering Regular Expressions, which is published by O'Reilly (see http:// ++www.oreilly.com/catalog/regex2/). ++ ++The documentation for the syntax and semantics of the regular expressions that ++are supported by PCRE is included in the PCRE distribution, and no further ++description is included here. The PCRE functions are called from Exim using the ++default option settings (that is, with no PCRE options set), except that the ++PCRE_CASELESS option is set when the matching is required to be ++case-insensitive. ++ ++In most cases, when a regular expression is required in an Exim configuration, ++it has to start with a circumflex, in order to distinguish it from plain text ++or an "ends with" wildcard. In this example of a configuration setting, the ++second item in the colon-separated list is a regular expression. ++ ++domains = a.b.c : ^\\d{3} : *.y.z : ... ++ ++The doubling of the backslash is required because of string expansion that ++precedes interpretation - see section 11.1 for more discussion of this issue, ++and a way of avoiding the need for doubling backslashes. The regular expression ++that is eventually used in this example contains just one backslash. The ++circumflex is included in the regular expression, and has the normal effect of ++"anchoring" it to the start of the string that is being matched. ++ ++There are, however, two cases where a circumflex is not required for the ++recognition of a regular expression: these are the match condition in a string ++expansion, and the matches condition in an Exim filter file. In these cases, ++the relevant string is always treated as a regular expression; if it does not ++start with a circumflex, the expression is not anchored, and can match anywhere ++in the subject string. ++ ++In all cases, if you want a regular expression to match at the end of a string, ++you must code the $ metacharacter to indicate this. For example: ++ ++domains = ^\\d{3}\\.example ++ ++matches the domain 123.example, but it also matches 123.example.com. You need ++to use: ++ ++domains = ^\\d{3}\\.example\$ ++ ++if you want example to be the top-level domain. The backslash before the $ is ++needed because string expansion also interprets dollar characters. ++ ++ ++ ++=============================================================================== ++9. FILE AND DATABASE LOOKUPS ++ ++Exim can be configured to look up data in files or databases as it processes ++messages. Two different kinds of syntax are used: ++ ++ 1. A string that is to be expanded may contain explicit lookup requests. These ++ cause parts of the string to be replaced by data that is obtained from the ++ lookup. Lookups of this type are conditional expansion items. Different ++ results can be defined for the cases of lookup success and failure. See ++ chapter 11, where string expansions are described in detail. ++ ++ 2. Lists of domains, hosts, and email addresses can contain lookup requests as ++ a way of avoiding excessively long linear lists. In this case, the data ++ that is returned by the lookup is often (but not always) discarded; whether ++ the lookup succeeds or fails is what really counts. These kinds of list are ++ described in chapter 10. ++ ++String expansions, lists, and lookups interact with each other in such a way ++that there is no order in which to describe any one of them that does not ++involve references to the others. Each of these three chapters makes more sense ++if you have read the other two first. If you are reading this for the first ++time, be aware that some of it will make a lot more sense after you have read ++chapters 10 and 11. ++ ++ ++9.1 Examples of different lookup syntax ++--------------------------------------- ++ ++It is easy to confuse the two different kinds of lookup, especially as the ++lists that may contain the second kind are always expanded before being ++processed as lists. Therefore, they may also contain lookups of the first kind. ++Be careful to distinguish between the following two examples: ++ ++domains = ${lookup{$sender_host_address}lsearch{/some/file}} ++domains = lsearch;/some/file ++ ++The first uses a string expansion, the result of which must be a domain list. ++No strings have been specified for a successful or a failing lookup; the ++defaults in this case are the looked-up data and an empty string, respectively. ++The expansion takes place before the string is processed as a list, and the ++file that is searched could contain lines like this: ++ ++192.168.3.4: domain1:domain2:... ++192.168.1.9: domain3:domain4:... ++ ++When the lookup succeeds, the result of the expansion is a list of domains (and ++possibly other types of item that are allowed in domain lists). ++ ++In the second example, the lookup is a single item in a domain list. It causes ++Exim to use a lookup to see if the domain that is being processed can be found ++in the file. The file could contains lines like this: ++ ++domain1: ++domain2: ++ ++Any data that follows the keys is not relevant when checking that the domain ++matches the list item. ++ ++It is possible, though no doubt confusing, to use both kinds of lookup at once. ++Consider a file containing lines like this: ++ ++192.168.5.6: lsearch;/another/file ++ ++If the value of $sender_host_address is 192.168.5.6, expansion of the first ++domains setting above generates the second setting, which therefore causes a ++second lookup to occur. ++ ++The rest of this chapter describes the different lookup types that are ++available. Any of them can be used in any part of the configuration where a ++lookup is permitted. ++ ++ ++9.2 Lookup types ++---------------- ++ ++Two different types of data lookup are implemented: ++ ++ * The single-key type requires the specification of a file in which to look, ++ and a single key to search for. The key must be a non-empty string for the ++ lookup to succeed. The lookup type determines how the file is searched. ++ ++ * The query-style type accepts a generalized database query. No particular ++ key value is assumed by Exim for query-style lookups. You can use whichever ++ Exim variables you need to construct the database query. ++ ++The code for each lookup type is in a separate source file that is included in ++the binary of Exim only if the corresponding compile-time option is set. The ++default settings in src/EDITME are: ++ ++LOOKUP_DBM=yes ++LOOKUP_LSEARCH=yes ++ ++which means that only linear searching and DBM lookups are included by default. ++For some types of lookup (e.g. SQL databases), you need to install appropriate ++libraries and header files before building Exim. ++ ++ ++9.3 Single-key lookup types ++--------------------------- ++ ++The following single-key lookup types are implemented: ++ ++ * cdb: The given file is searched as a Constant DataBase file, using the key ++ string without a terminating binary zero. The cdb format is designed for ++ indexed files that are read frequently and never updated, except by total ++ re-creation. As such, it is particularly suitable for large files ++ containing aliases or other indexed data referenced by an MTA. Information ++ about cdb can be found in several places: ++ ++ http://www.pobox.com/~djb/cdb.html ++ ftp://ftp.corpit.ru/pub/tinycdb/ ++ http://packages.debian.org/stable/utils/freecdb.html ++ ++ A cdb distribution is not needed in order to build Exim with cdb support, ++ because the code for reading cdb files is included directly in Exim itself. ++ However, no means of building or testing cdb files is provided with Exim, ++ so you need to obtain a cdb distribution in order to do this. ++ ++ * dbm: Calls to DBM library functions are used to extract data from the given ++ DBM file by looking up the record with the given key. A terminating binary ++ zero is included in the key that is passed to the DBM library. See section ++ 4.4 for a discussion of DBM libraries. ++ ++ For all versions of Berkeley DB, Exim uses the DB_HASH style of database ++ when building DBM files using the exim_dbmbuild utility. However, when ++ using Berkeley DB versions 3 or 4, it opens existing databases for reading ++ with the DB_UNKNOWN option. This enables it to handle any of the types of ++ database that the library supports, and can be useful for accessing DBM ++ files created by other applications. (For earlier DB versions, DB_HASH is ++ always used.) ++ ++ * dbmjz: This is the same as dbm, except that the lookup key is interpreted ++ as an Exim list; the elements of the list are joined together with ASCII ++ NUL characters to form the lookup key. An example usage would be to ++ authenticate incoming SMTP calls using the passwords from Cyrus SASL's /etc ++ /sasldb2 file with the gsasl authenticator or Exim's own cram_md5 ++ authenticator. ++ ++ * dbmnz: This is the same as dbm, except that a terminating binary zero is ++ not included in the key that is passed to the DBM library. You may need ++ this if you want to look up data in files that are created by or shared ++ with some other application that does not use terminating zeros. For ++ example, you need to use dbmnz rather than dbm if you want to authenticate ++ incoming SMTP calls using the passwords from Courier's /etc/ ++ userdbshadow.dat file. Exim's utility program for creating DBM files ( ++ exim_dbmbuild) includes the zeros by default, but has an option to omit ++ them (see section 52.9). ++ ++ * dsearch: The given file must be a directory; this is searched for an entry ++ whose name is the key by calling the lstat() function. The key may not ++ contain any forward slash characters. If lstat() succeeds, the result of ++ the lookup is the name of the entry, which may be a file, directory, ++ symbolic link, or any other kind of directory entry. An example of how this ++ lookup can be used to support virtual domains is given in section 49.7. ++ ++ * iplsearch: The given file is a text file containing keys and data. A key is ++ terminated by a colon or white space or the end of the line. The keys in ++ the file must be IP addresses, or IP addresses with CIDR masks. Keys that ++ involve IPv6 addresses must be enclosed in quotes to prevent the first ++ internal colon being interpreted as a key terminator. For example: ++ ++ 1.2.3.4: data for 1.2.3.4 ++ 192.168.0.0/16: data for 192.168.0.0/16 ++ "abcd::cdab": data for abcd::cdab ++ "abcd:abcd::/32" data for abcd:abcd::/32 ++ ++ The key for an iplsearch lookup must be an IP address (without a mask). The ++ file is searched linearly, using the CIDR masks where present, until a ++ matching key is found. The first key that matches is used; there is no ++ attempt to find a "best" match. Apart from the way the keys are matched, ++ the processing for iplsearch is the same as for lsearch. ++ ++ Warning 1: Unlike most other single-key lookup types, a file of data for ++ iplsearch can not be turned into a DBM or cdb file, because those lookup ++ types support only literal keys. ++ ++ Warning 2: In a host list, you must always use net-iplsearch so that the ++ implicit key is the host's IP address rather than its name (see section ++ 10.12). ++ ++ * lsearch: The given file is a text file that is searched linearly for a line ++ beginning with the search key, terminated by a colon or white space or the ++ end of the line. The search is case-insensitive; that is, upper and lower ++ case letters are treated as the same. The first occurrence of the key that ++ is found in the file is used. ++ ++ White space between the key and the colon is permitted. The remainder of ++ the line, with leading and trailing white space removed, is the data. This ++ can be continued onto subsequent lines by starting them with any amount of ++ white space, but only a single space character is included in the data at ++ such a junction. If the data begins with a colon, the key must be ++ terminated by a colon, for example: ++ ++ baduser: :fail: ++ ++ Empty lines and lines beginning with # are ignored, even if they occur in ++ the middle of an item. This is the traditional textual format of alias ++ files. Note that the keys in an lsearch file are literal strings. There is ++ no wildcarding of any kind. ++ ++ In most lsearch files, keys are not required to contain colons or # ++ characters, or white space. However, if you need this feature, it is ++ available. If a key begins with a doublequote character, it is terminated ++ only by a matching quote (or end of line), and the normal escaping rules ++ apply to its contents (see section 6.16). An optional colon is permitted ++ after quoted keys (exactly as for unquoted keys). There is no special ++ handling of quotes for the data part of an lsearch line. ++ ++ * nis: The given file is the name of a NIS map, and a NIS lookup is done with ++ the given key, without a terminating binary zero. There is a variant called ++ nis0 which does include the terminating binary zero in the key. This is ++ reportedly needed for Sun-style alias files. Exim does not recognize NIS ++ aliases; the full map names must be used. ++ ++ * wildlsearch or nwildlsearch: These search a file linearly, like lsearch, ++ but instead of being interpreted as a literal string, each key in the file ++ may be wildcarded. The difference between these two lookup types is that ++ for wildlsearch, each key in the file is string-expanded before being used, ++ whereas for nwildlsearch, no expansion takes place. ++ ++ Like lsearch, the testing is done case-insensitively. However, keys in the ++ file that are regular expressions can be made case-sensitive by the use of ++ "(-i)" within the pattern. The following forms of wildcard are recognized: ++ ++ 1. The string may begin with an asterisk to mean "ends with". For example: ++ ++ *.a.b.c data for anything.a.b.c ++ *fish data for anythingfish ++ ++ 2. The string may begin with a circumflex to indicate a regular ++ expression. For example, for wildlsearch: ++ ++ ^\N\d+\.a\.b\N data for <digits>.a.b ++ ++ Note the use of "\N" to disable expansion of the contents of the ++ regular expression. If you are using nwildlsearch, where the keys are ++ not string-expanded, the equivalent entry is: ++ ++ ^\d+\.a\.b data for <digits>.a.b ++ ++ The case-insensitive flag is set at the start of compiling the regular ++ expression, but it can be turned off by using "(-i)" at an appropriate ++ point. For example, to make the entire pattern case-sensitive: ++ ++ ^(?-i)\d+\.a\.b data for <digits>.a.b ++ ++ If the regular expression contains white space or colon characters, you ++ must either quote it (see lsearch above), or represent these characters ++ in other ways. For example, "\s" can be used for white space and "\x3A" ++ for a colon. This may be easier than quoting, because if you quote, you ++ have to escape all the backslashes inside the quotes. ++ ++ Note: It is not possible to capture substrings in a regular expression ++ match for later use, because the results of all lookups are cached. If ++ a lookup is repeated, the result is taken from the cache, and no actual ++ pattern matching takes place. The values of all the numeric variables ++ are unset after a (n)wildlsearch match. ++ ++ 3. Although I cannot see it being of much use, the general matching ++ function that is used to implement (n)wildlsearch means that the string ++ may begin with a lookup name terminated by a semicolon, and followed by ++ lookup data. For example: ++ ++ cdb;/some/file data for keys that match the file ++ ++ The data that is obtained from the nested lookup is discarded. ++ ++ Keys that do not match any of these patterns are interpreted literally. The ++ continuation rules for the data are the same as for lsearch, and keys may ++ be followed by optional colons. ++ ++ Warning: Unlike most other single-key lookup types, a file of data for (n) ++ wildlsearch can not be turned into a DBM or cdb file, because those lookup ++ types support only literal keys. ++ ++ ++9.4 Query-style lookup types ++---------------------------- ++ ++The supported query-style lookup types are listed below. Further details about ++many of them are given in later sections. ++ ++ * dnsdb: This does a DNS search for one or more records whose domain names ++ are given in the supplied query. The resulting data is the contents of the ++ records. See section 9.10. ++ ++ * ibase: This does a lookup in an InterBase database. ++ ++ * ldap: This does an LDAP lookup using a query in the form of a URL, and ++ returns attributes from a single entry. There is a variant called ldapm ++ that permits values from multiple entries to be returned. A third variant ++ called ldapdn returns the Distinguished Name of a single entry instead of ++ any attribute values. See section 9.13. ++ ++ * mysql: The format of the query is an SQL statement that is passed to a ++ MySQL database. See section 9.20. ++ ++ * nisplus: This does a NIS+ lookup using a query that can specify the name of ++ the field to be returned. See section 9.19. ++ ++ * oracle: The format of the query is an SQL statement that is passed to an ++ Oracle database. See section 9.20. ++ ++ * passwd is a query-style lookup with queries that are just user names. The ++ lookup calls getpwnam() to interrogate the system password data, and on ++ success, the result string is the same as you would get from an lsearch ++ lookup on a traditional /etc/passwd file, though with "*" for the password ++ value. For example: ++ ++ *:42:42:King Rat:/home/kr:/bin/bash ++ ++ * pgsql: The format of the query is an SQL statement that is passed to a ++ PostgreSQL database. See section 9.20. ++ ++ * sqlite: The format of the query is a file name followed by an SQL statement ++ that is passed to an SQLite database. See section 9.25. ++ ++ * testdb: This is a lookup type that is used for testing Exim. It is not ++ likely to be useful in normal operation. ++ ++ * whoson: Whoson (http://whoson.sourceforge.net) is a protocol that allows a ++ server to check whether a particular (dynamically allocated) IP address is ++ currently allocated to a known (trusted) user and, optionally, to obtain ++ the identity of the said user. For SMTP servers, Whoson was popular at one ++ time for "POP before SMTP" authentication, but that approach has been ++ superseded by SMTP authentication. In Exim, Whoson can be used to implement ++ "POP before SMTP" checking using ACL statements such as ++ ++ require condition = \ ++ ${lookup whoson {$sender_host_address}{yes}{no}} ++ ++ The query consists of a single IP address. The value returned is the name ++ of the authenticated user, which is stored in the variable $value. However, ++ in this example, the data in $value is not used; the result of the lookup ++ is one of the fixed strings "yes" or "no". ++ ++ ++9.5 Temporary errors in lookups ++------------------------------- ++ ++Lookup functions can return temporary error codes if the lookup cannot be ++completed. For example, an SQL or LDAP database might be unavailable. For this ++reason, it is not advisable to use a lookup that might do this for critical ++options such as a list of local domains. ++ ++When a lookup cannot be completed in a router or transport, delivery of the ++message (to the relevant address) is deferred, as for any other temporary ++error. In other circumstances Exim may assume the lookup has failed, or may ++give up altogether. ++ ++ ++9.6 Default values in single-key lookups ++---------------------------------------- ++ ++In this context, a "default value" is a value specified by the administrator ++that is to be used if a lookup fails. ++ ++Note: This section applies only to single-key lookups. For query-style lookups, ++the facilities of the query language must be used. An attempt to specify a ++default for a query-style lookup provokes an error. ++ ++If "*" is added to a single-key lookup type (for example, lsearch*) and the ++initial lookup fails, the key "*" is looked up in the file to provide a default ++value. See also the section on partial matching below. ++ ++Alternatively, if "*@" is added to a single-key lookup type (for example dbm*@) ++then, if the initial lookup fails and the key contains an @ character, a second ++lookup is done with everything before the last @ replaced by *. This makes it ++possible to provide per-domain defaults in alias files that include the domains ++in the keys. If the second lookup fails (or doesn't take place because there is ++no @ in the key), "*" is looked up. For example, a redirect router might ++contain: ++ ++data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}} ++ ++Suppose the address that is being processed is jane@eyre.example. Exim looks up ++these keys, in this order: ++ ++jane@eyre.example ++*@eyre.example ++* ++ ++The data is taken from whichever key it finds first. Note: In an lsearch file, ++this does not mean the first of these keys in the file. A complete scan is done ++for each key, and only if it is not found at all does Exim move on to try the ++next key. ++ ++ ++9.7 Partial matching in single-key lookups ++------------------------------------------ ++ ++The normal operation of a single-key lookup is to search the file for an exact ++match with the given key. However, in a number of situations where domains are ++being looked up, it is useful to be able to do partial matching. In this case, ++information in the file that has a key starting with "*." is matched by any ++domain that ends with the components that follow the full stop. For example, if ++a key in a DBM file is ++ ++*.dates.fict.example ++ ++then when partial matching is enabled this is matched by (amongst others) ++2001.dates.fict.example and 1984.dates.fict.example. It is also matched by ++dates.fict.example, if that does not appear as a separate key in the file. ++ ++Note: Partial matching is not available for query-style lookups. It is also not ++available for any lookup items in address lists (see section 10.19). ++ ++Partial matching is implemented by doing a series of separate lookups using ++keys constructed by modifying the original subject key. This means that it can ++be used with any of the single-key lookup types, provided that partial matching ++keys beginning with a special prefix (default "*.") are included in the data ++file. Keys in the file that do not begin with the prefix are matched only by ++unmodified subject keys when partial matching is in use. ++ ++Partial matching is requested by adding the string "partial-" to the front of ++the name of a single-key lookup type, for example, partial-dbm. When this is ++done, the subject key is first looked up unmodified; if that fails, "*." is ++added at the start of the subject key, and it is looked up again. If that ++fails, further lookups are tried with dot-separated components removed from the ++start of the subject key, one-by-one, and "*." added on the front of what ++remains. ++ ++A minimum number of two non-* components are required. This can be adjusted by ++including a number before the hyphen in the search type. For example, ++partial3-lsearch specifies a minimum of three non-* components in the modified ++keys. Omitting the number is equivalent to "partial2-". If the subject key is ++2250.dates.fict.example then the following keys are looked up when the minimum ++number of non-* components is two: ++ ++2250.dates.fict.example ++*.2250.dates.fict.example ++*.dates.fict.example ++*.fict.example ++ ++As soon as one key in the sequence is successfully looked up, the lookup ++finishes. ++ ++The use of "*." as the partial matching prefix is a default that can be ++changed. The motivation for this feature is to allow Exim to operate with file ++formats that are used by other MTAs. A different prefix can be supplied in ++parentheses instead of the hyphen after "partial". For example: ++ ++domains = partial(.)lsearch;/some/file ++ ++In this example, if the domain is a.b.c, the sequence of lookups is "a.b.c", ++".a.b.c", and ".b.c" (the default minimum of 2 non-wild components is ++unchanged). The prefix may consist of any punctuation characters other than a ++closing parenthesis. It may be empty, for example: ++ ++domains = partial1()cdb;/some/file ++ ++For this example, if the domain is a.b.c, the sequence of lookups is "a.b.c", ++"b.c", and "c". ++ ++If "partial0" is specified, what happens at the end (when the lookup with just ++one non-wild component has failed, and the original key is shortened right down ++to the null string) depends on the prefix: ++ ++ * If the prefix has zero length, the whole lookup fails. ++ ++ * If the prefix has length 1, a lookup for just the prefix is done. For ++ example, the final lookup for "partial0(.)" is for "." alone. ++ ++ * Otherwise, if the prefix ends in a dot, the dot is removed, and the ++ remainder is looked up. With the default prefix, therefore, the final ++ lookup is for "*" on its own. ++ ++ * Otherwise, the whole prefix is looked up. ++ ++If the search type ends in "*" or "*@" (see section 9.6 above), the search for ++an ultimate default that this implies happens after all partial lookups have ++failed. If "partial0" is specified, adding "*" to the search type has no effect ++with the default prefix, because the "*" key is already included in the ++sequence of partial lookups. However, there might be a use for lookup types ++such as "partial0(.)lsearch*". ++ ++The use of "*" in lookup partial matching differs from its use as a wildcard in ++domain lists and the like. Partial matching works only in terms of ++dot-separated components; a key such as "*fict.example" in a database file is ++useless, because the asterisk in a partial matching subject key is always ++followed by a dot. ++ ++ ++9.8 Lookup caching ++------------------ ++ ++Exim caches all lookup results in order to avoid needless repetition of ++lookups. However, because (apart from the daemon) Exim operates as a collection ++of independent, short-lived processes, this caching applies only within a ++single Exim process. There is no inter-process lookup caching facility. ++ ++For single-key lookups, Exim keeps the relevant files open in case there is ++another lookup that needs them. In some types of configuration this can lead to ++many files being kept open for messages with many recipients. To avoid hitting ++the operating system limit on the number of simultaneously open files, Exim ++closes the least recently used file when it needs to open more files than its ++own internal limit, which can be changed via the lookup_open_max option. ++ ++The single-key lookup files are closed and the lookup caches are flushed at ++strategic points during delivery - for example, after all routing is complete. ++ ++ ++9.9 Quoting lookup data ++----------------------- ++ ++When data from an incoming message is included in a query-style lookup, there ++is the possibility of special characters in the data messing up the syntax of ++the query. For example, a NIS+ query that contains ++ ++[name=$local_part] ++ ++will be broken if the local part happens to contain a closing square bracket. ++For NIS+, data can be enclosed in double quotes like this: ++ ++[name="$local_part"] ++ ++but this still leaves the problem of a double quote in the data. The rule for ++NIS+ is that double quotes must be doubled. Other lookup types have different ++rules, and to cope with the differing requirements, an expansion operator of ++the following form is provided: ++ ++${quote_<lookup-type>:<string>} ++ ++For example, the safest way to write the NIS+ query is ++ ++[name="${quote_nisplus:$local_part}"] ++ ++See chapter 11 for full coverage of string expansions. The quote operator can ++be used for all lookup types, but has no effect for single-key lookups, since ++no quoting is ever needed in their key strings. ++ ++ ++9.10 More about dnsdb ++--------------------- ++ ++The dnsdb lookup type uses the DNS as its database. A simple query consists of ++a record type and a domain name, separated by an equals sign. For example, an ++expansion string could contain: ++ ++${lookup dnsdb{mx=a.b.example}{$value}fail} ++ ++If the lookup succeeds, the result is placed in $value, which in this case is ++used on its own as the result. If the lookup does not succeed, the "fail" ++keyword causes a forced expansion failure - see section 11.4 for an explanation ++of what this means. ++ ++The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT, ++and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also ++configured). If no type is given, TXT is assumed. When the type is PTR, the ++data can be an IP address, written as normal; inversion and the addition of ++in-addr.arpa or ip6.arpa happens automatically. For example: ++ ++${lookup dnsdb{ptr=192.168.4.5}{$value}fail} ++ ++If the data for a PTR record is not a syntactically valid IP address, it is not ++altered and nothing is added. ++ ++For an MX lookup, both the preference value and the host name are returned for ++each record, separated by a space. For an SRV lookup, the priority, weight, ++port, and host name are returned for each record, separated by spaces. ++ ++For any record type, if multiple records are found (or, for A6 lookups, if a ++single record leads to multiple addresses), the data is returned as a ++concatenation, with newline as the default separator. The order, of course, ++depends on the DNS resolver. You can specify a different separator character ++between multiple records by putting a right angle-bracket followed immediately ++by the new separator at the start of the query. For example: ++ ++${lookup dnsdb{>: a=host1.example}} ++ ++It is permitted to specify a space as the separator character. Further white ++space is ignored. ++ ++For TXT records with multiple items of data, only the first item is returned, ++unless a separator for them is specified using a comma after the separator ++character followed immediately by the TXT record item separator. To concatenate ++items without a separator, use a semicolon instead. For SPF records the default ++behaviour is to concatenate multiple items without using a separator. ++ ++${lookup dnsdb{>\n,: txt=a.b.example}} ++${lookup dnsdb{>\n; txt=a.b.example}} ++${lookup dnsdb{spf=example.org}} ++ ++It is permitted to specify a space as the separator character. Further white ++space is ignored. ++ ++ ++9.11 Pseudo dnsdb record types ++------------------------------ ++ ++By default, both the preference value and the host name are returned for each ++MX record, separated by a space. If you want only host names, you can use the ++pseudo-type MXH: ++ ++${lookup dnsdb{mxh=a.b.example}} ++ ++In this case, the preference values are omitted, and just the host names are ++returned. ++ ++Another pseudo-type is ZNS (for "zone NS"). It performs a lookup for NS records ++on the given domain, but if none are found, it removes the first component of ++the domain name, and tries again. This process continues until NS records are ++found or there are no more components left (or there is a DNS error). In other ++words, it may return the name servers for a top-level domain, but it never ++returns the root name servers. If there are no NS records for the top-level ++domain, the lookup fails. Consider these examples: ++ ++${lookup dnsdb{zns=xxx.quercite.com}} ++${lookup dnsdb{zns=xxx.edu}} ++ ++Assuming that in each case there are no NS records for the full domain name, ++the first returns the name servers for quercite.com, and the second returns the ++name servers for edu. ++ ++You should be careful about how you use this lookup because, unless the ++top-level domain does not exist, the lookup always returns some host names. The ++sort of use to which this might be put is for seeing if the name servers for a ++given domain are on a blacklist. You can probably assume that the name servers ++for the high-level domains such as com or co.uk are not going to be on such a ++list. ++ ++A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV ++records according to the CSA rules, which are described in section 42.49. ++Although dnsdb supports SRV lookups directly, this is not sufficient because of ++the extra parent domain search behaviour of CSA. The result of a successful ++lookup such as: ++ ++${lookup dnsdb {csa=$sender_helo_name}} ++ ++has two space-separated fields: an authorization code and a target host name. ++The authorization code can be "Y" for yes, "N" for no, "X" for explicit ++authorization required but absent, or "?" for unknown. ++ ++The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA ++and then an A lookup. All results are returned; defer processing (see below) is ++handled separately for each lookup. Example: ++ ++${lookup dnsdb {>; a+=$sender_helo_name}} ++ ++ ++9.12 Multiple dnsdb lookups ++--------------------------- ++ ++In the previous sections, dnsdb lookups for a single domain are described. ++However, you can specify a list of domains or IP addresses in a single dnsdb ++lookup. The list is specified in the normal Exim way, with colon as the default ++separator, but with the ability to change this. For example: ++ ++${lookup dnsdb{one.domain.com:two.domain.com}} ++${lookup dnsdb{a=one.host.com:two.host.com}} ++${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}} ++ ++In order to retain backwards compatibility, there is one special case: if the ++lookup type is PTR and no change of separator is specified, Exim looks to see ++if the rest of the string is precisely one IPv6 address. In this case, it does ++not treat it as a list. ++ ++The data from each lookup is concatenated, with newline separators by default, ++in the same way that multiple DNS records for a single item are handled. A ++different separator can be specified, as described above. ++ ++The dnsdb lookup fails only if all the DNS lookups fail. If there is a ++temporary DNS error for any of them, the behaviour is controlled by an optional ++keyword followed by a comma that may appear before the record type. The ++possible keywords are "defer_strict", "defer_never", and "defer_lax". With ++"strict" behaviour, any temporary DNS error causes the whole lookup to defer. ++With "never" behaviour, a temporary DNS error is ignored, and the behaviour is ++as if the DNS lookup failed to find anything. With "lax" behaviour, all the ++queries are attempted, but a temporary DNS error causes the whole lookup to ++defer only if none of the other lookups succeed. The default is "lax", so the ++following lookups are equivalent: ++ ++${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}} ++${lookup dnsdb{a=one.host.com:two.host.com}} ++ ++Thus, in the default case, as long as at least one of the DNS lookups yields ++some data, the lookup succeeds. ++ ++ ++9.13 More about LDAP ++-------------------- ++ ++The original LDAP implementation came from the University of Michigan; this has ++become "Open LDAP", and there are now two different releases. Another ++implementation comes from Netscape, and Solaris 7 and subsequent releases ++contain inbuilt LDAP support. Unfortunately, though these are all compatible at ++the lookup function level, their error handling is different. For this reason ++it is necessary to set a compile-time variable when building Exim with LDAP, to ++indicate which LDAP library is in use. One of the following should appear in ++your Local/Makefile: ++ ++LDAP_LIB_TYPE=UMICHIGAN ++LDAP_LIB_TYPE=OPENLDAP1 ++LDAP_LIB_TYPE=OPENLDAP2 ++LDAP_LIB_TYPE=NETSCAPE ++LDAP_LIB_TYPE=SOLARIS ++ ++If LDAP_LIB_TYPE is not set, Exim assumes "OPENLDAP1", which has the same ++interface as the University of Michigan version. ++ ++There are three LDAP lookup types in Exim. These behave slightly differently in ++the way they handle the results of a query: ++ ++ * ldap requires the result to contain just one entry; if there are more, it ++ gives an error. ++ ++ * ldapdn also requires the result to contain just one entry, but it is the ++ Distinguished Name that is returned rather than any attribute values. ++ ++ * ldapm permits the result to contain more than one entry; the attributes ++ from all of them are returned. ++ ++For ldap and ldapm, if a query finds only entries with no attributes, Exim ++behaves as if the entry did not exist, and the lookup fails. The format of the ++data returned by a successful lookup is described in the next section. First we ++explain how LDAP queries are coded. ++ ++ ++9.14 Format of LDAP queries ++--------------------------- ++ ++An LDAP query takes the form of a URL as defined in RFC 2255. For example, in ++the configuration of a redirect router one might have this setting: ++ ++data = ${lookup ldap \ ++ {ldap:///cn=$local_part,o=University%20of%20Cambridge,\ ++ c=UK?mailbox?base?}} ++ ++The URL may begin with "ldap" or "ldaps" if your LDAP library supports secure ++(encrypted) LDAP connections. The second of these ensures that an encrypted TLS ++connection is used. ++ ++With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular ++LDAP connections, rather than the SSL-on-connect "ldaps". See the ++ldap_start_tls option. ++ ++ ++9.15 LDAP quoting ++----------------- ++ ++Two levels of quoting are required in LDAP queries, the first for LDAP itself ++and the second because the LDAP query is represented as a URL. Furthermore, ++within an LDAP query, two different kinds of quoting are required. For this ++reason, there are two different LDAP-specific quoting operators. ++ ++The quote_ldap operator is designed for use on strings that are part of filter ++specifications. Conceptually, it first does the following conversions on the ++string: ++ ++* => \2A ++( => \28 ++) => \29 ++\ => \5C ++ ++in accordance with RFC 2254. The resulting string is then quoted according to ++the rules for URLs, that is, all non-alphanumeric characters except ++ ++! $ ' - . _ ( ) * + ++ ++are converted to their hex values, preceded by a percent sign. For example: ++ ++${quote_ldap: a(bc)*, a<yz>; } ++ ++yields ++ ++%20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20 ++ ++Removing the URL quoting, this is (with a leading and a trailing space): ++ ++a\28bc\29\2A, a<yz>; ++ ++The quote_ldap_dn operator is designed for use on strings that are part of base ++DN specifications in queries. Conceptually, it first converts the string by ++inserting a backslash in front of any of the following characters: ++ ++, + " \ < > ; ++ ++It also inserts a backslash before any leading spaces or # characters, and ++before any trailing spaces. (These rules are in RFC 2253.) The resulting string ++is then quoted according to the rules for URLs. For example: ++ ++${quote_ldap_dn: a(bc)*, a<yz>; } ++ ++yields ++ ++%5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20 ++ ++Removing the URL quoting, this is (with a trailing space): ++ ++\ a(bc)*\, a\<yz\>\;\ ++ ++There are some further comments about quoting in the section on LDAP ++authentication below. ++ ++ ++9.16 LDAP connections ++--------------------- ++ ++The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP ++is in use, via a Unix domain socket. The example given above does not specify ++an LDAP server. A server that is reached by TCP/IP can be specified in a query ++by starting it with ++ ++ldap://<hostname>:<port>/... ++ ++If the port (and preceding colon) are omitted, the standard LDAP port (389) is ++used. When no server is specified in a query, a list of default servers is ++taken from the ldap_default_servers configuration option. This supplies a ++colon-separated list of servers which are tried in turn until one successfully ++handles a query, or there is a serious error. Successful handling either ++returns the requested data, or indicates that it does not exist. Serious errors ++are syntactical, or multiple values when only a single value is expected. ++Errors which cause the next server to be tried are connection failures, bind ++failures, and timeouts. ++ ++For each server name in the list, a port number can be given. The standard way ++of specifying a host and port is to use a colon separator (RFC 1738). Because ++ldap_default_servers is a colon-separated list, such colons have to be doubled. ++For example ++ ++ldap_default_servers = ldap1.example.com::145:ldap2.example.com ++ ++If ldap_default_servers is unset, a URL with no server name is passed to the ++LDAP library with no server name, and the library's default (normally the local ++host) is used. ++ ++If you are using the OpenLDAP library, you can connect to an LDAP server using ++a Unix domain socket instead of a TCP/IP connection. This is specified by using ++"ldapi" instead of "ldap" in LDAP queries. What follows here applies only to ++OpenLDAP. If Exim is compiled with a different LDAP library, this feature is ++not available. ++ ++For this type of connection, instead of a host name for the server, a pathname ++for the socket is required, and the port number is not relevant. The pathname ++can be specified either as an item in ldap_default_servers, or inline in the ++query. In the former case, you can have settings such as ++ ++ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain ++ ++When the pathname is given in the query, you have to escape the slashes as ++"%2F" to fit in with the LDAP URL syntax. For example: ++ ++${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=... ++ ++When Exim processes an LDAP lookup and finds that the "hostname" is really a ++pathname, it uses the Unix domain socket code, even if the query actually ++specifies "ldap" or "ldaps". In particular, no encryption is used for a socket ++connection. This behaviour means that you can use a setting of ++ldap_default_servers such as in the example above with traditional "ldap" or ++"ldaps" queries, and it will work. First, Exim tries a connection via the Unix ++domain socket; if that fails, it tries a TCP/IP connection to the backup host. ++ ++If an explicit "ldapi" type is given in a query when a host name is specified, ++an error is diagnosed. However, if there are more items in ldap_default_servers ++, they are tried. In other words: ++ ++ * Using a pathname with "ldap" or "ldaps" forces the use of the Unix domain ++ interface. ++ ++ * Using "ldapi" with a host name causes an error. ++ ++Using "ldapi" with no host or path in the query, and no setting of ++ldap_default_servers, does whatever the library does by default. ++ ++ ++9.17 LDAP authentication and control information ++------------------------------------------------ ++ ++The LDAP URL syntax provides no way of passing authentication and other control ++information to the server. To make this possible, the URL in an LDAP query may ++be preceded by any number of <name>=<value> settings, separated by spaces. If a ++value contains spaces it must be enclosed in double quotes, and when double ++quotes are used, backslash is interpreted in the usual way inside them. The ++following names are recognized: ++ ++DEREFERENCE set the dereferencing parameter ++NETTIME set a timeout for a network operation ++USER set the DN, for authenticating the LDAP bind ++PASS set the password, likewise ++REFERRALS set the referrals parameter ++SIZE set the limit for the number of entries returned ++TIME set the maximum waiting time for a query ++ ++The value of the DEREFERENCE parameter must be one of the words "never", ++"searching", "finding", or "always". The value of the REFERRALS parameter must ++be "follow" (the default) or "nofollow". The latter stops the LDAP library from ++trying to follow referrals issued by the LDAP server. ++ ++The name CONNECT is an obsolete name for NETTIME, retained for backwards ++compatibility. This timeout (specified as a number of seconds) is enforced from ++the client end for operations that can be carried out over a network. ++Specifically, it applies to network connections and calls to the ldap_result() ++function. If the value is greater than zero, it is used if ++LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or if ++LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape SDK 4.1). A ++value of zero forces an explicit setting of "no timeout" for Netscape SDK; for ++OpenLDAP no action is taken. ++ ++The TIME parameter (also a number of seconds) is passed to the server to set a ++server-side limit on the time taken to complete a search. ++ ++Here is an example of an LDAP query in an Exim lookup that uses some of these ++values. This is a single line, folded to fit on the page: ++ ++${lookup ldap ++ {user="cn=manager,o=University of Cambridge,c=UK" pass=secret ++ ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)} ++ {$value}fail} ++ ++The encoding of spaces as "%20" is a URL thing which should not be done for any ++of the auxiliary data. Exim configuration settings that include lookups which ++contain password information should be preceded by "hide" to prevent non-admin ++users from using the -bP option to see their values. ++ ++The auxiliary data items may be given in any order. The default is no ++connection timeout (the system timeout is used), no user or password, no limit ++on the number of entries returned, and no time limit on queries. ++ ++When a DN is quoted in the USER= setting for LDAP authentication, Exim removes ++any URL quoting that it may contain before passing it LDAP. Apparently some ++libraries do this for themselves, but some do not. Removing the URL quoting has ++two advantages: ++ ++ * It makes it possible to use the same quote_ldap_dn expansion for USER= DNs ++ as with DNs inside actual queries. ++ ++ * It permits spaces inside USER= DNs. ++ ++For example, a setting such as ++ ++USER=cn=${quote_ldap_dn:$1} ++ ++should work even if $1 contains spaces. ++ ++Expanded data for the PASS= value should be quoted using the quote expansion ++operator, rather than the LDAP quote operators. The only reason this field ++needs quoting is to ensure that it conforms to the Exim syntax, which does not ++allow unquoted spaces. For example: ++ ++PASS=${quote:$3} ++ ++The LDAP authentication mechanism can be used to check passwords as part of ++SMTP authentication. See the ldapauth expansion string condition in chapter 11. ++ ++ ++9.18 Format of data returned by LDAP ++------------------------------------ ++ ++The ldapdn lookup type returns the Distinguished Name from a single entry as a ++sequence of values, for example ++ ++cn=manager, o=University of Cambridge, c=UK ++ ++The ldap lookup type generates an error if more than one entry matches the ++search filter, whereas ldapm permits this case, and inserts a newline in the ++result between the data from different entries. It is possible for multiple ++values to be returned for both ldap and ldapm, but in the former case you know ++that whatever values are returned all came from a single entry in the ++directory. ++ ++In the common case where you specify a single attribute in your LDAP query, the ++result is not quoted, and does not contain the attribute name. If the attribute ++has multiple values, they are separated by commas. ++ ++If you specify multiple attributes, the result contains space-separated, quoted ++strings, each preceded by the attribute name and an equals sign. Within the ++quotes, the quote character, backslash, and newline are escaped with ++backslashes, and commas are used to separate multiple values for the attribute. ++Apart from the escaping, the string within quotes takes the same form as the ++output when a single attribute is requested. Specifying no attributes is the ++same as specifying all of an entry's attributes. ++ ++Here are some examples of the output format. The first line of each pair is an ++LDAP query, and the second is the data that is returned. The attribute called ++attr1 has two values, whereas attr2 has only one value: ++ ++ldap:///o=base?attr1?sub?(uid=fred) ++value1.1, value1.2 ++ ++ldap:///o=base?attr2?sub?(uid=fred) ++value two ++ ++ldap:///o=base?attr1,attr2?sub?(uid=fred) ++attr1="value1.1, value1.2" attr2="value two" ++ ++ldap:///o=base??sub?(uid=fred) ++objectClass="top" attr1="value1.1, value1.2" attr2="value two" ++ ++The extract operator in string expansions can be used to pick out individual ++fields from data that consists of key=value pairs. You can make use of Exim's ++-be option to run expansion tests and thereby check the results of LDAP ++lookups. ++ ++ ++9.19 More about NIS+ ++-------------------- ++ ++NIS+ queries consist of a NIS+ indexed name followed by an optional colon and ++field name. If this is given, the result of a successful query is the contents ++of the named field; otherwise the result consists of a concatenation of ++field-name=field-value pairs, separated by spaces. Empty values and values ++containing spaces are quoted. For example, the query ++ ++[name=mg1456],passwd.org_dir ++ ++might return the string ++ ++name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre" ++home=/home/mg1456 shell=/bin/bash shadow="" ++ ++(split over two lines here to fit on the page), whereas ++ ++[name=mg1456],passwd.org_dir:gcos ++ ++would just return ++ ++Martin Guerre ++ ++with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry ++for the given indexed key. The effect of the quote_nisplus expansion operator ++is to double any quote characters within the text. ++ ++ ++9.20 SQL lookups ++---------------- ++ ++Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite ++databases. Queries for these databases contain SQL statements, so an example ++might be ++ ++${lookup mysql{select mailbox from users where id='userx'}\ ++ {$value}fail} ++ ++If the result of the query contains more than one field, the data for each ++field in the row is returned, preceded by its name, so the result of ++ ++${lookup pgsql{select home,name from users where id='userx'}\ ++ {$value}} ++ ++might be ++ ++home=/home/userx name="Mister X" ++ ++Empty values and values containing spaces are double quoted, with embedded ++quotes escaped by a backslash. If the result of the query contains just one ++field, the value is passed back verbatim, without a field name, for example: ++ ++Mister X ++ ++If the result of the query yields more than one row, it is all concatenated, ++with a newline between the data for each row. ++ ++ ++9.21 More about MySQL, PostgreSQL, Oracle, and InterBase ++-------------------------------------------------------- ++ ++If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the ++mysql_servers, pgsql_servers, oracle_servers, or ibase_servers option (as ++appropriate) must be set to a colon-separated list of server information. (For ++MySQL and PostgreSQL only, the global option need not be set if all queries ++contain their own server information - see section 9.22.) Each item in the list ++is a slash-separated list of four items: host name, database name, user name, ++and password. In the case of Oracle, the host name field is used for the ++"service name", and the database name field is not used and should be empty. ++For example: ++ ++hide oracle_servers = oracle.plc.example//userx/abcdwxyz ++ ++Because password data is sensitive, you should always precede the setting with ++"hide", to prevent non-admin users from obtaining the setting via the -bP ++option. Here is an example where two MySQL servers are listed: ++ ++hide mysql_servers = localhost/users/root/secret:\ ++ otherhost/users/root/othersecret ++ ++For MySQL and PostgreSQL, a host may be specified as <name>:<port> but because ++this is a colon-separated list, the colon has to be doubled. For each query, ++these parameter groups are tried in order until a connection is made and a ++query is successfully processed. The result of a query may be that no data is ++found, but that is still a successful query. In other words, the list of ++servers provides a backup facility, not a list of different places to look. ++ ++The quote_mysql, quote_pgsql, and quote_oracle expansion operators convert ++newline, tab, carriage return, and backspace to \n, \t, \r, and \b ++respectively, and the characters single-quote, double-quote, and backslash ++itself are escaped with backslashes. The quote_pgsql expansion operator, in ++addition, escapes the percent and underscore characters. This cannot be done ++for MySQL because these escapes are not recognized in contexts where these ++characters are not special. ++ ++ ++9.22 Specifying the server in the query ++--------------------------------------- ++ ++For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase), ++it is possible to specify a list of servers with an individual query. This is ++done by starting the query with ++ ++servers=server1:server2:server3:...; ++ ++Each item in the list may take one of two forms: ++ ++ 1. If it contains no slashes it is assumed to be just a host name. The ++ appropriate global option (mysql_servers or pgsql_servers) is searched for ++ a host of the same name, and the remaining parameters (database, user, ++ password) are taken from there. ++ ++ 2. If it contains any slashes, it is taken as a complete parameter set. ++ ++The list of servers is used in exactly the same way as the global list. Once a ++connection to a server has happened and a query has been successfully executed, ++processing of the lookup ceases. ++ ++This feature is intended for use in master/slave situations where updates are ++occurring and you want to update the master rather than a slave. If the master ++is in the list as a backup for reading, you might have a global setting like ++this: ++ ++mysql_servers = slave1/db/name/pw:\ ++ slave2/db/name/pw:\ ++ master/db/name/pw ++ ++In an updating lookup, you could then write: ++ ++${lookup mysql{servers=master; UPDATE ...} } ++ ++That query would then be sent only to the master server. If, on the other hand, ++the master is not to be used for reading, and so is not present in the global ++option, you can still update it by a query of this form: ++ ++${lookup pgsql{servers=master/db/name/pw; UPDATE ...} } ++ ++ ++9.23 Special MySQL features ++--------------------------- ++ ++For MySQL, an empty host name or the use of "localhost" in mysql_servers causes ++a connection to the server on the local host by means of a Unix domain socket. ++An alternate socket can be specified in parentheses. The full syntax of each ++item in mysql_servers is: ++ ++<hostname>::<port>(<socket name>)/<database>/<user>/<password> ++ ++Any of the three sub-parts of the first field can be omitted. For normal use on ++the local host it can be left blank or set to just "localhost". ++ ++No database need be supplied - but if it is absent here, it must be given in ++the queries. ++ ++If a MySQL query is issued that does not request any data (an insert, update, ++or delete command), the result of the lookup is the number of rows affected. ++ ++Warning: This can be misleading. If an update does not actually change anything ++(for example, setting a field to the value it already has), the result is zero ++because no rows are affected. ++ ++ ++9.24 Special PostgreSQL features ++-------------------------------- ++ ++PostgreSQL lookups can also use Unix domain socket connections to the database. ++This is usually faster and costs less CPU time than a TCP/IP connection. ++However it can be used only if the mail server runs on the same machine as the ++database server. A configuration line for PostgreSQL via Unix domain sockets ++looks like this: ++ ++hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ... ++ ++In other words, instead of supplying a host name, a path to the socket is ++given. The path name is enclosed in parentheses so that its slashes aren't ++visually confused with the delimiters for the other server parameters. ++ ++If a PostgreSQL query is issued that does not request any data (an insert, ++update, or delete command), the result of the lookup is the number of rows ++affected. ++ ++ ++9.25 More about SQLite ++---------------------- ++ ++SQLite is different to the other SQL lookups because a file name is required in ++addition to the SQL query. An SQLite database is a single file, and there is no ++daemon as in the other SQL databases. The interface to Exim requires the name ++of the file, as an absolute path, to be given at the start of the query. It is ++separated from the query by white space. This means that the path name cannot ++contain white space. Here is a lookup expansion example: ++ ++${lookup sqlite {/some/thing/sqlitedb \ ++ select name from aliases where id='userx';}} ++ ++In a list, the syntax is similar. For example: ++ ++domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \ ++ select * from relays where ip='$sender_host_address'; ++ ++The only character affected by the quote_sqlite operator is a single quote, ++which it doubles. ++ ++The SQLite library handles multiple simultaneous accesses to the database ++internally. Multiple readers are permitted, but only one process can update at ++once. Attempts to access the database while it is being updated are rejected ++after a timeout period, during which the SQLite library waits for the lock to ++be released. In Exim, the default timeout is set to 5 seconds, but it can be ++changed by means of the sqlite_lock_timeout option. ++ ++ ++ ++=============================================================================== ++10. DOMAIN, HOST, ADDRESS, AND LOCAL PART LISTS ++ ++A number of Exim configuration options contain lists of domains, hosts, email ++addresses, or local parts. For example, the hold_domains option contains a list ++of domains whose delivery is currently suspended. These lists are also used as ++data in ACL statements (see chapter 42), and as arguments to expansion ++conditions such as match_domain. ++ ++Each item in one of these lists is a pattern to be matched against a domain, ++host, email address, or local part, respectively. In the sections below, the ++different types of pattern for each case are described, but first we cover some ++general facilities that apply to all four kinds of list. ++ ++ ++10.1 Expansion of lists ++----------------------- ++ ++Each list is expanded as a single string before it is used. The result of ++expansion must be a list, possibly containing empty items, which is split up ++into separate items for matching. By default, colon is the separator character, ++but this can be varied if necessary. See sections 6.19 and 6.21 for details of ++the list syntax; the second of these discusses the way to specify empty list ++items. ++ ++If the string expansion is forced to fail, Exim behaves as if the item it is ++testing (domain, host, address, or local part) is not in the list. Other ++expansion failures cause temporary errors. ++ ++If an item in a list is a regular expression, backslashes, dollars and possibly ++other special characters in the expression must be protected against ++misinterpretation by the string expander. The easiest way to do this is to use ++the "\N" expansion feature to indicate that the contents of the regular ++expression should not be expanded. For example, in an ACL you might have: ++ ++deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \ ++ ${lookup{$domain}lsearch{/badsenders/bydomain}} ++ ++The first item is a regular expression that is protected from expansion by "\ ++N", whereas the second uses the expansion to obtain a list of unwanted senders ++based on the receiving domain. ++ ++ ++10.2 Negated items in lists ++--------------------------- ++ ++Items in a list may be positive or negative. Negative items are indicated by a ++leading exclamation mark, which may be followed by optional white space. A list ++defines a set of items (domains, etc). When Exim processes one of these lists, ++it is trying to find out whether a domain, host, address, or local part ++(respectively) is in the set that is defined by the list. It works like this: ++ ++The list is scanned from left to right. If a positive item is matched, the ++subject that is being checked is in the set; if a negative item is matched, the ++subject is not in the set. If the end of the list is reached without the ++subject having matched any of the patterns, it is in the set if the last item ++was a negative one, but not if it was a positive one. For example, the list in ++ ++domainlist relay_to_domains = !a.b.c : *.b.c ++ ++matches any domain ending in .b.c except for a.b.c. Domains that match neither ++a.b.c nor *.b.c do not match, because the last item in the list is positive. ++However, if the setting were ++ ++domainlist relay_to_domains = !a.b.c ++ ++then all domains other than a.b.c would match because the last item in the list ++is negative. In other words, a list that ends with a negative item behaves as ++if it had an extra item ":*" on the end. ++ ++Another way of thinking about positive and negative items in lists is to read ++the connector as "or" after a positive item and as "and" after a negative item. ++ ++ ++10.3 File names in lists ++------------------------ ++ ++If an item in a domain, host, address, or local part list is an absolute file ++name (beginning with a slash character), each line of the file is read and ++processed as if it were an independent item in the list, except that further ++file names are not allowed, and no expansion of the data from the file takes ++place. Empty lines in the file are ignored, and the file may also contain ++comment lines: ++ ++ * For domain and host lists, if a # character appears anywhere in a line of ++ the file, it and all following characters are ignored. ++ ++ * Because local parts may legitimately contain # characters, a comment in an ++ address list or local part list file is recognized only if # is preceded by ++ white space or the start of the line. For example: ++ ++ not#comment@x.y.z # but this is a comment ++ ++Putting a file name in a list has the same effect as inserting each line of the ++file as an item in the list (blank lines and comments excepted). However, there ++is one important difference: the file is read each time the list is processed, ++so if its contents vary over time, Exim's behaviour changes. ++ ++If a file name is preceded by an exclamation mark, the sense of any match ++within the file is inverted. For example, if ++ ++hold_domains = !/etc/nohold-domains ++ ++and the file contains the lines ++ ++!a.b.c ++*.b.c ++ ++then a.b.c is in the set of domains defined by hold_domains, whereas any domain ++matching "*.b.c" is not. ++ ++ ++10.4 An lsearch file is not an out-of-line list ++----------------------------------------------- ++ ++As will be described in the sections that follow, lookups can be used in lists ++to provide indexed methods of checking list membership. There has been some ++confusion about the way lsearch lookups work in lists. Because an lsearch file ++contains plain text and is scanned sequentially, it is sometimes thought that ++it is allowed to contain wild cards and other kinds of non-constant pattern. ++This is not the case. The keys in an lsearch file are always fixed strings, ++just as for any other single-key lookup type. ++ ++If you want to use a file to contain wild-card patterns that form part of a ++list, just give the file name on its own, without a search type, as described ++in the previous section. You could also use the wildlsearch or nwildlsearch, ++but there is no advantage in doing this. ++ ++ ++10.5 Named lists ++---------------- ++ ++A list of domains, hosts, email addresses, or local parts can be given a name ++which is then used to refer to the list elsewhere in the configuration. This is ++particularly convenient if the same list is required in several different ++places. It also allows lists to be given meaningful names, which can improve ++the readability of the configuration. For example, it is conventional to define ++a domain list called local_domains for all the domains that are handled locally ++on a host, using a configuration line such as ++ ++domainlist local_domains = localhost:my.dom.example ++ ++Named lists are referenced by giving their name preceded by a plus sign, so, ++for example, a router that is intended to handle local domains would be ++configured with the line ++ ++domains = +local_domains ++ ++The first router in a configuration is often one that handles all domains ++except the local ones, using a configuration with a negated item like this: ++ ++dnslookup: ++ driver = dnslookup ++ domains = ! +local_domains ++ transport = remote_smtp ++ no_more ++ ++The four kinds of named list are created by configuration lines starting with ++the words domainlist, hostlist, addresslist, or localpartlist, respectively. ++Then there follows the name that you are defining, followed by an equals sign ++and the list itself. For example: ++ ++hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example ++addresslist bad_senders = cdb;/etc/badsenders ++ ++A named list may refer to other named lists: ++ ++domainlist dom1 = first.example : second.example ++domainlist dom2 = +dom1 : third.example ++domainlist dom3 = fourth.example : +dom2 : fifth.example ++ ++Warning: If the last item in a referenced list is a negative one, the effect ++may not be what you intended, because the negation does not propagate out to ++the higher level. For example, consider: ++ ++domainlist dom1 = !a.b ++domainlist dom2 = +dom1 : *.b ++ ++The second list specifies "either in the dom1 list or *.b". The first list ++specifies just "not a.b", so the domain x.y matches it. That means it matches ++the second list as well. The effect is not the same as ++ ++domainlist dom2 = !a.b : *.b ++ ++where x.y does not match. It's best to avoid negation altogether in referenced ++lists if you can. ++ ++Named lists may have a performance advantage. When Exim is routing an address ++or checking an incoming message, it caches the result of tests on named lists. ++So, if you have a setting such as ++ ++domains = +local_domains ++ ++on several of your routers or in several ACL statements, the actual test is ++done only for the first one. However, the caching works only if there are no ++expansions within the list itself or any sublists that it references. In other ++words, caching happens only for lists that are known to be the same each time ++they are referenced. ++ ++By default, there may be up to 16 named lists of each type. This limit can be ++extended by changing a compile-time variable. The use of domain and host lists ++is recommended for concepts such as local domains, relay domains, and relay ++hosts. The default configuration is set up like this. ++ ++ ++10.6 Named lists compared with macros ++------------------------------------- ++ ++At first sight, named lists might seem to be no different from macros in the ++configuration file. However, macros are just textual substitutions. If you ++write ++ ++ALIST = host1 : host2 ++auth_advertise_hosts = !ALIST ++ ++it probably won't do what you want, because that is exactly the same as ++ ++auth_advertise_hosts = !host1 : host2 ++ ++Notice that the second host name is not negated. However, if you use a host ++list, and write ++ ++hostlist alist = host1 : host2 ++auth_advertise_hosts = ! +alist ++ ++the negation applies to the whole list, and so that is equivalent to ++ ++auth_advertise_hosts = !host1 : !host2 ++ ++ ++10.7 Named list caching ++----------------------- ++ ++While processing a message, Exim caches the result of checking a named list if ++it is sure that the list is the same each time. In practice, this means that ++the cache operates only if the list contains no $ characters, which guarantees ++that it will not change when it is expanded. Sometimes, however, you may have ++an expanded list that you know will be the same each time within a given ++message. For example: ++ ++domainlist special_domains = \ ++ ${lookup{$sender_host_address}cdb{/some/file}} ++ ++This provides a list of domains that depends only on the sending host's IP ++address. If this domain list is referenced a number of times (for example, in ++several ACL lines, or in several routers) the result of the check is not cached ++by default, because Exim does not know that it is going to be the same list ++each time. ++ ++By appending "_cache" to "domainlist" you can tell Exim to go ahead and cache ++the result anyway. For example: ++ ++domainlist_cache special_domains = ${lookup{... ++ ++If you do this, you should be absolutely sure that caching is going to do the ++right thing in all cases. When in doubt, leave it out. ++ ++ ++10.8 Domain lists ++----------------- ++ ++Domain lists contain patterns that are to be matched against a mail domain. The ++following types of item may appear in domain lists: ++ ++ * If a pattern consists of a single @ character, it matches the local host ++ name, as set by the primary_hostname option (or defaulted). This makes it ++ possible to use the same configuration file on several different hosts that ++ differ only in their names. ++ ++ * If a pattern consists of the string "@[]" it matches an IP address enclosed ++ in square brackets (as in an email address that contains a domain literal), ++ but only if that IP address is recognized as local for email routing ++ purposes. The local_interfaces and extra_local_interfaces options can be ++ used to control which of a host's several IP addresses are treated as ++ local. In today's Internet, the use of domain literals is controversial. ++ ++ * If a pattern consists of the string "@mx_any" it matches any domain that ++ has an MX record pointing to the local host or to any host that is listed ++ in hosts_treat_as_local. The items "@mx_primary" and "@mx_secondary" are ++ similar, except that the first matches only when a primary MX target is the ++ local host, and the second only when no primary MX target is the local ++ host, but a secondary MX target is. "Primary" means an MX record with the ++ lowest preference value - there may of course be more than one of them. ++ ++ The MX lookup that takes place when matching a pattern of this type is ++ performed with the resolver options for widening names turned off. Thus, ++ for example, a single-component domain will not be expanded by adding the ++ resolver's default domain. See the qualify_single and search_parents ++ options of the dnslookup router for a discussion of domain widening. ++ ++ Sometimes you may want to ignore certain IP addresses when using one of ++ these patterns. You can specify this by following the pattern with "/ignore ++ ="<ip list>, where <ip list> is a list of IP addresses. These addresses are ++ ignored when processing the pattern (compare the ignore_target_hosts option ++ on a router). For example: ++ ++ domains = @mx_any/ignore=127.0.0.1 ++ ++ This example matches any domain that has an MX record pointing to one of ++ the local host's IP addresses other than 127.0.0.1. ++ ++ The list of IP addresses is in fact processed by the same code that ++ processes host lists, so it may contain CIDR-coded network specifications ++ and it may also contain negative items. ++ ++ Because the list of IP addresses is a sublist within a domain list, you ++ have to be careful about delimiters if there is more than one address. Like ++ any other list, the default delimiter can be changed. Thus, you might have: ++ ++ domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \ ++ an.other.domain : ... ++ ++ so that the sublist uses semicolons for delimiters. When IPv6 addresses are ++ involved, it is easiest to change the delimiter for the main list as well: ++ ++ domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \ ++ an.other.domain ? ... ++ ++ * If a pattern starts with an asterisk, the remaining characters of the ++ pattern are compared with the terminating characters of the domain. The use ++ of "*" in domain lists differs from its use in partial matching lookups. In ++ a domain list, the character following the asterisk need not be a dot, ++ whereas partial matching works only in terms of dot-separated components. ++ For example, a domain list item such as "*key.ex" matches donkey.ex as well ++ as cipher.key.ex. ++ ++ * If a pattern starts with a circumflex character, it is treated as a regular ++ expression, and matched against the domain using a regular expression ++ matching function. The circumflex is treated as part of the regular ++ expression. Email domains are case-independent, so this regular expression ++ match is by default case-independent, but you can make it case-dependent by ++ starting it with "(?-i)". References to descriptions of the syntax of ++ regular expressions are given in chapter 8. ++ ++ Warning: Because domain lists are expanded before being processed, you must ++ escape any backslash and dollar characters in the regular expression, or ++ use the special "\N" sequence (see chapter 11) to specify that it is not to ++ be expanded (unless you really do want to build a regular expression by ++ expansion, of course). ++ ++ * If a pattern starts with the name of a single-key lookup type followed by a ++ semicolon (for example, "dbm;" or "lsearch;"), the remainder of the pattern ++ must be a file name in a suitable format for the lookup type. For example, ++ for "cdb;" it must be an absolute path: ++ ++ domains = cdb;/etc/mail/local_domains.cdb ++ ++ The appropriate type of lookup is done on the file using the domain name as ++ the key. In most cases, the data that is looked up is not used; Exim is ++ interested only in whether or not the key is present in the file. However, ++ when a lookup is used for the domains option on a router or a domains ++ condition in an ACL statement, the data is preserved in the $domain_data ++ variable and can be referred to in other router options or other statements ++ in the same ACL. ++ ++ * Any of the single-key lookup type names may be preceded by "partial"<n>"-", ++ where the <n> is optional, for example, ++ ++ domains = partial-dbm;/partial/domains ++ ++ This causes partial matching logic to be invoked; a description of how this ++ works is given in section 9.7. ++ ++ * Any of the single-key lookup types may be followed by an asterisk. This ++ causes a default lookup for a key consisting of a single asterisk to be ++ done if the original lookup fails. This is not a useful feature when using ++ a domain list to select particular domains (because any domain would ++ match), but it might have value if the result of the lookup is being used ++ via the $domain_data expansion variable. ++ ++ * If the pattern starts with the name of a query-style lookup type followed ++ by a semicolon (for example, "nisplus;" or "ldap;"), the remainder of the ++ pattern must be an appropriate query for the lookup type, as described in ++ chapter 9. For example: ++ ++ hold_domains = mysql;select domain from holdlist \ ++ where domain = '${quote_mysql:$domain}'; ++ ++ In most cases, the data that is looked up is not used (so for an SQL query, ++ for example, it doesn't matter what field you select). Exim is interested ++ only in whether or not the query succeeds. However, when a lookup is used ++ for the domains option on a router, the data is preserved in the ++ $domain_data variable and can be referred to in other options. ++ ++ * If none of the above cases apply, a caseless textual comparison is made ++ between the pattern and the domain. ++ ++Here is an example that uses several different kinds of pattern: ++ ++domainlist funny_domains = \ ++ @ : \ ++ lib.unseen.edu : \ ++ *.foundation.fict.example : \ ++ \N^[1-2]\d{3}\.fict\.example$\N : \ ++ partial-dbm;/opt/data/penguin/book : \ ++ nis;domains.byname : \ ++ nisplus;[name=$domain,status=local],domains.org_dir ++ ++There are obvious processing trade-offs among the various matching modes. Using ++an asterisk is faster than a regular expression, and listing a few names ++explicitly probably is too. The use of a file or database lookup is expensive, ++but may be the only option if hundreds of names are required. Because the ++patterns are tested in order, it makes sense to put the most commonly matched ++patterns earlier. ++ ++ ++10.9 Host lists ++--------------- ++ ++Host lists are used to control what remote hosts are allowed to do. For ++example, some hosts may be allowed to use the local host as a relay, and some ++may be permitted to use the SMTP ETRN command. Hosts can be identified in two ++different ways, by name or by IP address. In a host list, some types of pattern ++are matched to a host name, and some are matched to an IP address. You need to ++be particularly careful with this when single-key lookups are involved, to ++ensure that the right value is being used as the key. ++ ++ ++10.10 Special host list patterns ++-------------------------------- ++ ++If a host list item is the empty string, it matches only when no remote host is ++involved. This is the case when a message is being received from a local ++process using SMTP on the standard input, that is, when a TCP/IP connection is ++not used. ++ ++The special pattern "*" in a host list matches any host or no host. Neither the ++IP address nor the name is actually inspected. ++ ++ ++10.11 Host list patterns that match by IP address ++------------------------------------------------- ++ ++If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket, ++the incoming address actually appears in the IPv6 host as "::ffff:"<v4address>. ++When such an address is tested against a host list, it is converted into a ++traditional IPv4 address first. (Not all operating systems accept IPv4 calls on ++IPv6 sockets, as there have been some security concerns.) ++ ++The following types of pattern in a host list check the remote host by ++inspecting its IP address: ++ ++ * If the pattern is a plain domain name (not a regular expression, not ++ starting with *, not a lookup of any kind), Exim calls the operating system ++ function to find the associated IP address(es). Exim uses the newer ++ getipnodebyname() function when available, otherwise gethostbyname(). This ++ typically causes a forward DNS lookup of the name. The result is compared ++ with the IP address of the subject host. ++ ++ If there is a temporary problem (such as a DNS timeout) with the host name ++ lookup, a temporary error occurs. For example, if the list is being used in ++ an ACL condition, the ACL gives a "defer" response, usually leading to a ++ temporary SMTP error code. If no IP address can be found for the host name, ++ what happens is described in section 10.14 below. ++ ++ * If the pattern is "@", the primary host name is substituted and used as a ++ domain name, as just described. ++ ++ * If the pattern is an IP address, it is matched against the IP address of ++ the subject host. IPv4 addresses are given in the normal "dotted-quad" ++ notation. IPv6 addresses can be given in colon-separated format, but the ++ colons have to be doubled so as not to be taken as item separators when the ++ default list separator is used. IPv6 addresses are recognized even when ++ Exim is compiled without IPv6 support. This means that if they appear in a ++ host list on an IPv4-only host, Exim will not treat them as host names. ++ They are just addresses that can never match a client host. ++ ++ * If the pattern is "@[]", it matches the IP address of any IP interface on ++ the local host. For example, if the local host is an IPv4 host with one ++ interface address 10.45.23.56, these two ACL statements have the same ++ effect: ++ ++ accept hosts = 127.0.0.1 : 10.45.23.56 ++ accept hosts = @[] ++ ++ * If the pattern is an IP address followed by a slash and a mask length (for ++ example 10.11.42.0/24), it is matched against the IP address of the subject ++ host under the given mask. This allows, an entire network of hosts to be ++ included (or excluded) by a single item. The mask uses CIDR notation; it ++ specifies the number of address bits that must match, starting from the ++ most significant end of the address. ++ ++ Note: The mask is not a count of addresses, nor is it the high number of a ++ range of addresses. It is the number of bits in the network portion of the ++ address. The above example specifies a 24-bit netmask, so it matches all ++ 256 addresses in the 10.11.42.0 network. An item such as ++ ++ 192.168.23.236/31 ++ ++ matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value ++ of 32 for an IPv4 address is the same as no mask at all; just a single ++ address matches. ++ ++ Here is another example which shows an IPv4 and an IPv6 network: ++ ++ recipient_unqualified_hosts = 192.168.0.0/16: \ ++ 3ffe::ffff::836f::::/48 ++ ++ The doubling of list separator characters applies only when these items ++ appear inline in a host list. It is not required when indirecting via a ++ file. For example: ++ ++ recipient_unqualified_hosts = /opt/exim/unqualnets ++ ++ could make use of a file containing ++ ++ 172.16.0.0/12 ++ 3ffe:ffff:836f::/48 ++ ++ to have exactly the same effect as the previous example. When listing IPv6 ++ addresses inline, it is usually more convenient to use the facility for ++ changing separator characters. This list contains the same two networks: ++ ++ recipient_unqualified_hosts = <; 172.16.0.0/12; \ ++ 3ffe:ffff:836f::/48 ++ ++ The separator is changed to semicolon by the leading "<;" at the start of ++ the list. ++ ++ ++10.12 Host list patterns for single-key lookups by host address ++--------------------------------------------------------------- ++ ++When a host is to be identified by a single-key lookup of its complete IP ++address, the pattern takes this form: ++ ++net-<single-key-search-type>;<search-data> ++ ++For example: ++ ++hosts_lookup = net-cdb;/hosts-by-ip.db ++ ++The text form of the IP address of the subject host is used as the lookup key. ++IPv6 addresses are converted to an unabbreviated form, using lower case ++letters, with dots as separators because colon is the key terminator in lsearch ++files. [Colons can in fact be used in keys in lsearch files by quoting the ++keys, but this is a facility that was added later.] The data returned by the ++lookup is not used. ++ ++Single-key lookups can also be performed using masked IP addresses, using ++patterns of this form: ++ ++net<number>-<single-key-search-type>;<search-data> ++ ++For example: ++ ++net24-dbm;/networks.db ++ ++The IP address of the subject host is masked using <number> as the mask length. ++A textual string is constructed from the masked value, followed by the mask, ++and this is used as the lookup key. For example, if the host's IP address is ++192.168.34.6, the key that is looked up for the above example is "192.168.34.0/ ++24". ++ ++When an IPv6 address is converted to a string, dots are normally used instead ++of colons, so that keys in lsearch files need not contain colons (which ++terminate lsearch keys). This was implemented some time before the ability to ++quote keys was made available in lsearch files. However, the more recently ++implemented iplsearch files do require colons in IPv6 keys (notated using the ++quoting facility) so as to distinguish them from IPv4 keys. For this reason, ++when the lookup type is iplsearch, IPv6 addresses are converted using colons ++and not dots. In all cases, full, unabbreviated IPv6 addresses are always used. ++ ++Ideally, it would be nice to tidy up this anomalous situation by changing to ++colons in all cases, given that quoting is now available for lsearch. However, ++this would be an incompatible change that might break some existing ++configurations. ++ ++Warning: Specifying net32- (for an IPv4 address) or net128- (for an IPv6 ++address) is not the same as specifying just net- without a number. In the ++former case the key strings include the mask value, whereas in the latter case ++the IP address is used on its own. ++ ++ ++10.13 Host list patterns that match by host name ++------------------------------------------------ ++ ++There are several types of pattern that require Exim to know the name of the ++remote host. These are either wildcard patterns or lookups by name. (If a ++complete hostname is given without any wildcarding, it is used to find an IP ++address to match against, as described in section 10.11 above.) ++ ++If the remote host name is not already known when Exim encounters one of these ++patterns, it has to be found from the IP address. Although many sites on the ++Internet are conscientious about maintaining reverse DNS data for their hosts, ++there are also many that do not do this. Consequently, a name cannot always be ++found, and this may lead to unwanted effects. Take care when configuring host ++lists with wildcarded name patterns. Consider what will happen if a name cannot ++be found. ++ ++Because of the problems of determining host names from IP addresses, matching ++against host names is not as common as matching against IP addresses. ++ ++By default, in order to find a host name, Exim first does a reverse DNS lookup; ++if no name is found in the DNS, the system function (gethostbyaddr() or ++getipnodebyaddr() if available) is tried. The order in which these lookups are ++done can be changed by setting the host_lookup_order option. For security, once ++Exim has found one or more names, it looks up the IP addresses for these names ++and compares them with the IP address that it started with. Only those names ++whose IP addresses match are accepted. Any other names are discarded. If no ++names are left, Exim behaves as if the host name cannot be found. In the most ++common case there is only one name and one IP address. ++ ++There are some options that control what happens if a host name cannot be ++found. These are described in section 10.14 below. ++ ++As a result of aliasing, hosts may have more than one name. When processing any ++of the following types of pattern, all the host's names are checked: ++ ++ * If a pattern starts with "*" the remainder of the item must match the end ++ of the host name. For example, "*.b.c" matches all hosts whose names end in ++ .b.c. This special simple form is provided because this is a very common ++ requirement. Other kinds of wildcarding require the use of a regular ++ expression. ++ ++ * If the item starts with "^" it is taken to be a regular expression which is ++ matched against the host name. Host names are case-independent, so this ++ regular expression match is by default case-independent, but you can make ++ it case-dependent by starting it with "(?-i)". References to descriptions ++ of the syntax of regular expressions are given in chapter 8. For example, ++ ++ ^(a|b)\.c\.d$ ++ ++ is a regular expression that matches either of the two hosts a.c.d or b.c.d ++ . When a regular expression is used in a host list, you must take care that ++ backslash and dollar characters are not misinterpreted as part of the ++ string expansion. The simplest way to do this is to use "\N" to mark that ++ part of the string as non-expandable. For example: ++ ++ sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : .... ++ ++ Warning: If you want to match a complete host name, you must include the ++ "$" terminating metacharacter in the regular expression, as in the above ++ example. Without it, a match at the start of the host name is all that is ++ required. ++ ++ ++10.14 Behaviour when an IP address or name cannot be found ++---------------------------------------------------------- ++ ++While processing a host list, Exim may need to look up an IP address from a ++name (see section 10.11), or it may need to look up a host name from an IP ++address (see section 10.13). In either case, the behaviour when it fails to ++find the information it is seeking is the same. ++ ++Note: This section applies to permanent lookup failures. It does not apply to ++temporary DNS errors, whose handling is described in the next section. ++ ++By default, Exim behaves as if the host does not match the list. This may not ++always be what you want to happen. To change Exim's behaviour, the special ++items "+include_unknown" or "+ignore_unknown" may appear in the list (at top ++level - they are not recognized in an indirected file). ++ ++ * If any item that follows "+include_unknown" requires information that ++ cannot found, Exim behaves as if the host does match the list. For example, ++ ++ host_reject_connection = +include_unknown:*.enemy.ex ++ ++ rejects connections from any host whose name matches "*.enemy.ex", and also ++ any hosts whose name it cannot find. ++ ++ * If any item that follows "+ignore_unknown" requires information that cannot ++ be found, Exim ignores that item and proceeds to the rest of the list. For ++ example: ++ ++ accept hosts = +ignore_unknown : friend.example : \ ++ 192.168.4.5 ++ ++ accepts from any host whose name is friend.example and from 192.168.4.5, ++ whether or not its host name can be found. Without "+ignore_unknown", if no ++ name can be found for 192.168.4.5, it is rejected. ++ ++Both "+include_unknown" and "+ignore_unknown" may appear in the same list. The ++effect of each one lasts until the next, or until the end of the list. ++ ++ ++10.15 Temporary DNS errors when looking up host information ++----------------------------------------------------------- ++ ++A temporary DNS lookup failure normally causes a defer action (except when ++dns_again_means_nonexist converts it into a permanent error). However, host ++lists can include "+ignore_defer" and "+include_defer", analagous to ++"+ignore_unknown" and "+include_unknown", as described in the previous section. ++These options should be used with care, probably only in non-critical host ++lists such as whitelists. ++ ++ ++10.16 Host list patterns for single-key lookups by host name ++------------------------------------------------------------ ++ ++If a pattern is of the form ++ ++<single-key-search-type>;<search-data> ++ ++for example ++ ++dbm;/host/accept/list ++ ++a single-key lookup is performed, using the host name as its key. If the lookup ++succeeds, the host matches the item. The actual data that is looked up is not ++used. ++ ++Reminder: With this kind of pattern, you must have host names as keys in the ++file, not IP addresses. If you want to do lookups based on IP addresses, you ++must precede the search type with "net-" (see section 10.12). There is, ++however, no reason why you could not use two items in the same list, one doing ++an address lookup and one doing a name lookup, both using the same file. ++ ++ ++10.17 Host list patterns for query-style lookups ++------------------------------------------------ ++ ++If a pattern is of the form ++ ++<query-style-search-type>;<query> ++ ++the query is obeyed, and if it succeeds, the host matches the item. The actual ++data that is looked up is not used. The variables $sender_host_address and ++$sender_host_name can be used in the query. For example: ++ ++hosts_lookup = pgsql;\ ++ select ip from hostlist where ip='$sender_host_address' ++ ++The value of $sender_host_address for an IPv6 address contains colons. You can ++use the sg expansion item to change this if you need to. If you want to use ++masked IP addresses in database queries, you can use the mask expansion ++operator. ++ ++If the query contains a reference to $sender_host_name, Exim automatically ++looks up the host name if it has not already done so. (See section 10.13 for ++comments on finding host names.) ++ ++Historical note: prior to release 4.30, Exim would always attempt to find a ++host name before running the query, unless the search type was preceded by ++"net-". This is no longer the case. For backwards compatibility, "net-" is ++still recognized for query-style lookups, but its presence or absence has no ++effect. (Of course, for single-key lookups, "net-" is important. See section ++10.12.) ++ ++ ++10.18 Mixing wildcarded host names and addresses in host lists ++-------------------------------------------------------------- ++ ++If you have name lookups or wildcarded host names and IP addresses in the same ++host list, you should normally put the IP addresses first. For example, in an ++ACL you could have: ++ ++accept hosts = 10.9.8.7 : *.friend.example ++ ++The reason for this lies in the left-to-right way that Exim processes lists. It ++can test IP addresses without doing any DNS lookups, but when it reaches an ++item that requires a host name, it fails if it cannot find a host name to ++compare with the pattern. If the above list is given in the opposite order, the ++accept statement fails for a host whose name cannot be found, even if its IP ++address is 10.9.8.7. ++ ++If you really do want to do the name check first, and still recognize the IP ++address, you can rewrite the ACL like this: ++ ++accept hosts = *.friend.example ++accept hosts = 10.9.8.7 ++ ++If the first accept fails, Exim goes on to try the second one. See chapter 42 ++for details of ACLs. ++ ++ ++10.19 Address lists ++------------------- ++ ++Address lists contain patterns that are matched against mail addresses. There ++is one special case to be considered: the sender address of a bounce message is ++always empty. You can test for this by providing an empty item in an address ++list. For example, you can set up a router to process bounce messages by using ++this option setting: ++ ++senders = : ++ ++The presence of the colon creates an empty item. If you do not provide any ++data, the list is empty and matches nothing. The empty sender can also be ++detected by a regular expression that matches an empty string, and by a ++query-style lookup that succeeds when $sender_address is empty. ++ ++Non-empty items in an address list can be straightforward email addresses. For ++example: ++ ++senders = jbc@askone.example : hs@anacreon.example ++ ++A certain amount of wildcarding is permitted. If a pattern contains an @ ++character, but is not a regular expression and does not begin with a ++semicolon-terminated lookup type (described below), the local part of the ++subject address is compared with the local part of the pattern, which may start ++with an asterisk. If the local parts match, the domain is checked in exactly ++the same way as for a pattern in a domain list. For example, the domain can be ++wildcarded, refer to a named list, or be a lookup: ++ ++deny senders = *@*.spamming.site:\ ++ *@+hostile_domains:\ ++ bozo@partial-lsearch;/list/of/dodgy/sites:\ ++ *@dbm;/bad/domains.db ++ ++If a local part that begins with an exclamation mark is required, it has to be ++specified using a regular expression, because otherwise the exclamation mark is ++treated as a sign of negation, as is standard in lists. ++ ++If a non-empty pattern that is not a regular expression or a lookup does not ++contain an @ character, it is matched against the domain part of the subject ++address. The only two formats that are recognized this way are a literal ++domain, or a domain pattern that starts with *. In both these cases, the effect ++is the same as if "*@" preceded the pattern. For example: ++ ++deny senders = enemy.domain : *.enemy.domain ++ ++The following kinds of more complicated address list pattern can match any ++address, including the empty address that is characteristic of bounce message ++senders: ++ ++ * If (after expansion) a pattern starts with "^", a regular expression match ++ is done against the complete address, with the pattern as the regular ++ expression. You must take care that backslash and dollar characters are not ++ misinterpreted as part of the string expansion. The simplest way to do this ++ is to use "\N" to mark that part of the string as non-expandable. For ++ example: ++ ++ deny senders = \N^.*this.*@example\.com$\N : \ ++ \N^\d{8}.+@spamhaus.example$\N : ... ++ ++ The "\N" sequences are removed by the expansion, so these items do indeed ++ start with "^" by the time they are being interpreted as address patterns. ++ ++ * Complete addresses can be looked up by using a pattern that starts with a ++ lookup type terminated by a semicolon, followed by the data for the lookup. ++ For example: ++ ++ deny senders = cdb;/etc/blocked.senders : \ ++ mysql;select address from blocked where \ ++ address='${quote_mysql:$sender_address}' ++ ++ Both query-style and single-key lookup types can be used. For a single-key ++ lookup type, Exim uses the complete address as the key. However, empty keys ++ are not supported for single-key lookups, so a match against the empty ++ address always fails. This restriction does not apply to query-style ++ lookups. ++ ++ Partial matching for single-key lookups (section 9.7) cannot be used, and ++ is ignored if specified, with an entry being written to the panic log. ++ However, you can configure lookup defaults, as described in section 9.6, ++ but this is useful only for the "*@" type of default. For example, with ++ this lookup: ++ ++ accept senders = lsearch*@;/some/file ++ ++ the file could contains lines like this: ++ ++ user1@domain1.example ++ *@domain2.example ++ ++ and for the sender address nimrod@jaeger.example, the sequence of keys that ++ are tried is: ++ ++ nimrod@jaeger.example ++ *@jaeger.example ++ * ++ ++ Warning 1: Do not include a line keyed by "*" in the file, because that ++ would mean that every address matches, thus rendering the test useless. ++ ++ Warning 2: Do not confuse these two kinds of item: ++ ++ deny recipients = dbm*@;/some/file ++ deny recipients = *@dbm;/some/file ++ ++ The first does a whole address lookup, with defaulting, as just described, ++ because it starts with a lookup type. The second matches the local part and ++ domain independently, as described in a bullet point below. ++ ++The following kinds of address list pattern can match only non-empty addresses. ++If the subject address is empty, a match against any of these pattern types ++always fails. ++ ++ * If a pattern starts with "@@" followed by a single-key lookup item (for ++ example, "@@lsearch;/some/file"), the address that is being checked is ++ split into a local part and a domain. The domain is looked up in the file. ++ If it is not found, there is no match. If it is found, the data that is ++ looked up from the file is treated as a colon-separated list of local part ++ patterns, each of which is matched against the subject local part in turn. ++ ++ The lookup may be a partial one, and/or one involving a search for a ++ default keyed by "*" (see section 9.6). The local part patterns that are ++ looked up can be regular expressions or begin with "*", or even be further ++ lookups. They may also be independently negated. For example, with ++ ++ deny senders = @@dbm;/etc/reject-by-domain ++ ++ the data from which the DBM file is built could contain lines like ++ ++ baddomain.com: !postmaster : * ++ ++ to reject all senders except postmaster from that domain. ++ ++ If a local part that actually begins with an exclamation mark is required, ++ it has to be specified using a regular expression. In lsearch files, an ++ entry may be split over several lines by indenting the second and ++ subsequent lines, but the separating colon must still be included at line ++ breaks. White space surrounding the colons is ignored. For example: ++ ++ aol.com: spammer1 : spammer2 : ^[0-9]+$ : ++ spammer3 : spammer4 ++ ++ As in all colon-separated lists in Exim, a colon can be included in an item ++ by doubling. ++ ++ If the last item in the list starts with a right angle-bracket, the ++ remainder of the item is taken as a new key to look up in order to obtain a ++ continuation list of local parts. The new key can be any sequence of ++ characters. Thus one might have entries like ++ ++ aol.com: spammer1 : spammer 2 : >* ++ xyz.com: spammer3 : >* ++ *: ^\d{8}$ ++ ++ in a file that was searched with @@dbm*, to specify a match for 8-digit ++ local parts for all domains, in addition to the specific local parts listed ++ for each domain. Of course, using this feature costs another lookup each ++ time a chain is followed, but the effort needed to maintain the data is ++ reduced. ++ ++ It is possible to construct loops using this facility, and in order to ++ catch them, the chains may be no more than fifty items long. ++ ++ * The @@<lookup> style of item can also be used with a query-style lookup, ++ but in this case, the chaining facility is not available. The lookup can ++ only return a single list of local parts. ++ ++Warning: There is an important difference between the address list items in ++these two examples: ++ ++senders = +my_list ++senders = *@+my_list ++ ++In the first one, "my_list" is a named address list, whereas in the second ++example it is a named domain list. ++ ++ ++10.20 Case of letters in address lists ++-------------------------------------- ++ ++Domains in email addresses are always handled caselessly, but for local parts ++case may be significant on some systems (see caseful_local_part for how Exim ++deals with this when routing addresses). However, RFC 2505 (Anti-Spam ++Recommendations for SMTP MTAs) suggests that matching of addresses to blocking ++lists should be done in a case-independent manner. Since most address lists in ++Exim are used for this kind of control, Exim attempts to do this by default. ++ ++The domain portion of an address is always lowercased before matching it to an ++address list. The local part is lowercased by default, and any string ++comparisons that take place are done caselessly. This means that the data in ++the address list itself, in files included as plain file names, and in any file ++that is looked up using the "@@" mechanism, can be in any case. However, the ++keys in files that are looked up by a search type other than lsearch (which ++works caselessly) must be in lower case, because these lookups are not ++case-independent. ++ ++To allow for the possibility of caseful address list matching, if an item in an ++address list is the string "+caseful", the original case of the local part is ++restored for any comparisons that follow, and string comparisons are no longer ++case-independent. This does not affect the domain, which remains in lower case. ++However, although independent matches on the domain alone are still performed ++caselessly, regular expressions that match against an entire address become ++case-sensitive after "+caseful" has been seen. ++ ++ ++10.21 Local part lists ++---------------------- ++ ++Case-sensitivity in local part lists is handled in the same way as for address ++lists, as just described. The "+caseful" item can be used if required. In a ++setting of the local_parts option in a router with caseful_local_part set ++false, the subject is lowercased and the matching is initially ++case-insensitive. In this case, "+caseful" will restore case-sensitive matching ++in the local part list, but not elsewhere in the router. If caseful_local_part ++is set true in a router, matching in the local_parts option is case-sensitive ++from the start. ++ ++If a local part list is indirected to a file (see section 10.3), comments are ++handled in the same way as address lists - they are recognized only if the # is ++preceded by white space or the start of the line. Otherwise, local part lists ++are matched in the same way as domain lists, except that the special items that ++refer to the local host ("@", "@[]", "@mx_any", "@mx_primary", and ++"@mx_secondary") are not recognized. Refer to section 10.8 for details of the ++other available item types. ++ ++ ++ ++=============================================================================== ++11. STRING EXPANSIONS ++ ++Many strings in Exim's run time configuration are expanded before use. Some of ++them are expanded every time they are used; others are expanded only once. ++ ++When a string is being expanded it is copied verbatim from left to right except ++when a dollar or backslash character is encountered. A dollar specifies the ++start of a portion of the string that is interpreted and replaced as described ++below in section 11.5 onwards. Backslash is used as an escape character, as ++described in the following section. ++ ++Whether a string is expanded depends upon the context. Usually this is solely ++dependent upon the option for which a value is sought; in this documentation, ++options for which string expansion is performed are marked with * after the ++data type. ACL rules always expand strings. A couple of expansion conditions do ++not expand some of the brace-delimited branches, for security reasons. ++ ++ ++11.1 Literal text in expanded strings ++------------------------------------- ++ ++An uninterpreted dollar can be included in an expanded string by putting a ++backslash in front of it. A backslash can be used to prevent any special ++character being treated specially in an expansion, including backslash itself. ++If the string appears in quotes in the configuration file, two backslashes are ++required because the quotes themselves cause interpretation of backslashes when ++the string is read in (see section 6.16). ++ ++A portion of the string can specified as non-expandable by placing it between ++two occurrences of "\N". This is particularly useful for protecting regular ++expressions, which often contain backslashes and dollar signs. For example: ++ ++deny senders = \N^\d{8}[a-z]@some\.site\.example$\N ++ ++On encountering the first "\N", the expander copies subsequent characters ++without interpretation until it reaches the next "\N" or the end of the string. ++ ++ ++11.2 Character escape sequences in expanded strings ++--------------------------------------------------- ++ ++A backslash followed by one of the letters "n", "r", or "t" in an expanded ++string is recognized as an escape sequence for the character newline, carriage ++return, or tab, respectively. A backslash followed by up to three octal digits ++is recognized as an octal encoding for a single character, and a backslash ++followed by "x" and up to two hexadecimal digits is a hexadecimal encoding. ++ ++These escape sequences are also recognized in quoted strings when they are read ++in. Their interpretation in expansions as well is useful for unquoted strings, ++and for other cases such as looked-up strings that are then expanded. ++ ++ ++11.3 Testing string expansions ++------------------------------ ++ ++Many expansions can be tested by calling Exim with the -be option. This takes ++the command arguments, or lines from the standard input if there are no ++arguments, runs them through the string expansion code, and writes the results ++to the standard output. Variables based on configuration values are set up, but ++since no message is being processed, variables such as $local_part have no ++value. Nevertheless the -be option can be useful for checking out file and ++database lookups, and the use of expansion operators such as sg, substr and ++nhash. ++ ++Exim gives up its root privilege when it is called with the -be option, and ++instead runs under the uid and gid it was called with, to prevent users from ++using -be for reading files to which they do not have access. ++ ++If you want to test expansions that include variables whose values are taken ++from a message, there are two other options that can be used. The -bem option ++is like -be except that it is followed by a file name. The file is read as a ++message before doing the test expansions. For example: ++ ++exim -bem /tmp/test.message '$h_subject:' ++ ++The -Mset option is used in conjunction with -be and is followed by an Exim ++message identifier. For example: ++ ++exim -be -Mset 1GrA8W-0004WS-LQ '$recipients' ++ ++This loads the message from Exim's spool before doing the test expansions, and ++is therefore restricted to admin users. ++ ++ ++11.4 Forced expansion failure ++----------------------------- ++ ++A number of expansions that are described in the following section have ++alternative "true" and "false" substrings, enclosed in brace characters (which ++are sometimes called "curly brackets"). Which of the two strings is used ++depends on some condition that is evaluated as part of the expansion. If, ++instead of a "false" substring, the word "fail" is used (not in braces), the ++entire string expansion fails in a way that can be detected by the code that ++requested the expansion. This is called "forced expansion failure", and its ++consequences depend on the circumstances. In some cases it is no different from ++any other expansion failure, but in others a different action may be taken. ++Such variations are mentioned in the documentation of the option that is being ++expanded. ++ ++ ++11.5 Expansion items ++-------------------- ++ ++The following items are recognized in expanded strings. White space may be used ++between sub-items that are keywords or substrings enclosed in braces inside an ++outer set of braces, to improve readability. Warning: Within braces, white ++space is significant. ++ ++$<variable name> or ${<variable name>} ++ ++ Substitute the contents of the named variable, for example: ++ ++ $local_part ++ ${domain} ++ ++ The second form can be used to separate the name from subsequent ++ alphanumeric characters. This form (using braces) is available only for ++ variables; it does not apply to message headers. The names of the variables ++ are given in section 11.9 below. If the name of a non-existent variable is ++ given, the expansion fails. ++ ++${<op>:<string>} ++ ++ The string is first itself expanded, and then the operation specified by < ++ op> is applied to it. For example: ++ ++ ${lc:$local_part} ++ ++ The string starts with the first character after the colon, which may be ++ leading white space. A list of operators is given in section 11.6 below. ++ The operator notation is used for simple expansion items that have just one ++ argument, because it reduces the number of braces and therefore makes the ++ string easier to understand. ++ ++$bheader_<header name>: or $bh_<header name>: ++ ++ This item inserts "basic" header lines. It is described with the header ++ expansion item below. ++ ++${acl{<name>}{<arg>}...} ++ ++ The name and zero to nine argument strings are first expanded separately. ++ The expanded arguments are assigned to the variables $acl_arg1 to $acl_arg9 ++ in order. Any unused are made empty. The variable $acl_narg is set to the ++ number of arguments. The named ACL (see chapter 42) is called and may use ++ the variables; if another acl expansion is used the values are restored ++ after it returns. If the ACL sets a value using a "message =" modifier and ++ returns accept or deny, the value becomes the result of the expansion. If ++ no message is set and the ACL returns accept or deny the expansion result ++ is an empty string. If the ACL returns defer the result is a forced-fail. ++ Otherwise the expansion fails. ++ ++${dlfunc{<file>}{<function>}{<arg>}{<arg>}...} ++ ++ This expansion dynamically loads and then calls a locally-written C ++ function. This functionality is available only if Exim is compiled with ++ ++ EXPAND_DLFUNC=yes ++ ++ set in Local/Makefile. Once loaded, Exim remembers the dynamically loaded ++ object so that it doesn't reload the same object file in the same Exim ++ process (but of course Exim does start new processes frequently). ++ ++ There may be from zero to eight arguments to the function. When compiling a ++ local function that is to be called in this way, local_scan.h should be ++ included. The Exim variables and functions that are defined by that API are ++ also available for dynamically loaded functions. The function itself must ++ have the following type: ++ ++ int dlfunction(uschar **yield, int argc, uschar *argv[]) ++ ++ Where "uschar" is a typedef for "unsigned char" in local_scan.h. The ++ function should return one of the following values: ++ ++ "OK": Success. The string that is placed in the variable yield is put into ++ the expanded string that is being built. ++ ++ "FAIL": A non-forced expansion failure occurs, with the error message taken ++ from yield, if it is set. ++ ++ "FAIL_FORCED": A forced expansion failure occurs, with the error message ++ taken from yield if it is set. ++ ++ "ERROR": Same as "FAIL", except that a panic log entry is written. ++ ++ When compiling a function that is to be used in this way with gcc, you need ++ to add -shared to the gcc command. Also, in the Exim build-time ++ configuration, you must add -export-dynamic to EXTRALIBS. ++ ++${extract{<key>}{<string1>}{<string2>}{<string3>}} ++ ++ The key and <string1> are first expanded separately. Leading and trailing ++ white space is removed from the key (but not from any of the strings). The ++ key must not consist entirely of digits. The expanded <string1> must be of ++ the form: ++ ++ <key1> = <value1> <key2> = <value2> ... ++ ++ where the equals signs and spaces (but not both) are optional. If any of ++ the values contain white space, they must be enclosed in double quotes, and ++ any values that are enclosed in double quotes are subject to escape ++ processing as described in section 6.16. The expanded <string1> is searched ++ for the value that corresponds to the key. The search is case-insensitive. ++ If the key is found, <string2> is expanded, and replaces the whole item; ++ otherwise <string3> is used. During the expansion of <string2> the variable ++ $value contains the value that has been extracted. Afterwards, it is ++ restored to any previous value it might have had. ++ ++ If {<string3>} is omitted, the item is replaced by an empty string if the ++ key is not found. If {<string2>} is also omitted, the value that was ++ extracted is used. Thus, for example, these two expansions are identical, ++ and yield "2001": ++ ++ ${extract{gid}{uid=1984 gid=2001}} ++ ${extract{gid}{uid=1984 gid=2001}{$value}} ++ ++ Instead of {<string3>} the word "fail" (not in curly brackets) can appear, ++ for example: ++ ++ ${extract{Z}{A=... B=...}{$value} fail } ++ ++ This forces an expansion failure (see section 11.4); {<string2>} must be ++ present for "fail" to be recognized. ++ ++${extract{<number>}{<separators>}{<string1>}{<string2>}{<string3>}} ++ ++ The <number> argument must consist entirely of decimal digits, apart from ++ leading and trailing white space, which is ignored. This is what ++ distinguishes this form of extract from the previous kind. It behaves in ++ the same way, except that, instead of extracting a named field, it extracts ++ from <string1> the field whose number is given as the first argument. You ++ can use $value in <string2> or "fail" instead of <string3> as before. ++ ++ The fields in the string are separated by any one of the characters in the ++ separator string. These may include space or tab characters. The first ++ field is numbered one. If the number is negative, the fields are counted ++ from the end of the string, with the rightmost one numbered -1. If the ++ number given is zero, the entire string is returned. If the modulus of the ++ number is greater than the number of fields in the string, the result is ++ the expansion of <string3>, or the empty string if <string3> is not ++ provided. For example: ++ ++ ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}} ++ ++ yields "42", and ++ ++ ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}} ++ ++ yields "99". Two successive separators mean that the field between them is ++ empty (for example, the fifth field above). ++ ++${filter{<string>}{<condition>}} ++ ++ After expansion, <string> is interpreted as a list, colon-separated by ++ default, but the separator can be changed in the usual way. For each item ++ in this list, its value is place in $item, and then the condition is ++ evaluated. If the condition is true, $item is added to the output as an ++ item in a new list; if the condition is false, the item is discarded. The ++ separator used for the output list is the same as the one used for the ++ input, but a separator setting is not included in the output. For example: ++ ++ ${filter{a:b:c}{!eq{$item}{b}} ++ ++ yields "a:c". At the end of the expansion, the value of $item is restored ++ to what it was before. See also the map and reduce expansion items. ++ ++${hash{<string1>}{<string2>}{<string3>}} ++ ++ This is a textual hashing function, and was the first to be implemented in ++ early versions of Exim. In current releases, there are other hashing ++ functions (numeric, MD5, and SHA-1), which are described below. ++ ++ The first two strings, after expansion, must be numbers. Call them <m> and ++ <n>. If you are using fixed values for these numbers, that is, if <string1> ++ and <string2> do not change when they are expanded, you can use the simpler ++ operator notation that avoids some of the braces: ++ ++ ${hash_<n>_<m>:<string>} ++ ++ The second number is optional (in both notations). If <n> is greater than ++ or equal to the length of the string, the expansion item returns the ++ string. Otherwise it computes a new string of length <n> by applying a ++ hashing function to the string. The new string consists of characters taken ++ from the first <m> characters of the string ++ ++ abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789 ++ ++ If <m> is not present the value 26 is used, so that only lower case letters ++ appear. For example: ++ ++ $hash{3}{monty}} yields jmg ++ $hash{5}{monty}} yields monty ++ $hash{4}{62}{monty python}} yields fbWx ++ ++$header_<header name>: or $h_<header name>:, $bheader_<header name>: or $bh_< ++ header name>:, $rheader_<header name>: or $rh_<header name>: ++ ++ Substitute the contents of the named message header line, for example ++ ++ $header_reply-to: ++ ++ The newline that terminates a header line is not included in the expansion, ++ but internal newlines (caused by splitting the header line over several ++ physical lines) may be present. ++ ++ The difference between rheader, bheader, and header is in the way the data ++ in the header line is interpreted. ++ ++ + rheader gives the original "raw" content of the header line, with no ++ processing at all, and without the removal of leading and trailing ++ white space. ++ ++ + bheader removes leading and trailing white space, and then decodes ++ base64 or quoted-printable MIME "words" within the header text, but ++ does no character set translation. If decoding of what looks ++ superficially like a MIME "word" fails, the raw string is returned. If ++ decoding produces a binary zero character, it is replaced by a question ++ mark - this is what Exim does for binary zeros that are actually ++ received in header lines. ++ ++ + header tries to translate the string as decoded by bheader to a ++ standard character set. This is an attempt to produce the same string ++ as would be displayed on a user's MUA. If translation fails, the ++ bheader string is returned. Translation is attempted only on operating ++ systems that support the iconv() function. This is indicated by the ++ compile-time macro HAVE_ICONV in a system Makefile or in Local/Makefile ++ . ++ ++ In a filter file, the target character set for header can be specified by a ++ command of the following form: ++ ++ headers charset "UTF-8" ++ ++ This command affects all references to $h_ (or $header_) expansions in ++ subsequently obeyed filter commands. In the absence of this command, the ++ target character set in a filter is taken from the setting of the ++ headers_charset option in the runtime configuration. The value of this ++ option defaults to the value of HEADERS_CHARSET in Local/Makefile. The ++ ultimate default is ISO-8859-1. ++ ++ Header names follow the syntax of RFC 2822, which states that they may ++ contain any printing characters except space and colon. Consequently, curly ++ brackets do not terminate header names, and should not be used to enclose ++ them as if they were variables. Attempting to do so causes a syntax error. ++ ++ Only header lines that are common to all copies of a message are visible to ++ this mechanism. These are the original header lines that are received with ++ the message, and any that are added by an ACL statement or by a system ++ filter. Header lines that are added to a particular copy of a message by a ++ router or transport are not accessible. ++ ++ For incoming SMTP messages, no header lines are visible in ACLs that are ++ obeyed before the DATA ACL, because the header structure is not set up ++ until the message is received. Header lines that are added in a RCPT ACL ++ (for example) are saved until the message's incoming header lines are ++ available, at which point they are added. When a DATA ACL is running, ++ however, header lines added by earlier ACLs are visible. ++ ++ Upper case and lower case letters are synonymous in header names. If the ++ following character is white space, the terminating colon may be omitted, ++ but this is not recommended, because you may then forget it when it is ++ needed. When white space terminates the header name, it is included in the ++ expanded string. If the message does not contain the given header, the ++ expansion item is replaced by an empty string. (See the def condition in ++ section 11.7 for a means of testing for the existence of a header.) ++ ++ If there is more than one header with the same name, they are all ++ concatenated to form the substitution string, up to a maximum length of ++ 64K. Unless rheader is being used, leading and trailing white space is ++ removed from each header before concatenation, and a completely empty ++ header is ignored. A newline character is then inserted between non-empty ++ headers, but there is no newline at the very end. For the header and ++ bheader expansion, for those headers that contain lists of addresses, a ++ comma is also inserted at the junctions between headers. This does not ++ happen for the rheader expansion. ++ ++${hmac{<hashname>}{<secret>}{<string>}} ++ ++ This function uses cryptographic hashing (either MD5 or SHA-1) to convert a ++ shared secret and some text into a message authentication code, as ++ specified in RFC 2104. This differs from "${md5:secret_text...}" or "$ ++ {sha1:secret_text...}" in that the hmac step adds a signature to the ++ cryptographic hash, allowing for authentication that is not possible with ++ MD5 or SHA-1 alone. The hash name must expand to either "md5" or "sha1" at ++ present. For example: ++ ++ ${hmac{md5}{somesecret}{$primary_hostname $tod_log}} ++ ++ For the hostname mail.example.com and time 2002-10-17 11:30:59, this ++ produces: ++ ++ dd97e3ba5d1a61b5006108f8c8252953 ++ ++ As an example of how this might be used, you might put in the main part of ++ an Exim configuration: ++ ++ SPAMSCAN_SECRET=cohgheeLei2thahw ++ ++ In a router or a transport you could then have: ++ ++ headers_add = \ ++ X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \ ++ ${hmac{md5}{SPAMSCAN_SECRET}\ ++ {${primary_hostname},${message_exim_id},$h_message-id:}} ++ ++ Then given a message, you can check where it was scanned by looking at the ++ X-Spam-Scanned: header line. If you know the secret, you can check that ++ this header line is authentic by recomputing the authentication code from ++ the host name, message ID and the Message-id: header line. This can be done ++ using Exim's -be option, or by other means, for example by using the ++ hmac_md5_hex() function in Perl. ++ ++${if <condition> {<string1>}{<string2>}} ++ ++ If <condition> is true, <string1> is expanded and replaces the whole item; ++ otherwise <string2> is used. The available conditions are described in ++ section 11.7 below. For example: ++ ++ ${if eq {$local_part}{postmaster} {yes}{no} } ++ ++ The second string need not be present; if it is not and the condition is ++ not true, the item is replaced with nothing. Alternatively, the word "fail" ++ may be present instead of the second string (without any curly brackets). ++ In this case, the expansion is forced to fail if the condition is not true ++ (see section 11.4). ++ ++ If both strings are omitted, the result is the string "true" if the ++ condition is true, and the empty string if the condition is false. This ++ makes it less cumbersome to write custom ACL and router conditions. For ++ example, instead of ++ ++ condition = ${if >{$acl_m4}{3}{true}{false}} ++ ++ you can use ++ ++ condition = ${if >{$acl_m4}{3}} ++ ++${length{<string1>}{<string2>}} ++ ++ The length item is used to extract the initial portion of a string. Both ++ strings are expanded, and the first one must yield a number, <n>, say. If ++ you are using a fixed value for the number, that is, if <string1> does not ++ change when expanded, you can use the simpler operator notation that avoids ++ some of the braces: ++ ++ ${length_<n>:<string>} ++ ++ The result of this item is either the first <n> characters or the whole of ++ <string2>, whichever is the shorter. Do not confuse length with strlen, ++ which gives the length of a string. ++ ++${lookup{<key>} <search type> {<file>} {<string1>} {<string2>}} ++ ++ This is the first of one of two different types of lookup item, which are ++ both described in the next item. ++ ++${lookup <search type> {<query>} {<string1>} {<string2>}} ++ ++ The two forms of lookup item specify data lookups in files and databases, ++ as discussed in chapter 9. The first form is used for single-key lookups, ++ and the second is used for query-style lookups. The <key>, <file>, and < ++ query> strings are expanded before use. ++ ++ If there is any white space in a lookup item which is part of a filter ++ command, a retry or rewrite rule, a routing rule for the manualroute ++ router, or any other place where white space is significant, the lookup ++ item must be enclosed in double quotes. The use of data lookups in users' ++ filter files may be locked out by the system administrator. ++ ++ If the lookup succeeds, <string1> is expanded and replaces the entire item. ++ During its expansion, the variable $value contains the data returned by the ++ lookup. Afterwards it reverts to the value it had previously (at the outer ++ level it is empty). If the lookup fails, <string2> is expanded and replaces ++ the entire item. If {<string2>} is omitted, the replacement is the empty ++ string on failure. If <string2> is provided, it can itself be a nested ++ lookup, thus providing a mechanism for looking up a default value when the ++ original lookup fails. ++ ++ If a nested lookup is used as part of <string1>, $value contains the data ++ for the outer lookup while the parameters of the second lookup are ++ expanded, and also while <string2> of the second lookup is expanded, should ++ the second lookup fail. Instead of {<string2>} the word "fail" can appear, ++ and in this case, if the lookup fails, the entire expansion is forced to ++ fail (see section 11.4). If both {<string1>} and {<string2>} are omitted, ++ the result is the looked up value in the case of a successful lookup, and ++ nothing in the case of failure. ++ ++ For single-key lookups, the string "partial" is permitted to precede the ++ search type in order to do partial matching, and * or *@ may follow a ++ search type to request default lookups if the key does not match (see ++ sections 9.6 and 9.7 for details). ++ ++ If a partial search is used, the variables $1 and $2 contain the wild and ++ non-wild parts of the key during the expansion of the replacement text. ++ They return to their previous values at the end of the lookup item. ++ ++ This example looks up the postmaster alias in the conventional alias file: ++ ++ ${lookup {postmaster} lsearch {/etc/aliases} {$value}} ++ ++ This example uses NIS+ to look up the full name of the user corresponding ++ to the local part of an address, forcing the expansion to fail if it is not ++ found: ++ ++ ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \ ++ {$value}fail} ++ ++${map{<string1>}{<string2>}} ++ ++ After expansion, <string1> is interpreted as a list, colon-separated by ++ default, but the separator can be changed in the usual way. For each item ++ in this list, its value is place in $item, and then <string2> is expanded ++ and added to the output as an item in a new list. The separator used for ++ the output list is the same as the one used for the input, but a separator ++ setting is not included in the output. For example: ++ ++ ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}} ++ ++ expands to "[a]:[b]:[c] (x)-(y)-(z)". At the end of the expansion, the ++ value of $item is restored to what it was before. See also the filter and ++ reduce expansion items. ++ ++${nhash{<string1>}{<string2>}{<string3>}} ++ ++ The three strings are expanded; the first two must yield numbers. Call them ++ <n> and <m>. If you are using fixed values for these numbers, that is, if < ++ string1> and <string2> do not change when they are expanded, you can use ++ the simpler operator notation that avoids some of the braces: ++ ++ ${nhash_<n>_<m>:<string>} ++ ++ The second number is optional (in both notations). If there is only one ++ number, the result is a number in the range 0-<n>-1. Otherwise, the string ++ is processed by a div/mod hash function that returns two numbers, separated ++ by a slash, in the ranges 0 to <n>-1 and 0 to <m>-1, respectively. For ++ example, ++ ++ ${nhash{8}{64}{supercalifragilisticexpialidocious}} ++ ++ returns the string "6/33". ++ ++${perl{<subroutine>}{<arg>}{<arg>}...} ++ ++ This item is available only if Exim has been built to include an embedded ++ Perl interpreter. The subroutine name and the arguments are first ++ separately expanded, and then the Perl subroutine is called with those ++ arguments. No additional arguments need be given; the maximum number ++ permitted, including the name of the subroutine, is nine. ++ ++ The return value of the subroutine is inserted into the expanded string, ++ unless the return value is undef. In that case, the expansion fails in the ++ same way as an explicit "fail" on a lookup item. The return value is a ++ scalar. Whatever you return is evaluated in a scalar context. For example, ++ if you return the name of a Perl vector, the return value is the size of ++ the vector, not its contents. ++ ++ If the subroutine exits by calling Perl's die function, the expansion fails ++ with the error message that was passed to die. More details of the embedded ++ Perl facility are given in chapter 12. ++ ++ The redirect router has an option called forbid_filter_perl which locks out ++ the use of this expansion item in filter files. ++ ++${prvs{<address>}{<secret>}{<keynumber>}} ++ ++ The first argument is a complete email address and the second is secret ++ keystring. The third argument, specifying a key number, is optional. If ++ absent, it defaults to 0. The result of the expansion is a prvs-signed ++ email address, to be typically used with the return_path option on an smtp ++ transport as part of a bounce address tag validation (BATV) scheme. For ++ more discussion and an example, see section 42.50. ++ ++${prvscheck{<address>}{<secret>}{<string>}} ++ ++ This expansion item is the complement of the prvs item. It is used for ++ checking prvs-signed addresses. If the expansion of the first argument does ++ not yield a syntactically valid prvs-signed address, the whole item expands ++ to the empty string. When the first argument does expand to a syntactically ++ valid prvs-signed address, the second argument is expanded, with the ++ prvs-decoded version of the address and the key number extracted from the ++ address in the variables $prvscheck_address and $prvscheck_keynum, ++ respectively. ++ ++ These two variables can be used in the expansion of the second argument to ++ retrieve the secret. The validity of the prvs-signed address is then ++ checked against the secret. The result is stored in the variable ++ $prvscheck_result, which is empty for failure or "1" for success. ++ ++ The third argument is optional; if it is missing, it defaults to an empty ++ string. This argument is now expanded. If the result is an empty string, ++ the result of the expansion is the decoded version of the address. This is ++ the case whether or not the signature was valid. Otherwise, the result of ++ the expansion is the expansion of the third argument. ++ ++ All three variables can be used in the expansion of the third argument. ++ However, once the expansion is complete, only $prvscheck_result remains ++ set. For more discussion and an example, see section 42.50. ++ ++${readfile{<file name>}{<eol string>}} ++ ++ The file name and end-of-line string are first expanded separately. The ++ file is then read, and its contents replace the entire item. All newline ++ characters in the file are replaced by the end-of-line string if it is ++ present. Otherwise, newlines are left in the string. String expansion is ++ not applied to the contents of the file. If you want this, you must wrap ++ the item in an expand operator. If the file cannot be read, the string ++ expansion fails. ++ ++ The redirect router has an option called forbid_filter_readfile which locks ++ out the use of this expansion item in filter files. ++ ++${readsocket{<name>}{<request>}{<timeout>}{<eol string>}{<fail string>}} ++ ++ This item inserts data from a Unix domain or Internet socket into the ++ expanded string. The minimal way of using it uses just two arguments, as in ++ these examples: ++ ++ ${readsocket{/socket/name}{request string}} ++ ${readsocket{inet:some.host:1234}{request string}} ++ ++ For a Unix domain socket, the first substring must be the path to the ++ socket. For an Internet socket, the first substring must contain "inet:" ++ followed by a host name or IP address, followed by a colon and a port, ++ which can be a number or the name of a TCP port in /etc/services. An IP ++ address may optionally be enclosed in square brackets. This is best for ++ IPv6 addresses. For example: ++ ++ ${readsocket{inet:[::1]:1234}{request string}} ++ ++ Only a single host name may be given, but if looking it up yields more than ++ one IP address, they are each tried in turn until a connection is made. For ++ both kinds of socket, Exim makes a connection, writes the request string ++ (unless it is an empty string) and reads from the socket until an ++ end-of-file is read. A timeout of 5 seconds is applied. Additional, ++ optional arguments extend what can be done. Firstly, you can vary the ++ timeout. For example: ++ ++ ${readsocket{/socket/name}{request string}{3s}} ++ ++ A fourth argument allows you to change any newlines that are in the data ++ that is read, in the same way as for readfile (see above). This example ++ turns them into spaces: ++ ++ ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }} ++ ++ As with all expansions, the substrings are expanded before the processing ++ happens. Errors in these sub-expansions cause the expansion to fail. In ++ addition, the following errors can occur: ++ ++ + Failure to create a socket file descriptor; ++ ++ + Failure to connect the socket; ++ ++ + Failure to write the request string; ++ ++ + Timeout on reading from the socket. ++ ++ By default, any of these errors causes the expansion to fail. However, if ++ you supply a fifth substring, it is expanded and used when any of the above ++ errors occurs. For example: ++ ++ ${readsocket{/socket/name}{request string}{3s}{\n}\ ++ {socket failure}} ++ ++ You can test for the existence of a Unix domain socket by wrapping this ++ expansion in "${if exists", but there is a race condition between that test ++ and the actual opening of the socket, so it is safer to use the fifth ++ argument if you want to be absolutely sure of avoiding an expansion error ++ for a non-existent Unix domain socket, or a failure to connect to an ++ Internet socket. ++ ++ The redirect router has an option called forbid_filter_readsocket which ++ locks out the use of this expansion item in filter files. ++ ++${reduce{<string1>}{<string2>}{<string3>}} ++ ++ This operation reduces a list to a single, scalar string. After expansion, ++ <string1> is interpreted as a list, colon-separated by default, but the ++ separator can be changed in the usual way. Then <string2> is expanded and ++ assigned to the $value variable. After this, each item in the <string1> ++ list is assigned to $item in turn, and <string3> is expanded for each of ++ them. The result of that expansion is assigned to $value before the next ++ iteration. When the end of the list is reached, the final value of $value ++ is added to the expansion output. The reduce expansion item can be used in ++ a number of ways. For example, to add up a list of numbers: ++ ++ ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}} ++ ++ The result of that expansion would be "6". The maximum of a list of numbers ++ can be found: ++ ++ ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}} ++ ++ At the end of a reduce expansion, the values of $item and $value are ++ restored to what they were before. See also the filter and map expansion ++ items. ++ ++$rheader_<header name>: or $rh_<header name>: ++ ++ This item inserts "raw" header lines. It is described with the header ++ expansion item above. ++ ++${run{<command> <args>}{<string1>}{<string2>}} ++ ++ The command and its arguments are first expanded separately, and then the ++ command is run in a separate process, but under the same uid and gid. As in ++ other command executions from Exim, a shell is not used by default. If you ++ want a shell, you must explicitly code it. ++ ++ The standard input for the command exists, but is empty. The standard ++ output and standard error are set to the same file descriptor. If the ++ command succeeds (gives a zero return code) <string1> is expanded and ++ replaces the entire item; during this expansion, the standard output/error ++ from the command is in the variable $value. If the command fails, <string2 ++ >, if present, is expanded and used. Once again, during the expansion, the ++ standard output/error from the command is in the variable $value. ++ ++ If <string2> is absent, the result is empty. Alternatively, <string2> can ++ be the word "fail" (not in braces) to force expansion failure if the ++ command does not succeed. If both strings are omitted, the result is ++ contents of the standard output/error on success, and nothing on failure. ++ ++ The standard output/error of the command is put in the variable $value. In ++ this ACL example, the output of a command is logged for the admin to ++ troubleshoot: ++ ++ warn condition = ${run{/usr/bin/id}{yes}{no}} ++ log_message = Output of id: $value ++ ++ If the command requires shell idioms, such as the > redirect operator, the ++ shell must be invoked directly, such as with: ++ ++ ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}} ++ ++ The return code from the command is put in the variable $runrc, and this ++ remains set afterwards, so in a filter file you can do things like this: ++ ++ if "${run{x y z}{}}$runrc" is 1 then ... ++ elif $runrc is 2 then ... ++ ... ++ endif ++ ++ If execution of the command fails (for example, the command does not ++ exist), the return code is 127 - the same code that shells use for ++ non-existent commands. ++ ++ Warning: In a router or transport, you cannot assume the order in which ++ option values are expanded, except for those preconditions whose order of ++ testing is documented. Therefore, you cannot reliably expect to set $runrc ++ by the expansion of one option, and use it in another. ++ ++ The redirect router has an option called forbid_filter_run which locks out ++ the use of this expansion item in filter files. ++ ++${sg{<subject>}{<regex>}{<replacement>}} ++ ++ This item works like Perl's substitution operator (s) with the global (/g) ++ option; hence its name. However, unlike the Perl equivalent, Exim does not ++ modify the subject string; instead it returns the modified string for ++ insertion into the overall expansion. The item takes three arguments: the ++ subject string, a regular expression, and a substitution string. For ++ example: ++ ++ ${sg{abcdefabcdef}{abc}{xyz}} ++ ++ yields "xyzdefxyzdef". Because all three arguments are expanded before use, ++ if any $ or \ characters are required in the regular expression or in the ++ substitution string, they have to be escaped. For example: ++ ++ ${sg{abcdef}{^(...)(...)\$}{\$2\$1}} ++ ++ yields "defabc", and ++ ++ ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}} ++ ++ yields "K1=A K4=D K3=C". Note the use of "\N" to protect the contents of ++ the regular expression from string expansion. ++ ++${substr{<string1>}{<string2>}{<string3>}} ++ ++ The three strings are expanded; the first two must yield numbers. Call them ++ <n> and <m>. If you are using fixed values for these numbers, that is, if < ++ string1> and <string2> do not change when they are expanded, you can use ++ the simpler operator notation that avoids some of the braces: ++ ++ ${substr_<n>_<m>:<string>} ++ ++ The second number is optional (in both notations). If it is absent in the ++ simpler format, the preceding underscore must also be omitted. ++ ++ The substr item can be used to extract more general substrings than length. ++ The first number, <n>, is a starting offset, and <m> is the length ++ required. For example ++ ++ ${substr{3}{2}{$local_part}} ++ ++ If the starting offset is greater than the string length the result is the ++ null string; if the length plus starting offset is greater than the string ++ length, the result is the right-hand part of the string, starting from the ++ given offset. The first character in the string has offset zero. ++ ++ The substr expansion item can take negative offset values to count from the ++ right-hand end of its operand. The last character is offset -1, the ++ second-last is offset -2, and so on. Thus, for example, ++ ++ ${substr{-5}{2}{1234567}} ++ ++ yields "34". If the absolute value of a negative offset is greater than the ++ length of the string, the substring starts at the beginning of the string, ++ and the length is reduced by the amount of overshoot. Thus, for example, ++ ++ ${substr{-5}{2}{12}} ++ ++ yields an empty string, but ++ ++ ${substr{-3}{2}{12}} ++ ++ yields "1". ++ ++ When the second number is omitted from substr, the remainder of the string ++ is taken if the offset is positive. If it is negative, all characters in ++ the string preceding the offset point are taken. For example, an offset of ++ -1 and no length, as in these semantically identical examples: ++ ++ ${substr_-1:abcde} ++ ${substr{-1}{abcde}} ++ ++ yields all but the last character of the string, that is, "abcd". ++ ++${tr{<subject>}{<characters>}{<replacements>}} ++ ++ This item does single-character translation on its subject string. The ++ second argument is a list of characters to be translated in the subject ++ string. Each matching character is replaced by the corresponding character ++ from the replacement list. For example ++ ++ ${tr{abcdea}{ac}{13}} ++ ++ yields "1b3de1". If there are duplicates in the second character string, ++ the last occurrence is used. If the third string is shorter than the ++ second, its last character is replicated. However, if it is empty, no ++ translation takes place. ++ ++ ++11.6 Expansion operators ++------------------------ ++ ++For expansion items that perform transformations on a single argument string, ++the "operator" notation is used because it is simpler and uses fewer braces. ++The substring is first expanded before the operation is applied to it. The ++following operations can be performed: ++ ++${address:<string>} ++ ++ The string is interpreted as an RFC 2822 address, as it might appear in a ++ header line, and the effective address is extracted from it. If the string ++ does not parse successfully, the result is empty. ++ ++${addresses:<string>} ++ ++ The string (after expansion) is interpreted as a list of addresses in RFC ++ 2822 format, such as can be found in a To: or Cc: header line. The ++ operative address (local-part@domain) is extracted from each item, and the ++ result of the expansion is a colon-separated list, with appropriate ++ doubling of colons should any happen to be present in the email addresses. ++ Syntactically invalid RFC2822 address items are omitted from the output. ++ ++ It is possible to specify a character other than colon for the output ++ separator by starting the string with > followed by the new separator ++ character. For example: ++ ++ ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)} ++ ++ expands to "ceo@up.stairs&sec@base.ment". Compare the address (singular) ++ expansion item, which extracts the working address from a single RFC2822 ++ address. See the filter, map, and reduce items for ways of processing ++ lists. ++ ++${base62:<digits>} ++ ++ The string must consist entirely of decimal digits. The number is converted ++ to base 62 and output as a string of six characters, including leading ++ zeros. In the few operating environments where Exim uses base 36 instead of ++ base 62 for its message identifiers (because those systems do not have ++ case-sensitive file names), base 36 is used by this operator, despite its ++ name. Note: Just to be absolutely clear: this is not base64 encoding. ++ ++${base62d:<base-62 digits>} ++ ++ The string must consist entirely of base-62 digits, or, in operating ++ environments where Exim uses base 36 instead of base 62 for its message ++ identifiers, base-36 digits. The number is converted to decimal and output ++ as a string. ++ ++${domain:<string>} ++ ++ The string is interpreted as an RFC 2822 address and the domain is ++ extracted from it. If the string does not parse successfully, the result is ++ empty. ++ ++${escape:<string>} ++ ++ If the string contains any non-printing characters, they are converted to ++ escape sequences starting with a backslash. Whether characters with the ++ most significant bit set (so-called "8-bit characters") count as printing ++ or not is controlled by the print_topbitchars option. ++ ++${eval:<string>} and ${eval10:<string>} ++ ++ These items supports simple arithmetic and bitwise logical operations in ++ expansion strings. The string (after expansion) must be a conventional ++ arithmetic expression, but it is limited to basic arithmetic operators, ++ bitwise logical operators, and parentheses. All operations are carried out ++ using integer arithmetic. The operator priorities are as follows (the same ++ as in the C programming language): ++ ++ highest: not (~), negate (-) ++ multiply (*), divide (/), remainder (%) ++ plus (+), minus (-) ++ shift-left (<<), shift-right (>>) ++ and (&) ++ xor (^) ++ lowest: or (|) ++ ++ Binary operators with the same priority are evaluated from left to right. ++ White space is permitted before or after operators. ++ ++ For eval, numbers may be decimal, octal (starting with "0") or hexadecimal ++ (starting with "0x"). For eval10, all numbers are taken as decimal, even if ++ they start with a leading zero; hexadecimal numbers are not permitted. This ++ can be useful when processing numbers extracted from dates or times, which ++ often do have leading zeros. ++ ++ A number may be followed by "K", "M" or "G" to multiply it by 1024, ++ 1024*1024 or 1024*1024*1024, respectively. Negative numbers are supported. ++ The result of the computation is a decimal representation of the answer ++ (without "K", "M" or "G"). For example: ++ ++ ${eval:1+1} yields 2 ++ ${eval:1+2*3} yields 7 ++ ${eval:(1+2)*3} yields 9 ++ ${eval:2+42%5} yields 4 ++ ${eval:0xc&5} yields 4 ++ ${eval:0xc|5} yields 13 ++ ${eval:0xc^5} yields 9 ++ ${eval:0xc>>1} yields 6 ++ ${eval:0xc<<1} yields 24 ++ ${eval:~255&0x1234} yields 4608 ++ ${eval:-(~255&0x1234)} yields -4608 ++ ++ As a more realistic example, in an ACL you might have ++ ++ deny message = Too many bad recipients ++ condition = \ ++ ${if and { \ ++ {>{$rcpt_count}{10}} \ ++ { \ ++ < \ ++ {$recipients_count} \ ++ {${eval:$rcpt_count/2}} \ ++ } \ ++ }{yes}{no}} ++ ++ The condition is true if there have been more than 10 RCPT commands and ++ fewer than half of them have resulted in a valid recipient. ++ ++${expand:<string>} ++ ++ The expand operator causes a string to be expanded for a second time. For ++ example, ++ ++ ${expand:${lookup{$domain}dbm{/some/file}{$value}}} ++ ++ first looks up a string in a file while expanding the operand for expand, ++ and then re-expands what it has found. ++ ++${from_utf8:<string>} ++ ++ The world is slowly moving towards Unicode, although there are no standards ++ for email yet. However, other applications (including some databases) are ++ starting to store data in Unicode, using UTF-8 encoding. This operator ++ converts from a UTF-8 string to an ISO-8859-1 string. UTF-8 code values ++ greater than 255 are converted to underscores. The input must be a valid ++ UTF-8 string. If it is not, the result is an undefined sequence of bytes. ++ ++ Unicode code points with values less than 256 are compatible with ASCII and ++ ISO-8859-1 (also known as Latin-1). For example, character 169 is the ++ copyright symbol in both cases, though the way it is encoded is different. ++ In UTF-8, more than one byte is needed for characters with code values ++ greater than 127, whereas ISO-8859-1 is a single-byte encoding (but thereby ++ limited to 256 characters). This makes translation from UTF-8 to ISO-8859-1 ++ straightforward. ++ ++${hash_<n>_<m>:<string>} ++ ++ The hash operator is a simpler interface to the hashing function that can ++ be used when the two parameters are fixed numbers (as opposed to strings ++ that change when expanded). The effect is the same as ++ ++ ${hash{<n>}{<m>}{<string>}} ++ ++ See the description of the general hash item above for details. The ++ abbreviation h can be used when hash is used as an operator. ++ ++${hex2b64:<hexstring>} ++ ++ This operator converts a hex string into one that is base64 encoded. This ++ can be useful for processing the output of the MD5 and SHA-1 hashing ++ functions. ++ ++${hexquote:<string>} ++ ++ This operator converts non-printable characters in a string into a hex ++ escape form. Byte values between 33 (!) and 126 (~) inclusive are left as ++ is, and other byte values are converted to "\xNN", for example a byt value ++ 127 is converted to "\x7f". ++ ++${lc:<string>} ++ ++ This forces the letters in the string into lower-case, for example: ++ ++ ${lc:$local_part} ++ ++${length_<number>:<string>} ++ ++ The length operator is a simpler interface to the length function that can ++ be used when the parameter is a fixed number (as opposed to a string that ++ changes when expanded). The effect is the same as ++ ++ ${length{<number>}{<string>}} ++ ++ See the description of the general length item above for details. Note that ++ length is not the same as strlen. The abbreviation l can be used when ++ length is used as an operator. ++ ++${listcount:<string>} ++ ++ The string is interpreted as a list and the number of items is returned. ++ ++${listnamed:<name>} and ${list_<type>name>} ++ ++ The name is interpreted as a named list and the content of the list is ++ returned, expanding any referenced lists, re-quoting as needed for ++ colon-separation. If the optional type if given it must be one of "a", "d", ++ "h" or "l" and selects address-, domain-, host- or localpart- lists to ++ search among respectively. Otherwise all types are searched in an undefined ++ order and the first matching list is returned. ++ ++${local_part:<string>} ++ ++ The string is interpreted as an RFC 2822 address and the local part is ++ extracted from it. If the string does not parse successfully, the result is ++ empty. ++ ++${mask:<IP address>/<bit count>} ++ ++ If the form of the string to be operated on is not an IP address followed ++ by a slash and an integer (that is, a network address in CIDR notation), ++ the expansion fails. Otherwise, this operator converts the IP address to ++ binary, masks off the least significant bits according to the bit count, ++ and converts the result back to text, with mask appended. For example, ++ ++ ${mask:10.111.131.206/28} ++ ++ returns the string "10.111.131.192/28". Since this operation is expected to ++ be mostly used for looking up masked addresses in files, the result for an ++ IPv6 address uses dots to separate components instead of colons, because ++ colon terminates a key string in lsearch files. So, for example, ++ ++ ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99} ++ ++ returns the string ++ ++ 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99 ++ ++ Letters in IPv6 addresses are always output in lower case. ++ ++${md5:<string>} ++ ++ The md5 operator computes the MD5 hash value of the string, and returns it ++ as a 32-digit hexadecimal number, in which any letters are in lower case. ++ ++${nhash_<n>_<m>:<string>} ++ ++ The nhash operator is a simpler interface to the numeric hashing function ++ that can be used when the two parameters are fixed numbers (as opposed to ++ strings that change when expanded). The effect is the same as ++ ++ ${nhash{<n>}{<m>}{<string>}} ++ ++ See the description of the general nhash item above for details. ++ ++${quote:<string>} ++ ++ The quote operator puts its argument into double quotes if it is an empty ++ string or contains anything other than letters, digits, underscores, dots, ++ and hyphens. Any occurrences of double quotes and backslashes are escaped ++ with a backslash. Newlines and carriage returns are converted to "\n" and " ++ \r", respectively For example, ++ ++ ${quote:ab"*"cd} ++ ++ becomes ++ ++ "ab\"*\"cd" ++ ++ The place where this is useful is when the argument is a substitution from ++ a variable or a message header. ++ ++${quote_local_part:<string>} ++ ++ This operator is like quote, except that it quotes the string only if ++ required to do so by the rules of RFC 2822 for quoting local parts. For ++ example, a plus sign would not cause quoting (but it would for quote). If ++ you are creating a new email address from the contents of $local_part (or ++ any other unknown data), you should always use this operator. ++ ++${quote_<lookup-type>:<string>} ++ ++ This operator applies lookup-specific quoting rules to the string. Each ++ query-style lookup type has its own quoting rules which are described with ++ the lookups in chapter 9. For example, ++ ++ ${quote_ldap:two * two} ++ ++ returns ++ ++ two%20%5C2A%20two ++ ++ For single-key lookup types, no quoting is ever necessary and this operator ++ yields an unchanged string. ++ ++${randint:<n>} ++ ++ This operator returns a somewhat random number which is less than the ++ supplied number and is at least 0. The quality of this randomness depends ++ on how Exim was built; the values are not suitable for keying material. If ++ Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. If Exim is ++ linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used, for ++ versions of GnuTLS with that function. Otherwise, the implementation may be ++ arc4random(), random() seeded by srandomdev() or srandom(), or a custom ++ implementation even weaker than random(). ++ ++${reverse_ip:<ipaddr>} ++ ++ This operator reverses an IP address; for IPv4 addresses, the result is in ++ dotted-quad decimal form, while for IPv6 addreses the result is in ++ dotted-nibble hexadecimal form. In both cases, this is the "natural" form ++ for DNS. For example, ++ ++ ${reverse_ip:192.0.2.4} ++ ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127} ++ ++ returns ++ ++ 4.2.0.192 ++ f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 ++ ++${rfc2047:<string>} ++ ++ This operator encodes text according to the rules of RFC 2047. This is an ++ encoding that is used in header lines to encode non-ASCII characters. It is ++ assumed that the input string is in the encoding specified by the ++ headers_charset option, which defaults to ISO-8859-1. If the string ++ contains only characters in the range 33-126, and no instances of the ++ characters ++ ++ ? = ( ) < > @ , ; : \ " . [ ] _ ++ ++ it is not modified. Otherwise, the result is the RFC 2047 encoding of the ++ string, using as many "encoded words" as necessary to encode all the ++ characters. ++ ++${rfc2047d:<string>} ++ ++ This operator decodes strings that are encoded as per RFC 2047. Binary zero ++ bytes are replaced by question marks. Characters are converted into the ++ character set defined by headers_charset. Overlong RFC 2047 "words" are not ++ recognized unless check_rfc2047_length is set false. ++ ++ Note: If you use $header_xxx: (or $h_xxx:) to access a header line, RFC ++ 2047 decoding is done automatically. You do not need to use this operator ++ as well. ++ ++${rxquote:<string>} ++ ++ The rxquote operator inserts a backslash before any non-alphanumeric ++ characters in its argument. This is useful when substituting the values of ++ variables or headers inside regular expressions. ++ ++${sha1:<string>} ++ ++ The sha1 operator computes the SHA-1 hash value of the string, and returns ++ it as a 40-digit hexadecimal number, in which any letters are in upper ++ case. ++ ++${stat:<string>} ++ ++ The string, after expansion, must be a file path. A call to the stat() ++ function is made for this path. If stat() fails, an error occurs and the ++ expansion fails. If it succeeds, the data from the stat replaces the item, ++ as a series of <name>=<value> pairs, where the values are all numerical, ++ except for the value of "smode". The names are: "mode" (giving the mode as ++ a 4-digit octal number), "smode" (giving the mode in symbolic format as a ++ 10-character string, as for the ls command), "inode", "device", "links", ++ "uid", "gid", "size", "atime", "mtime", and "ctime". You can extract ++ individual fields using the extract expansion item. ++ ++ The use of the stat expansion in users' filter files can be locked out by ++ the system administrator. Warning: The file size may be incorrect on 32-bit ++ systems for files larger than 2GB. ++ ++${str2b64:<string>} ++ ++ This operator converts a string into one that is base64 encoded. ++ ++${strlen:<string>} ++ ++ The item is replace by the length of the expanded string, expressed as a ++ decimal number. Note: Do not confuse strlen with length. ++ ++${substr_<start>_<length>:<string>} ++ ++ The substr operator is a simpler interface to the substr function that can ++ be used when the two parameters are fixed numbers (as opposed to strings ++ that change when expanded). The effect is the same as ++ ++ ${substr{<start>}{<length>}{<string>}} ++ ++ See the description of the general substr item above for details. The ++ abbreviation s can be used when substr is used as an operator. ++ ++${time_eval:<string>} ++ ++ This item converts an Exim time interval such as "2d4h5m" into a number of ++ seconds. ++ ++${time_interval:<string>} ++ ++ The argument (after sub-expansion) must be a sequence of decimal digits ++ that represents an interval of time as a number of seconds. It is converted ++ into a number of larger units and output in Exim's normal time format, for ++ example, "1w3d4h2m6s". ++ ++${uc:<string>} ++ ++ This forces the letters in the string into upper-case. ++ ++ ++11.7 Expansion conditions ++------------------------- ++ ++The following conditions are available for testing by the ${if construct while ++expanding strings: ++ ++!<condition> ++ ++ Preceding any condition with an exclamation mark negates the result of the ++ condition. ++ ++<symbolic operator> {<string1>}{<string2>} ++ ++ There are a number of symbolic operators for doing numeric comparisons. ++ They are: ++ ++ = equal ++ == equal ++ > greater ++ >= greater or equal ++ < less ++ <= less or equal ++ ++ For example: ++ ++ ${if >{$message_size}{10M} ... ++ ++ Note that the general negation operator provides for inequality testing. ++ The two strings must take the form of optionally signed decimal integers, ++ optionally followed by one of the letters "K", "M" or "G" (in either upper ++ or lower case), signifying multiplication by 1024, 1024*1024 or ++ 1024*1024*1024, respectively. As a special case, the numerical value of an ++ empty string is taken as zero. ++ ++ In all cases, a relative comparator OP is testing if <string1> OP <string2 ++ >; the above example is checking if $message_size is larger than 10M, not ++ if 10M is larger than $message_size. ++ ++acl {{<name>}{<arg1>}{<arg2>}...} ++ ++ The name and zero to nine argument strings are first expanded separately. ++ The expanded arguments are assigned to the variables $acl_arg1 to $acl_arg9 ++ in order. Any unused are made empty. The variable $acl_narg is set to the ++ number of arguments. The named ACL (see chapter 42) is called and may use ++ the variables; if another acl expansion is used the values are restored ++ after it returns. If the ACL sets a value using a "message =" modifier the ++ variable $value becomes the result of the expansion, otherwise it is empty. ++ If the ACL returns accept the condition is true; if deny, false. If the ACL ++ returns defer the result is a forced-fail. ++ ++bool {<string>} ++ ++ This condition turns a string holding a true or false representation into a ++ boolean state. It parses "true", "false", "yes" and "no" ++ (case-insensitively); also positive integer numbers map to true if ++ non-zero, false if zero. An empty string is treated as false. Leading and ++ trailing whitespace is ignored; thus a string consisting only of whitespace ++ is false. All other string values will result in expansion failure. ++ ++ When combined with ACL variables, this expansion condition will let you ++ make decisions in one place and act on those decisions in another place. ++ For example: ++ ++ ${if bool{$acl_m_privileged_sender} ... ++ ++bool_lax {<string>} ++ ++ Like bool, this condition turns a string into a boolean state. But where ++ bool accepts a strict set of strings, bool_lax uses the same loose ++ definition that the Router condition option uses. The empty string and the ++ values "false", "no" and "0" map to false, all others map to true. Leading ++ and trailing whitespace is ignored. ++ ++ Note that where "bool{00}" is false, "bool_lax{00}" is true. ++ ++crypteq {<string1>}{<string2>} ++ ++ This condition is included in the Exim binary if it is built to support any ++ authentication mechanisms (see chapter 33). Otherwise, it is necessary to ++ define SUPPORT_CRYPTEQ in Local/Makefile to get crypteq included in the ++ binary. ++ ++ The crypteq condition has two arguments. The first is encrypted and ++ compared against the second, which is already encrypted. The second string ++ may be in the LDAP form for storing encrypted strings, which starts with ++ the encryption type in curly brackets, followed by the data. If the second ++ string does not begin with "{" it is assumed to be encrypted with crypt() ++ or crypt16() (see below), since such strings cannot begin with "{". ++ Typically this will be a field from a password file. An example of an ++ encrypted string in LDAP form is: ++ ++ {md5}CY9rzUYh03PK3k6DJie09g== ++ ++ If such a string appears directly in an expansion, the curly brackets have ++ to be quoted, because they are part of the expansion syntax. For example: ++ ++ ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}} ++ ++ The following encryption types (whose names are matched case-independently) ++ are supported: ++ ++ + {md5} computes the MD5 digest of the first string, and expresses this ++ as printable characters to compare with the remainder of the second ++ string. If the length of the comparison string is 24, Exim assumes that ++ it is base64 encoded (as in the above example). If the length is 32, ++ Exim assumes that it is a hexadecimal encoding of the MD5 digest. If ++ the length not 24 or 32, the comparison fails. ++ ++ + {sha1} computes the SHA-1 digest of the first string, and expresses ++ this as printable characters to compare with the remainder of the ++ second string. If the length of the comparison string is 28, Exim ++ assumes that it is base64 encoded. If the length is 40, Exim assumes ++ that it is a hexadecimal encoding of the SHA-1 digest. If the length is ++ not 28 or 40, the comparison fails. ++ ++ + {crypt} calls the crypt() function, which traditionally used to use ++ only the first eight characters of the password. However, in modern ++ operating systems this is no longer true, and in many cases the entire ++ password is used, whatever its length. ++ ++ + {crypt16} calls the crypt16() function, which was originally created to ++ use up to 16 characters of the password in some operating systems. ++ Again, in modern operating systems, more characters may be used. ++ ++ Exim has its own version of crypt16(), which is just a double call to crypt ++ (). For operating systems that have their own version, setting HAVE_CRYPT16 ++ in Local/Makefile when building Exim causes it to use the operating system ++ version instead of its own. This option is set by default in the ++ OS-dependent Makefile for those operating systems that are known to support ++ crypt16(). ++ ++ Some years after Exim's crypt16() was implemented, a user discovered that ++ it was not using the same algorithm as some operating systems' versions. It ++ turns out that as well as crypt16() there is a function called bigcrypt() ++ in some operating systems. This may or may not use the same algorithm, and ++ both of them may be different to Exim's built-in crypt16(). ++ ++ However, since there is now a move away from the traditional crypt() ++ functions towards using SHA1 and other algorithms, tidying up this area of ++ Exim is seen as very low priority. ++ ++ If you do not put a encryption type (in curly brackets) in a crypteq ++ comparison, the default is usually either "{crypt}" or "{crypt16}", as ++ determined by the setting of DEFAULT_CRYPT in Local/Makefile. The default ++ default is "{crypt}". Whatever the default, you can always use either ++ function by specifying it explicitly in curly brackets. ++ ++def:<variable name> ++ ++ The def condition must be followed by the name of one of the expansion ++ variables defined in section 11.9. The condition is true if the variable ++ does not contain the empty string. For example: ++ ++ ${if def:sender_ident {from $sender_ident}} ++ ++ Note that the variable name is given without a leading $ character. If the ++ variable does not exist, the expansion fails. ++ ++def:header_<header name>: or def:h_<header name>: ++ ++ This condition is true if a message is being processed and the named header ++ exists in the message. For example, ++ ++ ${if def:header_reply-to:{$h_reply-to:}{$h_from:}} ++ ++ Note: No $ appears before header_ or h_ in the condition, and the header ++ name must be terminated by a colon if white space does not follow. ++ ++eq {<string1>}{<string2>}, eqi {<string1>}{<string2>} ++ ++ The two substrings are first expanded. The condition is true if the two ++ resulting strings are identical. For eq the comparison includes the case of ++ letters, whereas for eqi the comparison is case-independent. ++ ++exists {<file name>} ++ ++ The substring is first expanded and then interpreted as an absolute path. ++ The condition is true if the named file (or directory) exists. The ++ existence test is done by calling the stat() function. The use of the ++ exists test in users' filter files may be locked out by the system ++ administrator. ++ ++first_delivery ++ ++ This condition, which has no data, is true during a message's first ++ delivery attempt. It is false during any subsequent delivery attempts. ++ ++forall{<a list>}{<a condition>}, forany{<a list>}{<a condition>} ++ ++ These conditions iterate over a list. The first argument is expanded to ++ form the list. By default, the list separator is a colon, but it can be ++ changed by the normal method. The second argument is interpreted as a ++ condition that is to be applied to each item in the list in turn. During ++ the interpretation of the condition, the current list item is placed in a ++ variable called $item. ++ ++ + For forany, interpretation stops if the condition is true for any item, ++ and the result of the whole condition is true. If the condition is ++ false for all items in the list, the overall condition is false. ++ ++ + For forall, interpretation stops if the condition is false for any ++ item, and the result of the whole condition is false. If the condition ++ is true for all items in the list, the overall condition is true. ++ ++ Note that negation of forany means that the condition must be false for all ++ items for the overall condition to succeed, and negation of forall means ++ that the condition must be false for at least one item. In this example, ++ the list separator is changed to a comma: ++ ++ ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}} ++ ++ The value of $item is saved and restored while forany or forall is being ++ processed, to enable these expansion items to be nested. ++ ++ To scan a named list, expand it with the listnamed operator. ++ ++ge {<string1>}{<string2>}, gei {<string1>}{<string2>} ++ ++ The two substrings are first expanded. The condition is true if the first ++ string is lexically greater than or equal to the second string. For ge the ++ comparison includes the case of letters, whereas for gei the comparison is ++ case-independent. ++ ++gt {<string1>}{<string2>}, gti {<string1>}{<string2>} ++ ++ The two substrings are first expanded. The condition is true if the first ++ string is lexically greater than the second string. For gt the comparison ++ includes the case of letters, whereas for gti the comparison is ++ case-independent. ++ ++inlist {<string1>}{<string2>}, inlisti {<string1>}{<string2>} ++ ++ Both strings are expanded; the second string is treated as a list of simple ++ strings; if the first string is a member of the second, then the condition ++ is true. ++ ++ These are simpler to use versions of the more powerful forany condition. ++ Examples, and the forany equivalents: ++ ++ ${if inlist{needle}{foo:needle:bar}} ++ ${if forany{foo:needle:bar}{eq{$item}{needle}}} ++ ${if inlisti{Needle}{fOo:NeeDLE:bAr}} ++ ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}} ++ ++isip {<string>}, isip4 {<string>}, isip6 {<string>} ++ ++ The substring is first expanded, and then tested to see if it has the form ++ of an IP address. Both IPv4 and IPv6 addresses are valid for isip, whereas ++ isip4 and isip6 test specifically for IPv4 or IPv6 addresses. ++ ++ For an IPv4 address, the test is for four dot-separated components, each of ++ which consists of from one to three digits. For an IPv6 address, up to ++ eight colon-separated components are permitted, each containing from one to ++ four hexadecimal digits. There may be fewer than eight components if an ++ empty component (adjacent colons) is present. Only one empty component is ++ permitted. ++ ++ Note: The checks are just on the form of the address; actual numerical ++ values are not considered. Thus, for example, 999.999.999.999 passes the ++ IPv4 check. The main use of these tests is to distinguish between IP ++ addresses and host names, or between IPv4 and IPv6 addresses. For example, ++ you could use ++ ++ ${if isip4{$sender_host_address}... ++ ++ to test which IP version an incoming SMTP connection is using. ++ ++ldapauth {<ldap query>} ++ ++ This condition supports user authentication using LDAP. See section 9.13 ++ for details of how to use LDAP in lookups and the syntax of queries. For ++ this use, the query must contain a user name and password. The query itself ++ is not used, and can be empty. The condition is true if the password is not ++ empty, and the user name and password are accepted by the LDAP server. An ++ empty password is rejected without calling LDAP because LDAP binds with an ++ empty password are considered anonymous regardless of the username, and ++ will succeed in most configurations. See chapter 33 for details of SMTP ++ authentication, and chapter 34 for an example of how this can be used. ++ ++le {<string1>}{<string2>}, lei {<string1>}{<string2>} ++ ++ The two substrings are first expanded. The condition is true if the first ++ string is lexically less than or equal to the second string. For le the ++ comparison includes the case of letters, whereas for lei the comparison is ++ case-independent. ++ ++lt {<string1>}{<string2>}, lti {<string1>}{<string2>} ++ ++ The two substrings are first expanded. The condition is true if the first ++ string is lexically less than the second string. For lt the comparison ++ includes the case of letters, whereas for lti the comparison is ++ case-independent. ++ ++match {<string1>}{<string2>} ++ ++ The two substrings are first expanded. The second is then treated as a ++ regular expression and applied to the first. Because of the pre-expansion, ++ if the regular expression contains dollar, or backslash characters, they ++ must be escaped. Care must also be taken if the regular expression contains ++ braces (curly brackets). A closing brace must be escaped so that it is not ++ taken as a premature termination of <string2>. The easiest approach is to ++ use the "\N" feature to disable expansion of the regular expression. For ++ example, ++ ++ ${if match {$local_part}{\N^\d{3}\N} ... ++ ++ If the whole expansion string is in double quotes, further escaping of ++ backslashes is also required. ++ ++ The condition is true if the regular expression match succeeds. The regular ++ expression is not required to begin with a circumflex metacharacter, but if ++ there is no circumflex, the expression is not anchored, and it may match ++ anywhere in the subject, not just at the start. If you want the pattern to ++ match at the end of the subject, you must include the "$" metacharacter at ++ an appropriate point. ++ ++ At the start of an if expansion the values of the numeric variable ++ substitutions $1 etc. are remembered. Obeying a match condition that ++ succeeds causes them to be reset to the substrings of that condition and ++ they will have these values during the expansion of the success string. At ++ the end of the if expansion, the previous values are restored. After ++ testing a combination of conditions using or, the subsequent values of the ++ numeric variables are those of the condition that succeeded. ++ ++match_address {<string1>}{<string2>} ++ ++ See match_local_part. ++ ++match_domain {<string1>}{<string2>} ++ ++ See match_local_part. ++ ++match_ip {<string1>}{<string2>} ++ ++ This condition matches an IP address to a list of IP address patterns. It ++ must be followed by two argument strings. The first (after expansion) must ++ be an IP address or an empty string. The second (not expanded) is a ++ restricted host list that can match only an IP address, not a host name. ++ For example: ++ ++ ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}} ++ ++ The specific types of host list item that are permitted in the list are: ++ ++ + An IP address, optionally with a CIDR mask. ++ ++ + A single asterisk, which matches any IP address. ++ ++ + An empty item, which matches only if the IP address is empty. This ++ could be useful for testing for a locally submitted message or one from ++ specific hosts in a single test such as ++ ++ ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}} ++ ++ where the first item in the list is the empty string. ++ ++ + The item @[] matches any of the local host's interface addresses. ++ ++ + Single-key lookups are assumed to be like "net-" style lookups in host ++ lists, even if "net-" is not specified. There is never any attempt to ++ turn the IP address into a host name. The most common type of linear ++ search for match_ip is likely to be iplsearch, in which the file can ++ contain CIDR masks. For example: ++ ++ ${if match_ip{$sender_host_address}{iplsearch;/some/file}... ++ ++ It is of course possible to use other kinds of lookup, and in such a ++ case, you do need to specify the "net-" prefix if you want to specify a ++ specific address mask, for example: ++ ++ ${if match_ip{$sender_host_address}{net24-dbm;/some/file}... ++ ++ However, unless you are combining a match_ip condition with others, it ++ is just as easy to use the fact that a lookup is itself a condition, ++ and write: ++ ++ ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}... ++ ++ Note that <string2> is not itself subject to string expansion, unless Exim ++ was built with the EXPAND_LISTMATCH_RHS option. ++ ++ Consult section 10.11 for further details of these patterns. ++ ++match_local_part {<string1>}{<string2>} ++ ++ This condition, together with match_address and match_domain, make it ++ possible to test domain, address, and local part lists within expansions. ++ Each condition requires two arguments: an item and a list to match. A ++ trivial example is: ++ ++ ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}} ++ ++ In each case, the second argument may contain any of the allowable items ++ for a list of the appropriate type. Also, because the second argument ++ (after expansion) is a standard form of list, it is possible to refer to a ++ named list. Thus, you can use conditions like this: ++ ++ ${if match_domain{$domain}{+local_domains}{... ++ ++ For address lists, the matching starts off caselessly, but the "+caseful" ++ item can be used, as in all address lists, to cause subsequent items to ++ have their local parts matched casefully. Domains are always matched ++ caselessly. ++ ++ Note that <string2> is not itself subject to string expansion, unless Exim ++ was built with the EXPAND_LISTMATCH_RHS option. ++ ++ Note: Host lists are not supported in this way. This is because hosts have ++ two identities: a name and an IP address, and it is not clear how to ++ specify cleanly how such a test would work. However, IP addresses can be ++ matched using match_ip. ++ ++pam {<string1>:<string2>:...} ++ ++ Pluggable Authentication Modules (http://www.kernel.org/pub/linux/libs/pam/ ++ ) are a facility that is available in the latest releases of Solaris and in ++ some GNU/Linux distributions. The Exim support, which is intended for use ++ in conjunction with the SMTP AUTH command, is available only if Exim is ++ compiled with ++ ++ SUPPORT_PAM=yes ++ ++ in Local/Makefile. You probably need to add -lpam to EXTRALIBS, and in some ++ releases of GNU/Linux -ldl is also needed. ++ ++ The argument string is first expanded, and the result must be a ++ colon-separated list of strings. Leading and trailing white space is ++ ignored. The PAM module is initialized with the service name "exim" and the ++ user name taken from the first item in the colon-separated data string (< ++ string1>). The remaining items in the data string are passed over in ++ response to requests from the authentication function. In the simple case ++ there will only be one request, for a password, so the data consists of ++ just two strings. ++ ++ There can be problems if any of the strings are permitted to contain colon ++ characters. In the usual way, these have to be doubled to avoid being taken ++ as separators. If the data is being inserted from a variable, the sg ++ expansion item can be used to double any existing colons. For example, the ++ configuration of a LOGIN authenticator might contain this setting: ++ ++ server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}} ++ ++ For a PLAIN authenticator you could use: ++ ++ server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}} ++ ++ In some operating systems, PAM authentication can be done only from a ++ process running as root. Since Exim is running as the Exim user when ++ receiving messages, this means that PAM cannot be used directly in those ++ systems. A patched version of the pam_unix module that comes with the Linux ++ PAM package is available from http://www.e-admin.de/pam_exim/. The patched ++ module allows one special uid/gid combination, in addition to root, to ++ authenticate. If you build the patched module to allow the Exim user and ++ group, PAM can then be used from an Exim authenticator. ++ ++pwcheck {<string1>:<string2>} ++ ++ This condition supports user authentication using the Cyrus pwcheck daemon. ++ This is one way of making it possible for passwords to be checked by a ++ process that is not running as root. Note: The use of pwcheck is now ++ deprecated. Its replacement is saslauthd (see below). ++ ++ The pwcheck support is not included in Exim by default. You need to specify ++ the location of the pwcheck daemon's socket in Local/Makefile before ++ building Exim. For example: ++ ++ CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck ++ ++ You do not need to install the full Cyrus software suite in order to use ++ the pwcheck daemon. You can compile and install just the daemon alone from ++ the Cyrus SASL library. Ensure that exim is the only user that has access ++ to the /var/pwcheck directory. ++ ++ The pwcheck condition takes one argument, which must be the user name and ++ password, separated by a colon. For example, in a LOGIN authenticator ++ configuration, you might have this: ++ ++ server_condition = ${if pwcheck{$auth1:$auth2}} ++ ++ Again, for a PLAIN authenticator configuration, this would be: ++ ++ server_condition = ${if pwcheck{$auth2:$auth3}} ++ ++queue_running ++ ++ This condition, which has no data, is true during delivery attempts that ++ are initiated by queue runner processes, and false otherwise. ++ ++radius {<authentication string>} ++ ++ Radius authentication (RFC 2865) is supported in a similar way to PAM. You ++ must set RADIUS_CONFIG_FILE in Local/Makefile to specify the location of ++ the Radius client configuration file in order to build Exim with Radius ++ support. ++ ++ With just that one setting, Exim expects to be linked with the radiusclient ++ library, using the original API. If you are using release 0.4.0 or later of ++ this library, you need to set ++ ++ RADIUS_LIB_TYPE=RADIUSCLIENTNEW ++ ++ in Local/Makefile when building Exim. You can also link Exim with the ++ libradius library that comes with FreeBSD. To do this, set ++ ++ RADIUS_LIB_TYPE=RADLIB ++ ++ in Local/Makefile, in addition to setting RADIUS_CONFIGURE_FILE. You may ++ also have to supply a suitable setting in EXTRALIBS so that the Radius ++ library can be found when Exim is linked. ++ ++ The string specified by RADIUS_CONFIG_FILE is expanded and passed to the ++ Radius client library, which calls the Radius server. The condition is true ++ if the authentication is successful. For example: ++ ++ server_condition = ${if radius{<arguments>}} ++ ++saslauthd {{<user>}{<password>}{<service>}{<realm>}} ++ ++ This condition supports user authentication using the Cyrus saslauthd ++ daemon. This replaces the older pwcheck daemon, which is now deprecated. ++ Using this daemon is one way of making it possible for passwords to be ++ checked by a process that is not running as root. ++ ++ The saslauthd support is not included in Exim by default. You need to ++ specify the location of the saslauthd daemon's socket in Local/Makefile ++ before building Exim. For example: ++ ++ CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux ++ ++ You do not need to install the full Cyrus software suite in order to use ++ the saslauthd daemon. You can compile and install just the daemon alone ++ from the Cyrus SASL library. ++ ++ Up to four arguments can be supplied to the saslauthd condition, but only ++ two are mandatory. For example: ++ ++ server_condition = ${if saslauthd{{$auth1}{$auth2}}} ++ ++ The service and the realm are optional (which is why the arguments are ++ enclosed in their own set of braces). For details of the meaning of the ++ service and realm, and how to run the daemon, consult the Cyrus ++ documentation. ++ ++ ++11.8 Combining expansion conditions ++----------------------------------- ++ ++Several conditions can be tested at once by combining them using the and and or ++combination conditions. Note that and and or are complete conditions on their ++own, and precede their lists of sub-conditions. Each sub-condition must be ++enclosed in braces within the overall braces that contain the list. No ++repetition of if is used. ++ ++or {{<cond1>}{<cond2>}...} ++ ++ The sub-conditions are evaluated from left to right. The condition is true ++ if any one of the sub-conditions is true. For example, ++ ++ ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}... ++ ++ When a true sub-condition is found, the following ones are parsed but not ++ evaluated. If there are several "match" sub-conditions the values of the ++ numeric variables afterwards are taken from the first one that succeeds. ++ ++and {{<cond1>}{<cond2>}...} ++ ++ The sub-conditions are evaluated from left to right. The condition is true ++ if all of the sub-conditions are true. If there are several "match" ++ sub-conditions, the values of the numeric variables afterwards are taken ++ from the last one. When a false sub-condition is found, the following ones ++ are parsed but not evaluated. ++ ++ ++11.9 Expansion variables ++------------------------ ++ ++This section contains an alphabetical list of all the expansion variables. Some ++of them are available only when Exim is compiled with specific options such as ++support for TLS or the content scanning extension. ++ ++$0, $1, etc ++ ++ When a match expansion condition succeeds, these variables contain the ++ captured substrings identified by the regular expression during subsequent ++ processing of the success string of the containing if expansion item. ++ However, they do not retain their values afterwards; in fact, their ++ previous values are restored at the end of processing an if item. The ++ numerical variables may also be set externally by some other matching ++ process which precedes the expansion of the string. For example, the ++ commands available in Exim filter files include an if command with its own ++ regular expression matching condition. ++ ++$acl_c... ++ ++ Values can be placed in these variables by the set modifier in an ACL. They ++ can be given any name that starts with $acl_c and is at least six ++ characters long, but the sixth character must be either a digit or an ++ underscore. For example: $acl_c5, $acl_c_mycount. The values of the ++ $acl_c... variables persist throughout the lifetime of an SMTP connection. ++ They can be used to pass information between ACLs and between different ++ invocations of the same ACL. When a message is received, the values of ++ these variables are saved with the message, and can be accessed by filters, ++ routers, and transports during subsequent delivery. ++ ++$acl_m... ++ ++ These variables are like the $acl_c... variables, except that their values ++ are reset after a message has been received. Thus, if several messages are ++ received in one SMTP connection, $acl_m... values are not passed on from ++ one message to the next, as $acl_c... values are. The $acl_m... variables ++ are also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. ++ When a message is received, the values of these variables are saved with ++ the message, and can be accessed by filters, routers, and transports during ++ subsequent delivery. ++ ++$acl_verify_message ++ ++ After an address verification has failed, this variable contains the ++ failure message. It retains its value for use in subsequent modifiers. The ++ message can be preserved by coding like this: ++ ++ warn !verify = sender ++ set acl_m0 = $acl_verify_message ++ ++ You can use $acl_verify_message during the expansion of the message or ++ log_message modifiers, to include information about the verification ++ failure. ++ ++$address_data ++ ++ This variable is set by means of the address_data option in routers. The ++ value then remains with the address while it is processed by subsequent ++ routers and eventually a transport. If the transport is handling multiple ++ addresses, the value from the first address is used. See chapter 15 for ++ more details. Note: The contents of $address_data are visible in user ++ filter files. ++ ++ If $address_data is set when the routers are called from an ACL to verify a ++ recipient address, the final value is still in the variable for subsequent ++ conditions and modifiers of the ACL statement. If routing the address ++ caused it to be redirected to just one address, the child address is also ++ routed as part of the verification, and in this case the final value of ++ $address_data is from the child's routing. ++ ++ If $address_data is set when the routers are called from an ACL to verify a ++ sender address, the final value is also preserved, but this time in ++ $sender_address_data, to distinguish it from data from a recipient address. ++ ++ In both cases (recipient and sender verification), the value does not ++ persist after the end of the current ACL statement. If you want to preserve ++ these values for longer, you can save them in ACL variables. ++ ++$address_file ++ ++ When, as a result of aliasing, forwarding, or filtering, a message is ++ directed to a specific file, this variable holds the name of the file when ++ the transport is running. At other times, the variable is empty. For ++ example, using the default configuration, if user r2d2 has a .forward file ++ containing ++ ++ /home/r2d2/savemail ++ ++ then when the address_file transport is running, $address_file contains the ++ text string "/home/r2d2/savemail". For Sieve filters, the value may be ++ "inbox" or a relative folder name. It is then up to the transport ++ configuration to generate an appropriate absolute path to the relevant ++ file. ++ ++$address_pipe ++ ++ When, as a result of aliasing or forwarding, a message is directed to a ++ pipe, this variable holds the pipe command when the transport is running. ++ ++$auth1 - $auth3 ++ ++ These variables are used in SMTP authenticators (see chapters 34-40). ++ Elsewhere, they are empty. ++ ++$authenticated_id ++ ++ When a server successfully authenticates a client it may be configured to ++ preserve some of the authentication information in the variable ++ $authenticated_id (see chapter 33). For example, a user/password ++ authenticator configuration might preserve the user name for use in the ++ routers. Note that this is not the same information that is saved in ++ $sender_host_authenticated. When a message is submitted locally (that is, ++ not over a TCP connection) the value of $authenticated_id is normally the ++ login name of the calling process. However, a trusted user can override ++ this by means of the -oMai command line option. ++ ++$authenticated_fail_id ++ ++ When an authentication attempt fails, the variable $authenticated_fail_id ++ will contain the failed authentication id. If more than one authentication ++ id is attempted, it will contain only the last one. The variable is ++ available for processing in the ACL's, generally the quit or notquit ACL. A ++ message to a local recipient could still be accepted without requiring ++ authentication, which means this variable could also be visible in all of ++ the ACL's as well. ++ ++$authenticated_sender ++ ++ When acting as a server, Exim takes note of the AUTH= parameter on an ++ incoming SMTP MAIL command if it believes the sender is sufficiently ++ trusted, as described in section 33.2. Unless the data is the string "<>", ++ it is set as the authenticated sender of the message, and the value is ++ available during delivery in the $authenticated_sender variable. If the ++ sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the ++ data. ++ ++ When a message is submitted locally (that is, not over a TCP connection), ++ the value of $authenticated_sender is an address constructed from the login ++ name of the calling process and $qualify_domain, except that a trusted user ++ can override this by means of the -oMas command line option. ++ ++$authentication_failed ++ ++ This variable is set to "1" in an Exim server if a client issues an AUTH ++ command that does not succeed. Otherwise it is set to "0". This makes it ++ possible to distinguish between "did not try to authenticate" ( ++ $sender_host_authenticated is empty and $authentication_failed is set to ++ "0") and "tried to authenticate but failed" ($sender_host_authenticated is ++ empty and $authentication_failed is set to "1"). Failure includes any ++ negative response to an AUTH command, including (for example) an attempt to ++ use an undefined mechanism. ++ ++$av_failed ++ ++ This variable is available when Exim is compiled with the content-scanning ++ extension. It is set to "0" by default, but will be set to "1" if any ++ problem occurs with the virus scanner (specified by av_scanner) during the ++ ACL malware condition. ++ ++$body_linecount ++ ++ When a message is being received or delivered, this variable contains the ++ number of lines in the message's body. See also $message_linecount. ++ ++$body_zerocount ++ ++ When a message is being received or delivered, this variable contains the ++ number of binary zero bytes (ASCII NULs) in the message's body. ++ ++$bounce_recipient ++ ++ This is set to the recipient address of a bounce message while Exim is ++ creating it. It is useful if a customized bounce message text file is in ++ use (see chapter 48). ++ ++$bounce_return_size_limit ++ ++ This contains the value set in the bounce_return_size_limit option, rounded ++ up to a multiple of 1000. It is useful when a customized error message text ++ file is in use (see chapter 48). ++ ++$caller_gid ++ ++ The real group id under which the process that called Exim was running. ++ This is not the same as the group id of the originator of a message (see ++ $originator_gid). If Exim re-execs itself, this variable in the new ++ incarnation normally contains the Exim gid. ++ ++$caller_uid ++ ++ The real user id under which the process that called Exim was running. This ++ is not the same as the user id of the originator of a message (see ++ $originator_uid). If Exim re-execs itself, this variable in the new ++ incarnation normally contains the Exim uid. ++ ++$compile_date ++ ++ The date on which the Exim binary was compiled. ++ ++$compile_number ++ ++ The building process for Exim keeps a count of the number of times it has ++ been compiled. This serves to distinguish different compilations of the ++ same version of the program. ++ ++$demime_errorlevel ++ ++ This variable is available when Exim is compiled with the content-scanning ++ extension and the obsolete demime condition. For details, see section 43.6. ++ ++$demime_reason ++ ++ This variable is available when Exim is compiled with the content-scanning ++ extension and the obsolete demime condition. For details, see section 43.6. ++ ++$dnslist_domain, $dnslist_matched, $dnslist_text, $dnslist_value ++ ++ When a DNS (black) list lookup succeeds, these variables are set to contain ++ the following data from the lookup: the list's domain name, the key that ++ was looked up, the contents of any associated TXT record, and the value ++ from the main A record. See section 42.31 for more details. ++ ++$domain ++ ++ When an address is being routed, or delivered on its own, this variable ++ contains the domain. Uppercase letters in the domain are converted into ++ lower case for $domain. ++ ++ Global address rewriting happens when a message is received, so the value ++ of $domain during routing and delivery is the value after rewriting. ++ $domain is set during user filtering, but not during system filtering, ++ because a message may have many recipients and the system filter is called ++ just once. ++ ++ When more than one address is being delivered at once (for example, several ++ RCPT commands in one SMTP delivery), $domain is set only if they all have ++ the same domain. Transports can be restricted to handling only one domain ++ at a time if the value of $domain is required at transport time - this is ++ the default for local transports. For further details of the environment in ++ which local transports are run, see chapter 23. ++ ++ At the end of a delivery, if all deferred addresses have the same domain, ++ it is set in $domain during the expansion of delay_warning_condition. ++ ++ The $domain variable is also used in some other circumstances: ++ ++ + When an ACL is running for a RCPT command, $domain contains the domain ++ of the recipient address. The domain of the sender address is in ++ $sender_address_domain at both MAIL time and at RCPT time. $domain is ++ not normally set during the running of the MAIL ACL. However, if the ++ sender address is verified with a callout during the MAIL ACL, the ++ sender domain is placed in $domain during the expansions of hosts, ++ interface, and port in the smtp transport. ++ ++ + When a rewrite item is being processed (see chapter 31), $domain ++ contains the domain portion of the address that is being rewritten; it ++ can be used in the expansion of the replacement address, for example, ++ to rewrite domains by file lookup. ++ ++ + With one important exception, whenever a domain list is being scanned, ++ $domain contains the subject domain. Exception: When a domain list in a ++ sender_domains condition in an ACL is being processed, the subject ++ domain is in $sender_address_domain and not in $domain. It works this ++ way so that, in a RCPT ACL, the sender domain list can be dependent on ++ the recipient domain (which is what is in $domain at this time). ++ ++ + When the smtp_etrn_command option is being expanded, $domain contains ++ the complete argument of the ETRN command (see section 47.8). ++ ++$domain_data ++ ++ When the domains option on a router matches a domain by means of a lookup, ++ the data read by the lookup is available during the running of the router ++ as $domain_data. In addition, if the driver routes the address to a ++ transport, the value is available in that transport. If the transport is ++ handling multiple addresses, the value from the first address is used. ++ ++ $domain_data is also set when the domains condition in an ACL matches a ++ domain by means of a lookup. The data read by the lookup is available ++ during the rest of the ACL statement. In all other situations, this ++ variable expands to nothing. ++ ++$exim_gid ++ ++ This variable contains the numerical value of the Exim group id. ++ ++$exim_path ++ ++ This variable contains the path to the Exim binary. ++ ++$exim_uid ++ ++ This variable contains the numerical value of the Exim user id. ++ ++$found_extension ++ ++ This variable is available when Exim is compiled with the content-scanning ++ extension and the obsolete demime condition. For details, see section 43.6. ++ ++$header_<name> ++ ++ This is not strictly an expansion variable. It is expansion syntax for ++ inserting the message header line with the given name. Note that the name ++ must be terminated by colon or white space, because it may contain a wide ++ variety of characters. Note also that braces must not be used. ++ ++$headers_added ++ ++ Within an ACL this variable contains the headers added so far by the ACL ++ modifier add_header (section 42.23). The headers are a newline-separated ++ list. ++ ++$home ++ ++ When the check_local_user option is set for a router, the user's home ++ directory is placed in $home when the check succeeds. In particular, this ++ means it is set during the running of users' filter files. A router may ++ also explicitly set a home directory for use by a transport; this can be ++ overridden by a setting on the transport itself. ++ ++ When running a filter test via the -bf option, $home is set to the value of ++ the environment variable HOME. ++ ++$host ++ ++ If a router assigns an address to a transport (any transport), and passes a ++ list of hosts with the address, the value of $host when the transport ++ starts to run is the name of the first host on the list. Note that this ++ applies both to local and remote transports. ++ ++ For the smtp transport, if there is more than one host, the value of $host ++ changes as the transport works its way through the list. In particular, ++ when the smtp transport is expanding its options for encryption using TLS, ++ or for specifying a transport filter (see chapter 24), $host contains the ++ name of the host to which it is connected. ++ ++ When used in the client part of an authenticator configuration (see chapter ++ 33), $host contains the name of the server to which the client is ++ connected. ++ ++$host_address ++ ++ This variable is set to the remote host's IP address whenever $host is set ++ for a remote connection. It is also set to the IP address that is being ++ checked when the ignore_target_hosts option is being processed. ++ ++$host_data ++ ++ If a hosts condition in an ACL is satisfied by means of a lookup, the ++ result of the lookup is made available in the $host_data variable. This ++ allows you, for example, to do things like this: ++ ++ deny hosts = net-lsearch;/some/file ++ message = $host_data ++ ++$host_lookup_deferred ++ ++ This variable normally contains "0", as does $host_lookup_failed. When a ++ message comes from a remote host and there is an attempt to look up the ++ host's name from its IP address, and the attempt is not successful, one of ++ these variables is set to "1". ++ ++ + If the lookup receives a definite negative response (for example, a DNS ++ lookup succeeded, but no records were found), $host_lookup_failed is ++ set to "1". ++ ++ + If there is any kind of problem during the lookup, such that Exim ++ cannot tell whether or not the host name is defined (for example, a ++ timeout for a DNS lookup), $host_lookup_deferred is set to "1". ++ ++ Looking up a host's name from its IP address consists of more than just a ++ single reverse lookup. Exim checks that a forward lookup of at least one of ++ the names it receives from a reverse lookup yields the original IP address. ++ If this is not the case, Exim does not accept the looked up name(s), and ++ $host_lookup_failed is set to "1". Thus, being able to find a name from an ++ IP address (for example, the existence of a PTR record in the DNS) is not ++ sufficient on its own for the success of a host name lookup. If the reverse ++ lookup succeeds, but there is a lookup problem such as a timeout when ++ checking the result, the name is not accepted, and $host_lookup_deferred is ++ set to "1". See also $sender_host_name. ++ ++$host_lookup_failed ++ ++ See $host_lookup_deferred. ++ ++$inode ++ ++ The only time this variable is set is while expanding the directory_file ++ option in the appendfile transport. The variable contains the inode number ++ of the temporary file which is about to be renamed. It can be used to ++ construct a unique name for the file. ++ ++$interface_address ++ ++ This is an obsolete name for $received_ip_address. ++ ++$interface_port ++ ++ This is an obsolete name for $received_port. ++ ++$item ++ ++ This variable is used during the expansion of forall and forany conditions ++ (see section 11.7), and filter, map, and reduce items (see section 11.7). ++ In other circumstances, it is empty. ++ ++$ldap_dn ++ ++ This variable, which is available only when Exim is compiled with LDAP ++ support, contains the DN from the last entry in the most recently ++ successful LDAP lookup. ++ ++$load_average ++ ++ This variable contains the system load average, multiplied by 1000 so that ++ it is an integer. For example, if the load average is 0.21, the value of ++ the variable is 210. The value is recomputed every time the variable is ++ referenced. ++ ++$local_part ++ ++ When an address is being routed, or delivered on its own, this variable ++ contains the local part. When a number of addresses are being delivered ++ together (for example, multiple RCPT commands in an SMTP session), ++ $local_part is not set. ++ ++ Global address rewriting happens when a message is received, so the value ++ of $local_part during routing and delivery is the value after rewriting. ++ $local_part is set during user filtering, but not during system filtering, ++ because a message may have many recipients and the system filter is called ++ just once. ++ ++ If a local part prefix or suffix has been recognized, it is not included in ++ the value of $local_part during routing and subsequent delivery. The values ++ of any prefix or suffix are in $local_part_prefix and $local_part_suffix, ++ respectively. ++ ++ When a message is being delivered to a file, pipe, or autoreply transport ++ as a result of aliasing or forwarding, $local_part is set to the local part ++ of the parent address, not to the file name or command (see $address_file ++ and $address_pipe). ++ ++ When an ACL is running for a RCPT command, $local_part contains the local ++ part of the recipient address. ++ ++ When a rewrite item is being processed (see chapter 31), $local_part ++ contains the local part of the address that is being rewritten; it can be ++ used in the expansion of the replacement address, for example. ++ ++ In all cases, all quoting is removed from the local part. For example, for ++ both the addresses ++ ++ "abc:xyz"@test.example ++ abc\:xyz@test.example ++ ++ the value of $local_part is ++ ++ abc:xyz ++ ++ If you use $local_part to create another address, you should always wrap it ++ inside a quoting operator. For example, in a redirect router you could ++ have: ++ ++ data = ${quote_local_part:$local_part}@new.domain.example ++ ++ Note: The value of $local_part is normally lower cased. If you want to ++ process local parts in a case-dependent manner in a router, you can set the ++ caseful_local_part option (see chapter 15). ++ ++$local_part_data ++ ++ When the local_parts option on a router matches a local part by means of a ++ lookup, the data read by the lookup is available during the running of the ++ router as $local_part_data. In addition, if the driver routes the address ++ to a transport, the value is available in that transport. If the transport ++ is handling multiple addresses, the value from the first address is used. ++ ++ $local_part_data is also set when the local_parts condition in an ACL ++ matches a local part by means of a lookup. The data read by the lookup is ++ available during the rest of the ACL statement. In all other situations, ++ this variable expands to nothing. ++ ++$local_part_prefix ++ ++ When an address is being routed or delivered, and a specific prefix for the ++ local part was recognized, it is available in this variable, having been ++ removed from $local_part. ++ ++$local_part_suffix ++ ++ When an address is being routed or delivered, and a specific suffix for the ++ local part was recognized, it is available in this variable, having been ++ removed from $local_part. ++ ++$local_scan_data ++ ++ This variable contains the text returned by the local_scan() function when ++ a message is received. See chapter 44 for more details. ++ ++$local_user_gid ++ ++ See $local_user_uid. ++ ++$local_user_uid ++ ++ This variable and $local_user_gid are set to the uid and gid after the ++ check_local_user router precondition succeeds. This means that their values ++ are available for the remaining preconditions (senders, require_files, and ++ condition), for the address_data expansion, and for any router-specific ++ expansions. At all other times, the values in these variables are "(uid_t) ++ (-1)" and "(gid_t)(-1)", respectively. ++ ++$localhost_number ++ ++ This contains the expanded value of the localhost_number option. The ++ expansion happens after the main options have been read. ++ ++$log_inodes ++ ++ The number of free inodes in the disk partition where Exim's log files are ++ being written. The value is recalculated whenever the variable is ++ referenced. If the relevant file system does not have the concept of ++ inodes, the value of is -1. See also the check_log_inodes option. ++ ++$log_space ++ ++ The amount of free space (as a number of kilobytes) in the disk partition ++ where Exim's log files are being written. The value is recalculated ++ whenever the variable is referenced. If the operating system does not have ++ the ability to find the amount of free space (only true for experimental ++ systems), the space value is -1. See also the check_log_space option. ++ ++$mailstore_basename ++ ++ This variable is set only when doing deliveries in "mailstore" format in ++ the appendfile transport. During the expansion of the mailstore_prefix, ++ mailstore_suffix, message_prefix, and message_suffix options, it contains ++ the basename of the files that are being written, that is, the name without ++ the ".tmp", ".env", or ".msg" suffix. At all other times, this variable is ++ empty. ++ ++$malware_name ++ ++ This variable is available when Exim is compiled with the content-scanning ++ extension. It is set to the name of the virus that was found when the ACL ++ malware condition is true (see section 43.1). ++ ++$max_received_linelength ++ ++ This variable contains the number of bytes in the longest line that was ++ received as part of the message, not counting the line termination ++ character(s). ++ ++$message_age ++ ++ This variable is set at the start of a delivery attempt to contain the ++ number of seconds since the message was received. It does not change during ++ a single delivery attempt. ++ ++$message_body ++ ++ This variable contains the initial portion of a message's body while it is ++ being delivered, and is intended mainly for use in filter files. The ++ maximum number of characters of the body that are put into the variable is ++ set by the message_body_visible configuration option; the default is 500. ++ ++ By default, newlines are converted into spaces in $message_body, to make it ++ easier to search for phrases that might be split over a line break. ++ However, this can be disabled by setting message_body_newlines to be true. ++ Binary zeros are always converted into spaces. ++ ++$message_body_end ++ ++ This variable contains the final portion of a message's body while it is ++ being delivered. The format and maximum size are as for $message_body. ++ ++$message_body_size ++ ++ When a message is being delivered, this variable contains the size of the ++ body in bytes. The count starts from the character after the blank line ++ that separates the body from the header. Newlines are included in the ++ count. See also $message_size, $body_linecount, and $body_zerocount. ++ ++$message_exim_id ++ ++ When a message is being received or delivered, this variable contains the ++ unique message id that is generated and used by Exim to identify the ++ message. An id is not created for a message until after its header has been ++ successfully received. Note: This is not the contents of the Message-ID: ++ header line; it is the local id that Exim assigns to the message, for ++ example: "1BXTIK-0001yO-VA". ++ ++$message_headers ++ ++ This variable contains a concatenation of all the header lines when a ++ message is being processed, except for lines added by routers or ++ transports. The header lines are separated by newline characters. Their ++ contents are decoded in the same way as a header line that is inserted by ++ bheader. ++ ++$message_headers_raw ++ ++ This variable is like $message_headers except that no processing of the ++ contents of header lines is done. ++ ++$message_id ++ ++ This is an old name for $message_exim_id, which is now deprecated. ++ ++$message_linecount ++ ++ This variable contains the total number of lines in the header and body of ++ the message. Compare $body_linecount, which is the count for the body only. ++ During the DATA and content-scanning ACLs, $message_linecount contains the ++ number of lines received. Before delivery happens (that is, before filters, ++ routers, and transports run) the count is increased to include the ++ Received: header line that Exim standardly adds, and also any other header ++ lines that are added by ACLs. The blank line that separates the message ++ header from the body is not counted. ++ ++ As with the special case of $message_size, during the expansion of the ++ appendfile transport's maildir_tag option in maildir format, the value of ++ $message_linecount is the precise size of the number of newlines in the ++ file that has been written (minus one for the blank line between the header ++ and the body). ++ ++ Here is an example of the use of this variable in a DATA ACL: ++ ++ deny message = Too many lines in message header ++ condition = \ ++ ${if <{250}{${eval:$message_linecount - $body_linecount}}} ++ ++ In the MAIL and RCPT ACLs, the value is zero because at that stage the ++ message has not yet been received. ++ ++$message_size ++ ++ When a message is being processed, this variable contains its size in ++ bytes. In most cases, the size includes those headers that were received ++ with the message, but not those (such as Envelope-to:) that are added to ++ individual deliveries as they are written. However, there is one special ++ case: during the expansion of the maildir_tag option in the appendfile ++ transport while doing a delivery in maildir format, the value of ++ $message_size is the precise size of the file that has been written. See ++ also $message_body_size, $body_linecount, and $body_zerocount. ++ ++ While running a per message ACL (mail/rcpt/predata), $message_size contains ++ the size supplied on the MAIL command, or -1 if no size was given. The ++ value may not, of course, be truthful. ++ ++$mime_xxx ++ ++ A number of variables whose names start with $mime are available when Exim ++ is compiled with the content-scanning extension. For details, see section ++ 43.4. ++ ++$n0 - $n9 ++ ++ These variables are counters that can be incremented by means of the add ++ command in filter files. ++ ++$original_domain ++ ++ When a top-level address is being processed for delivery, this contains the ++ same value as $domain. However, if a "child" address (for example, ++ generated by an alias, forward, or filter file) is being processed, this ++ variable contains the domain of the original address (lower cased). This ++ differs from $parent_domain only when there is more than one level of ++ aliasing or forwarding. When more than one address is being delivered in a ++ single transport run, $original_domain is not set. ++ ++ If a new address is created by means of a deliver command in a system ++ filter, it is set up with an artificial "parent" address. This has the ++ local part system-filter and the default qualify domain. ++ ++$original_local_part ++ ++ When a top-level address is being processed for delivery, this contains the ++ same value as $local_part, unless a prefix or suffix was removed from the ++ local part, because $original_local_part always contains the full local ++ part. When a "child" address (for example, generated by an alias, forward, ++ or filter file) is being processed, this variable contains the full local ++ part of the original address. ++ ++ If the router that did the redirection processed the local part ++ case-insensitively, the value in $original_local_part is in lower case. ++ This variable differs from $parent_local_part only when there is more than ++ one level of aliasing or forwarding. When more than one address is being ++ delivered in a single transport run, $original_local_part is not set. ++ ++ If a new address is created by means of a deliver command in a system ++ filter, it is set up with an artificial "parent" address. This has the ++ local part system-filter and the default qualify domain. ++ ++$originator_gid ++ ++ This variable contains the value of $caller_gid that was set when the ++ message was received. For messages received via the command line, this is ++ the gid of the sending user. For messages received by SMTP over TCP/IP, ++ this is normally the gid of the Exim user. ++ ++$originator_uid ++ ++ The value of $caller_uid that was set when the message was received. For ++ messages received via the command line, this is the uid of the sending ++ user. For messages received by SMTP over TCP/IP, this is normally the uid ++ of the Exim user. ++ ++$parent_domain ++ ++ This variable is similar to $original_domain (see above), except that it ++ refers to the immediately preceding parent address. ++ ++$parent_local_part ++ ++ This variable is similar to $original_local_part (see above), except that ++ it refers to the immediately preceding parent address. ++ ++$pid ++ ++ This variable contains the current process id. ++ ++$pipe_addresses ++ ++ This is not an expansion variable, but is mentioned here because the string ++ "$pipe_addresses" is handled specially in the command specification for the ++ pipe transport (chapter 29) and in transport filters (described under ++ transport_filter in chapter 24). It cannot be used in general expansion ++ strings, and provokes an "unknown variable" error if encountered. ++ ++$primary_hostname ++ ++ This variable contains the value set by primary_hostname in the ++ configuration file, or read by the uname() function. If uname() returns a ++ single-component name, Exim calls gethostbyname() (or getipnodebyname() ++ where available) in an attempt to acquire a fully qualified host name. See ++ also $smtp_active_hostname. ++ ++$prvscheck_address ++ ++ This variable is used in conjunction with the prvscheck expansion item, ++ which is described in sections 11.5 and 42.50. ++ ++$prvscheck_keynum ++ ++ This variable is used in conjunction with the prvscheck expansion item, ++ which is described in sections 11.5 and 42.50. ++ ++$prvscheck_result ++ ++ This variable is used in conjunction with the prvscheck expansion item, ++ which is described in sections 11.5 and 42.50. ++ ++$qualify_domain ++ ++ The value set for the qualify_domain option in the configuration file. ++ ++$qualify_recipient ++ ++ The value set for the qualify_recipient option in the configuration file, ++ or if not set, the value of $qualify_domain. ++ ++$rcpt_count ++ ++ When a message is being received by SMTP, this variable contains the number ++ of RCPT commands received for the current message. If this variable is used ++ in a RCPT ACL, its value includes the current command. ++ ++$rcpt_defer_count ++ ++ When a message is being received by SMTP, this variable contains the number ++ of RCPT commands in the current message that have previously been rejected ++ with a temporary (4xx) response. ++ ++$rcpt_fail_count ++ ++ When a message is being received by SMTP, this variable contains the number ++ of RCPT commands in the current message that have previously been rejected ++ with a permanent (5xx) response. ++ ++$received_count ++ ++ This variable contains the number of Received: header lines in the message, ++ including the one added by Exim (so its value is always greater than zero). ++ It is available in the DATA ACL, the non-SMTP ACL, and while routing and ++ delivering. ++ ++$received_for ++ ++ If there is only a single recipient address in an incoming message, this ++ variable contains that address when the Received: header line is being ++ built. The value is copied after recipient rewriting has happened, but ++ before the local_scan() function is run. ++ ++$received_ip_address ++ ++ As soon as an Exim server starts processing an incoming TCP/IP connection, ++ this variable is set to the address of the local IP interface, and ++ $received_port is set to the local port number. (The remote IP address and ++ port are in $sender_host_address and $sender_host_port.) When testing with ++ -bh, the port value is -1 unless it has been set using the -oMi command ++ line option. ++ ++ As well as being useful in ACLs (including the "connect" ACL), these ++ variable could be used, for example, to make the file name for a TLS ++ certificate depend on which interface and/or port is being used for the ++ incoming connection. The values of $received_ip_address and $received_port ++ are saved with any messages that are received, thus making these variables ++ available at delivery time. ++ ++ Note: There are no equivalent variables for outgoing connections, because ++ the values are unknown (unless they are explicitly set by options of the ++ smtp transport). ++ ++$received_port ++ ++ See $received_ip_address. ++ ++$received_protocol ++ ++ When a message is being processed, this variable contains the name of the ++ protocol by which it was received. Most of the names used by Exim are ++ defined by RFCs 821, 2821, and 3848. They start with "smtp" (the client ++ used HELO) or "esmtp" (the client used EHLO). This can be followed by "s" ++ for secure (encrypted) and/or "a" for authenticated. Thus, for example, if ++ the protocol is set to "esmtpsa", the message was received over an ++ encrypted SMTP connection and the client was successfully authenticated. ++ ++ Exim uses the protocol name "smtps" for the case when encryption is ++ automatically set up on connection without the use of STARTTLS (see ++ tls_on_connect_ports), and the client uses HELO to initiate the encrypted ++ SMTP session. The name "smtps" is also used for the rare situation where ++ the client initially uses EHLO, sets up an encrypted connection using ++ STARTTLS, and then uses HELO afterwards. ++ ++ The -oMr option provides a way of specifying a custom protocol name for ++ messages that are injected locally by trusted callers. This is commonly ++ used to identify messages that are being re-injected after some kind of ++ scanning. ++ ++$received_time ++ ++ This variable contains the date and time when the current message was ++ received, as a number of seconds since the start of the Unix epoch. ++ ++$recipient_data ++ ++ This variable is set after an indexing lookup success in an ACL recipients ++ condition. It contains the data from the lookup, and the value remains set ++ until the next recipients test. Thus, you can do things like this: ++ ++ require recipients = cdb*@;/some/file ++ deny some further test involving $recipient_data ++ ++ Warning: This variable is set only when a lookup is used as an indexing ++ method in the address list, using the semicolon syntax as in the example ++ above. The variable is not set for a lookup that is used as part of the ++ string expansion that all such lists undergo before being interpreted. ++ ++$recipient_verify_failure ++ ++ In an ACL, when a recipient verification fails, this variable contains ++ information about the failure. It is set to one of the following words: ++ ++ + "qualify": The address was unqualified (no domain), and the message was ++ neither local nor came from an exempted host. ++ ++ + "route": Routing failed. ++ ++ + "mail": Routing succeeded, and a callout was attempted; rejection ++ occurred at or before the MAIL command (that is, on initial connection, ++ HELO, or MAIL). ++ ++ + "recipient": The RCPT command in a callout was rejected. ++ ++ + "postmaster": The postmaster check in a callout was rejected. ++ ++ The main use of this variable is expected to be to distinguish between ++ rejections of MAIL and rejections of RCPT. ++ ++$recipients ++ ++ This variable contains a list of envelope recipients for a message. A comma ++ and a space separate the addresses in the replacement text. However, the ++ variable is not generally available, to prevent exposure of Bcc recipients ++ in unprivileged users' filter files. You can use $recipients only in these ++ cases: ++ ++ 1. In a system filter file. ++ ++ 2. In the ACLs associated with the DATA command and with non-SMTP ++ messages, that is, the ACLs defined by acl_smtp_predata, acl_smtp_data, ++ acl_smtp_mime, acl_not_smtp_start, acl_not_smtp, and acl_not_smtp_mime. ++ ++ 3. From within a local_scan() function. ++ ++$recipients_count ++ ++ When a message is being processed, this variable contains the number of ++ envelope recipients that came with the message. Duplicates are not excluded ++ from the count. While a message is being received over SMTP, the number ++ increases for each accepted recipient. It can be referenced in an ACL. ++ ++$regex_match_string ++ ++ This variable is set to contain the matching regular expression after a ++ regex ACL condition has matched (see section 43.5). ++ ++$reply_address ++ ++ When a message is being processed, this variable contains the contents of ++ the Reply-To: header line if one exists and it is not empty, or otherwise ++ the contents of the From: header line. Apart from the removal of leading ++ white space, the value is not processed in any way. In particular, no RFC ++ 2047 decoding or character code translation takes place. ++ ++$return_path ++ ++ When a message is being delivered, this variable contains the return path - ++ the sender field that will be sent as part of the envelope. It is not ++ enclosed in <> characters. At the start of routing an address, $return_path ++ has the same value as $sender_address, but if, for example, an incoming ++ message to a mailing list has been expanded by a router which specifies a ++ different address for bounce messages, $return_path subsequently contains ++ the new bounce address, whereas $sender_address always contains the ++ original sender address that was received with the message. In other words, ++ $sender_address contains the incoming envelope sender, and $return_path ++ contains the outgoing envelope sender. ++ ++$return_size_limit ++ ++ This is an obsolete name for $bounce_return_size_limit. ++ ++$router_name ++ ++ During the running of a router this variable contains its name. ++ ++$runrc ++ ++ This variable contains the return code from a command that is run by the $ ++ {run...} expansion item. Warning: In a router or transport, you cannot ++ assume the order in which option values are expanded, except for those ++ preconditions whose order of testing is documented. Therefore, you cannot ++ reliably expect to set $runrc by the expansion of one option, and use it in ++ another. ++ ++$self_hostname ++ ++ When an address is routed to a supposedly remote host that turns out to be ++ the local host, what happens is controlled by the self generic router ++ option. One of its values causes the address to be passed to another ++ router. When this happens, $self_hostname is set to the name of the local ++ host that the original router encountered. In other circumstances its ++ contents are null. ++ ++$sender_address ++ ++ When a message is being processed, this variable contains the sender's ++ address that was received in the message's envelope. The case of letters in ++ the address is retained, in both the local part and the domain. For bounce ++ messages, the value of this variable is the empty string. See also ++ $return_path. ++ ++$sender_address_data ++ ++ If $address_data is set when the routers are called from an ACL to verify a ++ sender address, the final value is preserved in $sender_address_data, to ++ distinguish it from data from a recipient address. The value does not ++ persist after the end of the current ACL statement. If you want to preserve ++ it for longer, you can save it in an ACL variable. ++ ++$sender_address_domain ++ ++ The domain portion of $sender_address. ++ ++$sender_address_local_part ++ ++ The local part portion of $sender_address. ++ ++$sender_data ++ ++ This variable is set after a lookup success in an ACL senders condition or ++ in a router senders option. It contains the data from the lookup, and the ++ value remains set until the next senders test. Thus, you can do things like ++ this: ++ ++ require senders = cdb*@;/some/file ++ deny some further test involving $sender_data ++ ++ Warning: This variable is set only when a lookup is used as an indexing ++ method in the address list, using the semicolon syntax as in the example ++ above. The variable is not set for a lookup that is used as part of the ++ string expansion that all such lists undergo before being interpreted. ++ ++$sender_fullhost ++ ++ When a message is received from a remote host, this variable contains the ++ host name and IP address in a single string. It ends with the IP address in ++ square brackets, followed by a colon and a port number if the logging of ++ ports is enabled. The format of the rest of the string depends on whether ++ the host issued a HELO or EHLO SMTP command, and whether the host name was ++ verified by looking up its IP address. (Looking up the IP address can be ++ forced by the host_lookup option, independent of verification.) A plain ++ host name at the start of the string is a verified host name; if this is ++ not present, verification either failed or was not requested. A host name ++ in parentheses is the argument of a HELO or EHLO command. This is omitted ++ if it is identical to the verified host name or to the host's IP address in ++ square brackets. ++ ++$sender_helo_name ++ ++ When a message is received from a remote host that has issued a HELO or ++ EHLO command, the argument of that command is placed in this variable. It ++ is also set if HELO or EHLO is used when a message is received using SMTP ++ locally via the -bs or -bS options. ++ ++$sender_host_address ++ ++ When a message is received from a remote host, this variable contains that ++ host's IP address. For locally submitted messages, it is empty. ++ ++$sender_host_authenticated ++ ++ This variable contains the name (not the public name) of the authenticator ++ driver that successfully authenticated the client from which the message ++ was received. It is empty if there was no successful authentication. See ++ also $authenticated_id. ++ ++$sender_host_dnssec ++ ++ If $sender_host_name has been populated (by reference, hosts_lookup or ++ otherwise) then this boolean will have been set true if, and only if, the ++ resolver library states that the reverse DNS was authenticated data. At all ++ other times, this variable is false. ++ ++ It is likely that you will need to coerce DNSSEC support on in the resolver ++ library, by setting: ++ ++ dns_use_dnssec = 1 ++ ++ Exim does not perform DNSSEC validation itself, instead leaving that to a ++ validating resolver (eg, unbound, or bind with suitable configuration). ++ ++ Exim does not (currently) check to see if the forward DNS was also secured ++ with DNSSEC, only the reverse DNS. ++ ++ If you have changed host_lookup_order so that "bydns" is not the first ++ mechanism in the list, then this variable will be false. ++ ++$sender_host_name ++ ++ When a message is received from a remote host, this variable contains the ++ host's name as obtained by looking up its IP address. For messages received ++ by other means, this variable is empty. ++ ++ If the host name has not previously been looked up, a reference to ++ $sender_host_name triggers a lookup (for messages from remote hosts). A ++ looked up name is accepted only if it leads back to the original IP address ++ via a forward lookup. If either the reverse or the forward lookup fails to ++ find any data, or if the forward lookup does not yield the original IP ++ address, $sender_host_name remains empty, and $host_lookup_failed is set to ++ "1". ++ ++ However, if either of the lookups cannot be completed (for example, there ++ is a DNS timeout), $host_lookup_deferred is set to "1", and ++ $host_lookup_failed remains set to "0". ++ ++ Once $host_lookup_failed is set to "1", Exim does not try to look up the ++ host name again if there is a subsequent reference to $sender_host_name in ++ the same Exim process, but it does try again if $host_lookup_deferred is ++ set to "1". ++ ++ Exim does not automatically look up every calling host's name. If you want ++ maximum efficiency, you should arrange your configuration so that it avoids ++ these lookups altogether. The lookup happens only if one or more of the ++ following are true: ++ ++ + A string containing $sender_host_name is expanded. ++ ++ + The calling host matches the list in host_lookup. In the default ++ configuration, this option is set to *, so it must be changed if ++ lookups are to be avoided. (In the code, the default for host_lookup is ++ unset.) ++ ++ + Exim needs the host name in order to test an item in a host list. The ++ items that require this are described in sections 10.13 and 10.16. ++ ++ + The calling host matches helo_try_verify_hosts or helo_verify_hosts. In ++ this case, the host name is required to compare with the name quoted in ++ any EHLO or HELO commands that the client issues. ++ ++ + The remote host issues a EHLO or HELO command that quotes one of the ++ domains in helo_lookup_domains. The default value of this option is ++ ++ helo_lookup_domains = @ : @[] ++ ++ which causes a lookup if a remote host (incorrectly) gives the server's ++ name or IP address in an EHLO or HELO command. ++ ++$sender_host_port ++ ++ When a message is received from a remote host, this variable contains the ++ port number that was used on the remote host. ++ ++$sender_ident ++ ++ When a message is received from a remote host, this variable contains the ++ identification received in response to an RFC 1413 request. When a message ++ has been received locally, this variable contains the login name of the ++ user that called Exim. ++ ++$sender_rate_xxx ++ ++ A number of variables whose names begin $sender_rate_ are set as part of ++ the ratelimit ACL condition. Details are given in section 42.37. ++ ++$sender_rcvhost ++ ++ This is provided specifically for use in Received: headers. It starts with ++ either the verified host name (as obtained from a reverse DNS lookup) or, ++ if there is no verified host name, the IP address in square brackets. After ++ that there may be text in parentheses. When the first item is a verified ++ host name, the first thing in the parentheses is the IP address in square ++ brackets, followed by a colon and a port number if port logging is enabled. ++ When the first item is an IP address, the port is recorded as "port=xxxx" ++ inside the parentheses. ++ ++ There may also be items of the form "helo=xxxx" if HELO or EHLO was used ++ and its argument was not identical to the real host name or IP address, and ++ "ident=xxxx" if an RFC 1413 ident string is available. If all three items ++ are present in the parentheses, a newline and tab are inserted into the ++ string, to improve the formatting of the Received: header. ++ ++$sender_verify_failure ++ ++ In an ACL, when a sender verification fails, this variable contains ++ information about the failure. The details are the same as for ++ $recipient_verify_failure. ++ ++$sending_ip_address ++ ++ This variable is set whenever an outgoing SMTP connection to another host ++ has been set up. It contains the IP address of the local interface that is ++ being used. This is useful if a host that has more than one IP address ++ wants to take on different personalities depending on which one is being ++ used. For incoming connections, see $received_ip_address. ++ ++$sending_port ++ ++ This variable is set whenever an outgoing SMTP connection to another host ++ has been set up. It contains the local port that is being used. For ++ incoming connections, see $received_port. ++ ++$smtp_active_hostname ++ ++ During an incoming SMTP session, this variable contains the value of the ++ active host name, as specified by the smtp_active_hostname option. The ++ value of $smtp_active_hostname is saved with any message that is received, ++ so its value can be consulted during routing and delivery. ++ ++$smtp_command ++ ++ During the processing of an incoming SMTP command, this variable contains ++ the entire command. This makes it possible to distinguish between HELO and ++ EHLO in the HELO ACL, and also to distinguish between commands such as ++ these: ++ ++ MAIL FROM:<> ++ MAIL FROM: <> ++ ++ For a MAIL command, extra parameters such as SIZE can be inspected. For a ++ RCPT command, the address in $smtp_command is the original address before ++ any rewriting, whereas the values in $local_part and $domain are taken from ++ the address after SMTP-time rewriting. ++ ++$smtp_command_argument ++ ++ While an ACL is running to check an SMTP command, this variable contains ++ the argument, that is, the text that follows the command name, with leading ++ white space removed. Following the introduction of $smtp_command, this ++ variable is somewhat redundant, but is retained for backwards ++ compatibility. ++ ++$smtp_count_at_connection_start ++ ++ This variable is set greater than zero only in processes spawned by the ++ Exim daemon for handling incoming SMTP connections. The name is ++ deliberately long, in order to emphasize what the contents are. When the ++ daemon accepts a new connection, it increments this variable. A copy of the ++ variable is passed to the child process that handles the connection, but ++ its value is fixed, and never changes. It is only an approximation of how ++ many incoming connections there actually are, because many other ++ connections may come and go while a single connection is being processed. ++ When a child process terminates, the daemon decrements its copy of the ++ variable. ++ ++$sn0 - $sn9 ++ ++ These variables are copies of the values of the $n0 - $n9 accumulators that ++ were current at the end of the system filter file. This allows a system ++ filter file to set values that can be tested in users' filter files. For ++ example, a system filter could set a value indicating how likely it is that ++ a message is junk mail. ++ ++$spam_xxx ++ ++ A number of variables whose names start with $spam are available when Exim ++ is compiled with the content-scanning extension. For details, see section ++ 43.2. ++ ++$spool_directory ++ ++ The name of Exim's spool directory. ++ ++$spool_inodes ++ ++ The number of free inodes in the disk partition where Exim's spool files ++ are being written. The value is recalculated whenever the variable is ++ referenced. If the relevant file system does not have the concept of ++ inodes, the value of is -1. See also the check_spool_inodes option. ++ ++$spool_space ++ ++ The amount of free space (as a number of kilobytes) in the disk partition ++ where Exim's spool files are being written. The value is recalculated ++ whenever the variable is referenced. If the operating system does not have ++ the ability to find the amount of free space (only true for experimental ++ systems), the space value is -1. For example, to check in an ACL that there ++ is at least 50 megabytes free on the spool, you could write: ++ ++ condition = ${if > {$spool_space}{50000}} ++ ++ See also the check_spool_space option. ++ ++$thisaddress ++ ++ This variable is set only during the processing of the foranyaddress ++ command in a filter file. Its use is explained in the description of that ++ command, which can be found in the separate document entitled Exim's ++ interfaces to mail filtering. ++ ++$tls_in_bits ++ ++ Contains an approximation of the TLS cipher's bit-strength on the inbound ++ connection; the meaning of this depends upon the TLS implementation used. ++ If TLS has not been negotiated, the value will be 0. The value of this is ++ automatically fed into the Cyrus SASL authenticator when acting as a ++ server, to specify the "external SSF" (a SASL term). ++ ++ The deprecated $tls_bits variable refers to the inbound side except when ++ used in the context of an outbound SMTP delivery, when it refers to the ++ outbound. ++ ++$tls_out_bits ++ ++ Contains an approximation of the TLS cipher's bit-strength on an outbound ++ SMTP connection; the meaning of this depends upon the TLS implementation ++ used. If TLS has not been negotiated, the value will be 0. ++ ++$tls_in_certificate_verified ++ ++ This variable is set to "1" if a TLS certificate was verified when the ++ message was received, and "0" otherwise. ++ ++ The deprecated $tls_certificate_verfied variable refers to the inbound side ++ except when used in the context of an outbound SMTP delivery, when it ++ refers to the outbound. ++ ++$tls_out_certificate_verified ++ ++ This variable is set to "1" if a TLS certificate was verified when an ++ outbound SMTP connection was made, and "0" otherwise. ++ ++$tls_in_cipher ++ ++ When a message is received from a remote host over an encrypted SMTP ++ connection, this variable is set to the cipher suite that was negotiated, ++ for example DES-CBC3-SHA. In other circumstances, in particular, for ++ message received over unencrypted connections, the variable is empty. ++ Testing $tls_cipher for emptiness is one way of distinguishing between ++ encrypted and non-encrypted connections during ACL processing. ++ ++ The deprecated $tls_cipher variable is the same as $tls_in_cipher during ++ message reception, but in the context of an outward SMTP delivery taking ++ place via the smtp transport becomes the same as $tls_out_cipher. ++ ++$tls_out_cipher ++ ++ This variable is cleared before any outgoing SMTP connection is made, and ++ then set to the outgoing cipher suite if one is negotiated. See chapter 41 ++ for details of TLS support and chapter 30 for details of the smtp ++ transport. ++ ++$tls_in_peerdn ++ ++ When a message is received from a remote host over an encrypted SMTP ++ connection, and Exim is configured to request a certificate from the ++ client, the value of the Distinguished Name of the certificate is made ++ available in the $tls_in_peerdn during subsequent processing. ++ ++ The deprecated $tls_peerdn variable refers to the inbound side except when ++ used in the context of an outbound SMTP delivery, when it refers to the ++ outbound. ++ ++$tls_out_peerdn ++ ++ When a message is being delivered to a remote host over an encrypted SMTP ++ connection, and Exim is configured to request a certificate from the ++ server, the value of the Distinguished Name of the certificate is made ++ available in the $tls_out_peerdn during subsequent processing. ++ ++$tls_in_sni ++ ++ When a TLS session is being established, if the client sends the Server ++ Name Indication extension, the value will be placed in this variable. If ++ the variable appears in tls_certificate then this option and some others, ++ described in 41.10, will be re-expanded early in the TLS session, to permit ++ a different certificate to be presented (and optionally a different key to ++ be used) to the client, based upon the value of the SNI extension. ++ ++ The deprecated $tls_sni variable refers to the inbound side except when ++ used in the context of an outbound SMTP delivery, when it refers to the ++ outbound. ++ ++$tls_out_sni ++ ++ During outbound SMTP deliveries, this variable reflects the value of the ++ tls_sni option on the transport. ++ ++$tod_bsdinbox ++ ++ The time of day and the date, in the format required for BSD-style mailbox ++ files, for example: Thu Oct 17 17:14:09 1995. ++ ++$tod_epoch ++ ++ The time and date as a number of seconds since the start of the Unix epoch. ++ ++$tod_epoch_l ++ ++ The time and date as a number of microseconds since the start of the Unix ++ epoch. ++ ++$tod_full ++ ++ A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40 ++ +0100. The timezone is always given as a numerical offset from UTC, with ++ positive values used for timezones that are ahead (east) of UTC, and ++ negative values for those that are behind (west). ++ ++$tod_log ++ ++ The time and date in the format used for writing Exim's log files, for ++ example: 1995-10-12 15:32:29, but without a timezone. ++ ++$tod_logfile ++ ++ This variable contains the date in the format yyyymmdd. This is the format ++ that is used for datestamping log files when log_file_path contains the ++ "%D" flag. ++ ++$tod_zone ++ ++ This variable contains the numerical value of the local timezone, for ++ example: -0500. ++ ++$tod_zulu ++ ++ This variable contains the UTC date and time in "Zulu" format, as specified ++ by ISO 8601, for example: 20030221154023Z. ++ ++$transport_name ++ ++ During the running of a transport, this variable contains its name. ++ ++$value ++ ++ This variable contains the result of an expansion lookup, extraction ++ operation, or external command, as described above. It is also used during ++ a reduce expansion. ++ ++$version_number ++ ++ The version number of Exim. ++ ++$warn_message_delay ++ ++ This variable is set only during the creation of a message warning about a ++ delivery delay. Details of its use are explained in section 48.2. ++ ++$warn_message_recipients ++ ++ This variable is set only during the creation of a message warning about a ++ delivery delay. Details of its use are explained in section 48.2. ++ ++ ++ ++=============================================================================== ++12. EMBEDDED PERL ++ ++Exim can be built to include an embedded Perl interpreter. When this is done, ++Perl subroutines can be called as part of the string expansion process. To make ++use of the Perl support, you need version 5.004 or later of Perl installed on ++your system. To include the embedded interpreter in the Exim binary, include ++the line ++ ++EXIM_PERL = perl.o ++ ++in your Local/Makefile and then build Exim in the normal way. ++ ++ ++12.1 Setting up so Perl can be used ++----------------------------------- ++ ++Access to Perl subroutines is via a global configuration option called ++perl_startup and an expansion string operator ${perl ...}. If there is no ++perl_startup option in the Exim configuration file then no Perl interpreter is ++started and there is almost no overhead for Exim (since none of the Perl ++library will be paged in unless used). If there is a perl_startup option then ++the associated value is taken to be Perl code which is executed in a newly ++created Perl interpreter. ++ ++The value of perl_startup is not expanded in the Exim sense, so you do not need ++backslashes before any characters to escape special meanings. The option should ++usually be something like ++ ++perl_startup = do '/etc/exim.pl' ++ ++where /etc/exim.pl is Perl code which defines any subroutines you want to use ++from Exim. Exim can be configured either to start up a Perl interpreter as soon ++as it is entered, or to wait until the first time it is needed. Starting the ++interpreter at the beginning ensures that it is done while Exim still has its ++setuid privilege, but can impose an unnecessary overhead if Perl is not in fact ++used in a particular run. Also, note that this does not mean that Exim is ++necessarily running as root when Perl is called at a later time. By default, ++the interpreter is started only when it is needed, but this can be changed in ++two ways: ++ ++ * Setting perl_at_start (a boolean option) in the configuration requests a ++ startup when Exim is entered. ++ ++ * The command line option -ps also requests a startup when Exim is entered, ++ overriding the setting of perl_at_start. ++ ++There is also a command line option -pd (for delay) which suppresses the ++initial startup, even if perl_at_start is set. ++ ++ ++12.2 Calling Perl subroutines ++----------------------------- ++ ++When the configuration file includes a perl_startup option you can make use of ++the string expansion item to call the Perl subroutines that are defined by the ++perl_startup code. The operator is used in any of the following forms: ++ ++${perl{foo}} ++${perl{foo}{argument}} ++${perl{foo}{argument1}{argument2} ... } ++ ++which calls the subroutine foo with the given arguments. A maximum of eight ++arguments may be passed. Passing more than this results in an expansion failure ++with an error message of the form ++ ++Too many arguments passed to Perl subroutine "foo" (max is 8) ++ ++The return value of the Perl subroutine is evaluated in a scalar context before ++it is passed back to Exim to be inserted into the expanded string. If the ++return value is undef, the expansion is forced to fail in the same way as an ++explicit "fail" on an if or lookup item. If the subroutine aborts by obeying ++Perl's die function, the expansion fails with the error message that was passed ++to die. ++ ++ ++12.3 Calling Exim functions from Perl ++------------------------------------- ++ ++Within any Perl code called from Exim, the function Exim::expand_string() is ++available to call back into Exim's string expansion function. For example, the ++Perl code ++ ++my $lp = Exim::expand_string('$local_part'); ++ ++makes the current Exim $local_part available in the Perl variable $lp. Note ++those are single quotes and not double quotes to protect against $local_part ++being interpolated as a Perl variable. ++ ++If the string expansion is forced to fail by a "fail" item, the result of ++Exim::expand_string() is undef. If there is a syntax error in the expansion ++string, the Perl call from the original expansion string fails with an ++appropriate error message, in the same way as if die were used. ++ ++Two other Exim functions are available for use from within Perl code. ++Exim::debug_write() writes a string to the standard error stream if Exim's ++debugging is enabled. If you want a newline at the end, you must supply it. ++Exim::log_write() writes a string to Exim's main log, adding a leading ++timestamp. In this case, you should not supply a terminating newline. ++ ++ ++12.4 Use of standard output and error by Perl ++--------------------------------------------- ++ ++You should not write to the standard error or output streams from within your ++Perl code, as it is not defined how these are set up. In versions of Exim ++before 4.50, it is possible for the standard output or error to refer to the ++SMTP connection during message reception via the daemon. Writing to this stream ++is certain to cause chaos. From Exim 4.50 onwards, the standard output and ++error streams are connected to /dev/null in the daemon. The chaos is avoided, ++but the output is lost. ++ ++The Perl warn statement writes to the standard error stream by default. Calls ++to warn may be embedded in Perl modules that you use, but over which you have ++no control. When Exim starts up the Perl interpreter, it arranges for output ++from the warn statement to be written to the Exim main log. You can change this ++by including appropriate Perl magic somewhere in your Perl code. For example, ++to discard warn output completely, you need this: ++ ++$SIG{__WARN__} = sub { }; ++ ++Whenever a warn is obeyed, the anonymous subroutine is called. In this example, ++the code for the subroutine is empty, so it does nothing, but you can include ++any Perl code that you like. The text of the warn message is passed as the ++first subroutine argument. ++ ++ ++ ++=============================================================================== ++13. STARTING THE DAEMON AND THE USE OF NETWORK INTERFACES ++ ++A host that is connected to a TCP/IP network may have one or more physical ++hardware network interfaces. Each of these interfaces may be configured as one ++or more "logical" interfaces, which are the entities that a program actually ++works with. Each of these logical interfaces is associated with an IP address. ++In addition, TCP/IP software supports "loopback" interfaces (127.0.0.1 in IPv4 ++and ::1 in IPv6), which do not use any physical hardware. Exim requires ++knowledge about the host's interfaces for use in three different circumstances: ++ ++ 1. When a listening daemon is started, Exim needs to know which interfaces and ++ ports to listen on. ++ ++ 2. When Exim is routing an address, it needs to know which IP addresses are ++ associated with local interfaces. This is required for the correct ++ processing of MX lists by removing the local host and others with the same ++ or higher priority values. Also, Exim needs to detect cases when an address ++ is routed to an IP address that in fact belongs to the local host. Unless ++ the self router option or the allow_localhost option of the smtp transport ++ is set (as appropriate), this is treated as an error situation. ++ ++ 3. When Exim connects to a remote host, it may need to know which interface to ++ use for the outgoing connection. ++ ++Exim's default behaviour is likely to be appropriate in the vast majority of ++cases. If your host has only one interface, and you want all its IP addresses ++to be treated in the same way, and you are using only the standard SMTP port, ++you should not need to take any special action. The rest of this chapter does ++not apply to you. ++ ++In a more complicated situation you may want to listen only on certain ++interfaces, or on different ports, and for this reason there are a number of ++options that can be used to influence Exim's behaviour. The rest of this ++chapter describes how they operate. ++ ++When a message is received over TCP/IP, the interface and port that were ++actually used are set in $received_ip_address and $received_port. ++ ++ ++13.1 Starting a listening daemon ++-------------------------------- ++ ++When a listening daemon is started (by means of the -bd command line option), ++the interfaces and ports on which it listens are controlled by the following ++options: ++ ++ * daemon_smtp_ports contains a list of default ports. (For backward ++ compatibility, this option can also be specified in the singular.) ++ ++ * local_interfaces contains list of interface IP addresses on which to ++ listen. Each item may optionally also specify a port. ++ ++The default list separator in both cases is a colon, but this can be changed as ++described in section 6.19. When IPv6 addresses are involved, it is usually best ++to change the separator to avoid having to double all the colons. For example: ++ ++local_interfaces = <; 127.0.0.1 ; \ ++ 192.168.23.65 ; \ ++ ::1 ; \ ++ 3ffe:ffff:836f::fe86:a061 ++ ++There are two different formats for specifying a port along with an IP address ++in local_interfaces: ++ ++ 1. The port is added onto the address with a dot separator. For example, to ++ listen on port 1234 on two different IP addresses: ++ ++ local_interfaces = <; 192.168.23.65.1234 ; \ ++ 3ffe:ffff:836f::fe86:a061.1234 ++ ++ 2. The IP address is enclosed in square brackets, and the port is added with a ++ colon separator, for example: ++ ++ local_interfaces = <; [192.168.23.65]:1234 ; \ ++ [3ffe:ffff:836f::fe86:a061]:1234 ++ ++When a port is not specified, the value of daemon_smtp_ports is used. The ++default setting contains just one port: ++ ++daemon_smtp_ports = smtp ++ ++If more than one port is listed, each interface that does not have its own port ++specified listens on all of them. Ports that are listed in daemon_smtp_ports ++can be identified either by name (defined in /etc/services) or by number. ++However, when ports are given with individual IP addresses in local_interfaces, ++only numbers (not names) can be used. ++ ++ ++13.2 Special IP listening addresses ++----------------------------------- ++ ++The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted as ++"all IPv4 interfaces" and "all IPv6 interfaces", respectively. In each case, ++Exim tells the TCP/IP stack to "listen on all IPvx interfaces" instead of ++setting up separate listening sockets for each interface. The default value of ++local_interfaces is ++ ++local_interfaces = 0.0.0.0 ++ ++when Exim is built without IPv6 support; otherwise it is: ++ ++local_interfaces = <; ::0 ; 0.0.0.0 ++ ++Thus, by default, Exim listens on all available interfaces, on the SMTP port. ++ ++ ++13.3 Overriding local_interfaces and daemon_smtp_ports ++------------------------------------------------------ ++ ++The -oX command line option can be used to override the values of ++daemon_smtp_ports and/or local_interfaces for a particular daemon instance. ++Another way of doing this would be to use macros and the -D option. However, ++-oX can be used by any admin user, whereas modification of the runtime ++configuration by -D is allowed only when the caller is root or exim. ++ ++The value of -oX is a list of items. The default colon separator can be changed ++in the usual way if required. If there are any items that do not contain dots ++or colons (that is, are not IP addresses), the value of daemon_smtp_ports is ++replaced by the list of those items. If there are any items that do contain ++dots or colons, the value of local_interfaces is replaced by those items. Thus, ++for example, ++ ++-oX 1225 ++ ++overrides daemon_smtp_ports, but leaves local_interfaces unchanged, whereas ++ ++-oX 192.168.34.5.1125 ++ ++overrides local_interfaces, leaving daemon_smtp_ports unchanged. (However, ++since local_interfaces now contains no items without ports, the value of ++daemon_smtp_ports is no longer relevant in this example.) ++ ++ ++13.4 Support for the obsolete SSMTP (or SMTPS) protocol ++------------------------------------------------------- ++ ++Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used ++before the STARTTLS command was standardized for SMTP. Some legacy clients ++still use this protocol. If the tls_on_connect_ports option is set to a list of ++port numbers, connections to those ports must use SSMTP. The most common use of ++this option is expected to be ++ ++tls_on_connect_ports = 465 ++ ++because 465 is the usual port number used by the legacy clients. There is also ++a command line option -tls-on-connect, which forces all ports to behave in this ++way when a daemon is started. ++ ++Warning: Setting tls_on_connect_ports does not of itself cause the daemon to ++listen on those ports. You must still specify them in daemon_smtp_ports, ++local_interfaces, or the -oX option. (This is because tls_on_connect_ports ++applies to inetd connections as well as to connections via the daemon.) ++ ++ ++13.5 IPv6 address scopes ++------------------------ ++ ++IPv6 addresses have "scopes", and a host with multiple hardware interfaces can, ++in principle, have the same link-local IPv6 address on different interfaces. ++Thus, additional information is needed, over and above the IP address, to ++distinguish individual interfaces. A convention of using a percent sign ++followed by something (often the interface name) has been adopted in some ++cases, leading to addresses like this: ++ ++fe80::202:b3ff:fe03:45c1%eth0 ++ ++To accommodate this usage, a percent sign followed by an arbitrary string is ++allowed at the end of an IPv6 address. By default, Exim calls getaddrinfo() to ++convert a textual IPv6 address for actual use. This function recognizes the ++percent convention in operating systems that support it, and it processes the ++address appropriately. Unfortunately, some older libraries have problems with ++getaddrinfo(). If ++ ++IPV6_USE_INET_PTON=yes ++ ++is set in Local/Makefile (or an OS-dependent Makefile) when Exim is built, Exim ++uses inet_pton() to convert a textual IPv6 address for actual use, instead of ++getaddrinfo(). (Before version 4.14, it always used this function.) Of course, ++this means that the additional functionality of getaddrinfo() - recognizing ++scoped addresses - is lost. ++ ++ ++13.6 Disabling IPv6 ++------------------- ++ ++Sometimes it happens that an Exim binary that was compiled with IPv6 support is ++run on a host whose kernel does not support IPv6. The binary will fall back to ++using IPv4, but it may waste resources looking up AAAA records, and trying to ++connect to IPv6 addresses, causing delays to mail delivery. If you set the ++disable_ipv6 option true, even if the Exim binary has IPv6 support, no IPv6 ++activities take place. AAAA records are never looked up, and any IPv6 addresses ++that are listed in local_interfaces, data for the manualroute router, etc. are ++ignored. If IP literals are enabled, the ipliteral router declines to handle ++IPv6 literal addresses. ++ ++On the other hand, when IPv6 is in use, there may be times when you want to ++disable it for certain hosts or domains. You can use the dns_ipv4_lookup option ++to globally suppress the lookup of AAAA records for specified domains, and you ++can use the ignore_target_hosts generic router option to ignore IPv6 addresses ++in an individual router. ++ ++ ++13.7 Examples of starting a listening daemon ++-------------------------------------------- ++ ++The default case in an IPv6 environment is ++ ++daemon_smtp_ports = smtp ++local_interfaces = <; ::0 ; 0.0.0.0 ++ ++This specifies listening on the smtp port on all IPv6 and IPv4 interfaces. ++Either one or two sockets may be used, depending on the characteristics of the ++TCP/IP stack. (This is complicated and messy; for more information, read the ++comments in the daemon.c source file.) ++ ++To specify listening on ports 25 and 26 on all interfaces: ++ ++daemon_smtp_ports = 25 : 26 ++ ++(leaving local_interfaces at the default setting) or, more explicitly: ++ ++local_interfaces = <; ::0.25 ; ::0.26 \ ++ 0.0.0.0.25 ; 0.0.0.0.26 ++ ++To listen on the default port on all IPv4 interfaces, and on port 26 on the ++IPv4 loopback address only: ++ ++local_interfaces = 0.0.0.0 : 127.0.0.1.26 ++ ++To specify listening on the default port on specific interfaces only: ++ ++local_interfaces = 10.0.0.67 : 192.168.34.67 ++ ++Warning: Such a setting excludes listening on the loopback interfaces. ++ ++ ++13.8 Recognizing the local host ++------------------------------- ++ ++The local_interfaces option is also used when Exim needs to determine whether ++or not an IP address refers to the local host. That is, the IP addresses of all ++the interfaces on which a daemon is listening are always treated as local. ++ ++For this usage, port numbers in local_interfaces are ignored. If either of the ++items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of available ++interfaces from the operating system, and extracts the relevant (that is, IPv4 ++or IPv6) addresses to use for checking. ++ ++Some systems set up large numbers of virtual interfaces in order to provide ++many virtual web servers. In this situation, you may want to listen for email ++on only a few of the available interfaces, but nevertheless treat all ++interfaces as local when routing. You can do this by setting ++extra_local_interfaces to a list of IP addresses, possibly including the "all" ++wildcard values. These addresses are recognized as local, but are not used for ++listening. Consider this example: ++ ++local_interfaces = <; 127.0.0.1 ; ::1 ; \ ++ 192.168.53.235 ; \ ++ 3ffe:2101:12:1:a00:20ff:fe86:a061 ++ ++extra_local_interfaces = <; ::0 ; 0.0.0.0 ++ ++The daemon listens on the loopback interfaces and just one IPv4 and one IPv6 ++address, but all available interface addresses are treated as local when Exim ++is routing. ++ ++In some environments the local host name may be in an MX list, but with an IP ++address that is not assigned to any local interface. In other cases it may be ++desirable to treat other host names as if they referred to the local host. Both ++these cases can be handled by setting the hosts_treat_as_local option. This ++contains host names rather than IP addresses. When a host is referenced during ++routing, either via an MX record or directly, it is treated as the local host ++if its name matches hosts_treat_as_local, or if any of its IP addresses match ++local_interfaces or extra_local_interfaces. ++ ++ ++13.9 Delivering to a remote host ++-------------------------------- ++ ++Delivery to a remote host is handled by the smtp transport. By default, it ++allows the system's TCP/IP functions to choose which interface to use (if there ++is more than one) when connecting to a remote host. However, the interface ++option can be set to specify which interface is used. See the description of ++the smtp transport in chapter 30 for more details. ++ ++ ++ ++=============================================================================== ++14. MAIN CONFIGURATION ++ ++The first part of the run time configuration file contains three types of item: ++ ++ * Macro definitions: These lines start with an upper case letter. See section ++ 6.4 for details of macro processing. ++ ++ * Named list definitions: These lines start with one of the words ++ "domainlist", "hostlist", "addresslist", or "localpartlist". Their use is ++ described in section 10.5. ++ ++ * Main configuration settings: Each setting occupies one line of the file ++ (with possible continuations). If any setting is preceded by the word ++ "hide", the -bP command line option displays its value to admin users only. ++ See section 6.10 for a description of the syntax of these option settings. ++ ++This chapter specifies all the main configuration options, along with their ++types and default values. For ease of finding a particular option, they appear ++in alphabetical order in section 14.23 below. However, because there are now so ++many options, they are first listed briefly in functional groups, as an aid to ++finding the name of the option you are looking for. Some options are listed in ++more than one group. ++ ++ ++14.1 Miscellaneous ++------------------ ++ ++bi_command to run for -bi command line option ++disable_ipv6 do no IPv6 processing ++keep_malformed for broken files - should not happen ++localhost_number for unique message ids in clusters ++message_body_newlines retain newlines in $message_body ++message_body_visible how much to show in $message_body ++mua_wrapper run in "MUA wrapper" mode ++print_topbitchars top-bit characters are printing ++timezone force time zone ++ ++ ++14.2 Exim parameters ++-------------------- ++ ++exim_group override compiled-in value ++exim_path override compiled-in value ++exim_user override compiled-in value ++primary_hostname default from uname() ++split_spool_directory use multiple directories ++spool_directory override compiled-in value ++ ++ ++14.3 Privilege controls ++----------------------- ++ ++admin_groups groups that are Exim admin users ++deliver_drop_privilege drop root for delivery processes ++local_from_check insert Sender: if necessary ++local_from_prefix for testing From: for local sender ++local_from_suffix for testing From: for local sender ++local_sender_retain keep Sender: from untrusted user ++never_users do not run deliveries as these ++prod_requires_admin forced delivery requires admin user ++queue_list_requires_admin queue listing requires admin user ++trusted_groups groups that are trusted ++trusted_users users that are trusted ++ ++ ++14.4 Logging ++------------ ++ ++hosts_connection_nolog exemption from connect logging ++log_file_path override compiled-in value ++log_selector set/unset optional logging ++log_timezone add timezone to log lines ++message_logs create per-message logs ++preserve_message_logs after message completion ++process_log_path for SIGUSR1 and exiwhat ++syslog_duplication controls duplicate log lines on syslog ++syslog_facility set syslog "facility" field ++syslog_processname set syslog "ident" field ++syslog_timestamp timestamp syslog lines ++write_rejectlog control use of message log ++ ++ ++14.5 Frozen messages ++-------------------- ++ ++auto_thaw sets time for retrying frozen messages ++freeze_tell send message when freezing ++move_frozen_messages to another directory ++timeout_frozen_after keep frozen messages only so long ++ ++ ++14.6 Data lookups ++----------------- ++ ++ibase_servers InterBase servers ++ldap_ca_cert_dir dir of CA certs to verify LDAP server's ++ldap_ca_cert_file file of CA certs to verify LDAP server's ++ldap_cert_file client cert file for LDAP ++ldap_cert_key client key file for LDAP ++ldap_cipher_suite TLS negotiation preference control ++ldap_default_servers used if no server in query ++ldap_require_cert action to take without LDAP server cert ++ldap_start_tls require TLS within LDAP ++ldap_version set protocol version ++lookup_open_max lookup files held open ++mysql_servers default MySQL servers ++oracle_servers Oracle servers ++pgsql_servers default PostgreSQL servers ++sqlite_lock_timeout as it says ++ ++ ++14.7 Message ids ++---------------- ++ ++message_id_header_domain used to build Message-ID: header ++message_id_header_text ditto ++ ++ ++14.8 Embedded Perl Startup ++-------------------------- ++ ++perl_at_start always start the interpreter ++perl_startup code to obey when starting Perl ++ ++ ++14.9 Daemon ++----------- ++ ++daemon_smtp_ports default ports ++daemon_startup_retries number of times to retry ++daemon_startup_sleep time to sleep between tries ++extra_local_interfaces not necessarily listened on ++local_interfaces on which to listen, with optional ports ++pid_file_path override compiled-in value ++queue_run_max maximum simultaneous queue runners ++ ++ ++14.10 Resource control ++---------------------- ++ ++check_log_inodes before accepting a message ++check_log_space before accepting a message ++check_spool_inodes before accepting a message ++check_spool_space before accepting a message ++deliver_queue_load_max no queue deliveries if load high ++queue_only_load queue incoming if load high ++queue_only_load_latch don't re-evaluate load for each message ++queue_run_max maximum simultaneous queue runners ++remote_max_parallel parallel SMTP delivery per message ++smtp_accept_max simultaneous incoming connections ++smtp_accept_max_nonmail non-mail commands ++smtp_accept_max_nonmail_hosts hosts to which the limit applies ++smtp_accept_max_per_connection messages per connection ++smtp_accept_max_per_host connections from one host ++smtp_accept_queue queue mail if more connections ++smtp_accept_queue_per_connection queue if more messages per connection ++smtp_accept_reserve only reserve hosts if more connections ++smtp_check_spool_space from SIZE on MAIL command ++smtp_connect_backlog passed to TCP/IP stack ++smtp_load_reserve SMTP from reserved hosts if load high ++smtp_reserve_hosts these are the reserve hosts ++ ++ ++14.11 Policy controls ++--------------------- ++ ++acl_not_smtp ACL for non-SMTP messages ++acl_not_smtp_mime ACL for non-SMTP MIME parts ++acl_not_smtp_start ACL for start of non-SMTP message ++acl_smtp_auth ACL for AUTH ++acl_smtp_connect ACL for connection ++acl_smtp_data ACL for DATA ++acl_smtp_dkim ACL for DKIM verification ++acl_smtp_etrn ACL for ETRN ++acl_smtp_expn ACL for EXPN ++acl_smtp_helo ACL for EHLO or HELO ++acl_smtp_mail ACL for MAIL ++acl_smtp_mailauth ACL for AUTH on MAIL command ++acl_smtp_mime ACL for MIME parts ++acl_smtp_predata ACL for start of data ++acl_smtp_quit ACL for QUIT ++acl_smtp_rcpt ACL for RCPT ++acl_smtp_starttls ACL for STARTTLS ++acl_smtp_vrfy ACL for VRFY ++av_scanner specify virus scanner ++check_rfc2047_length check length of RFC 2047 "encoded words" ++dns_csa_search_limit control CSA parent search depth ++dns_csa_use_reverse en/disable CSA IP reverse search ++header_maxsize total size of message header ++header_line_maxsize individual header line limit ++helo_accept_junk_hosts allow syntactic junk from these hosts ++helo_allow_chars allow illegal chars in HELO names ++helo_lookup_domains lookup hostname for these HELO names ++helo_try_verify_hosts HELO soft-checked for these hosts ++helo_verify_hosts HELO hard-checked for these hosts ++host_lookup host name looked up for these hosts ++host_lookup_order order of DNS and local name lookups ++host_reject_connection reject connection from these hosts ++hosts_treat_as_local useful in some cluster configurations ++local_scan_timeout timeout for local_scan() ++message_size_limit for all messages ++percent_hack_domains recognize %-hack for these domains ++spamd_address set interface to SpamAssassin ++strict_acl_vars object to unset ACL variables ++ ++ ++14.12 Callout cache ++------------------- ++ ++callout_domain_negative_expire timeout for negative domain cache item ++callout_domain_positive_expire timeout for positive domain cache item ++callout_negative_expire timeout for negative address cache item ++callout_positive_expire timeout for positive address cache item ++callout_random_local_part string to use for "random" testing ++ ++ ++14.13 TLS ++--------- ++ ++gnutls_compat_mode use GnuTLS compatibility mode ++gnutls_enable_pkcs11 allow GnuTLS to autoload PKCS11 modules ++openssl_options adjust OpenSSL compatibility options ++tls_advertise_hosts advertise TLS to these hosts ++tls_certificate location of server certificate ++tls_crl certificate revocation list ++tls_dh_max_bits clamp D-H bit count suggestion ++tls_dhparam DH parameters for server ++tls_on_connect_ports specify SSMTP (SMTPS) ports ++tls_privatekey location of server private key ++tls_remember_esmtp don't reset after starting TLS ++tls_require_ciphers specify acceptable ciphers ++tls_try_verify_hosts try to verify client certificate ++tls_verify_certificates expected client certificates ++tls_verify_hosts insist on client certificate verify ++ ++ ++14.14 Local user handling ++------------------------- ++ ++finduser_retries useful in NIS environments ++gecos_name used when creating Sender: ++gecos_pattern ditto ++max_username_length for systems that truncate ++unknown_login used when no login name found ++unknown_username ditto ++uucp_from_pattern for recognizing "From " lines ++uucp_from_sender ditto ++ ++ ++14.15 All incoming messages (SMTP and non-SMTP) ++----------------------------------------------- ++ ++header_maxsize total size of message header ++header_line_maxsize individual header line limit ++message_size_limit applies to all messages ++percent_hack_domains recognize %-hack for these domains ++received_header_text expanded to make Received: ++received_headers_max for mail loop detection ++recipients_max limit per message ++recipients_max_reject permanently reject excess recipients ++ ++ ++14.16 Non-SMTP incoming messages ++-------------------------------- ++ ++receive_timeout for non-SMTP messages ++ ++ ++14.17 Incoming SMTP messages ++---------------------------- ++ ++See also the Policy controls section above. ++ ++host_lookup host name looked up for these hosts ++host_lookup_order order of DNS and local name lookups ++recipient_unqualified_hosts may send unqualified recipients ++rfc1413_hosts make ident calls to these hosts ++rfc1413_query_timeout zero disables ident calls ++sender_unqualified_hosts may send unqualified senders ++smtp_accept_keepalive some TCP/IP magic ++smtp_accept_max simultaneous incoming connections ++smtp_accept_max_nonmail non-mail commands ++smtp_accept_max_nonmail_hosts hosts to which the limit applies ++smtp_accept_max_per_connection messages per connection ++smtp_accept_max_per_host connections from one host ++smtp_accept_queue queue mail if more connections ++smtp_accept_queue_per_connection queue if more messages per connection ++smtp_accept_reserve only reserve hosts if more connections ++smtp_active_hostname host name to use in messages ++smtp_banner text for welcome banner ++smtp_check_spool_space from SIZE on MAIL command ++smtp_connect_backlog passed to TCP/IP stack ++smtp_enforce_sync of SMTP command/responses ++smtp_etrn_command what to run for ETRN ++smtp_etrn_serialize only one at once ++smtp_load_reserve only reserve hosts if this load ++smtp_max_unknown_commands before dropping connection ++smtp_ratelimit_hosts apply ratelimiting to these hosts ++smtp_ratelimit_mail ratelimit for MAIL commands ++smtp_ratelimit_rcpt ratelimit for RCPT commands ++smtp_receive_timeout per command or data line ++smtp_reserve_hosts these are the reserve hosts ++smtp_return_error_details give detail on rejections ++ ++ ++14.18 SMTP extensions ++--------------------- ++ ++accept_8bitmime advertise 8BITMIME ++auth_advertise_hosts advertise AUTH to these hosts ++ignore_fromline_hosts allow "From " from these hosts ++ignore_fromline_local allow "From " from local SMTP ++pipelining_advertise_hosts advertise pipelining to these hosts ++tls_advertise_hosts advertise TLS to these hosts ++ ++ ++14.19 Processing messages ++------------------------- ++ ++allow_domain_literals recognize domain literal syntax ++allow_mx_to_ip allow MX to point to IP address ++allow_utf8_domains in addresses ++check_rfc2047_length check length of RFC 2047 "encoded words" ++delivery_date_remove from incoming messages ++envelope_to_remove from incoming messages ++extract_addresses_remove_arguments affects -t processing ++headers_charset default for translations ++qualify_domain default for senders ++qualify_recipient default for recipients ++return_path_remove from incoming messages ++strip_excess_angle_brackets in addresses ++strip_trailing_dot at end of addresses ++untrusted_set_sender untrusted can set envelope sender ++ ++ ++14.20 System filter ++------------------- ++ ++system_filter locate system filter ++system_filter_directory_transport transport for delivery to a directory ++system_filter_file_transport transport for delivery to a file ++system_filter_group group for filter running ++system_filter_pipe_transport transport for delivery to a pipe ++system_filter_reply_transport transport for autoreply delivery ++system_filter_user user for filter running ++ ++ ++14.21 Routing and delivery ++-------------------------- ++ ++disable_ipv6 do no IPv6 processing ++dns_again_means_nonexist for broken domains ++dns_check_names_pattern pre-DNS syntax check ++dns_ipv4_lookup only v4 lookup for these domains ++dns_retrans parameter for resolver ++dns_retry parameter for resolver ++dns_use_dnssec parameter for resolver ++dns_use_edns0 parameter for resolver ++hold_domains hold delivery for these domains ++local_interfaces for routing checks ++queue_domains no immediate delivery for these ++queue_only no immediate delivery at all ++queue_only_file no immediate delivery if file exists ++queue_only_load no immediate delivery if load is high ++queue_only_load_latch don't re-evaluate load for each message ++queue_only_override allow command line to override ++queue_run_in_order order of arrival ++queue_run_max of simultaneous queue runners ++queue_smtp_domains no immediate SMTP delivery for these ++remote_max_parallel parallel SMTP delivery per message ++remote_sort_domains order of remote deliveries ++retry_data_expire timeout for retry data ++retry_interval_max safety net for retry rules ++ ++ ++14.22 Bounce and warning messages ++--------------------------------- ++ ++bounce_message_file content of bounce ++bounce_message_text content of bounce ++bounce_return_body include body if returning message ++bounce_return_message include original message in bounce ++bounce_return_size_limit limit on returned message ++bounce_sender_authentication send authenticated sender with bounce ++dsn_from set From: contents in bounces ++errors_copy copy bounce messages ++errors_reply_to Reply-to: in bounces ++delay_warning time schedule ++delay_warning_condition condition for warning messages ++ignore_bounce_errors_after discard undeliverable bounces ++smtp_return_error_details give detail on rejections ++warn_message_file content of warning message ++ ++ ++14.23 Alphabetical list of main options ++--------------------------------------- ++ ++Those options that undergo string expansion before use are marked with *. ++ +++-----------------------------------------------------+ ++|accept_8bitmime|Use: main|Type: boolean|Default: true| +++-----------------------------------------------------+ ++ ++This option causes Exim to send 8BITMIME in its response to an SMTP EHLO ++command, and to accept the BODY= parameter on MAIL commands. However, though ++Exim is 8-bit clean, it is not a protocol converter, and it takes no steps to ++do anything special with messages received by this route. ++ ++Historically Exim kept this option off by default, but the maintainers feel ++that in today's Internet, this causes more problems than it solves. It now ++defaults to true. A more detailed analysis of the issues is provided by Dan ++Bernstein: ++ ++http://cr.yp.to/smtp/8bitmime.html ++ ++To log received 8BITMIME status use ++ ++log_selector = +8bitmime ++ +++---------------------------------------------------+ ++|acl_not_smtp|Use: main|Type: string*|Default: unset| +++---------------------------------------------------+ ++ ++This option defines the ACL that is run when a non-SMTP message has been read ++and is on the point of being accepted. See chapter 42 for further details. ++ +++--------------------------------------------------------+ ++|acl_not_smtp_mime|Use: main|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option defines the ACL that is run for individual MIME parts of non-SMTP ++messages. It operates in exactly the same way as acl_smtp_mime operates for ++SMTP messages. ++ +++---------------------------------------------------------+ ++|acl_not_smtp_start|Use: main|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++This option defines the ACL that is run before Exim starts reading a non-SMTP ++message. See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_auth|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP AUTH command is received. ++See chapter 42 for further details. ++ +++-------------------------------------------------------+ ++|acl_smtp_connect|Use: main|Type: string*|Default: unset| +++-------------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP connection is received. ++See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_data|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run after an SMTP DATA command has been ++processed and the message itself has been received, but before the final ++acknowledgment is sent. See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_etrn|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP ETRN command is received. ++See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_expn|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP EXPN command is received. ++See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_helo|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP EHLO or HELO command is ++received. See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_mail|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP MAIL command is received. ++See chapter 42 for further details. ++ +++--------------------------------------------------------+ ++|acl_smtp_mailauth|Use: main|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option defines the ACL that is run when there is an AUTH parameter on a ++MAIL command. See chapter 42 for details of ACLs, and chapter 33 for details of ++authentication. ++ +++----------------------------------------------------+ ++|acl_smtp_mime|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option is available when Exim is built with the content-scanning ++extension. It defines the ACL that is run for each MIME part in a message. See ++section 43.4 for details. ++ +++-------------------------------------------------------+ ++|acl_smtp_predata|Use: main|Type: string*|Default: unset| +++-------------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP DATA command is received, ++before the message itself is received. See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_quit|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP QUIT command is received. ++See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_rcpt|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP RCPT command is received. ++See chapter 42 for further details. ++ +++--------------------------------------------------------+ ++|acl_smtp_starttls|Use: main|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP STARTTLS command is ++received. See chapter 42 for further details. ++ +++----------------------------------------------------+ ++|acl_smtp_vrfy|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option defines the ACL that is run when an SMTP VRFY command is received. ++See chapter 42 for further details. ++ +++--------------------------------------------------------+ ++|admin_groups|Use: main|Type: string list*|Default: unset| +++--------------------------------------------------------+ ++ ++This option is expanded just once, at the start of Exim's processing. If the ++current group or any of the supplementary groups of an Exim caller is in this ++colon-separated list, the caller has admin privileges. If all your system ++programmers are in a specific group, for example, you can give them all Exim ++admin privileges by putting that group in admin_groups. However, this does not ++permit them to read Exim's spool files (whose group owner is the Exim gid). To ++permit this, you have to add individuals to the Exim group. ++ +++------------------------------------------------------------+ ++|allow_domain_literals|Use: main|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is set, the RFC 2822 domain literal format is permitted in email ++addresses. The option is not set by default, because the domain literal format ++is not normally required these days, and few people know about it. It has, ++however, been exploited by mail abusers. ++ ++Unfortunately, it seems that some DNS black list maintainers are using this ++format to report black listing to postmasters. If you want to accept messages ++addressed to your hosts by IP address, you need to set allow_domain_literals ++true, and also to add "@[]" to the list of local domains (defined in the named ++domain list local_domains in the default configuration). This "magic string" ++matches the domain literal form of all the local host's IP addresses. ++ +++-----------------------------------------------------+ ++|allow_mx_to_ip|Use: main|Type: boolean|Default: false| +++-----------------------------------------------------+ ++ ++It appears that more and more DNS zone administrators are breaking the rules ++and putting domain names that look like IP addresses on the right hand side of ++MX records. Exim follows the rules and rejects this, giving an error message ++that explains the mis-configuration. However, some other MTAs support this ++practice, so to avoid "Why can't Exim do this?" complaints, allow_mx_to_ip ++exists, in order to enable this heinous activity. It is not recommended, except ++when you have no other choice. ++ +++---------------------------------------------------------+ ++|allow_utf8_domains|Use: main|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++Lots of discussion is going on about internationalized domain names. One camp ++is strongly in favour of just using UTF-8 characters, and it seems that at ++least two other MTAs permit this. This option allows Exim users to experiment ++if they wish. ++ ++If it is set true, Exim's domain parsing function allows valid UTF-8 ++multicharacters to appear in domain name components, in addition to letters, ++digits, and hyphens. However, just setting this option is not enough; if you ++want to look up these domain names in the DNS, you must also adjust the value ++of dns_check_names_pattern to match the extended form. A suitable setting is: ++ ++dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\ ++ (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$ ++ ++Alternatively, you can just disable this feature by setting ++ ++dns_check_names_pattern = ++ ++That is, set the option to an empty string so that no check is done. ++ +++----------------------------------------------------------+ ++|auth_advertise_hosts|Use: main|Type: host list*|Default: *| +++----------------------------------------------------------+ ++ ++If any server authentication mechanisms are configured, Exim advertises them in ++response to an EHLO command only if the calling host matches this list. ++Otherwise, Exim does not advertise AUTH. Exim does not accept AUTH commands ++from clients to which it has not advertised the availability of AUTH. The ++advertising of individual authentication mechanisms can be controlled by the ++use of the server_advertise_condition generic authenticator option on the ++individual authenticators. See chapter 33 for further details. ++ ++Certain mail clients (for example, Netscape) require the user to provide a name ++and password for authentication if AUTH is advertised, even though it may not ++be needed (the host may accept messages from hosts on its local LAN without ++authentication, for example). The auth_advertise_hosts option can be used to ++make these clients more friendly by excluding them from the set of hosts to ++which Exim advertises AUTH. ++ ++If you want to advertise the availability of AUTH only when the connection is ++encrypted using TLS, you can make use of the fact that the value of this option ++is expanded, with a setting like this: ++ ++auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}} ++ ++If $tls_in_cipher is empty, the session is not encrypted, and the result of the ++expansion is empty, thus matching no hosts. Otherwise, the result of the ++expansion is *, which matches all hosts. ++ +++------------------------------------------+ ++|auto_thaw|Use: main|Type: time|Default: 0s| +++------------------------------------------+ ++ ++If this option is set to a time greater than zero, a queue runner will try a ++new delivery attempt on any frozen message, other than a bounce message, if ++this much time has passed since it was frozen. This may result in the message ++being re-frozen if nothing has changed since the last attempt. It is a way of ++saying "keep on trying, even though there are big problems". ++ ++Note: This is an old option, which predates timeout_frozen_after and ++ignore_bounce_errors_after. It is retained for compatibility, but it is not ++thought to be very useful any more, and its use should probably be avoided. ++ +++----------------------------------------------------+ ++|av_scanner|Use: main|Type: string|Default: see below| +++----------------------------------------------------+ ++ ++This option is available if Exim is built with the content-scanning extension. ++It specifies which anti-virus scanner to use. The default value is: ++ ++sophie:/var/run/sophie ++ ++If the value of av_scanner starts with a dollar character, it is expanded ++before use. See section 43.1 for further details. ++ +++------------------------------------------------+ ++|bi_command|Use: main|Type: string|Default: unset| +++------------------------------------------------+ ++ ++This option supplies the name of a command that is run when Exim is called with ++the -bi option (see chapter 5). The string value is just the command name, it ++is not a complete command line. If an argument is required, it must come from ++the -oA command line option. ++ +++---------------------------------------------------------+ ++|bounce_message_file|Use: main|Type: string|Default: unset| +++---------------------------------------------------------+ ++ ++This option defines a template file containing paragraphs of text to be used ++for constructing bounce messages. Details of the file's contents are given in ++chapter 48. See also warn_message_file. ++ +++---------------------------------------------------------+ ++|bounce_message_text|Use: main|Type: string|Default: unset| +++---------------------------------------------------------+ ++ ++When this option is set, its contents are included in the default bounce ++message immediately after "This message was created automatically by mail ++delivery software." It is not used if bounce_message_file is set. ++ +++--------------------------------------------------------+ ++|bounce_return_body|Use: main|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++This option controls whether the body of an incoming message is included in a ++bounce message when bounce_return_message is true. The default setting causes ++the entire message, both header and body, to be returned (subject to the value ++of bounce_return_size_limit). If this option is false, only the message header ++is included. In the case of a non-SMTP message containing an error that is ++detected during reception, only those header lines preceding the point at which ++the error was detected are returned. ++ +++-----------------------------------------------------------+ ++|bounce_return_message|Use: main|Type: boolean|Default: true| +++-----------------------------------------------------------+ ++ ++If this option is set false, none of the original message is included in bounce ++messages generated by Exim. See also bounce_return_size_limit and ++bounce_return_body. ++ +++--------------------------------------------------------------+ ++|bounce_return_size_limit|Use: main|Type: integer|Default: 100K| +++--------------------------------------------------------------+ ++ ++This option sets a limit in bytes on the size of messages that are returned to ++senders as part of bounce messages when bounce_return_message is true. The ++limit should be less than the value of the global message_size_limit and of any ++message_size_limit settings on transports, to allow for the bounce text that ++Exim generates. If this option is set to zero there is no limit. ++ ++When the body of any message that is to be included in a bounce message is ++greater than the limit, it is truncated, and a comment pointing this out is ++added at the top. The actual cutoff may be greater than the value given, owing ++to the use of buffering for transferring the message in chunks (typically 8K in ++size). The idea is to save bandwidth on those undeliverable 15-megabyte ++messages. ++ +++------------------------------------------------------------------+ ++|bounce_sender_authentication|Use: main|Type: string|Default: unset| +++------------------------------------------------------------------+ ++ ++This option provides an authenticated sender address that is sent with any ++bounce messages generated by Exim that are sent over an authenticated SMTP ++connection. A typical setting might be: ++ ++bounce_sender_authentication = mailer-daemon@my.domain.example ++ ++which would cause bounce messages to be sent using the SMTP command: ++ ++MAIL FROM:<> AUTH=mailer-daemon@my.domain.example ++ ++The value of bounce_sender_authentication must always be a complete email ++address. ++ +++---------------------------------------------------------------+ ++|callout_domain_negative_expire|Use: main|Type: time|Default: 3h| +++---------------------------------------------------------------+ ++ ++This option specifies the expiry time for negative callout cache data for a ++domain. See section 42.44 for details of callout verification, and section ++42.46 for details of the caching. ++ +++---------------------------------------------------------------+ ++|callout_domain_positive_expire|Use: main|Type: time|Default: 7d| +++---------------------------------------------------------------+ ++ ++This option specifies the expiry time for positive callout cache data for a ++domain. See section 42.44 for details of callout verification, and section ++42.46 for details of the caching. ++ +++--------------------------------------------------------+ ++|callout_negative_expire|Use: main|Type: time|Default: 2h| +++--------------------------------------------------------+ ++ ++This option specifies the expiry time for negative callout cache data for an ++address. See section 42.44 for details of callout verification, and section ++42.46 for details of the caching. ++ +++---------------------------------------------------------+ ++|callout_positive_expire|Use: main|Type: time|Default: 24h| +++---------------------------------------------------------+ ++ ++This option specifies the expiry time for positive callout cache data for an ++address. See section 42.44 for details of callout verification, and section ++42.46 for details of the caching. ++ +++--------------------------------------------------------------------+ ++|callout_random_local_part|Use: main|Type: string*|Default: see below| +++--------------------------------------------------------------------+ ++ ++This option defines the "random" local part that can be used as part of callout ++verification. The default value is ++ ++$primary_hostname-$tod_epoch-testing ++ ++See section 42.45 for details of how this value is used. ++ +++---------------------------------------------------+ ++|check_log_inodes|Use: main|Type: integer|Default: 0| +++---------------------------------------------------+ ++ ++See check_spool_space below. ++ +++--------------------------------------------------+ ++|check_log_space|Use: main|Type: integer|Default: 0| +++--------------------------------------------------+ ++ ++See check_spool_space below. ++ +++----------------------------------------------------------+ ++|check_rfc2047_length|Use: main|Type: boolean|Default: true| +++----------------------------------------------------------+ ++ ++RFC 2047 defines a way of encoding non-ASCII characters in headers using a ++system of "encoded words". The RFC specifies a maximum length for an encoded ++word; strings to be encoded that exceed this length are supposed to use ++multiple encoded words. By default, Exim does not recognize encoded words that ++exceed the maximum length. However, it seems that some software, in violation ++of the RFC, generates overlong encoded words. If check_rfc2047_length is set ++false, Exim recognizes encoded words of any length. ++ +++-----------------------------------------------------+ ++|check_spool_inodes|Use: main|Type: integer|Default: 0| +++-----------------------------------------------------+ ++ ++See check_spool_space below. ++ +++----------------------------------------------------+ ++|check_spool_space|Use: main|Type: integer|Default: 0| +++----------------------------------------------------+ ++ ++The four check_... options allow for checking of disk resources before a ++message is accepted. ++ ++When any of these options are set, they apply to all incoming messages. If you ++want to apply different checks to different kinds of message, you can do so by ++testing the variables $log_inodes, $log_space, $spool_inodes, and $spool_space ++in an ACL with appropriate additional conditions. ++ ++check_spool_space and check_spool_inodes check the spool partition if either ++value is greater than zero, for example: ++ ++check_spool_space = 10M ++check_spool_inodes = 100 ++ ++The spool partition is the one that contains the directory defined by ++SPOOL_DIRECTORY in Local/Makefile. It is used for holding messages in transit. ++ ++check_log_space and check_log_inodes check the partition in which log files are ++written if either is greater than zero. These should be set only if ++log_file_path and spool_directory refer to different partitions. ++ ++If there is less space or fewer inodes than requested, Exim refuses to accept ++incoming mail. In the case of SMTP input this is done by giving a 452 temporary ++error response to the MAIL command. If ESMTP is in use and there was a SIZE ++parameter on the MAIL command, its value is added to the check_spool_space ++value, and the check is performed even if check_spool_space is zero, unless ++no_smtp_check_spool_space is set. ++ ++The values for check_spool_space and check_log_space are held as a number of ++kilobytes. If a non-multiple of 1024 is specified, it is rounded up. ++ ++For non-SMTP input and for batched SMTP input, the test is done at start-up; on ++failure a message is written to stderr and Exim exits with a non-zero code, as ++it obviously cannot send an error message of any kind. ++ +++--------------------------------------------------------+ ++|daemon_smtp_ports|Use: main|Type: string|Default: "smtp"| +++--------------------------------------------------------+ ++ ++This option specifies one or more default SMTP ports on which the Exim daemon ++listens. See chapter 13 for details of how it is used. For backward ++compatibility, daemon_smtp_port (singular) is a synonym. ++ +++---------------------------------------------------------+ ++|daemon_startup_retries|Use: main|Type: integer|Default: 9| +++---------------------------------------------------------+ ++ ++This option, along with daemon_startup_sleep, controls the retrying done by the ++daemon at startup when it cannot immediately bind a listening socket (typically ++because the socket is already in use): daemon_startup_retries defines the ++number of retries after the first failure, and daemon_startup_sleep defines the ++length of time to wait between retries. ++ +++------------------------------------------------------+ ++|daemon_startup_sleep|Use: main|Type: time|Default: 30s| +++------------------------------------------------------+ ++ ++See daemon_startup_retries. ++ +++----------------------------------------------------+ ++|delay_warning|Use: main|Type: time list|Default: 24h| +++----------------------------------------------------+ ++ ++When a message is delayed, Exim sends a warning message to the sender at ++intervals specified by this option. The data is a colon-separated list of times ++after which to send warning messages. If the value of the option is an empty ++string or a zero time, no warnings are sent. Up to 10 times may be given. If a ++message has been on the queue for longer than the last time, the last interval ++between the times is used to compute subsequent warning times. For example, ++with ++ ++delay_warning = 4h:8h:24h ++ ++the first message is sent after 4 hours, the second after 8 hours, and the ++third one after 24 hours. After that, messages are sent every 16 hours, because ++that is the interval between the last two times on the list. If you set just ++one time, it specifies the repeat interval. For example, with: ++ ++delay_warning = 6h ++ ++messages are repeated every six hours. To stop warnings after a given time, set ++a very large time at the end of the list. For example: ++ ++delay_warning = 2h:12h:99d ++ +++------------------------------------------------------------------+ ++|delay_warning_condition|Use: main|Type: string*|Default: see below| +++------------------------------------------------------------------+ ++ ++The string is expanded at the time a warning message might be sent. If all the ++deferred addresses have the same domain, it is set in $domain during the ++expansion. Otherwise $domain is empty. If the result of the expansion is a ++forced failure, an empty string, or a string matching any of "0", "no" or ++"false" (the comparison being done caselessly) then the warning message is not ++sent. The default is: ++ ++delay_warning_condition = ${if or {\ ++ { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\ ++ { match{$h_precedence:}{(?i)bulk|list|junk} }\ ++ { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\ ++ } {no}{yes}} ++ ++This suppresses the sending of warnings for messages that contain List-ID:, ++List-Post:, or List-Subscribe: headers, or have "bulk", "list" or "junk" in a ++Precedence: header, or have "auto-generated" or "auto-replied" in an ++Auto-Submitted: header. ++ +++-------------------------------------------------------------+ ++|deliver_drop_privilege|Use: main|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++If this option is set true, Exim drops its root privilege at the start of a ++delivery process, and runs as the Exim user throughout. This severely restricts ++the kinds of local delivery that are possible, but is viable in certain types ++of configuration. There is a discussion about the use of root privilege in ++chapter 54. ++ +++-----------------------------------------------------------------+ ++|deliver_queue_load_max|Use: main|Type: fixed-point|Default: unset| +++-----------------------------------------------------------------+ ++ ++When this option is set, a queue run is abandoned if the system load average ++becomes greater than the value of the option. The option has no effect on ++ancient operating systems on which Exim cannot determine the load average. See ++also queue_only_load and smtp_load_reserve. ++ +++----------------------------------------------------------+ ++|delivery_date_remove|Use: main|Type: boolean|Default: true| +++----------------------------------------------------------+ ++ ++Exim's transports have an option for adding a Delivery-date: header to a ++message when it is delivered, in exactly the same way as Return-path: is ++handled. Delivery-date: records the actual time of delivery. Such headers ++should not be present in incoming messages, and this option causes them to be ++removed at the time the message is received, to avoid any problems that might ++occur when a delivered message is subsequently sent on to some other recipient. ++ +++----------------------------------------------------+ ++|disable_fsync|Use: main|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++This option is available only if Exim was built with the compile-time option ++ENABLE_DISABLE_FSYNC. When this is not set, a reference to disable_fsync in a ++runtime configuration generates an "unknown option" error. You should not build ++Exim with ENABLE_DISABLE_FSYNC or set disable_fsync unless you really, really, ++really understand what you are doing. No pre-compiled distributions of Exim ++should ever make this option available. ++ ++When disable_fsync is set true, Exim no longer calls fsync() to force updated ++files' data to be written to disc before continuing. Unexpected events such as ++crashes and power outages may cause data to be lost or scrambled. Here be ++Dragons. Beware. ++ +++---------------------------------------------------+ ++|disable_ipv6|Use: main|Type: boolean|Default: false| +++---------------------------------------------------+ ++ ++If this option is set true, even if the Exim binary has IPv6 support, no IPv6 ++activities take place. AAAA records are never looked up, and any IPv6 addresses ++that are listed in local_interfaces, data for the manualroute router, etc. are ++ignored. If IP literals are enabled, the ipliteral router declines to handle ++IPv6 literal addresses. ++ +++--------------------------------------------------------------------+ ++|dns_again_means_nonexist|Use: main|Type: domain list*|Default: unset| +++--------------------------------------------------------------------+ ++ ++DNS lookups give a "try again" response for the DNS errors "non-authoritative ++host not found" and "SERVERFAIL". This can cause Exim to keep trying to deliver ++a message, or to give repeated temporary errors to incoming mail. Sometimes the ++effect is caused by a badly set up name server and may persist for a long time. ++If a domain which exhibits this problem matches anything in ++dns_again_means_nonexist, it is treated as if it did not exist. This option ++should be used with care. You can make it apply to reverse lookups by a setting ++such as this: ++ ++dns_again_means_nonexist = *.in-addr.arpa ++ ++This option applies to all DNS lookups that Exim does. It also applies when the ++gethostbyname() or getipnodebyname() functions give temporary errors, since ++these are most likely to be caused by DNS lookup problems. The dnslookup router ++has some options of its own for controlling what happens when lookups for MX or ++SRV records give temporary errors. These more specific options are applied ++after this global option. ++ +++-----------------------------------------------------------------+ ++|dns_check_names_pattern|Use: main|Type: string|Default: see below| +++-----------------------------------------------------------------+ ++ ++When this option is set to a non-empty string, it causes Exim to check domain ++names for characters that are not allowed in host names before handing them to ++the DNS resolver, because some resolvers give temporary errors for names that ++contain unusual characters. If a domain name contains any unwanted characters, ++a "not found" result is forced, and the resolver is not called. The check is ++done by matching the domain name against a regular expression, which is the ++value of this option. The default pattern is ++ ++dns_check_names_pattern = \ ++ (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$ ++ ++which permits only letters, digits, slashes, and hyphens in components, but ++they must start and end with a letter or digit. Slashes are not, in fact, ++permitted in host names, but they are found in certain NS records (which can be ++accessed in Exim by using a dnsdb lookup). If you set allow_utf8_domains, you ++must modify this pattern, or set the option to an empty string. ++ +++-------------------------------------------------------+ ++|dns_csa_search_limit|Use: main|Type: integer|Default: 5| +++-------------------------------------------------------+ ++ ++This option controls the depth of parental searching for CSA SRV records in the ++DNS, as described in more detail in section 42.49. ++ +++---------------------------------------------------------+ ++|dns_csa_use_reverse|Use: main|Type: boolean|Default: true| +++---------------------------------------------------------+ ++ ++This option controls whether or not an IP address, given as a CSA domain, is ++reversed and looked up in the reverse DNS, as described in more detail in ++section 42.49. ++ +++-----------------------------------------------------------+ ++|dns_ipv4_lookup|Use: main|Type: domain list*|Default: unset| +++-----------------------------------------------------------+ ++ ++When Exim is compiled with IPv6 support and disable_ipv6 is not set, it looks ++for IPv6 address records (AAAA records) as well as IPv4 address records (A ++records) when trying to find IP addresses for hosts, unless the host's domain ++matches this list. ++ ++This is a fudge to help with name servers that give big delays or otherwise do ++not work for the AAAA record type. In due course, when the world's name servers ++have all been upgraded, there should be no need for this option. ++ +++--------------------------------------------+ ++|dns_retrans|Use: main|Type: time|Default: 0s| +++--------------------------------------------+ ++ ++The options dns_retrans and dns_retry can be used to set the retransmission and ++retry parameters for DNS lookups. Values of zero (the defaults) leave the ++system default settings unchanged. The first value is the time between retries, ++and the second is the number of retries. It isn't totally clear exactly how ++these settings affect the total time a DNS lookup may take. I haven't found any ++documentation about timeouts on DNS lookups; these parameter values are ++available in the external resolver interface structure, but nowhere does it ++seem to describe how they are used or what you might want to set in them. ++ +++--------------------------------------------+ ++|dns_retry|Use: main|Type: integer|Default: 0| +++--------------------------------------------+ ++ ++See dns_retrans above. ++ +++--------------------------------------------------+ ++|dns_use_dnssec|Use: main|Type: integer|Default: -1| +++--------------------------------------------------+ ++ ++If this option is set to a non-negative number then Exim will initialise the ++DNS resolver library to either use or not use DNSSEC, overriding the system ++default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. ++ ++If the resolver library does not support DNSSEC then this option has no effect. ++ +++-------------------------------------------------+ ++|dns_use_edns0|Use: main|Type: integer|Default: -1| +++-------------------------------------------------+ ++ ++If this option is set to a non-negative number then Exim will initialise the ++DNS resolver library to either use or not use EDNS0 extensions, overriding the ++system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0 on. ++ ++If the resolver library does not support EDNS0 then this option has no effect. ++ +++----------------------------------------------+ ++|drop_cr|Use: main|Type: boolean|Default: false| +++----------------------------------------------+ ++ ++This is an obsolete option that is now a no-op. It used to affect the way Exim ++handled CR and LF characters in incoming messages. What happens now is ++described in section 46.2. ++ +++---------------------------------------------------+ ++|dsn_from|Use: main|Type: string*|Default: see below| +++---------------------------------------------------+ ++ ++This option can be used to vary the contents of From: header lines in bounces ++and other automatically generated messages ("Delivery Status Notifications" - ++hence the name of the option). The default setting is: ++ ++dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain> ++ ++The value is expanded every time it is needed. If the expansion fails, a panic ++is logged, and the default value is used. ++ +++--------------------------------------------------------+ ++|envelope_to_remove|Use: main|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++Exim's transports have an option for adding an Envelope-to: header to a message ++when it is delivered, in exactly the same way as Return-path: is handled. ++Envelope-to: records the original recipient address from the messages's ++envelope that caused the delivery to happen. Such headers should not be present ++in incoming messages, and this option causes them to be removed at the time the ++message is received, to avoid any problems that might occur when a delivered ++message is subsequently sent on to some other recipient. ++ +++-------------------------------------------------------+ ++|errors_copy|Use: main|Type: string list*|Default: unset| +++-------------------------------------------------------+ ++ ++Setting this option causes Exim to send bcc copies of bounce messages that it ++generates to other addresses. Note: This does not apply to bounce messages ++coming from elsewhere. The value of the option is a colon-separated list of ++items. Each item consists of a pattern, terminated by white space, followed by ++a comma-separated list of email addresses. If a pattern contains spaces, it ++must be enclosed in double quotes. ++ ++Each pattern is processed in the same way as a single item in an address list ++(see section 10.19). When a pattern matches the recipient of the bounce ++message, the message is copied to the addresses on the list. The items are ++scanned in order, and once a matching one is found, no further items are ++examined. For example: ++ ++errors_copy = spqr@mydomain postmaster@mydomain.example :\ ++ rqps@mydomain hostmaster@mydomain.example,\ ++ postmaster@mydomain.example ++ ++The address list is expanded before use. The expansion variables $local_part ++and $domain are set from the original recipient of the error message, and if ++there was any wildcard matching in the pattern, the expansion variables $0, $1, ++etc. are set in the normal way. ++ +++-----------------------------------------------------+ ++|errors_reply_to|Use: main|Type: string|Default: unset| +++-----------------------------------------------------+ ++ ++By default, Exim's bounce and delivery warning messages contain the header line ++ ++From: Mail Delivery System <Mailer-Daemon@qualify-domain> ++ ++where qualify-domain is the value of the qualify_domain option. A warning ++message that is generated by the quota_warn_message option in an appendfile ++transport may contain its own From: header line that overrides the default. ++ ++Experience shows that people reply to bounce messages. If the errors_reply_to ++option is set, a Reply-To: header is added to bounce and warning messages. For ++example: ++ ++errors_reply_to = postmaster@my.domain.example ++ ++The value of the option is not expanded. It must specify a valid RFC 2822 ++address. However, if a warning message that is generated by the ++quota_warn_message option in an appendfile transport contain its own Reply-To: ++header line, the value of the errors_reply_to option is not used. ++ +++------------------------------------------------------------------+ ++|exim_group|Use: main|Type: string|Default: compile-time configured| +++------------------------------------------------------------------+ ++ ++This option changes the gid under which Exim runs when it gives up root ++privilege. The default value is compiled into the binary. The value of this ++option is used only when exim_user is also set. Unless it consists entirely of ++digits, the string is looked up using getgrnam(), and failure causes a ++configuration error. See chapter 54 for a discussion of security issues. ++ +++---------------------------------------------------+ ++|exim_path|Use: main|Type: string|Default: see below| +++---------------------------------------------------+ ++ ++This option specifies the path name of the Exim binary, which is used when Exim ++needs to re-exec itself. The default is set up to point to the file exim in the ++directory configured at compile time by the BIN_DIRECTORY setting. It is ++necessary to change exim_path if, exceptionally, Exim is run from some other ++place. Warning: Do not use a macro to define the value of this option, because ++you will break those Exim utilities that scan the configuration file to find ++where the binary is. (They then use the -bP option to extract option settings ++such as the value of spool_directory.) ++ +++-----------------------------------------------------------------+ ++|exim_user|Use: main|Type: string|Default: compile-time configured| +++-----------------------------------------------------------------+ ++ ++This option changes the uid under which Exim runs when it gives up root ++privilege. The default value is compiled into the binary. Ownership of the run ++time configuration file and the use of the -C and -D command line options is ++checked against the values in the binary, not what is set here. ++ ++Unless it consists entirely of digits, the string is looked up using getpwnam() ++, and failure causes a configuration error. If exim_group is not also supplied, ++the gid is taken from the result of getpwnam() if it is used. See chapter 54 ++for a discussion of security issues. ++ +++-----------------------------------------------------------------+ ++|extra_local_interfaces|Use: main|Type: string list|Default: unset| +++-----------------------------------------------------------------+ ++ ++This option defines network interfaces that are to be considered local when ++routing, but which are not used for listening by the daemon. See section 13.8 ++for details. ++ +++---------------------------------------------------------------------------+ ++|extract_addresses_remove_ arguments|Use: main|Type: boolean|Default: true| +++---------------------------------------------------------------------------+ ++ ++According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses ++are present on the command line when the -t option is used to build an envelope ++from a message's To:, Cc: and Bcc: headers, the command line addresses are ++removed from the recipients list. This is also how Smail behaves. However, ++other Sendmail documentation (the O'Reilly book) states that command line ++addresses are added to those obtained from the header lines. When ++extract_addresses_remove_arguments is true (the default), Exim subtracts ++argument headers. If it is set false, Exim adds rather than removes argument ++addresses. ++ +++---------------------------------------------------+ ++|finduser_retries|Use: main|Type: integer|Default: 0| +++---------------------------------------------------+ ++ ++On systems running NIS or other schemes in which user and group information is ++distributed from a remote system, there can be times when getpwnam() and ++related functions fail, even when given valid data, because things time out. ++Unfortunately these failures cannot be distinguished from genuine "not found" ++errors. If finduser_retries is set greater than zero, Exim will try that many ++extra times to find a user or a group, waiting for one second between retries. ++ ++You should not set this option greater than zero if your user information is in ++a traditional /etc/passwd file, because it will cause Exim needlessly to search ++the file multiple times for non-existent users, and also cause delay. ++ +++-----------------------------------------------------------------------+ ++|freeze_tell|Use: main|Type: string list, comma separated|Default: unset| +++-----------------------------------------------------------------------+ ++ ++On encountering certain errors, or when configured to do so in a system filter, ++ACL, or special router, Exim freezes a message. This means that no further ++delivery attempts take place until an administrator thaws the message, or the ++auto_thaw, ignore_bounce_errors_after, or timeout_frozen_after feature cause it ++to be processed. If freeze_tell is set, Exim generates a warning message ++whenever it freezes something, unless the message it is freezing is a ++locally-generated bounce message. (Without this exception there is the ++possibility of looping.) The warning message is sent to the addresses supplied ++as the comma-separated value of this option. If several of the message's ++addresses cause freezing, only a single message is sent. If the freezing was ++automatic, the reason(s) for freezing can be found in the message log. If you ++configure freezing in a filter or ACL, you must arrange for any logging that ++you require. ++ +++-------------------------------------------------+ ++|gecos_name|Use: main|Type: string*|Default: unset| +++-------------------------------------------------+ ++ ++Some operating systems, notably HP-UX, use the "gecos" field in the system ++password file to hold other information in addition to users' real names. Exim ++looks up this field for use when it is creating Sender: or From: headers. If ++either gecos_pattern or gecos_name are unset, the contents of the field are ++used unchanged, except that, if an ampersand is encountered, it is replaced by ++the user's login name with the first character forced to upper case, since this ++is a convention that is observed on many systems. ++ ++When these options are set, gecos_pattern is treated as a regular expression ++that is to be applied to the field (again with & replaced by the login name), ++and if it matches, gecos_name is expanded and used as the user's name. ++ ++Numeric variables such as $1, $2, etc. can be used in the expansion to pick up ++sub-fields that were matched by the pattern. In HP-UX, where the user's name ++terminates at the first comma, the following can be used: ++ ++gecos_pattern = ([^,]*) ++gecos_name = $1 ++ +++---------------------------------------------------+ ++|gecos_pattern|Use: main|Type: string|Default: unset| +++---------------------------------------------------+ ++ ++See gecos_name above. ++ +++---------------------------------------------------------+ ++|gnutls_compat_mode|Use: main|Type: boolean|Default: unset| +++---------------------------------------------------------+ ++ ++This option controls whether GnuTLS is used in compatibility mode in an Exim ++server. This reduces security slightly, but improves interworking with older ++implementations of TLS. ++ ++option gnutls_enable_pkcs11 main boolean unset This option will let GnuTLS ++(2.12.0 or later) autoload PKCS11 modules with the p11-kit configuration files ++in /etc/pkcs11/modules/. ++ ++See http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs for ++documentation. ++ +++---------------------------------------------------------+ ++|headers_charset|Use: main|Type: string|Default: see below| +++---------------------------------------------------------+ ++ ++This option sets a default character set for translating from encoded MIME ++"words" in header lines, when referenced by an $h_xxx expansion item. The ++default is the value of HEADERS_CHARSET in Local/Makefile. The ultimate default ++is ISO-8859-1. For more details see the description of header insertions in ++section 11.5. ++ +++---------------------------------------------------------+ ++|header_maxsize|Use: main|Type: integer|Default: see below| +++---------------------------------------------------------+ ++ ++This option controls the overall maximum size of a message's header section. ++The default is the value of HEADER_MAXSIZE in Local/Makefile; the default for ++that is 1M. Messages with larger header sections are rejected. ++ +++------------------------------------------------------+ ++|header_line_maxsize|Use: main|Type: integer|Default: 0| +++------------------------------------------------------+ ++ ++This option limits the length of any individual header line in a message, after ++all the continuations have been joined together. Messages with individual ++header lines that are longer than the limit are rejected. The default value of ++zero means "no limit". ++ +++----------------------------------------------------------------+ ++|helo_accept_junk_hosts|Use: main|Type: host list*|Default: unset| +++----------------------------------------------------------------+ ++ ++Exim checks the syntax of HELO and EHLO commands for incoming SMTP mail, and ++gives an error response for invalid data. Unfortunately, there are some SMTP ++clients that send syntactic junk. They can be accommodated by setting this ++option. Note that this is a syntax check only. See helo_verify_hosts if you ++want to do semantic checking. See also helo_allow_chars for a way of extending ++the permitted character set. ++ +++------------------------------------------------------+ ++|helo_allow_chars|Use: main|Type: string|Default: unset| +++------------------------------------------------------+ ++ ++This option can be set to a string of rogue characters that are permitted in ++all EHLO and HELO names in addition to the standard letters, digits, hyphens, ++and dots. If you really must allow underscores, you can set ++ ++helo_allow_chars = _ ++ ++Note that the value is one string, not a list. ++ +++-----------------------------------------------------------------+ ++|helo_lookup_domains|Use: main|Type: domain list*|Default: "@:@[]"| +++-----------------------------------------------------------------+ ++ ++If the domain given by a client in a HELO or EHLO command matches this list, a ++reverse lookup is done in order to establish the host's true name. The default ++forces a lookup if the client host gives the server's name or any of its IP ++addresses (in brackets), something that broken clients have been seen to do. ++ +++---------------------------------------------------------------+ ++|helo_try_verify_hosts|Use: main|Type: host list*|Default: unset| +++---------------------------------------------------------------+ ++ ++By default, Exim just checks the syntax of HELO and EHLO commands (see ++helo_accept_junk_hosts and helo_allow_chars). However, some sites like to do ++more extensive checking of the data supplied by these commands. The ACL ++condition "verify = helo" is provided to make this possible. Formerly, it was ++necessary also to set this option (helo_try_verify_hosts) to force the check to ++occur. From release 4.53 onwards, this is no longer necessary. If the check has ++not been done before "verify = helo" is encountered, it is done at that time. ++Consequently, this option is obsolete. Its specification is retained here for ++backwards compatibility. ++ ++When an EHLO or HELO command is received, if the calling host matches ++helo_try_verify_hosts, Exim checks that the host name given in the HELO or EHLO ++command either: ++ ++ * is an IP literal matching the calling address of the host, or ++ ++ * matches the host name that Exim obtains by doing a reverse lookup of the ++ calling host address, or ++ ++ * when looked up using gethostbyname() (or getipnodebyname() when available) ++ yields the calling host address. ++ ++However, the EHLO or HELO command is not rejected if any of the checks fail. ++Processing continues, but the result of the check is remembered, and can be ++detected later in an ACL by the "verify = helo" condition. ++ +++-----------------------------------------------------------+ ++|helo_verify_hosts|Use: main|Type: host list*|Default: unset| +++-----------------------------------------------------------+ ++ ++Like helo_try_verify_hosts, this option is obsolete, and retained only for ++backwards compatibility. For hosts that match this option, Exim checks the host ++name given in the HELO or EHLO in the same way as for helo_try_verify_hosts. If ++the check fails, the HELO or EHLO command is rejected with a 550 error, and ++entries are written to the main and reject logs. If a MAIL command is received ++before EHLO or HELO, it is rejected with a 503 error. ++ +++--------------------------------------------------------+ ++|hold_domains|Use: main|Type: domain list*|Default: unset| +++--------------------------------------------------------+ ++ ++This option allows mail for particular domains to be held on the queue ++manually. The option is overridden if a message delivery is forced with the -M, ++-qf, -Rf or -Sf options, and also while testing or verifying addresses using ++-bt or -bv. Otherwise, if a domain matches an item in hold_domains, no routing ++or delivery for that address is done, and it is deferred every time the message ++is looked at. ++ ++This option is intended as a temporary operational measure for delaying the ++delivery of mail while some problem is being sorted out, or some new ++configuration tested. If you just want to delay the processing of some domains ++until a queue run occurs, you should use queue_domains or queue_smtp_domains, ++not hold_domains. ++ ++A setting of hold_domains does not override Exim's code for removing messages ++from the queue if they have been there longer than the longest retry time in ++any retry rule. If you want to hold messages for longer than the normal retry ++times, insert a dummy retry rule with a long retry time. ++ +++-----------------------------------------------------+ ++|host_lookup|Use: main|Type: host list*|Default: unset| +++-----------------------------------------------------+ ++ ++Exim does not look up the name of a calling host from its IP address unless it ++is required to compare against some host list, or the host matches ++helo_try_verify_hosts or helo_verify_hosts, or the host matches this option ++(which normally contains IP addresses rather than host names). The default ++configuration file contains ++ ++host_lookup = * ++ ++which causes a lookup to happen for all hosts. If the expense of these lookups ++is felt to be too great, the setting can be changed or removed. ++ ++After a successful reverse lookup, Exim does a forward lookup on the name it ++has obtained, to verify that it yields the IP address that it started with. If ++this check fails, Exim behaves as if the name lookup failed. ++ ++After any kind of failure, the host name (in $sender_host_name) remains unset, ++and $host_lookup_failed is set to the string "1". See also ++dns_again_means_nonexist, helo_lookup_domains, and "verify = ++reverse_host_lookup" in ACLs. ++ +++---------------------------------------------------------------------+ ++|host_lookup_order|Use: main|Type: string list|Default: "bydns:byaddr"| +++---------------------------------------------------------------------+ ++ ++This option specifies the order of different lookup methods when Exim is trying ++to find a host name from an IP address. The default is to do a DNS lookup ++first, and then to try a local lookup (using gethostbyaddr() or equivalent) if ++that fails. You can change the order of these lookups, or omit one entirely, if ++you want. ++ ++Warning: The "byaddr" method does not always yield aliases when there are ++multiple PTR records in the DNS and the IP address is not listed in /etc/hosts. ++Different operating systems give different results in this case. That is why ++the default tries a DNS lookup first. ++ +++----------------------------------------------------------------+ ++|host_reject_connection|Use: main|Type: host list*|Default: unset| +++----------------------------------------------------------------+ ++ ++If this option is set, incoming SMTP calls from the hosts listed are rejected ++as soon as the connection is made. This option is obsolete, and retained only ++for backward compatibility, because nowadays the ACL specified by ++acl_smtp_connect can also reject incoming connections immediately. ++ ++The ability to give an immediate rejection (either by this option or using an ++ACL) is provided for use in unusual cases. Many hosts will just try again, ++sometimes without much delay. Normally, it is better to use an ACL to reject ++incoming messages at a later stage, such as after RCPT commands. See chapter 42 ++. ++ +++----------------------------------------------------------------+ ++|hosts_connection_nolog|Use: main|Type: host list*|Default: unset| +++----------------------------------------------------------------+ ++ ++This option defines a list of hosts for which connection logging does not ++happen, even though the smtp_connection log selector is set. For example, you ++might want not to log SMTP connections from local processes, or from 127.0.0.1, ++or from your local LAN. This option is consulted in the main loop of the ++daemon; you should therefore strive to restrict its value to a short inline ++list of IP addresses and networks. To disable logging SMTP connections from ++local processes, you must create a host list with an empty item. For example: ++ ++hosts_connection_nolog = : ++ ++If the smtp_connection log selector is not set, this option has no effect. ++ +++----------------------------------------------------------------+ ++|hosts_treat_as_local|Use: main|Type: domain list*|Default: unset| +++----------------------------------------------------------------+ ++ ++If this option is set, any host names that match the domain list are treated as ++if they were the local host when Exim is scanning host lists obtained from MX ++records or other sources. Note that the value of this option is a domain list, ++not a host list, because it is always used to check host names, not IP ++addresses. ++ ++This option also applies when Exim is matching the special items "@mx_any", ++"@mx_primary", and "@mx_secondary" in a domain list (see section 10.8), and ++when checking the hosts option in the smtp transport for the local host (see ++the allow_localhost option in that transport). See also local_interfaces, ++extra_local_interfaces, and chapter 13, which contains a discussion about local ++network interfaces and recognizing the local host. ++ +++--------------------------------------------------------+ ++|ibase_servers|Use: main|Type: string list|Default: unset| +++--------------------------------------------------------+ ++ ++This option provides a list of InterBase servers and associated connection ++data, to be used in conjunction with ibase lookups (see section 9.21). The ++option is available only if Exim has been built with InterBase support. ++ +++------------------------------------------------------------+ ++|ignore_bounce_errors_after|Use: main|Type: time|Default: 10w| +++------------------------------------------------------------+ ++ ++This option affects the processing of bounce messages that cannot be delivered, ++that is, those that suffer a permanent delivery failure. (Bounce messages that ++suffer temporary delivery failures are of course retried in the usual way.) ++ ++After a permanent delivery failure, bounce messages are frozen, because there ++is no sender to whom they can be returned. When a frozen bounce message has ++been on the queue for more than the given time, it is unfrozen at the next ++queue run, and a further delivery is attempted. If delivery fails again, the ++bounce message is discarded. This makes it possible to keep failed bounce ++messages around for a shorter time than the normal maximum retry time for ++frozen messages. For example, ++ ++ignore_bounce_errors_after = 12h ++ ++retries failed bounce message deliveries after 12 hours, discarding any further ++failures. If the value of this option is set to a zero time period, bounce ++failures are discarded immediately. Setting a very long time (as in the default ++value) has the effect of disabling this option. For ways of automatically ++dealing with other kinds of frozen message, see auto_thaw and ++timeout_frozen_after. ++ +++---------------------------------------------------------------+ ++|ignore_fromline_hosts|Use: main|Type: host list*|Default: unset| +++---------------------------------------------------------------+ ++ ++Some broken SMTP clients insist on sending a UUCP-like "From " line before the ++headers of a message. By default this is treated as the start of the message's ++body, which means that any following headers are not recognized as such. Exim ++can be made to ignore it by setting ignore_fromline_hosts to match those hosts ++that insist on sending it. If the sender is actually a local process rather ++than a remote host, and is using -bs to inject the messages, ++ignore_fromline_local must be set to achieve this effect. ++ +++------------------------------------------------------------+ ++|ignore_fromline_local|Use: main|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++See ignore_fromline_hosts above. ++ +++-----------------------------------------------+ ++|keep_malformed|Use: main|Type: time|Default: 4d| +++-----------------------------------------------+ ++ ++This option specifies the length of time to keep messages whose spool files ++have been corrupted in some way. This should, of course, never happen. At the ++next attempt to deliver such a message, it gets removed. The incident is ++logged. ++ +++------------------------------------------------------+ ++|ldap_ca_cert_dir|Use: main|Type: string|Default: unset| +++------------------------------------------------------+ ++ ++This option indicates which directory contains CA certificates for verifying a ++TLS certificate presented by an LDAP server. While Exim does not provide a ++default value, your SSL library may. Analogous to tls_verify_certificates but ++as a client-side option for LDAP and constrained to be a directory. ++ +++-------------------------------------------------------+ ++|ldap_ca_cert_file|Use: main|Type: string|Default: unset| +++-------------------------------------------------------+ ++ ++This option indicates which file contains CA certificates for verifying a TLS ++certificate presented by an LDAP server. While Exim does not provide a default ++value, your SSL library may. Analogous to tls_verify_certificates but as a ++client-side option for LDAP and constrained to be a file. ++ +++----------------------------------------------------+ ++|ldap_cert_file|Use: main|Type: string|Default: unset| +++----------------------------------------------------+ ++ ++This option indicates which file contains an TLS client certificate which Exim ++should present to the LDAP server during TLS negotiation. Should be used ++together with ldap_cert_key. ++ +++---------------------------------------------------+ ++|ldap_cert_key|Use: main|Type: string|Default: unset| +++---------------------------------------------------+ ++ ++This option indicates which file contains the secret/private key to use to ++prove identity to the LDAP server during TLS negotiation. Should be used ++together with ldap_cert_file, which contains the identity to be proven. ++ +++-------------------------------------------------------+ ++|ldap_cipher_suite|Use: main|Type: string|Default: unset| +++-------------------------------------------------------+ ++ ++This controls the TLS cipher-suite negotiation during TLS negotiation with the ++LDAP server. See 41.4 for more details of the format of cipher-suite options ++with OpenSSL (as used by LDAP client libraries). ++ +++---------------------------------------------------------------+ ++|ldap_default_servers|Use: main|Type: string list|Default: unset| +++---------------------------------------------------------------+ ++ ++This option provides a list of LDAP servers which are tried in turn when an ++LDAP query does not contain a server. See section 9.14 for details of LDAP ++queries. This option is available only when Exim has been built with LDAP ++support. ++ +++--------------------------------------------------------+ ++|ldap_require_cert|Use: main|Type: string|Default: unset.| +++--------------------------------------------------------+ ++ ++This should be one of the values "hard", "demand", "allow", "try" or "never". A ++value other than one of these is interpreted as "never". See the entry ++"TLS_REQCERT" in your system man page for ldap.conf(5). Although Exim does not ++set a default, the LDAP library probably defaults to hard/demand. ++ +++-----------------------------------------------------+ ++|ldap_start_tls|Use: main|Type: boolean|Default: false| +++-----------------------------------------------------+ ++ ++If set, Exim will attempt to negotiate TLS with the LDAP server when connecting ++on a regular LDAP port. This is the LDAP equivalent of SMTP's "STARTTLS". This ++is distinct from using "ldaps", which is the LDAP form of SSL-on-connect. In ++the event of failure to negotiate TLS, the action taken is controlled by ++ldap_require_cert. ++ +++---------------------------------------------------+ ++|ldap_version|Use: main|Type: integer|Default: unset| +++---------------------------------------------------+ ++ ++This option can be used to force Exim to set a specific protocol version for ++LDAP. If it option is unset, it is shown by the -bP command line option as -1. ++When this is the case, the default is 3 if LDAP_VERSION3 is defined in the LDAP ++headers; otherwise it is 2. This option is available only when Exim has been ++built with LDAP support. ++ +++------------------------------------------------------+ ++|local_from_check|Use: main|Type: boolean|Default: true| +++------------------------------------------------------+ ++ ++When a message is submitted locally (that is, not over a TCP/IP connection) by ++an untrusted user, Exim removes any existing Sender: header line, and checks ++that the From: header line matches the login of the calling user and the domain ++specified by qualify_domain. ++ ++Note: An unqualified address (no domain) in the From: header in a locally ++submitted message is automatically qualified by Exim, unless the -bnq command ++line option is used. ++ ++You can use local_from_prefix and local_from_suffix to permit affixes on the ++local part. If the From: header line does not match, Exim adds a Sender: header ++with an address constructed from the calling user's login and the default ++qualify domain. ++ ++If local_from_check is set false, the From: header check is disabled, and no ++Sender: header is ever added. If, in addition, you want to retain Sender: ++header lines supplied by untrusted users, you must also set local_sender_retain ++to be true. ++ ++These options affect only the header lines in the message. The envelope sender ++is still forced to be the login id at the qualify domain unless ++untrusted_set_sender permits the user to supply an envelope sender. ++ ++For messages received over TCP/IP, an ACL can specify "submission mode" to ++request similar header line checking. See section 46.16, which has more details ++about Sender: processing. ++ +++-------------------------------------------------------+ ++|local_from_prefix|Use: main|Type: string|Default: unset| +++-------------------------------------------------------+ ++ ++When Exim checks the From: header line of locally submitted messages for ++matching the login id (see local_from_check above), it can be configured to ++ignore certain prefixes and suffixes in the local part of the address. This is ++done by setting local_from_prefix and/or local_from_suffix to appropriate ++lists, in the same form as the local_part_prefix and local_part_suffix router ++options (see chapter 15). For example, if ++ ++local_from_prefix = *- ++ ++is set, a From: line containing ++ ++From: anything-user@your.domain.example ++ ++will not cause a Sender: header to be added if user@your.domain.example matches ++the actual sender address that is constructed from the login name and qualify ++domain. ++ +++-------------------------------------------------------+ ++|local_from_suffix|Use: main|Type: string|Default: unset| +++-------------------------------------------------------+ ++ ++See local_from_prefix above. ++ +++---------------------------------------------------------------+ ++|local_interfaces|Use: main|Type: string list|Default: see below| +++---------------------------------------------------------------+ ++ ++This option controls which network interfaces are used by the daemon for ++listening; they are also used to identify the local host when routing. Chapter ++13 contains a full description of this option and the related options ++daemon_smtp_ports, extra_local_interfaces, hosts_treat_as_local, and ++tls_on_connect_ports. The default value for local_interfaces is ++ ++local_interfaces = 0.0.0.0 ++ ++when Exim is built without IPv6 support; otherwise it is ++ ++local_interfaces = <; ::0 ; 0.0.0.0 ++ +++---------------------------------------------------+ ++|local_scan_timeout|Use: main|Type: time|Default: 5m| +++---------------------------------------------------+ ++ ++This timeout applies to the local_scan() function (see chapter 44). Zero means ++"no timeout". If the timeout is exceeded, the incoming message is rejected with ++a temporary error if it is an SMTP message. For a non-SMTP message, the message ++is dropped and Exim ends with a non-zero code. The incident is logged on the ++main and reject logs. ++ +++----------------------------------------------------------+ ++|local_sender_retain|Use: main|Type: boolean|Default: false| +++----------------------------------------------------------+ ++ ++When a message is submitted locally (that is, not over a TCP/IP connection) by ++an untrusted user, Exim removes any existing Sender: header line. If you do not ++want this to happen, you must set local_sender_retain, and you must also set ++local_from_check to be false (Exim will complain if you do not). See also the ++ACL modifier "control = suppress_local_fixups". Section 46.16 has more details ++about Sender: processing. ++ +++-------------------------------------------------------+ ++|localhost_number|Use: main|Type: string*|Default: unset| +++-------------------------------------------------------+ ++ ++Exim's message ids are normally unique only within the local host. If ++uniqueness among a set of hosts is required, each host must set a different ++value for the localhost_number option. The string is expanded immediately after ++reading the configuration file (so that a number can be computed from the host ++name, for example) and the result of the expansion must be a number in the ++range 0-16 (or 0-10 on operating systems with case-insensitive file systems). ++This is available in subsequent string expansions via the variable ++$localhost_number. When localhost_number is set, the final two characters of ++the message id, instead of just being a fractional part of the time, are ++computed from the time and the local host number as described in section 3.4. ++ +++-----------------------------------------------------------------------+ ++|log_file_path|Use: main|Type: string list*|Default: set at compile time| +++-----------------------------------------------------------------------+ ++ ++This option sets the path which is used to determine the names of Exim's log ++files, or indicates that logging is to be to syslog, or both. It is expanded ++when Exim is entered, so it can, for example, contain a reference to the host ++name. If no specific path is set for the log files at compile or run time, they ++are written in a sub-directory called log in Exim's spool directory. Chapter 51 ++contains further details about Exim's logging, and section 51.1 describes how ++the contents of log_file_path are used. If this string is fixed at your ++installation (contains no expansion variables) it is recommended that you do ++not set this option in the configuration file, but instead supply the path ++using LOG_FILE_PATH in Local/Makefile so that it is available to Exim for ++logging errors detected early on - in particular, failure to read the ++configuration file. ++ +++--------------------------------------------------+ ++|log_selector|Use: main|Type: string|Default: unset| +++--------------------------------------------------+ ++ ++This option can be used to reduce or increase the number of things that Exim ++writes to its log files. Its argument is made up of names preceded by plus or ++minus characters. For example: ++ ++log_selector = +arguments -retry_defer ++ ++A list of possible names and what they control is given in the chapter on ++logging, in section 51.15. ++ +++---------------------------------------------------+ ++|log_timezone|Use: main|Type: boolean|Default: false| +++---------------------------------------------------+ ++ ++By default, the timestamps on log lines are in local time without the timezone. ++This means that if your timezone changes twice a year, the timestamps in log ++lines are ambiguous for an hour when the clocks go back. One way of avoiding ++this problem is to set the timezone to UTC. An alternative is to set ++log_timezone true. This turns on the addition of the timezone offset to ++timestamps in log lines. Turning on this option can add quite a lot to the size ++of log files because each line is extended by 6 characters. Note that the ++$tod_log variable contains the log timestamp without the zone, but there is ++another variable called $tod_zone that contains just the timezone offset. ++ +++---------------------------------------------------+ ++|lookup_open_max|Use: main|Type: integer|Default: 25| +++---------------------------------------------------+ ++ ++This option limits the number of simultaneously open files for single-key ++lookups that use regular files (that is, lsearch, dbm, and cdb). Exim normally ++keeps these files open during routing, because often the same file is required ++several times. If the limit is reached, Exim closes the least recently used ++file. Note that if you are using the ndbm library, it actually opens two files ++for each logical DBM database, though it still counts as one for the purposes ++of lookup_open_max. If you are getting "too many open files" errors with NDBM, ++you need to reduce the value of lookup_open_max. ++ +++------------------------------------------------------+ ++|max_username_length|Use: main|Type: integer|Default: 0| +++------------------------------------------------------+ ++ ++Some operating systems are broken in that they truncate long arguments to ++getpwnam() to eight characters, instead of returning "no such user". If this ++option is set greater than zero, any attempt to call getpwnam() with an ++argument that is longer behaves as if getpwnam() failed. ++ +++---------------------------------------------------------+ ++|message_body_newlines|Use: main|Type: bool|Default: false| +++---------------------------------------------------------+ ++ ++By default, newlines in the message body are replaced by spaces when setting ++the $message_body and $message_body_end expansion variables. If this option is ++set true, this no longer happens. ++ +++---------------------------------------------------------+ ++|message_body_visible|Use: main|Type: integer|Default: 500| +++---------------------------------------------------------+ ++ ++This option specifies how much of a message's body is to be included in the ++$message_body and $message_body_end expansion variables. ++ +++---------------------------------------------------------------+ ++|message_id_header_domain|Use: main|Type: string*|Default: unset| +++---------------------------------------------------------------+ ++ ++If this option is set, the string is expanded and used as the right hand side ++(domain) of the Message-ID: header that Exim creates if a locally-originated ++incoming message does not have one. "Locally-originated" means "not received ++over TCP/IP." Otherwise, the primary host name is used. Only letters, digits, ++dot and hyphen are accepted; any other characters are replaced by hyphens. If ++the expansion is forced to fail, or if the result is an empty string, the ++option is ignored. ++ +++-------------------------------------------------------------+ ++|message_id_header_text|Use: main|Type: string*|Default: unset| +++-------------------------------------------------------------+ ++ ++If this variable is set, the string is expanded and used to augment the text of ++the Message-id: header that Exim creates if a locally-originated incoming ++message does not have one. The text of this header is required by RFC 2822 to ++take the form of an address. By default, Exim uses its internal message id as ++the local part, and the primary host name as the domain. If this option is set, ++it is expanded, and provided the expansion is not forced to fail, and does not ++yield an empty string, the result is inserted into the header immediately ++before the @, separated from the internal message id by a dot. Any characters ++that are illegal in an address are automatically converted into hyphens. This ++means that variables such as $tod_log can be used, because the spaces and ++colons will become hyphens. ++ +++--------------------------------------------------+ ++|message_logs|Use: main|Type: boolean|Default: true| +++--------------------------------------------------+ ++ ++If this option is turned off, per-message log files are not created in the ++msglog spool sub-directory. This reduces the amount of disk I/O required by ++Exim, by reducing the number of files involved in handling a message from a ++minimum of four (header spool file, body spool file, delivery journal, and ++per-message log) to three. The other major I/O activity is Exim's main log, ++which is not affected by this option. ++ +++-------------------------------------------------------+ ++|message_size_limit|Use: main|Type: string*|Default: 50M| +++-------------------------------------------------------+ ++ ++This option limits the maximum size of message that Exim will process. The ++value is expanded for each incoming connection so, for example, it can be made ++to depend on the IP address of the remote host for messages arriving via TCP/ ++IP. After expansion, the value must be a sequence of decimal digits, optionally ++followed by K or M. ++ ++Note: This limit cannot be made to depend on a message's sender or any other ++properties of an individual message, because it has to be advertised in the ++server's response to EHLO. String expansion failure causes a temporary error. A ++value of zero means no limit, but its use is not recommended. See also ++bounce_return_size_limit. ++ ++Incoming SMTP messages are failed with a 552 error if the limit is exceeded; ++locally-generated messages either get a stderr message or a delivery failure ++message to the sender, depending on the -oe setting. Rejection of an oversized ++message is logged in both the main and the reject logs. See also the generic ++transport option message_size_limit, which limits the size of message that an ++individual transport can process. ++ ++If you use a virus-scanner and set this option to to a value larger than the ++maximum size that your virus-scanner is configured to support, you may get ++failures triggered by large mails. The right size to configure for the ++virus-scanner depends upon what data is passed and the options in use but it's ++probably safest to just set it to a little larger than this value. Eg, with a ++default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M, ++some problems may result. ++ ++A value of 0 will disable size limit checking; Exim will still advertise the ++SIZE extension in an EHLO response, but without a limit, so as to permit SMTP ++clients to still indicate the message size along with the MAIL verb. ++ +++-----------------------------------------------------------+ ++|move_frozen_messages|Use: main|Type: boolean|Default: false| +++-----------------------------------------------------------+ ++ ++This option, which is available only if Exim has been built with the setting ++ ++SUPPORT_MOVE_FROZEN_MESSAGES=yes ++ ++in Local/Makefile, causes frozen messages and their message logs to be moved ++from the input and msglog directories on the spool to Finput and Fmsglog, ++respectively. There is currently no support in Exim or the standard utilities ++for handling such moved messages, and they do not show up in lists generated by ++-bp or by the Exim monitor. ++ +++--------------------------------------------------+ ++|mua_wrapper|Use: main|Type: boolean|Default: false| +++--------------------------------------------------+ ++ ++Setting this option true causes Exim to run in a very restrictive mode in which ++it passes messages synchronously to a smart host. Chapter 50 contains a full ++description of this facility. ++ +++--------------------------------------------------------+ ++|mysql_servers|Use: main|Type: string list|Default: unset| +++--------------------------------------------------------+ ++ ++This option provides a list of MySQL servers and associated connection data, to ++be used in conjunction with mysql lookups (see section 9.21). The option is ++available only if Exim has been built with MySQL support. ++ +++-------------------------------------------------------+ ++|never_users|Use: main|Type: string list*|Default: unset| +++-------------------------------------------------------+ ++ ++This option is expanded just once, at the start of Exim's processing. Local ++message deliveries are normally run in processes that are setuid to the ++recipient, and remote deliveries are normally run under Exim's own uid and gid. ++It is usually desirable to prevent any deliveries from running as root, as a ++safety precaution. ++ ++When Exim is built, an option called FIXED_NEVER_USERS can be set to a list of ++users that must not be used for local deliveries. This list is fixed in the ++binary and cannot be overridden by the configuration file. By default, it ++contains just the single user name "root". The never_users runtime option can ++be used to add more users to the fixed list. ++ ++If a message is to be delivered as one of the users on the fixed list or the ++never_users list, an error occurs, and delivery is deferred. A common example ++is ++ ++never_users = root:daemon:bin ++ ++Including root is redundant if it is also on the fixed list, but it does no ++harm. This option overrides the pipe_as_creator option of the pipe transport ++driver. ++ +++--------------------------------------------------------------+ ++|openssl_options|Use: main|Type: string list|Default: +no_sslv2| +++--------------------------------------------------------------+ ++ ++This option allows an administrator to adjust the SSL options applied by ++OpenSSL to connections. It is given as a space-separated list of items, each ++one to be +added or -subtracted from the current value. ++ ++This option is only available if Exim is built against OpenSSL. The values ++available for this option vary according to the age of your OpenSSL install. ++The "all" value controls a subset of flags which are available, typically the ++bug workaround options. The SSL_CTX_set_options man page will list the values ++known on your system and Exim should support all the "bug workaround" options ++and many of the "modifying" options. The Exim names lose the leading "SSL_OP_" ++and are lower-cased. ++ ++Note that adjusting the options can have severe impact upon the security of SSL ++as used by Exim. It is possible to disable safety checks and shoot yourself in ++the foot in various unpleasant ways. This option should not be adjusted ++lightly. An unrecognised item will be detected at startup, by invoking Exim ++with the -bV flag. ++ ++Historical note: prior to release 4.80, Exim defaulted this value to ++"+dont_insert_empty_fragments", which may still be needed for compatibility ++with some clients, but which lowers security by increasing exposure to some now ++infamous attacks. ++ ++An example: ++ ++# Make both old MS and old Eudora happy: ++openssl_options = -all +microsoft_big_sslv3_buffer \ ++ +dont_insert_empty_fragments ++ ++Possible options may include: ++ ++ * "all" ++ ++ * "allow_unsafe_legacy_renegotiation" ++ ++ * "cipher_server_preference" ++ ++ * "dont_insert_empty_fragments" ++ ++ * "ephemeral_rsa" ++ ++ * "legacy_server_connect" ++ ++ * "microsoft_big_sslv3_buffer" ++ ++ * "microsoft_sess_id_bug" ++ ++ * "msie_sslv2_rsa_padding" ++ ++ * "netscape_challenge_bug" ++ ++ * "netscape_reuse_cipher_change_bug" ++ ++ * "no_compression" ++ ++ * "no_session_resumption_on_renegotiation" ++ ++ * "no_sslv2" ++ ++ * "no_sslv3" ++ ++ * "no_ticket" ++ ++ * "no_tlsv1" ++ ++ * "no_tlsv1_1" ++ ++ * "no_tlsv1_2" ++ ++ * "safari_ecdhe_ecdsa_bug" ++ ++ * "single_dh_use" ++ ++ * "single_ecdh_use" ++ ++ * "ssleay_080_client_dh_bug" ++ ++ * "sslref2_reuse_cert_type_bug" ++ ++ * "tls_block_padding_bug" ++ ++ * "tls_d5_bug" ++ ++ * "tls_rollback_bug" ++ ++As an aside, the "safari_ecdhe_ecdsa_bug" item is a misnomer and affects all ++clients connecting using the MacOS SecureTransport TLS facility prior to MacOS ++10.8.4, including email clients. If you see old MacOS clients failing to ++negotiate TLS then this option value might help, provided that your OpenSSL ++release is new enough to contain this work-around. This may be a situation ++where you have to upgrade OpenSSL to get buggy clients working. ++ +++---------------------------------------------------------+ ++|oracle_servers|Use: main|Type: string list|Default: unset| +++---------------------------------------------------------+ ++ ++This option provides a list of Oracle servers and associated connection data, ++to be used in conjunction with oracle lookups (see section 9.21). The option is ++available only if Exim has been built with Oracle support. ++ +++----------------------------------------------------------------+ ++|percent_hack_domains|Use: main|Type: domain list*|Default: unset| +++----------------------------------------------------------------+ ++ ++The "percent hack" is the convention whereby a local part containing a percent ++sign is re-interpreted as a new email address, with the percent replaced by @. ++This is sometimes called "source routing", though that term is also applied to ++RFC 2822 addresses that begin with an @ character. If this option is set, Exim ++implements the percent facility for those domains listed, but no others. This ++happens before an incoming SMTP address is tested against an ACL. ++ ++Warning: The "percent hack" has often been abused by people who are trying to ++get round relaying restrictions. For this reason, it is best avoided if at all ++possible. Unfortunately, a number of less security-conscious MTAs implement it ++unconditionally. If you are running Exim on a gateway host, and routing mail ++through to internal MTAs without processing the local parts, it is a good idea ++to reject recipient addresses with percent characters in their local parts. ++Exim's default configuration does this. ++ +++----------------------------------------------------+ ++|perl_at_start|Use: main|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++This option is available only when Exim is built with an embedded Perl ++interpreter. See chapter 12 for details of its use. ++ +++--------------------------------------------------+ ++|perl_startup|Use: main|Type: string|Default: unset| +++--------------------------------------------------+ ++ ++This option is available only when Exim is built with an embedded Perl ++interpreter. See chapter 12 for details of its use. ++ +++--------------------------------------------------------+ ++|pgsql_servers|Use: main|Type: string list|Default: unset| +++--------------------------------------------------------+ ++ ++This option provides a list of PostgreSQL servers and associated connection ++data, to be used in conjunction with pgsql lookups (see section 9.21). The ++option is available only if Exim has been built with PostgreSQL support. ++ +++------------------------------------------------------------------+ ++|pid_file_path|Use: main|Type: string*|Default: set at compile time| +++------------------------------------------------------------------+ ++ ++This option sets the name of the file to which the Exim daemon writes its ++process id. The string is expanded, so it can contain, for example, references ++to the host name: ++ ++pid_file_path = /var/log/$primary_hostname/exim.pid ++ ++If no path is set, the pid is written to the file exim-daemon.pid in Exim's ++spool directory. The value set by the option can be overridden by the -oP ++command line option. A pid file is not written if a "non-standard" daemon is ++run by means of the -oX option, unless a path is explicitly supplied by -oP. ++ +++----------------------------------------------------------------+ ++|pipelining_advertise_hosts|Use: main|Type: host list*|Default: *| +++----------------------------------------------------------------+ ++ ++This option can be used to suppress the advertisement of the SMTP PIPELINING ++extension to specific hosts. See also the no_pipelining control in section ++42.21. When PIPELINING is not advertised and smtp_enforce_sync is true, an Exim ++server enforces strict synchronization for each SMTP command and response. When ++PIPELINING is advertised, Exim assumes that clients will use it; "out of order" ++commands that are "expected" do not count as protocol errors (see ++smtp_max_synprot_errors). ++ +++------------------------------------------------------------+ ++|preserve_message_logs|Use: main|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is set, message log files are not deleted when messages are ++completed. Instead, they are moved to a sub-directory of the spool directory ++called msglog.OLD, where they remain available for statistical or debugging ++purposes. This is a dangerous option to set on systems with any appreciable ++volume of mail. Use with care! ++ +++----------------------------------------------------------+ ++|primary_hostname|Use: main|Type: string|Default: see below| +++----------------------------------------------------------+ ++ ++This specifies the name of the current host. It is used in the default EHLO or ++HELO command for outgoing SMTP messages (changeable via the helo_data option in ++the smtp transport), and as the default for qualify_domain. The value is also ++used by default in some SMTP response messages from an Exim server. This can be ++changed dynamically by setting smtp_active_hostname. ++ ++If primary_hostname is not set, Exim calls uname() to find the host name. If ++this fails, Exim panics and dies. If the name returned by uname() contains only ++one component, Exim passes it to gethostbyname() (or getipnodebyname() when ++available) in order to obtain the fully qualified version. The variable ++$primary_hostname contains the host name, whether set explicitly by this ++option, or defaulted. ++ +++--------------------------------------------------------+ ++|print_topbitchars|Use: main|Type: boolean|Default: false| +++--------------------------------------------------------+ ++ ++By default, Exim considers only those characters whose codes lie in the range ++32-126 to be printing characters. In a number of circumstances (for example, ++when writing log entries) non-printing characters are converted into escape ++sequences, primarily to avoid messing up the layout. If print_topbitchars is ++set, code values of 128 and above are also considered to be printing ++characters. ++ ++This option also affects the header syntax checks performed by the autoreply ++transport, and whether Exim uses RFC 2047 encoding of the user's full name when ++constructing From: and Sender: addresses (as described in section 46.18). ++Setting this option can cause Exim to generate eight bit message headers that ++do not conform to the standards. ++ +++------------------------------------------------------+ ++|process_log_path|Use: main|Type: string|Default: unset| +++------------------------------------------------------+ ++ ++This option sets the name of the file to which an Exim process writes its ++"process log" when sent a USR1 signal. This is used by the exiwhat utility ++script. If this option is unset, the file called exim-process.info in Exim's ++spool directory is used. The ability to specify the name explicitly can be ++useful in environments where two different Exims are running, using different ++spool directories. ++ +++---------------------------------------------------------+ ++|prod_requires_admin|Use: main|Type: boolean|Default: true| +++---------------------------------------------------------+ ++ ++The -M, -R, and -q command-line options require the caller to be an admin user ++unless prod_requires_admin is set false. See also queue_list_requires_admin. ++ +++--------------------------------------------------------+ ++|qualify_domain|Use: main|Type: string|Default: see below| +++--------------------------------------------------------+ ++ ++This option specifies the domain name that is added to any envelope sender ++addresses that do not have a domain qualification. It also applies to recipient ++addresses if qualify_recipient is not set. Unqualified addresses are accepted ++by default only for locally-generated messages. Qualification is also applied ++to addresses in header lines such as From: and To: for locally-generated ++messages, unless the -bnq command line option is used. ++ ++Messages from external sources must always contain fully qualified addresses, ++unless the sending host matches sender_unqualified_hosts or ++recipient_unqualified_hosts (as appropriate), in which case incoming addresses ++are qualified with qualify_domain or qualify_recipient as necessary. ++Internally, Exim always works with fully qualified envelope addresses. If ++qualify_domain is not set, it defaults to the primary_hostname value. ++ +++-----------------------------------------------------------+ ++|qualify_recipient|Use: main|Type: string|Default: see below| +++-----------------------------------------------------------+ ++ ++This option allows you to specify a different domain for qualifying recipient ++addresses to the one that is used for senders. See qualify_domain above. ++ +++---------------------------------------------------------+ ++|queue_domains|Use: main|Type: domain list*|Default: unset| +++---------------------------------------------------------+ ++ ++This option lists domains for which immediate delivery is not required. A ++delivery process is started whenever a message is received, but only those ++domains that do not match are processed. All other deliveries wait until the ++next queue run. See also hold_domains and queue_smtp_domains. ++ +++---------------------------------------------------------------+ ++|queue_list_requires_admin|Use: main|Type: boolean|Default: true| +++---------------------------------------------------------------+ ++ ++The -bp command-line option, which lists the messages that are on the queue, ++requires the caller to be an admin user unless queue_list_requires_admin is set ++false. See also prod_requires_admin. ++ +++-------------------------------------------------+ ++|queue_only|Use: main|Type: boolean|Default: false| +++-------------------------------------------------+ ++ ++If queue_only is set, a delivery process is not automatically started whenever ++a message is received. Instead, the message waits on the queue for the next ++queue run. Even if queue_only is false, incoming messages may not get delivered ++immediately when certain conditions (such as heavy load) occur. ++ ++The -odq command line has the same effect as queue_only. The -odb and -odi ++command line options override queue_only unless queue_only_override is set ++false. See also queue_only_file, queue_only_load, and smtp_accept_queue. ++ +++-----------------------------------------------------+ ++|queue_only_file|Use: main|Type: string|Default: unset| +++-----------------------------------------------------+ ++ ++This option can be set to a colon-separated list of absolute path names, each ++one optionally preceded by "smtp". When Exim is receiving a message, it tests ++for the existence of each listed path using a call to stat(). For each path ++that exists, the corresponding queueing option is set. For paths with no ++prefix, queue_only is set; for paths prefixed by "smtp", queue_smtp_domains is ++set to match all domains. So, for example, ++ ++queue_only_file = smtp/some/file ++ ++causes Exim to behave as if queue_smtp_domains were set to "*" whenever /some/ ++file exists. ++ +++----------------------------------------------------------+ ++|queue_only_load|Use: main|Type: fixed-point|Default: unset| +++----------------------------------------------------------+ ++ ++If the system load average is higher than this value, incoming messages from ++all sources are queued, and no automatic deliveries are started. If this ++happens during local or remote SMTP input, all subsequent messages received on ++the same SMTP connection are queued by default, whatever happens to the load in ++the meantime, but this can be changed by setting queue_only_load_latch false. ++ ++Deliveries will subsequently be performed by queue runner processes. This ++option has no effect on ancient operating systems on which Exim cannot ++determine the load average. See also deliver_queue_load_max and ++smtp_load_reserve. ++ +++-----------------------------------------------------------+ ++|queue_only_load_latch|Use: main|Type: boolean|Default: true| +++-----------------------------------------------------------+ ++ ++When this option is true (the default), once one message has been queued ++because the load average is higher than the value set by queue_only_load, all ++subsequent messages received on the same SMTP connection are also queued. This ++is a deliberate choice; even though the load average may fall below the ++threshold, it doesn't seem right to deliver later messages on the same ++connection when not delivering earlier ones. However, there are special ++circumstances such as very long-lived connections from scanning appliances ++where this is not the best strategy. In such cases, queue_only_load_latch ++should be set false. This causes the value of the load average to be ++re-evaluated for each message. ++ +++---------------------------------------------------------+ ++|queue_only_override|Use: main|Type: boolean|Default: true| +++---------------------------------------------------------+ ++ ++When this option is true, the -odx command line options override the setting of ++queue_only or queue_only_file in the configuration file. If queue_only_override ++is set false, the -odx options cannot be used to override; they are accepted, ++but ignored. ++ +++---------------------------------------------------------+ ++|queue_run_in_order|Use: main|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is set, queue runs happen in order of message arrival instead of ++in an arbitrary order. For this to happen, a complete list of the entire queue ++must be set up before the deliveries start. When the queue is all held in a ++single directory (the default), a single list is created for both the ordered ++and the non-ordered cases. However, if split_spool_directory is set, a single ++list is not created when queue_run_in_order is false. In this case, the ++sub-directories are processed one at a time (in a random order), and this ++avoids setting up one huge list for the whole queue. Thus, setting ++queue_run_in_order with split_spool_directory may degrade performance when the ++queue is large, because of the extra work in setting up the single, large list. ++In most situations, queue_run_in_order should not be set. ++ +++------------------------------------------------+ ++|queue_run_max|Use: main|Type: integer|Default: 5| +++------------------------------------------------+ ++ ++This controls the maximum number of queue runner processes that an Exim daemon ++can run simultaneously. This does not mean that it starts them all at once, but ++rather that if the maximum number are still running when the time comes to ++start another one, it refrains from starting another one. This can happen with ++very large queues and/or very sluggish deliveries. This option does not, ++however, interlock with other processes, so additional queue runners can be ++started by other means, or by killing and restarting the daemon. ++ ++Setting this option to zero does not suppress queue runs; rather, it disables ++the limit, allowing any number of simultaneous queue runner processes to be ++run. If you do not want queue runs to occur, omit the -qxx setting on the ++daemon's command line. ++ +++--------------------------------------------------------------+ ++|queue_smtp_domains|Use: main|Type: domain list*|Default: unset| +++--------------------------------------------------------------+ ++ ++When this option is set, a delivery process is started whenever a message is ++received, routing is performed, and local deliveries take place. However, if ++any SMTP deliveries are required for domains that match queue_smtp_domains, ++they are not immediately delivered, but instead the message waits on the queue ++for the next queue run. Since routing of the message has taken place, Exim ++knows to which remote hosts it must be delivered, and so when the queue run ++happens, multiple messages for the same host are delivered over a single SMTP ++connection. The -odqs command line option causes all SMTP deliveries to be ++queued in this way, and is equivalent to setting queue_smtp_domains to "*". See ++also hold_domains and queue_domains. ++ +++------------------------------------------------+ ++|receive_timeout|Use: main|Type: time|Default: 0s| +++------------------------------------------------+ ++ ++This option sets the timeout for accepting a non-SMTP message, that is, the ++maximum time that Exim waits when reading a message on the standard input. If ++the value is zero, it will wait for ever. This setting is overridden by the -or ++command line option. The timeout for incoming SMTP messages is controlled by ++smtp_receive_timeout. ++ +++---------------------------------------------------------------+ ++|received_header_text|Use: main|Type: string*|Default: see below| +++---------------------------------------------------------------+ ++ ++This string defines the contents of the Received: message header that is added ++to each message, except for the timestamp, which is automatically added on at ++the end (preceded by a semicolon). The string is expanded each time it is used. ++If the expansion yields an empty string, no Received: header line is added to ++the message. Otherwise, the string should start with the text "Received:" and ++conform to the RFC 2822 specification for Received: header lines. The default ++setting is: ++ ++received_header_text = Received: \ ++ ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\ ++ {${if def:sender_ident \ ++ {from ${quote_local_part:$sender_ident} }}\ ++ ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\ ++ by $primary_hostname \ ++ ${if def:received_protocol {with $received_protocol}} \ ++ ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\ ++ (Exim $version_number)\n\t\ ++ ${if def:sender_address \ ++ {(envelope-from <$sender_address>)\n\t}}\ ++ id $message_exim_id\ ++ ${if def:received_for {\n\tfor $received_for}} ++ ++The reference to the TLS cipher is omitted when Exim is built without TLS ++support. The use of conditional expansions ensures that this works for both ++locally generated messages and messages received from remote hosts, giving ++header lines such as the following: ++ ++Received: from scrooge.carol.example ([192.168.12.25] ident=root) ++by marley.carol.example with esmtp (Exim 4.00) ++(envelope-from <bob@carol.example>) ++id 16IOWa-00019l-00 ++for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000 ++Received: by scrooge.carol.example with local (Exim 4.00) ++id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000 ++ ++Until the body of the message has been received, the timestamp is the time when ++the message started to be received. Once the body has arrived, and all policy ++checks have taken place, the timestamp is updated to the time at which the ++message was accepted. ++ +++--------------------------------------------------------+ ++|received_headers_max|Use: main|Type: integer|Default: 30| +++--------------------------------------------------------+ ++ ++When a message is to be delivered, the number of Received: headers is counted, ++and if it is greater than this parameter, a mail loop is assumed to have ++occurred, the delivery is abandoned, and an error message is generated. This ++applies to both local and remote deliveries. ++ +++---------------------------------------------------------------------+ ++|recipient_unqualified_hosts|Use: main|Type: host list*|Default: unset| +++---------------------------------------------------------------------+ ++ ++This option lists those hosts from which Exim is prepared to accept unqualified ++recipient addresses in message envelopes. The addresses are made fully ++qualified by the addition of the qualify_recipient value. This option also ++affects message header lines. Exim does not reject unqualified recipient ++addresses in headers, but it qualifies them only if the message came from a ++host that matches recipient_unqualified_hosts, or if the message was submitted ++locally (not using TCP/IP), and the -bnq option was not set. ++ +++-------------------------------------------------+ ++|recipients_max|Use: main|Type: integer|Default: 0| +++-------------------------------------------------+ ++ ++If this option is set greater than zero, it specifies the maximum number of ++original recipients for any message. Additional recipients that are generated ++by aliasing or forwarding do not count. SMTP messages get a 452 response for ++all recipients over the limit; earlier recipients are delivered as normal. ++Non-SMTP messages with too many recipients are failed, and no deliveries are ++done. ++ ++Note: The RFCs specify that an SMTP server should accept at least 100 RCPT ++commands in a single message. ++ +++------------------------------------------------------------+ ++|recipients_max_reject|Use: main|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is set true, Exim rejects SMTP messages containing too many ++recipients by giving 552 errors to the surplus RCPT commands, and a 554 error ++to the eventual DATA command. Otherwise (the default) it gives a 452 error to ++the surplus RCPT commands and accepts the message on behalf of the initial set ++of recipients. The remote server should then re-send the message for the ++remaining recipients at a later time. ++ +++------------------------------------------------------+ ++|remote_max_parallel|Use: main|Type: integer|Default: 2| +++------------------------------------------------------+ ++ ++This option controls parallel delivery of one message to a number of remote ++hosts. If the value is less than 2, parallel delivery is disabled, and Exim ++does all the remote deliveries for a message one by one. Otherwise, if a single ++message has to be delivered to more than one remote host, or if several copies ++have to be sent to the same remote host, up to remote_max_parallel deliveries ++are done simultaneously. If more than remote_max_parallel deliveries are ++required, the maximum number of processes are started, and as each one ++finishes, another is begun. The order of starting processes is the same as if ++sequential delivery were being done, and can be controlled by the ++remote_sort_domains option. If parallel delivery takes place while running with ++debugging turned on, the debugging output from each delivery process is tagged ++with its process id. ++ ++This option controls only the maximum number of parallel deliveries for one ++message in one Exim delivery process. Because Exim has no central queue ++manager, there is no way of controlling the total number of simultaneous ++deliveries if the configuration allows a delivery attempt as soon as a message ++is received. ++ ++If you want to control the total number of deliveries on the system, you need ++to set the queue_only option. This ensures that all incoming messages are added ++to the queue without starting a delivery process. Then set up an Exim daemon to ++start queue runner processes at appropriate intervals (probably fairly often, ++for example, every minute), and limit the total number of queue runners by ++setting the queue_run_max parameter. Because each queue runner delivers only ++one message at a time, the maximum number of deliveries that can then take ++place at once is queue_run_max multiplied by remote_max_parallel. ++ ++If it is purely remote deliveries you want to control, use queue_smtp_domains ++instead of queue_only. This has the added benefit of doing the SMTP routing ++before queueing, so that several messages for the same host will eventually get ++delivered down the same connection. ++ +++---------------------------------------------------------------+ ++|remote_sort_domains|Use: main|Type: domain list*|Default: unset| +++---------------------------------------------------------------+ ++ ++When there are a number of remote deliveries for a message, they are sorted by ++domain into the order given by this list. For example, ++ ++remote_sort_domains = *.cam.ac.uk:*.uk ++ ++would attempt to deliver to all addresses in the cam.ac.uk domain first, then ++to those in the uk domain, then to any others. ++ +++--------------------------------------------------+ ++|retry_data_expire|Use: main|Type: time|Default: 7d| +++--------------------------------------------------+ ++ ++This option sets a "use before" time on retry information in Exim's hints ++database. Any older retry data is ignored. This means that, for example, once a ++host has not been tried for 7 days, Exim behaves as if it has no knowledge of ++past failures. ++ +++----------------------------------------------------+ ++|retry_interval_max|Use: main|Type: time|Default: 24h| +++----------------------------------------------------+ ++ ++Chapter 32 describes Exim's mechanisms for controlling the intervals between ++delivery attempts for messages that cannot be delivered straight away. This ++option sets an overall limit to the length of time between retries. It cannot ++be set greater than 24 hours; any attempt to do so forces the default value. ++ +++--------------------------------------------------------+ ++|return_path_remove|Use: main|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++RFC 2821, section 4.4, states that an SMTP server must insert a Return-path: ++header line into a message when it makes a "final delivery". The Return-path: ++header preserves the sender address as received in the MAIL command. This ++description implies that this header should not be present in an incoming ++message. If return_path_remove is true, any existing Return-path: headers are ++removed from messages at the time they are received. Exim's transports have ++options for adding Return-path: headers at the time of delivery. They are ++normally used only for final local deliveries. ++ +++-------------------------------------------------------+ ++|return_size_limit|Use: main|Type: integer|Default: 100K| +++-------------------------------------------------------+ ++ ++This option is an obsolete synonym for bounce_return_size_limit. ++ +++---------------------------------------------------+ ++|rfc1413_hosts|Use: main|Type: host list*|Default: *| +++---------------------------------------------------+ ++ ++RFC 1413 identification calls are made to any client host which matches an item ++in the list. ++ +++------------------------------------------------------+ ++|rfc1413_query_timeout|Use: main|Type: time|Default: 5s| +++------------------------------------------------------+ ++ ++This sets the timeout on RFC 1413 identification calls. If it is set to zero, ++no RFC 1413 calls are ever made. ++ +++------------------------------------------------------------------+ ++|sender_unqualified_hosts|Use: main|Type: host list*|Default: unset| +++------------------------------------------------------------------+ ++ ++This option lists those hosts from which Exim is prepared to accept unqualified ++sender addresses. The addresses are made fully qualified by the addition of ++qualify_domain. This option also affects message header lines. Exim does not ++reject unqualified addresses in headers that contain sender addresses, but it ++qualifies them only if the message came from a host that matches ++sender_unqualified_hosts, or if the message was submitted locally (not using ++TCP/IP), and the -bnq option was not set. ++ +++-----------------------------------------------------------+ ++|smtp_accept_keepalive|Use: main|Type: boolean|Default: true| +++-----------------------------------------------------------+ ++ ++This option controls the setting of the SO_KEEPALIVE option on incoming TCP/IP ++socket connections. When set, it causes the kernel to probe idle connections ++periodically, by sending packets with "old" sequence numbers. The other end of ++the connection should send an acknowledgment if the connection is still okay or ++a reset if the connection has been aborted. The reason for doing this is that ++it has the beneficial effect of freeing up certain types of connection that can ++get stuck when the remote host is disconnected without tidying up the TCP/IP ++call properly. The keepalive mechanism takes several hours to detect ++unreachable hosts. ++ +++---------------------------------------------------+ ++|smtp_accept_max|Use: main|Type: integer|Default: 20| +++---------------------------------------------------+ ++ ++This option specifies the maximum number of simultaneous incoming SMTP calls ++that Exim will accept. It applies only to the listening daemon; there is no ++control (in Exim) when incoming SMTP is being handled by inetd. If the value is ++set to zero, no limit is applied. However, it is required to be non-zero if ++either smtp_accept_max_per_host or smtp_accept_queue is set. See also ++smtp_accept_reserve and smtp_load_reserve. ++ ++A new SMTP connection is immediately rejected if the smtp_accept_max limit has ++been reached. If not, Exim first checks smtp_accept_max_per_host. If that limit ++has not been reached for the client host, smtp_accept_reserve and ++smtp_load_reserve are then checked before accepting the connection. ++ +++-----------------------------------------------------------+ ++|smtp_accept_max_nonmail|Use: main|Type: integer|Default: 10| +++-----------------------------------------------------------+ ++ ++Exim counts the number of "non-mail" commands in an SMTP session, and drops the ++connection if there are too many. This option defines "too many". The check ++catches some denial-of-service attacks, repeated failing AUTHs, or a mad client ++looping sending EHLO, for example. The check is applied only if the client host ++matches smtp_accept_max_nonmail_hosts. ++ ++When a new message is expected, one occurrence of RSET is not counted. This ++allows a client to send one RSET between messages (this is not necessary, but ++some clients do it). Exim also allows one uncounted occurrence of HELO or EHLO, ++and one occurrence of STARTTLS between messages. After starting up a TLS ++session, another EHLO is expected, and so it too is not counted. The first ++occurrence of AUTH in a connection, or immediately following STARTTLS is not ++counted. Otherwise, all commands other than MAIL, RCPT, DATA, and QUIT are ++counted. ++ +++-------------------------------------------------------------------+ ++|smtp_accept_max_nonmail_hosts|Use: main|Type: host list*|Default: *| +++-------------------------------------------------------------------+ ++ ++You can control which hosts are subject to the smtp_accept_max_nonmail check by ++setting this option. The default value makes it apply to all hosts. By changing ++the value, you can exclude any badly-behaved hosts that you have to live with. ++ +++--------------------------------------------------------------------+ ++|smtp_accept_max_per_connection|Use: main|Type: integer|Default: 1000| +++--------------------------------------------------------------------+ ++ ++The value of this option limits the number of MAIL commands that Exim is ++prepared to accept over a single SMTP connection, whether or not each command ++results in the transfer of a message. After the limit is reached, a 421 ++response is given to subsequent MAIL commands. This limit is a safety ++precaution against a client that goes mad (incidents of this type have been ++seen). ++ +++---------------------------------------------------------------+ ++|smtp_accept_max_per_host|Use: main|Type: string*|Default: unset| +++---------------------------------------------------------------+ ++ ++This option restricts the number of simultaneous IP connections from a single ++host (strictly, from a single IP address) to the Exim daemon. The option is ++expanded, to enable different limits to be applied to different hosts by ++reference to $sender_host_address. Once the limit is reached, additional ++connection attempts from the same host are rejected with error code 421. This ++is entirely independent of smtp_accept_reserve. The option's default value of ++zero imposes no limit. If this option is set greater than zero, it is required ++that smtp_accept_max be non-zero. ++ ++Warning: When setting this option you should not use any expansion ++constructions that take an appreciable amount of time. The expansion and test ++happen in the main daemon loop, in order to reject additional connections ++without forking additional processes (otherwise a denial-of-service attack ++could cause a vast number or processes to be created). While the daemon is ++doing this processing, it cannot accept any other incoming connections. ++ +++----------------------------------------------------+ ++|smtp_accept_queue|Use: main|Type: integer|Default: 0| +++----------------------------------------------------+ ++ ++If the number of simultaneous incoming SMTP connections being handled via the ++listening daemon exceeds this value, messages received by SMTP are just placed ++on the queue; no delivery processes are started automatically. The count is ++fixed at the start of an SMTP connection. It cannot be updated in the ++subprocess that receives messages, and so the queueing or not queueing applies ++to all messages received in the same connection. ++ ++A value of zero implies no limit, and clearly any non-zero value is useful only ++if it is less than the smtp_accept_max value (unless that is zero). See also ++queue_only, queue_only_load, queue_smtp_domains, and the various -odx command ++line options. ++ +++-----------------------------------------------------------------------+ ++|smtp_accept_queue_per_ connection|Use: main|Type: integer|Default: 10| +++-----------------------------------------------------------------------+ ++ ++This option limits the number of delivery processes that Exim starts ++automatically when receiving messages via SMTP, whether via the daemon or by ++the use of -bs or -bS. If the value of the option is greater than zero, and the ++number of messages received in a single SMTP session exceeds this number, ++subsequent messages are placed on the queue, but no delivery processes are ++started. This helps to limit the number of Exim processes when a server ++restarts after downtime and there is a lot of mail waiting for it on other ++systems. On large systems, the default should probably be increased, and on ++dial-in client systems it should probably be set to zero (that is, disabled). ++ +++------------------------------------------------------+ ++|smtp_accept_reserve|Use: main|Type: integer|Default: 0| +++------------------------------------------------------+ ++ ++When smtp_accept_max is set greater than zero, this option specifies a number ++of SMTP connections that are reserved for connections from the hosts that are ++specified in smtp_reserve_hosts. The value set in smtp_accept_max includes this ++reserve pool. The specified hosts are not restricted to this number of ++connections; the option specifies a minimum number of connection slots for ++them, not a maximum. It is a guarantee that this group of hosts can always get ++at least smtp_accept_reserve connections. However, the limit specified by ++smtp_accept_max_per_host is still applied to each individual host. ++ ++For example, if smtp_accept_max is set to 50 and smtp_accept_reserve is set to ++5, once there are 45 active connections (from any hosts), new connections are ++accepted only from hosts listed in smtp_reserve_hosts, provided the other ++criteria for acceptance are met. ++ +++-----------------------------------------------------------+ ++|smtp_active_hostname|Use: main|Type: string*|Default: unset| +++-----------------------------------------------------------+ ++ ++This option is provided for multi-homed servers that want to masquerade as ++several different hosts. At the start of an incoming SMTP connection, its value ++is expanded and used instead of the value of $primary_hostname in SMTP ++responses. For example, it is used as domain name in the response to an ++incoming HELO or EHLO command. ++ ++The active hostname is placed in the $smtp_active_hostname variable, which is ++saved with any messages that are received. It is therefore available for use in ++routers and transports when the message is later delivered. ++ ++If this option is unset, or if its expansion is forced to fail, or if the ++expansion results in an empty string, the value of $primary_hostname is used. ++Other expansion failures cause a message to be written to the main and panic ++logs, and the SMTP command receives a temporary error. Typically, the value of ++smtp_active_hostname depends on the incoming interface address. For example: ++ ++smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\ ++ {cox.mydomain}{box.mydomain}} ++ ++Although $smtp_active_hostname is primarily concerned with incoming messages, ++it is also used as the default for HELO commands in callout verification if ++there is no remote transport from which to obtain a helo_data value. ++ +++------------------------------------------------------+ ++|smtp_banner|Use: main|Type: string*|Default: see below| +++------------------------------------------------------+ ++ ++This string, which is expanded every time it is used, is output as the initial ++positive response to an SMTP connection. The default setting is: ++ ++smtp_banner = $smtp_active_hostname ESMTP Exim \ ++ $version_number $tod_full ++ ++Failure to expand the string causes a panic error. If you want to create a ++multiline response to the initial SMTP connection, use "\n" in the string at ++appropriate points, but not at the end. Note that the 220 code is not included ++in this string. Exim adds it automatically (several times in the case of a ++multiline response). ++ +++------------------------------------------------------------+ ++|smtp_check_spool_space|Use: main|Type: boolean|Default: true| +++------------------------------------------------------------+ ++ ++When this option is set, if an incoming SMTP session encounters the SIZE option ++on a MAIL command, it checks that there is enough space in the spool ++directory's partition to accept a message of that size, while still leaving ++free the amount specified by check_spool_space (even if that value is zero). If ++there isn't enough space, a temporary error code is returned. ++ +++--------------------------------------------------------+ ++|smtp_connect_backlog|Use: main|Type: integer|Default: 20| +++--------------------------------------------------------+ ++ ++This option specifies a maximum number of waiting SMTP connections. Exim passes ++this value to the TCP/IP system when it sets up its listener. Once this number ++of connections are waiting for the daemon's attention, subsequent connection ++attempts are refused at the TCP/IP level. At least, that is what the manuals ++say; in some circumstances such connection attempts have been observed to time ++out instead. For large systems it is probably a good idea to increase the value ++(to 50, say). It also gives some protection against denial-of-service attacks ++by SYN flooding. ++ +++-------------------------------------------------------+ ++|smtp_enforce_sync|Use: main|Type: boolean|Default: true| +++-------------------------------------------------------+ ++ ++The SMTP protocol specification requires the client to wait for a response from ++the server at certain points in the dialogue. Without PIPELINING these ++synchronization points are after every command; with PIPELINING they are fewer, ++but they still exist. ++ ++Some spamming sites send out a complete set of SMTP commands without waiting ++for any response. Exim protects against this by rejecting a message if the ++client has sent further input when it should not have. The error response "554 ++SMTP synchronization error" is sent, and the connection is dropped. Testing for ++this error cannot be perfect because of transmission delays (unexpected input ++may be on its way but not yet received when Exim checks). However, it does ++detect many instances. ++ ++The check can be globally disabled by setting smtp_enforce_sync false. If you ++want to disable the check selectively (for example, only for certain hosts), ++you can do so by an appropriate use of a control modifier in an ACL (see ++section 42.21). See also pipelining_advertise_hosts. ++ +++--------------------------------------------------------+ ++|smtp_etrn_command|Use: main|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++If this option is set, the given command is run whenever an SMTP ETRN command ++is received from a host that is permitted to issue such commands (see chapter ++42). The string is split up into separate arguments which are independently ++expanded. The expansion variable $domain is set to the argument of the ETRN ++command, and no syntax checking is done on it. For example: ++ ++smtp_etrn_command = /etc/etrn_command $domain \ ++ $sender_host_address ++ ++A new process is created to run the command, but Exim does not wait for it to ++complete. Consequently, its status cannot be checked. If the command cannot be ++run, a line is written to the panic log, but the ETRN caller still receives a ++250 success response. Exim is normally running under its own uid when receiving ++SMTP, so it is not possible for it to change the uid before running the ++command. ++ +++---------------------------------------------------------+ ++|smtp_etrn_serialize|Use: main|Type: boolean|Default: true| +++---------------------------------------------------------+ ++ ++When this option is set, it prevents the simultaneous execution of more than ++one identical command as a result of ETRN in an SMTP connection. See section ++47.8 for details. ++ +++------------------------------------------------------------+ ++|smtp_load_reserve|Use: main|Type: fixed-point|Default: unset| +++------------------------------------------------------------+ ++ ++If the system load average ever gets higher than this, incoming SMTP calls are ++accepted only from those hosts that match an entry in smtp_reserve_hosts. If ++smtp_reserve_hosts is not set, no incoming SMTP calls are accepted when the ++load is over the limit. The option has no effect on ancient operating systems ++on which Exim cannot determine the load average. See also ++deliver_queue_load_max and queue_only_load. ++ +++----------------------------------------------------------+ ++|smtp_max_synprot_errors|Use: main|Type: integer|Default: 3| +++----------------------------------------------------------+ ++ ++Exim rejects SMTP commands that contain syntax or protocol errors. In ++particular, a syntactically invalid email address, as in this command: ++ ++RCPT TO:<abc xyz@a.b.c> ++ ++causes immediate rejection of the command, before any other tests are done. ++(The ACL cannot be run if there is no valid address to set up for it.) An ++example of a protocol error is receiving RCPT before MAIL. If there are too ++many syntax or protocol errors in one SMTP session, the connection is dropped. ++The limit is set by this option. ++ ++When the PIPELINING extension to SMTP is in use, some protocol errors are ++"expected", for instance, a RCPT command after a rejected MAIL command. Exim ++assumes that PIPELINING will be used if it advertises it (see ++pipelining_advertise_hosts), and in this situation, "expected" errors do not ++count towards the limit. ++ +++------------------------------------------------------------+ ++|smtp_max_unknown_commands|Use: main|Type: integer|Default: 3| +++------------------------------------------------------------+ ++ ++If there are too many unrecognized commands in an incoming SMTP session, an ++Exim server drops the connection. This is a defence against some kinds of abuse ++that subvert web clients into making connections to SMTP ports; in these ++circumstances, a number of non-SMTP command lines are sent first. ++ +++--------------------------------------------------------------+ ++|smtp_ratelimit_hosts|Use: main|Type: host list*|Default: unset| +++--------------------------------------------------------------+ ++ ++Some sites find it helpful to be able to limit the rate at which certain hosts ++can send them messages, and the rate at which an individual message can specify ++recipients. ++ ++Exim has two rate-limiting facilities. This section describes the older ++facility, which can limit rates within a single connection. The newer ratelimit ++ACL condition can limit rates across all connections. See section 42.37 for ++details of the newer facility. ++ ++When a host matches smtp_ratelimit_hosts, the values of smtp_ratelimit_mail and ++smtp_ratelimit_rcpt are used to control the rate of acceptance of MAIL and RCPT ++commands in a single SMTP session, respectively. Each option, if set, must ++contain a set of four comma-separated values: ++ ++ * A threshold, before which there is no rate limiting. ++ ++ * An initial time delay. Unlike other times in Exim, numbers with decimal ++ fractional parts are allowed here. ++ ++ * A factor by which to increase the delay each time. ++ ++ * A maximum value for the delay. This should normally be less than 5 minutes, ++ because after that time, the client is liable to timeout the SMTP command. ++ ++For example, these settings have been used successfully at the site which first ++suggested this feature, for controlling mail from their customers: ++ ++smtp_ratelimit_mail = 2,0.5s,1.05,4m ++smtp_ratelimit_rcpt = 4,0.25s,1.015,4m ++ ++The first setting specifies delays that are applied to MAIL commands after two ++have been received over a single connection. The initial delay is 0.5 seconds, ++increasing by a factor of 1.05 each time. The second setting applies delays to ++RCPT commands when more than four occur in a single message. ++ +++---------------------------------------------------------+ ++|smtp_ratelimit_mail|Use: main|Type: string|Default: unset| +++---------------------------------------------------------+ ++ ++See smtp_ratelimit_hosts above. ++ +++---------------------------------------------------------+ ++|smtp_ratelimit_rcpt|Use: main|Type: string|Default: unset| +++---------------------------------------------------------+ ++ ++See smtp_ratelimit_hosts above. ++ +++-----------------------------------------------------+ ++|smtp_receive_timeout|Use: main|Type: time|Default: 5m| +++-----------------------------------------------------+ ++ ++This sets a timeout value for SMTP reception. It applies to all forms of SMTP ++input, including batch SMTP. If a line of input (either an SMTP command or a ++data line) is not received within this time, the SMTP connection is dropped and ++the message is abandoned. A line is written to the log containing one of the ++following messages: ++ ++SMTP command timeout on connection from... ++SMTP data timeout on connection from... ++ ++The former means that Exim was expecting to read an SMTP command; the latter ++means that it was in the DATA phase, reading the contents of a message. ++ ++The value set by this option can be overridden by the -os command-line option. ++A setting of zero time disables the timeout, but this should never be used for ++SMTP over TCP/IP. (It can be useful in some cases of local input using -bs or ++-bS.) For non-SMTP input, the reception timeout is controlled by ++receive_timeout and -or. ++ +++------------------------------------------------------------+ ++|smtp_reserve_hosts|Use: main|Type: host list*|Default: unset| +++------------------------------------------------------------+ ++ ++This option defines hosts for which SMTP connections are reserved; see ++smtp_accept_reserve and smtp_load_reserve above. ++ +++----------------------------------------------------------------+ ++|smtp_return_error_details|Use: main|Type: boolean|Default: false| +++----------------------------------------------------------------+ ++ ++In the default state, Exim uses bland messages such as "Administrative ++prohibition" when it rejects SMTP commands for policy reasons. Many sysadmins ++like this because it gives away little information to spammers. However, some ++other sysadmins who are applying strict checking policies want to give out much ++fuller information about failures. Setting smtp_return_error_details true ++causes Exim to be more forthcoming. For example, instead of "Administrative ++prohibition", it might give: ++ ++550-Rejected after DATA: '>' missing at end of address: ++550 failing address in "From" header is: <user@dom.ain ++ +++-------------------------------------------------------+ ++|spamd_address|Use: main|Type: string|Default: see below| +++-------------------------------------------------------+ ++ ++This option is available when Exim is compiled with the content-scanning ++extension. It specifies how Exim connects to SpamAssassin's spamd daemon. The ++default value is ++ ++127.0.0.1 783 ++ ++See section 43.2 for more details. ++ +++------------------------------------------------------------+ ++|split_spool_directory|Use: main|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is set, it causes Exim to split its input directory into 62 ++subdirectories, each with a single alphanumeric character as its name. The ++sixth character of the message id is used to allocate messages to ++subdirectories; this is the least significant base-62 digit of the time of ++arrival of the message. ++ ++Splitting up the spool in this way may provide better performance on systems ++where there are long mail queues, by reducing the number of files in any one ++directory. The msglog directory is also split up in a similar way to the input ++directory; however, if preserve_message_logs is set, all old msglog files are ++still placed in the single directory msglog.OLD. ++ ++It is not necessary to take any special action for existing messages when ++changing split_spool_directory. Exim notices messages that are in the "wrong" ++place, and continues to process them. If the option is turned off after a ++period of being on, the subdirectories will eventually empty and be ++automatically deleted. ++ ++When split_spool_directory is set, the behaviour of queue runner processes ++changes. Instead of creating a list of all messages in the queue, and then ++trying to deliver each one in turn, it constructs a list of those in one ++sub-directory and tries to deliver them, before moving on to the next ++sub-directory. The sub-directories are processed in a random order. This ++spreads out the scanning of the input directories, and uses less memory. It is ++particularly beneficial when there are lots of messages on the queue. However, ++if queue_run_in_order is set, none of this new processing happens. The entire ++queue has to be scanned and sorted before any deliveries can start. ++ +++--------------------------------------------------------------------+ ++|spool_directory|Use: main|Type: string*|Default: set at compile time| +++--------------------------------------------------------------------+ ++ ++This defines the directory in which Exim keeps its spool, that is, the messages ++it is waiting to deliver. The default value is taken from the compile-time ++configuration setting, if there is one. If not, this option must be set. The ++string is expanded, so it can contain, for example, a reference to ++$primary_hostname. ++ ++If the spool directory name is fixed on your installation, it is recommended ++that you set it at build time rather than from this option, particularly if the ++log files are being written to the spool directory (see log_file_path). ++Otherwise log files cannot be used for errors that are detected early on, such ++as failures in the configuration file. ++ ++By using this option to override the compiled-in path, it is possible to run ++tests of Exim without using the standard spool. ++ +++----------------------------------------------------+ ++|sqlite_lock_timeout|Use: main|Type: time|Default: 5s| +++----------------------------------------------------+ ++ ++This option controls the timeout that the sqlite lookup uses when trying to ++access an SQLite database. See section 9.25 for more details. ++ +++------------------------------------------------------+ ++|strict_acl_vars|Use: main|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++This option controls what happens if a syntactically valid but undefined ACL ++variable is referenced. If it is false (the default), an empty string is ++substituted; if it is true, an error is generated. See section 42.18 for ++details of ACL variables. ++ +++------------------------------------------------------------------+ ++|strip_excess_angle_brackets|Use: main|Type: boolean|Default: false| +++------------------------------------------------------------------+ ++ ++If this option is set, redundant pairs of angle brackets round "route-addr" ++items in addresses are stripped. For example, <<xxx@a.b.c.d>> is treated as ++<xxx@a.b.c.d>. If this is in the envelope and the message is passed on to ++another MTA, the excess angle brackets are not passed on. If this option is not ++set, multiple pairs of angle brackets cause a syntax error. ++ +++---------------------------------------------------------+ ++|strip_trailing_dot|Use: main|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is set, a trailing dot at the end of a domain in an address is ++ignored. If this is in the envelope and the message is passed on to another ++MTA, the dot is not passed on. If this option is not set, a dot at the end of a ++domain causes a syntax error. However, addresses in header lines are checked ++only when an ACL requests header syntax checking. ++ +++--------------------------------------------------------+ ++|syslog_duplication|Use: main|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++When Exim is logging to syslog, it writes the log lines for its three separate ++logs at different syslog priorities so that they can in principle be separated ++on the logging hosts. Some installations do not require this separation, and in ++those cases, the duplication of certain log lines is a nuisance. If ++syslog_duplication is set false, only one copy of any particular log line is ++written to syslog. For lines that normally go to both the main log and the ++reject log, the reject log version (possibly containing message header lines) ++is written, at LOG_NOTICE priority. Lines that normally go to both the main and ++the panic log are written at the LOG_ALERT priority. ++ +++-----------------------------------------------------+ ++|syslog_facility|Use: main|Type: string|Default: unset| +++-----------------------------------------------------+ ++ ++This option sets the syslog "facility" name, used when Exim is logging to ++syslog. The value must be one of the strings "mail", "user", "news", "uucp", ++"daemon", or "localx" where x is a digit between 0 and 7. If this option is ++unset, "mail" is used. See chapter 51 for details of Exim's logging. ++ +++---------------------------------------------------------+ ++|syslog_processname|Use: main|Type: string|Default: "exim"| +++---------------------------------------------------------+ ++ ++This option sets the syslog "ident" name, used when Exim is logging to syslog. ++The value must be no longer than 32 characters. See chapter 51 for details of ++Exim's logging. ++ +++------------------------------------------------------+ ++|syslog_timestamp|Use: main|Type: boolean|Default: true| +++------------------------------------------------------+ ++ ++If syslog_timestamp is set false, the timestamps on Exim's log lines are ++omitted when these lines are sent to syslog. See chapter 51 for details of ++Exim's logging. ++ +++----------------------------------------------------+ ++|system_filter|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This option specifies an Exim filter file that is applied to all messages at ++the start of each delivery attempt, before any routing is done. System filters ++must be Exim filters; they cannot be Sieve filters. If the system filter ++generates any deliveries to files or pipes, or any new mail messages, the ++appropriate system_filter_..._transport option(s) must be set, to define which ++transports are to be used. Details of this facility are given in chapter 45. ++ +++------------------------------------------------------------------------+ ++|system_filter_directory_transport|Use: main|Type: string*|Default: unset| +++------------------------------------------------------------------------+ ++ ++This sets the name of the transport driver that is to be used when the save ++command in a system message filter specifies a path ending in "/", implying ++delivery of each message into a separate file in some directory. During the ++delivery, the variable $address_file contains the path name. ++ +++-------------------------------------------------------------------+ ++|system_filter_file_transport|Use: main|Type: string*|Default: unset| +++-------------------------------------------------------------------+ ++ ++This sets the name of the transport driver that is to be used when the save ++command in a system message filter specifies a path not ending in "/". During ++the delivery, the variable $address_file contains the path name. ++ +++---------------------------------------------------------+ ++|system_filter_group|Use: main|Type: string|Default: unset| +++---------------------------------------------------------+ ++ ++This option is used only when system_filter_user is also set. It sets the gid ++under which the system filter is run, overriding any gid that is associated ++with the user. The value may be numerical or symbolic. ++ +++-------------------------------------------------------------------+ ++|system_filter_pipe_transport|Use: main|Type: string*|Default: unset| +++-------------------------------------------------------------------+ ++ ++This specifies the transport driver that is to be used when a pipe command is ++used in a system filter. During the delivery, the variable $address_pipe ++contains the pipe command. ++ +++--------------------------------------------------------------------+ ++|system_filter_reply_transport|Use: main|Type: string*|Default: unset| +++--------------------------------------------------------------------+ ++ ++This specifies the transport driver that is to be used when a mail command is ++used in a system filter. ++ +++--------------------------------------------------------+ ++|system_filter_user|Use: main|Type: string|Default: unset| +++--------------------------------------------------------+ ++ ++If this option is set to root, the system filter is run in the main Exim ++delivery process, as root. Otherwise, the system filter runs in a separate ++process, as the given user, defaulting to the Exim run-time user. Unless the ++string consists entirely of digits, it is looked up in the password data. ++Failure to find the named user causes a configuration error. The gid is either ++taken from the password data, or specified by system_filter_group. When the uid ++is specified numerically, system_filter_group is required to be set. ++ ++If the system filter generates any pipe, file, or reply deliveries, the uid ++under which the filter is run is used when transporting them, unless a ++transport option overrides. ++ +++-------------------------------------------------+ ++|tcp_nodelay|Use: main|Type: boolean|Default: true| +++-------------------------------------------------+ ++ ++If this option is set false, it stops the Exim daemon setting the TCP_NODELAY ++option on its listening sockets. Setting TCP_NODELAY turns off the "Nagle ++algorithm", which is a way of improving network performance in interactive ++(character-by-character) situations. Turning it off should improve Exim's ++performance a bit, so that is what happens by default. However, it appears that ++some broken clients cannot cope, and time out. Hence this option. It affects ++only those sockets that are set up for listening by the daemon. Sockets created ++by the smtp transport for delivering mail always set TCP_NODELAY. ++ +++-----------------------------------------------------+ ++|timeout_frozen_after|Use: main|Type: time|Default: 0s| +++-----------------------------------------------------+ ++ ++If timeout_frozen_after is set to a time greater than zero, a frozen message of ++any kind that has been on the queue for longer than the given time is ++automatically cancelled at the next queue run. If the frozen message is a ++bounce message, it is just discarded; otherwise, a bounce is sent to the ++sender, in a similar manner to cancellation by the -Mg command line option. If ++you want to timeout frozen bounce messages earlier than other kinds of frozen ++message, see ignore_bounce_errors_after. ++ ++Note: the default value of zero means no timeouts; with this setting, frozen ++messages remain on the queue forever (except for any frozen bounce messages ++that are released by ignore_bounce_errors_after). ++ +++----------------------------------------------+ ++|timezone|Use: main|Type: string|Default: unset| +++----------------------------------------------+ ++ ++The value of timezone is used to set the environment variable TZ while running ++Exim (if it is different on entry). This ensures that all timestamps created by ++Exim are in the required timezone. If you want all your timestamps to be in UTC ++(aka GMT) you should set ++ ++timezone = UTC ++ ++The default value is taken from TIMEZONE_DEFAULT in Local/Makefile, or, if that ++is not set, from the value of the TZ environment variable when Exim is built. ++If timezone is set to the empty string, either at build or run time, any ++existing TZ variable is removed from the environment when Exim runs. This is ++appropriate behaviour for obtaining wall-clock time on some, but unfortunately ++not all, operating systems. ++ +++-------------------------------------------------------------+ ++|tls_advertise_hosts|Use: main|Type: host list*|Default: unset| +++-------------------------------------------------------------+ ++ ++When Exim is built with support for TLS encrypted connections, the availability ++of the STARTTLS command to set up an encrypted session is advertised in ++response to EHLO only to those client hosts that match this option. See chapter ++41 for details of Exim's support for TLS. ++ +++------------------------------------------------------+ ++|tls_certificate|Use: main|Type: string*|Default: unset| +++------------------------------------------------------+ ++ ++The value of this option is expanded, and must then be the absolute path to a ++file which contains the server's certificates. The server's private key is also ++assumed to be in this file if tls_privatekey is unset. See chapter 41 for ++further details. ++ ++Note: The certificates defined by this option are used only when Exim is ++receiving incoming messages as a server. If you want to supply certificates for ++use when sending messages as a client, you must set the tls_certificate option ++in the relevant smtp transport. ++ ++If the option contains $tls_out_sni and Exim is built against OpenSSL, then if ++the OpenSSL build supports TLS extensions and the TLS client sends the Server ++Name Indication extension, then this option and others documented in 41.10 will ++be re-expanded. ++ +++----------------------------------------------+ ++|tls_crl|Use: main|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++This option specifies a certificate revocation list. The expanded value must be ++the name of a file that contains a CRL in PEM format. ++ ++See 41.10 for discussion of when this option might be re-expanded. ++ +++-----------------------------------------------------+ ++|tls_dh_max_bits|Use: main|Type: integer|Default: 2236| +++-----------------------------------------------------+ ++ ++The number of bits used for Diffie-Hellman key-exchange may be suggested by the ++chosen TLS library. That value might prove to be too high for interoperability. ++This option provides a maximum clamp on the value suggested, trading off ++security for interoperability. ++ ++The value must be at least 1024. ++ ++The value 2236 was chosen because, at time of adding the option, it was the ++hard-coded maximum value supported by the NSS cryptographic library, as used by ++Thunderbird, while GnuTLS was suggesting 2432 bits as normal. ++ ++If you prefer more security and are willing to break some clients, raise this ++number. ++ ++Note that the value passed to GnuTLS for *generating* a new prime may be a ++little less than this figure, because GnuTLS is inexact and may produce a ++larger prime than requested. ++ +++--------------------------------------------------+ ++|tls_dhparam|Use: main|Type: string*|Default: unset| +++--------------------------------------------------+ ++ ++The value of this option is expanded and indicates the source of DH parameters ++to be used by Exim. ++ ++If it is a filename starting with a "/", then it names a file from which DH ++parameters should be loaded. If the file exists, it should hold a PEM-encoded ++PKCS#3 representation of the DH prime. If the file does not exist, for OpenSSL ++it is an error. For GnuTLS, Exim will attempt to create the file and fill it ++with a generated DH prime. For OpenSSL, if the DH bit-count from loading the ++file is greater than tls_dh_max_bits then it will be ignored, and treated as ++though the tls_dhparam were set to "none". ++ ++If this option expands to the string "none", then no DH parameters will be ++loaded by Exim. ++ ++If this option expands to the string "historic" and Exim is using GnuTLS, then ++Exim will attempt to load a file from inside the spool directory. If the file ++does not exist, Exim will attempt to create it. See section 41.3 for further ++details. ++ ++If Exim is using OpenSSL and this option is empty or unset, then Exim will load ++a default DH prime; the default is the 2048 bit prime described in section 2.2 ++of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which in ++IKE is assigned number 23. ++ ++Otherwise, the option must expand to the name used by Exim for any of a number ++of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses ++"ike" followed by the number used by IKE, of "default" which corresponds to ++"ike23". ++ ++The available primes are: "ike1", "ike2", "ike5", "ike14", "ike15", "ike16", ++"ike17", "ike18", "ike22", "ike23" (aka "default") and "ike24". ++ ++Some of these will be too small to be accepted by clients. Some may be too ++large to be accepted by clients. ++ ++The TLS protocol does not negotiate an acceptable size for this; clients tend ++to hard-drop connections if what is offered by the server is unacceptable, ++whether too large or too small, and there's no provision for the client to tell ++the server what these constraints are. Thus, as a server operator, you need to ++make an educated guess as to what is most likely to work for your userbase. ++ ++Some known size constraints suggest that a bit-size in the range 2048 to 2236 ++is most likely to maximise interoperability. The upper bound comes from ++applications using the Mozilla Network Security Services (NSS) library, which ++used to set its "DH_MAX_P_BITS" upper-bound to 2236. This affects many mail ++user agents (MUAs). The lower bound comes from Debian installs of Exim4 prior ++to the 4.80 release, as Debian used to patch Exim to raise the minimum ++acceptable bound from 1024 to 2048. ++ +++---------------------------------------------------------------+ ++|tls_on_connect_ports|Use: main|Type: string list|Default: unset| +++---------------------------------------------------------------+ ++ ++This option specifies a list of incoming SSMTP (aka SMTPS) ports that should ++operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately ++set up without waiting for the client to issue a STARTTLS command. For further ++details, see section 13.4. ++ +++-----------------------------------------------------+ ++|tls_privatekey|Use: main|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++The value of this option is expanded, and must then be the absolute path to a ++file which contains the server's private key. If this option is unset, or if ++the expansion is forced to fail, or the result is an empty string, the private ++key is assumed to be in the same file as the server's certificates. See chapter ++41 for further details. ++ ++See 41.10 for discussion of when this option might be re-expanded. ++ +++---------------------------------------------------------+ ++|tls_remember_esmtp|Use: main|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is set true, Exim violates the RFCs by remembering that it is in ++"esmtp" state after successfully negotiating a TLS session. This provides ++support for broken clients that fail to send a new EHLO after starting a TLS ++session. ++ +++----------------------------------------------------------+ ++|tls_require_ciphers|Use: main|Type: string*|Default: unset| +++----------------------------------------------------------+ ++ ++This option controls which ciphers can be used for incoming TLS connections. ++The smtp transport has an option of the same name for controlling outgoing ++connections. This option is expanded for each connection, so can be varied for ++different clients if required. The value of this option must be a list of ++permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control ++in somewhat different ways. If GnuTLS is being used, the client controls the ++preference order of the available ciphers. Details are given in sections 41.4 ++and 41.5. ++ +++--------------------------------------------------------------+ ++|tls_try_verify_hosts|Use: main|Type: host list*|Default: unset| +++--------------------------------------------------------------+ ++ ++See tls_verify_hosts below. ++ +++--------------------------------------------------------------+ ++|tls_verify_certificates|Use: main|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++The value of this option is expanded, and must then be the absolute path to a ++file containing permitted certificates for clients that match tls_verify_hosts ++or tls_try_verify_hosts. Alternatively, if you are using OpenSSL, you can set ++tls_verify_certificates to the name of a directory containing certificate ++files. This does not work with GnuTLS; the option must be set to the name of a ++single file if you are using GnuTLS. ++ ++These certificates should be for the certificate authorities trusted, rather ++than the public cert of individual clients. With both OpenSSL and GnuTLS, if ++the value is a file then the certificates are sent by Exim as a server to ++connecting clients, defining the list of accepted certificate authorities. Thus ++the values defined should be considered public data. To avoid this, use OpenSSL ++with a directory. ++ ++See 41.10 for discussion of when this option might be re-expanded. ++ ++A forced expansion failure or setting to an empty string is equivalent to being ++unset. ++ +++----------------------------------------------------------+ ++|tls_verify_hosts|Use: main|Type: host list*|Default: unset| +++----------------------------------------------------------+ ++ ++This option, along with tls_try_verify_hosts, controls the checking of ++certificates from clients. The expected certificates are defined by ++tls_verify_certificates, which must be set. A configuration error occurs if ++either tls_verify_hosts or tls_try_verify_hosts is set and ++tls_verify_certificates is not set. ++ ++Any client that matches tls_verify_hosts is constrained by ++tls_verify_certificates. When the client initiates a TLS session, it must ++present one of the listed certificates. If it does not, the connection is ++aborted. Warning: Including a host in tls_verify_hosts does not require the ++host to use TLS. It can still send SMTP commands through unencrypted ++connections. Forcing a client to use TLS has to be done separately using an ACL ++to reject inappropriate commands when the connection is not encrypted. ++ ++A weaker form of checking is provided by tls_try_verify_hosts. If a client ++matches this option (but not tls_verify_hosts), Exim requests a certificate and ++checks it against tls_verify_certificates, but does not abort the connection if ++there is no certificate or if it does not match. This state can be detected in ++an ACL, which makes it possible to implement policies such as "accept for relay ++only if a verified certificate has been received, but accept for local delivery ++if encrypted, even without a verified certificate". ++ ++Client hosts that match neither of these lists are not asked to present ++certificates. ++ +++----------------------------------------------------------+ ++|trusted_groups|Use: main|Type: string list*|Default: unset| +++----------------------------------------------------------+ ++ ++This option is expanded just once, at the start of Exim's processing. If this ++option is set, any process that is running in one of the listed groups, or ++which has one of them as a supplementary group, is trusted. The groups can be ++specified numerically or by name. See section 5.2 for details of what trusted ++callers are permitted to do. If neither trusted_groups nor trusted_users is ++set, only root and the Exim user are trusted. ++ +++---------------------------------------------------------+ ++|trusted_users|Use: main|Type: string list*|Default: unset| +++---------------------------------------------------------+ ++ ++This option is expanded just once, at the start of Exim's processing. If this ++option is set, any process that is running as one of the listed users is ++trusted. The users can be specified numerically or by name. See section 5.2 for ++details of what trusted callers are permitted to do. If neither trusted_groups ++nor trusted_users is set, only root and the Exim user are trusted. ++ +++----------------------------------------------------+ ++|unknown_login|Use: main|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This is a specialized feature for use in unusual configurations. By default, if ++the uid of the caller of Exim cannot be looked up using getpwuid(), Exim gives ++up. The unknown_login option can be used to set a login name to be used in this ++circumstance. It is expanded, so values like user$caller_uid can be set. When ++unknown_login is used, the value of unknown_username is used for the user's ++real name (gecos field), unless this has been set by the -F option. ++ +++------------------------------------------------------+ ++|unknown_username|Use: main|Type: string|Default: unset| +++------------------------------------------------------+ ++ ++See unknown_login. ++ +++-----------------------------------------------------------------+ ++|untrusted_set_sender|Use: main|Type: address list*|Default: unset| +++-----------------------------------------------------------------+ ++ ++When an untrusted user submits a message to Exim using the standard input, Exim ++normally creates an envelope sender address from the user's login and the ++default qualification domain. Data from the -f option (for setting envelope ++senders on non-SMTP messages) or the SMTP MAIL command (if -bs or -bS is used) ++is ignored. ++ ++However, untrusted users are permitted to set an empty envelope sender address, ++to declare that a message should never generate any bounces. For example: ++ ++exim -f '<>' user@domain.example ++ ++The untrusted_set_sender option allows you to permit untrusted users to set ++other envelope sender addresses in a controlled way. When it is set, untrusted ++users are allowed to set envelope sender addresses that match any of the ++patterns in the list. Like all address lists, the string is expanded. The ++identity of the user is in $sender_ident, so you can, for example, restrict ++users to setting senders that start with their login ids followed by a hyphen ++by a setting like this: ++ ++untrusted_set_sender = ^$sender_ident- ++ ++If you want to allow untrusted users to set envelope sender addresses without ++restriction, you can use ++ ++untrusted_set_sender = * ++ ++The untrusted_set_sender option applies to all forms of local input, but only ++to the setting of the envelope sender. It does not permit untrusted users to ++use the other options which trusted user can use to override message ++parameters. Furthermore, it does not stop Exim from removing an existing ++Sender: header in the message, or from adding a Sender: header if necessary. ++See local_sender_retain and local_from_check for ways of overriding these ++actions. The handling of the Sender: header is also described in section 46.16. ++ ++The log line for a message's arrival shows the envelope sender following "<=". ++For local messages, the user's login always follows, after "U=". In -bp ++displays, and in the Exim monitor, if an untrusted user sets an envelope sender ++address, the user's login is shown in parentheses after the sender address. ++ +++-----------------------------------------------------------+ ++|uucp_from_pattern|Use: main|Type: string|Default: see below| +++-----------------------------------------------------------+ ++ ++Some applications that pass messages to an MTA via a command line interface use ++an initial line starting with "From " to pass the envelope sender. In ++particular, this is used by UUCP software. Exim recognizes such a line by means ++of a regular expression that is set in uucp_from_pattern. When the pattern ++matches, the sender address is constructed by expanding the contents of ++uucp_from_sender, provided that the caller of Exim is a trusted user. The ++default pattern recognizes lines in the following two forms: ++ ++From ph10 Fri Jan 5 12:35 GMT 1996 ++From ph10 Fri, 7 Jan 97 14:00:00 GMT ++ ++The pattern can be seen by running ++ ++exim -bP uucp_from_pattern ++ ++It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit ++year in the second case. The first word after "From " is matched in the regular ++expression by a parenthesized subpattern. The default value for ++uucp_from_sender is "$1", which therefore just uses this first word ("ph10" in ++the example above) as the message's sender. See also ignore_fromline_hosts. ++ +++------------------------------------------------------+ ++|uucp_from_sender|Use: main|Type: string*|Default: "$1"| +++------------------------------------------------------+ ++ ++See uucp_from_pattern above. ++ +++-------------------------------------------------------+ ++|warn_message_file|Use: main|Type: string|Default: unset| +++-------------------------------------------------------+ ++ ++This option defines a template file containing paragraphs of text to be used ++for constructing the warning message which is sent by Exim when a message has ++been on the queue for a specified amount of time, as specified by delay_warning ++. Details of the file's contents are given in chapter 48. See also ++bounce_message_file. ++ +++-----------------------------------------------------+ ++|write_rejectlog|Use: main|Type: boolean|Default: true| +++-----------------------------------------------------+ ++ ++If this option is set false, Exim no longer writes anything to the reject log. ++See chapter 51 for details of what Exim writes to its logs. ++ ++ ++ ++=============================================================================== ++15. GENERIC OPTIONS FOR ROUTERS ++ ++This chapter describes the generic options that apply to all routers. Those ++that are preconditions are marked with ** in the "use" field. ++ ++For a general description of how a router operates, see sections 3.10 and 3.12. ++The latter specifies the order in which the preconditions are tested. The order ++of expansion of the options that provide data for a transport is: errors_to, ++headers_add, headers_remove, transport. ++ +++------------------------------------------------------+ ++|address_data|Use: routers|Type: string*|Default: unset| +++------------------------------------------------------+ ++ ++The string is expanded just before the router is run, that is, after all the ++precondition tests have succeeded. If the expansion is forced to fail, the ++router declines, the value of address_data remains unchanged, and the more ++option controls what happens next. Other expansion failures cause delivery of ++the address to be deferred. ++ ++When the expansion succeeds, the value is retained with the address, and can be ++accessed using the variable $address_data in the current router, subsequent ++routers, and the eventual transport. ++ ++Warning: If the current or any subsequent router is a redirect router that runs ++a user's filter file, the contents of $address_data are accessible in the ++filter. This is not normally a problem, because such data is usually either not ++confidential or it "belongs" to the current user, but if you do put ++confidential data into $address_data you need to remember this point. ++ ++Even if the router declines or passes, the value of $address_data remains with ++the address, though it can be changed by another address_data setting on a ++subsequent router. If a router generates child addresses, the value of ++$address_data propagates to them. This also applies to the special kind of ++"child" that is generated by a router with the unseen option. ++ ++The idea of address_data is that you can use it to look up a lot of data for ++the address once, and then pick out parts of the data later. For example, you ++could use a single LDAP lookup to return a string of the form ++ ++uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward ++ ++In the transport you could pick out the mailbox by a setting such as ++ ++file = ${extract{mailbox}{$address_data}} ++ ++This makes the configuration file less messy, and also reduces the number of ++lookups (though Exim does cache lookups). ++ ++The address_data facility is also useful as a means of passing information from ++one router to another, and from a router to a transport. In addition, if ++$address_data is set by a router when verifying a recipient address from an ++ACL, it remains available for use in the rest of the ACL statement. After ++verifying a sender, the value is transferred to $sender_address_data. ++ +++-------------------------------------------------------+ ++|address_test|Use: routers**|Type: boolean|Default: true| +++-------------------------------------------------------+ ++ ++If this option is set false, the router is skipped when routing is being tested ++by means of the -bt command line option. This can be a convenience when your ++first router sends messages to an external scanner, because it saves you having ++to set the "already scanned" indicator when testing real address routing. ++ +++--------------------------------------------------------------+ ++|cannot_route_message|Use: routers|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++This option specifies a text message that is used when an address cannot be ++routed because Exim has run out of routers. The default message is "Unrouteable ++address". This option is useful only on routers that have more set false, or on ++the very last router in a configuration, because the value that is used is ++taken from the last router that is considered. This includes a router that is ++skipped because its preconditions are not met, as well as a router that ++declines. For example, using the default configuration, you could put: ++ ++cannot_route_message = Remote domain not found in DNS ++ ++on the first router, which is a dnslookup router with more set false, and ++ ++cannot_route_message = Unknown local user ++ ++on the final router that checks for local users. If string expansion fails for ++this option, the default message is used. Unless the expansion failure was ++explicitly forced, a message about the failure is written to the main and panic ++logs, in addition to the normal message about the routing failure. ++ +++------------------------------------------------------------+ ++|caseful_local_part|Use: routers|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++By default, routers handle the local parts of addresses in a case-insensitive ++manner, though the actual case is preserved for transmission with the message. ++If you want the case of letters to be significant in a router, you must set ++this option true. For individual router options that contain address or local ++part lists (for example, local_parts), case-sensitive matching can be turned on ++by "+caseful" as a list item. See section 10.20 for more details. ++ ++The value of the $local_part variable is forced to lower case while a router is ++running unless caseful_local_part is set. When a router assigns an address to a ++transport, the value of $local_part when the transport runs is the same as it ++was in the router. Similarly, when a router generates child addresses by ++aliasing or forwarding, the values of $original_local_part and ++$parent_local_part are those that were used by the redirecting router. ++ ++This option applies to the processing of an address by a router. When a ++recipient address is being processed in an ACL, there is a separate control ++modifier that can be used to specify case-sensitive processing within the ACL ++(see section 42.21). ++ +++------------------------------------------------------------+ ++|check_local_user|Use: routers**|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++When this option is true, Exim checks that the local part of the recipient ++address (with affixes removed if relevant) is the name of an account on the ++local system. The check is done by calling the getpwnam() function rather than ++trying to read /etc/passwd directly. This means that other methods of holding ++password data (such as NIS) are supported. If the local part is a local user, ++$home is set from the password data, and can be tested in other preconditions ++that are evaluated after this one (the order of evaluation is given in section ++3.12). However, the value of $home can be overridden by router_home_directory. ++If the local part is not a local user, the router is skipped. ++ ++If you want to check that the local part is either the name of a local user or ++matches something else, you cannot combine check_local_user with a setting of ++local_parts, because that specifies the logical and of the two conditions. ++However, you can use a passwd lookup in a local_parts setting to achieve this. ++For example: ++ ++local_parts = passwd;$local_part : lsearch;/etc/other/users ++ ++Note, however, that the side effects of check_local_user (such as setting up a ++home directory) do not occur when a passwd lookup is used in a local_parts (or ++any other) precondition. ++ +++-----------------------------------------------------+ ++|condition|Use: routers**|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++This option specifies a general precondition test that has to succeed for the ++router to be called. The condition option is the last precondition to be ++evaluated (see section 3.12). The string is expanded, and if the result is a ++forced failure, or an empty string, or one of the strings "0" or "no" or ++"false" (checked without regard to the case of the letters), the router is ++skipped, and the address is offered to the next one. ++ ++If the result is any other value, the router is run (as this is the last ++precondition to be evaluated, all the other preconditions must be true). ++ ++This option is unusual in that multiple condition options may be present. All ++condition options must succeed. ++ ++The condition option provides a means of applying custom conditions to the ++running of routers. Note that in the case of a simple conditional expansion, ++the default expansion values are exactly what is wanted. For example: ++ ++condition = ${if >{$message_age}{600}} ++ ++Because of the default behaviour of the string expansion, this is equivalent to ++ ++condition = ${if >{$message_age}{600}{true}{}} ++ ++A multiple condition example, which succeeds: ++ ++condition = ${if >{$message_age}{600}} ++condition = ${if !eq{${lc:$local_part}}{postmaster}} ++condition = foobar ++ ++If the expansion fails (other than forced failure) delivery is deferred. Some ++of the other precondition options are common special cases that could in fact ++be specified using condition. ++ +++-----------------------------------------------------+ ++|debug_print|Use: routers|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++If this option is set and debugging is enabled (see the -d command line option) ++or in address-testing mode (see the -bt command line option), the string is ++expanded and included in the debugging output. If expansion of the string ++fails, the error message is written to the debugging output, and Exim carries ++on processing. This option is provided to help with checking out the values of ++variables and so on when debugging router configurations. For example, if a ++condition option appears not to be working, debug_print can be used to output ++the variables it references. The output happens after checks for domains, ++local_parts, and check_local_user but before any other preconditions are ++tested. A newline is added to the text if it does not end with one. The ++variable $router_name contains the name of the router. ++ +++---------------------------------------------------------+ ++|disable_logging|Use: routers|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is set true, nothing is logged for any routing errors or for any ++deliveries caused by this router. You should not set this option unless you ++really, really know what you are doing. See also the generic transport option ++of the same name. ++ +++--------------------------------------------------------+ ++|domains|Use: routers**|Type: domain list*|Default: unset| +++--------------------------------------------------------+ ++ ++If this option is set, the router is skipped unless the current domain matches ++the list. If the match is achieved by means of a file lookup, the data that the ++lookup returned for the domain is placed in $domain_data for use in string ++expansions of the driver's private options. See section 3.12 for a list of the ++order in which preconditions are evaluated. ++ +++-----------------------------------------------+ ++|driver|Use: routers|Type: string|Default: unset| +++-----------------------------------------------+ ++ ++This option must always be set. It specifies which of the available routers is ++to be used. ++ +++---------------------------------------------------+ ++|errors_to|Use: routers|Type: string*|Default: unset| +++---------------------------------------------------+ ++ ++If a router successfully handles an address, it may assign the address to a ++transport for delivery or it may generate child addresses. In both cases, if ++there is a delivery problem during later processing, the resulting bounce ++message is sent to the address that results from expanding this string, ++provided that the address verifies successfully. The errors_to option is ++expanded before headers_add, headers_remove, and transport. ++ ++The errors_to setting associated with an address can be overridden if it ++subsequently passes through other routers that have their own errors_to ++settings, or if the message is delivered by a transport with a return_path ++setting. ++ ++If errors_to is unset, or the expansion is forced to fail, or the result of the ++expansion fails to verify, the errors address associated with the incoming ++address is used. At top level, this is the envelope sender. A non-forced ++expansion failure causes delivery to be deferred. ++ ++If an address for which errors_to has been set ends up being delivered over ++SMTP, the envelope sender for that delivery is the errors_to value, so that any ++bounces that are generated by other MTAs on the delivery route are also sent ++there. You can set errors_to to the empty string by either of these settings: ++ ++errors_to = ++errors_to = "" ++ ++An expansion item that yields an empty string has the same effect. If you do ++this, a locally detected delivery error for addresses processed by this router ++no longer gives rise to a bounce message; the error is discarded. If the ++address is delivered to a remote host, the return path is set to "<>", unless ++overridden by the return_path option on the transport. ++ ++If for some reason you want to discard local errors, but use a non-empty MAIL ++command for remote delivery, you can preserve the original return path in ++$address_data in the router, and reinstate it in the transport by setting ++return_path. ++ ++The most common use of errors_to is to direct mailing list bounces to the ++manager of the list, as described in section 49.2, or to implement VERP ++(Variable Envelope Return Paths) (see section 49.6). ++ +++-----------------------------------------------+ ++|expn|Use: routers**|Type: boolean|Default: true| +++-----------------------------------------------+ ++ ++If this option is turned off, the router is skipped when testing an address as ++a result of processing an SMTP EXPN command. You might, for example, want to ++turn it off on a router for users' .forward files, while leaving it on for the ++system alias file. See section 3.12 for a list of the order in which ++preconditions are evaluated. ++ ++The use of the SMTP EXPN command is controlled by an ACL (see chapter 42). When ++Exim is running an EXPN command, it is similar to testing an address with -bt. ++Compare VRFY, whose counterpart is -bv. ++ +++-----------------------------------------------------+ ++|fail_verify|Use: routers|Type: boolean|Default: false| +++-----------------------------------------------------+ ++ ++Setting this option has the effect of setting both fail_verify_sender and ++fail_verify_recipient to the same value. ++ +++---------------------------------------------------------------+ ++|fail_verify_recipient|Use: routers|Type: boolean|Default: false| +++---------------------------------------------------------------+ ++ ++If this option is true and an address is accepted by this router when verifying ++a recipient, verification fails. ++ +++------------------------------------------------------------+ ++|fail_verify_sender|Use: routers|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is true and an address is accepted by this router when verifying ++a sender, verification fails. ++ +++------------------------------------------------------------+ ++|fallback_hosts|Use: routers|Type: string list|Default: unset| +++------------------------------------------------------------+ ++ ++String expansion is not applied to this option. The argument must be a ++colon-separated list of host names or IP addresses. The list separator can be ++changed (see section 6.19), and a port can be specified with each name or ++address. In fact, the format of each item is exactly the same as defined for ++the list of hosts in a manualroute router (see section 20.5). ++ ++If a router queues an address for a remote transport, this host list is ++associated with the address, and used instead of the transport's fallback host ++list. If hosts_randomize is set on the transport, the order of the list is ++randomized for each use. See the fallback_hosts option of the smtp transport ++for further details. ++ +++---------------------------------------------------+ ++|group|Use: routers|Type: string*|Default: see below| +++---------------------------------------------------+ ++ ++When a router queues an address for a transport, and the transport does not ++specify a group, the group given here is used when running the delivery ++process. The group may be specified numerically or by name. If expansion fails, ++the error is logged and delivery is deferred. The default is unset, unless ++check_local_user is set, when the default is taken from the password ++information. See also initgroups and user and the discussion in chapter 23. ++ +++-----------------------------------------------------+ ++|headers_add|Use: routers|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++This option specifies a string of text that is expanded at routing time, and ++associated with any addresses that are accepted by the router. However, this ++option has no effect when an address is just being verified. The way in which ++the text is used to add header lines at transport time is described in section ++46.17. New header lines are not actually added until the message is in the ++process of being transported. This means that references to header lines in ++string expansions in the transport's configuration do not "see" the added ++header lines. ++ ++The headers_add option is expanded after errors_to, but before headers_remove ++and transport. If the expanded string is empty, or if the expansion is forced ++to fail, the option has no effect. Other expansion failures are treated as ++configuration errors. ++ ++Unlike most options, headers_add can be specified multiple times for a router; ++all listed headers are added. ++ ++Warning 1: The headers_add option cannot be used for a redirect router that has ++the one_time option set. ++ ++Warning 2: If the unseen option is set on the router, all header additions are ++deleted when the address is passed on to subsequent routers. For a redirect ++router, if a generated address is the same as the incoming address, this can ++lead to duplicate addresses with different header modifications. Exim does not ++do duplicate deliveries (except, in certain circumstances, to pipes -- see ++section 22.7), but it is undefined which of the duplicates is discarded, so ++this ambiguous situation should be avoided. The repeat_use option of the ++redirect router may be of help. ++ +++--------------------------------------------------------+ ++|headers_remove|Use: routers|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option specifies a string of text that is expanded at routing time, and ++associated with any addresses that are accepted by the router. However, this ++option has no effect when an address is just being verified. The way in which ++the text is used to remove header lines at transport time is described in ++section 46.17. Header lines are not actually removed until the message is in ++the process of being transported. This means that references to header lines in ++string expansions in the transport's configuration still "see" the original ++header lines. ++ ++The headers_remove option is expanded after errors_to and headers_add, but ++before transport. If the expansion is forced to fail, the option has no effect. ++Other expansion failures are treated as configuration errors. ++ ++Unlike most options, headers_remove can be specified multiple times for a ++router; all listed headers are removed. ++ ++Warning 1: The headers_remove option cannot be used for a redirect router that ++has the one_time option set. ++ ++Warning 2: If the unseen option is set on the router, all header removal ++requests are deleted when the address is passed on to subsequent routers, and ++this can lead to problems with duplicates -- see the similar warning for ++headers_add above. ++ +++----------------------------------------------------------------+ ++|ignore_target_hosts|Use: routers|Type: host list*|Default: unset| +++----------------------------------------------------------------+ ++ ++Although this option is a host list, it should normally contain IP address ++entries rather than names. If any host that is looked up by the router has an ++IP address that matches an item in this list, Exim behaves as if that IP ++address did not exist. This option allows you to cope with rogue DNS entries ++like ++ ++remote.domain.example. A 127.0.0.1 ++ ++by setting ++ ++ignore_target_hosts = 127.0.0.1 ++ ++on the relevant router. If all the hosts found by a dnslookup router are ++discarded in this way, the router declines. In a conventional configuration, an ++attempt to mail to such a domain would normally provoke the "unrouteable ++domain" error, and an attempt to verify an address in the domain would fail. ++Similarly, if ignore_target_hosts is set on an ipliteral router, the router ++declines if presented with one of the listed addresses. ++ ++You can use this option to disable the use of IPv4 or IPv6 for mail delivery by ++means of the first or the second of the following settings, respectively: ++ ++ignore_target_hosts = 0.0.0.0/0 ++ignore_target_hosts = <; 0::0/0 ++ ++The pattern in the first line matches all IPv4 addresses, whereas the pattern ++in the second line matches all IPv6 addresses. ++ ++This option may also be useful for ignoring link-local and site-local IPv6 ++addresses. Because, like all host lists, the value of ignore_target_hosts is ++expanded before use as a list, it is possible to make it dependent on the ++domain that is being routed. ++ ++During its expansion, $host_address is set to the IP address that is being ++checked. ++ +++----------------------------------------------------+ ++|initgroups|Use: routers|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++If the router queues an address for a transport, and this option is true, and ++the uid supplied by the router is not overridden by the transport, the ++initgroups() function is called when running the transport to ensure that any ++additional groups associated with the uid are set up. See also group and user ++and the discussion in chapter 23. ++ +++-----------------------------------------------------------------+ ++|local_part_prefix|Use: routers**|Type: string list|Default: unset| +++-----------------------------------------------------------------+ ++ ++If this option is set, the router is skipped unless the local part starts with ++one of the given strings, or local_part_prefix_optional is true. See section ++3.12 for a list of the order in which preconditions are evaluated. ++ ++The list is scanned from left to right, and the first prefix that matches is ++used. A limited form of wildcard is available; if the prefix begins with an ++asterisk, it matches the longest possible sequence of arbitrary characters at ++the start of the local part. An asterisk should therefore always be followed by ++some character that does not occur in normal local parts. Wildcarding can be ++used to set up multiple user mailboxes, as described in section 49.8. ++ ++During the testing of the local_parts option, and while the router is running, ++the prefix is removed from the local part, and is available in the expansion ++variable $local_part_prefix. When a message is being delivered, if the router ++accepts the address, this remains true during subsequent delivery by a ++transport. In particular, the local part that is transmitted in the RCPT ++command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. ++This behaviour can be overridden by setting rcpt_include_affixes true on the ++relevant transport. ++ ++When an address is being verified, local_part_prefix affects only the behaviour ++of the router. If the callout feature of verification is in use, this means ++that the full address, including the prefix, will be used during the callout. ++ ++The prefix facility is commonly used to handle local parts of the form ++owner-something. Another common use is to support local parts of the form ++real-username to bypass a user's .forward file - helpful when trying to tell a ++user their forwarding is broken - by placing a router like this one immediately ++before the router that handles .forward files: ++ ++real_localuser: ++ driver = accept ++ local_part_prefix = real- ++ check_local_user ++ transport = local_delivery ++ ++For security, it would probably be a good idea to restrict the use of this ++router to locally-generated messages, using a condition such as this: ++ ++ condition = ${if match {$sender_host_address}\ ++ {\N^(|127\.0\.0\.1)$\N}} ++ ++If both local_part_prefix and local_part_suffix are set for a router, both ++conditions must be met if not optional. Care must be taken if wildcards are ++used in both a prefix and a suffix on the same router. Different separator ++characters must be used to avoid ambiguity. ++ +++--------------------------------------------------------------------+ ++|local_part_prefix_optional|Use: routers|Type: boolean|Default: false| +++--------------------------------------------------------------------+ ++ ++See local_part_prefix above. ++ +++-----------------------------------------------------------------+ ++|local_part_suffix|Use: routers**|Type: string list|Default: unset| +++-----------------------------------------------------------------+ ++ ++This option operates in the same way as local_part_prefix, except that the ++local part must end (rather than start) with the given string, the ++local_part_suffix_optional option determines whether the suffix is mandatory, ++and the wildcard * character, if present, must be the last character of the ++suffix. This option facility is commonly used to handle local parts of the form ++something-request and multiple user mailboxes of the form username-foo. ++ +++--------------------------------------------------------------------+ ++|local_part_suffix_optional|Use: routers|Type: boolean|Default: false| +++--------------------------------------------------------------------+ ++ ++See local_part_suffix above. ++ +++----------------------------------------------------------------+ ++|local_parts|Use: routers**|Type: local part list*|Default: unset| +++----------------------------------------------------------------+ ++ ++The router is run only if the local part of the address matches the list. See ++section 3.12 for a list of the order in which preconditions are evaluated, and ++section 10.21 for a discussion of local part lists. Because the string is ++expanded, it is possible to make it depend on the domain, for example: ++ ++local_parts = dbm;/usr/local/specials/$domain ++ ++If the match is achieved by a lookup, the data that the lookup returned for the ++local part is placed in the variable $local_part_data for use in expansions of ++the router's private options. You might use this option, for example, if you ++have a large number of local virtual domains, and you want to send all ++postmaster mail to the same place without having to set up an alias in each ++virtual domain: ++ ++postmaster: ++ driver = redirect ++ local_parts = postmaster ++ data = postmaster@real.domain.example ++ +++----------------------------------------------------------+ ++|log_as_local|Use: routers|Type: boolean|Default: see below| +++----------------------------------------------------------+ ++ ++Exim has two logging styles for delivery, the idea being to make local ++deliveries stand out more visibly from remote ones. In the "local" style, the ++recipient address is given just as the local part, without a domain. The use of ++this style is controlled by this option. It defaults to true for the accept ++router, and false for all the others. This option applies only when a router ++assigns an address to a transport. It has no effect on routers that redirect ++addresses. ++ +++----------------------------------------------+ ++|more|Use: routers|Type: boolean*|Default: true| +++----------------------------------------------+ ++ ++The result of string expansion for this option must be a valid boolean value, ++that is, one of the strings "yes", "no", "true", or "false". Any other result ++causes an error, and delivery is deferred. If the expansion is forced to fail, ++the default value for the option (true) is used. Other failures cause delivery ++to be deferred. ++ ++If this option is set false, and the router declines to handle the address, no ++further routers are tried, routing fails, and the address is bounced. However, ++if the router explicitly passes an address to the following router by means of ++the setting ++ ++self = pass ++ ++or otherwise, the setting of more is ignored. Also, the setting of more does ++not affect the behaviour if one of the precondition tests fails. In that case, ++the address is always passed to the next router. ++ ++Note that address_data is not considered to be a precondition. If its expansion ++is forced to fail, the router declines, and the value of more controls what ++happens next. ++ +++---------------------------------------------------------+ ++|pass_on_timeout|Use: routers|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If a router times out during a host lookup, it normally causes deferral of the ++address. If pass_on_timeout is set, the address is passed on to the next ++router, overriding no_more. This may be helpful for systems that are ++intermittently connected to the Internet, or those that want to pass to a smart ++host any messages that cannot immediately be delivered. ++ ++There are occasional other temporary errors that can occur while doing DNS ++lookups. They are treated in the same way as a timeout, and this option applies ++to all of them. ++ +++----------------------------------------------------+ ++|pass_router|Use: routers|Type: string|Default: unset| +++----------------------------------------------------+ ++ ++Routers that recognize the generic self option (dnslookup, ipliteral, and ++manualroute) are able to return "pass", forcing routing to continue, and ++overriding a false setting of more. When one of these routers returns "pass", ++the address is normally handed on to the next router in sequence. This can be ++changed by setting pass_router to the name of another router. However (unlike ++redirect_router) the named router must be below the current router, to avoid ++loops. Note that this option applies only to the special case of "pass". It ++does not apply when a router returns "decline" because it cannot handle an ++address. ++ +++--------------------------------------------------------+ ++|redirect_router|Use: routers|Type: string|Default: unset| +++--------------------------------------------------------+ ++ ++Sometimes an administrator knows that it is pointless to reprocess addresses ++generated from alias or forward files with the same router again. For example, ++if an alias file translates real names into login ids there is no point ++searching the alias file a second time, especially if it is a large file. ++ ++The redirect_router option can be set to the name of any router instance. It ++causes the routing of any generated addresses to start at the named router ++instead of at the first router. This option has no effect if the router in ++which it is set does not generate new addresses. ++ +++--------------------------------------------------------------+ ++|require_files|Use: routers**|Type: string list*|Default: unset| +++--------------------------------------------------------------+ ++ ++This option provides a general mechanism for predicating the running of a ++router on the existence or non-existence of certain files or directories. ++Before running a router, as one of its precondition tests, Exim works its way ++through the require_files list, expanding each item separately. ++ ++Because the list is split before expansion, any colons in expansion items must ++be doubled, or the facility for using a different list separator must be used. ++If any expansion is forced to fail, the item is ignored. Other expansion ++failures cause routing of the address to be deferred. ++ ++If any expanded string is empty, it is ignored. Otherwise, except as described ++below, each string must be a fully qualified file path, optionally preceded by ++"!". The paths are passed to the stat() function to test for the existence of ++the files or directories. The router is skipped if any paths not preceded by "! ++" do not exist, or if any paths preceded by "!" do exist. ++ ++If stat() cannot determine whether a file exists or not, delivery of the ++message is deferred. This can happen when NFS-mounted filesystems are ++unavailable. ++ ++This option is checked after the domains, local_parts, and senders options, so ++you cannot use it to check for the existence of a file in which to look up a ++domain, local part, or sender. (See section 3.12 for a full list of the order ++in which preconditions are evaluated.) However, as these options are all ++expanded, you can use the exists expansion condition to make such tests. The ++require_files option is intended for checking files that the router may be ++going to use internally, or which are needed by a transport (for example ++.procmailrc). ++ ++During delivery, the stat() function is run as root, but there is a facility ++for some checking of the accessibility of a file by another user. This is not a ++proper permissions check, but just a "rough" check that operates as follows: ++ ++If an item in a require_files list does not contain any forward slash ++characters, it is taken to be the user (and optional group, separated by a ++comma) to be checked for subsequent files in the list. If no group is specified ++but the user is specified symbolically, the gid associated with the uid is ++used. For example: ++ ++require_files = mail:/some/file ++require_files = $local_part:$home/.procmailrc ++ ++If a user or group name in a require_files list does not exist, the ++require_files condition fails. ++ ++Exim performs the check by scanning along the components of the file path, and ++checking the access for the given uid and gid. It checks for "x" access on ++directories, and "r" access on the final file. Note that this means that file ++access control lists, if the operating system has them, are ignored. ++ ++Warning 1: When the router is being run to verify addresses for an incoming ++SMTP message, Exim is not running as root, but under its own uid. This may ++affect the result of a require_files check. In particular, stat() may yield the ++error EACCES ("Permission denied"). This means that the Exim user is not ++permitted to read one of the directories on the file's path. ++ ++Warning 2: Even when Exim is running as root while delivering a message, stat() ++can yield EACCES for a file in an NFS directory that is mounted without root ++access. In this case, if a check for access by a particular user is requested, ++Exim creates a subprocess that runs as that user, and tries the check again in ++that process. ++ ++The default action for handling an unresolved EACCES is to consider it to be ++caused by a configuration error, and routing is deferred because the existence ++or non-existence of the file cannot be determined. However, in some ++circumstances it may be desirable to treat this condition as if the file did ++not exist. If the file name (or the exclamation mark that precedes the file ++name for non-existence) is preceded by a plus sign, the EACCES error is treated ++as if the file did not exist. For example: ++ ++require_files = +/some/file ++ ++If the router is not an essential part of verification (for example, it handles ++users' .forward files), another solution is to set the verify option false so ++that the router is skipped when verifying. ++ +++------------------------------------------------------------------+ ++|retry_use_local_part|Use: routers|Type: boolean|Default: see below| +++------------------------------------------------------------------+ ++ ++When a delivery suffers a temporary routing failure, a retry record is created ++in Exim's hints database. For addresses whose routing depends only on the ++domain, the key for the retry record should not involve the local part, but for ++other addresses, both the domain and the local part should be included. ++Usually, remote routing is of the former kind, and local routing is of the ++latter kind. ++ ++This option controls whether the local part is used to form the key for retry ++hints for addresses that suffer temporary errors while being handled by this ++router. The default value is true for any router that has check_local_user set, ++and false otherwise. Note that this option does not apply to hints keys for ++transport delays; they are controlled by a generic transport option of the same ++name. ++ ++The setting of retry_use_local_part applies only to the router on which it ++appears. If the router generates child addresses, they are routed ++independently; this setting does not become attached to them. ++ +++---------------------------------------------------------------+ ++|router_home_directory|Use: routers|Type: string*|Default: unset| +++---------------------------------------------------------------+ ++ ++This option sets a home directory for use while the router is running. (Compare ++transport_home_directory, which sets a home directory for later transporting.) ++In particular, if used on a redirect router, this option sets a value for $home ++while a filter is running. The value is expanded; forced expansion failure ++causes the option to be ignored - other failures cause the router to defer. ++ ++Expansion of router_home_directory happens immediately after the ++check_local_user test (if configured), before any further expansions take ++place. (See section 3.12 for a list of the order in which preconditions are ++evaluated.) While the router is running, router_home_directory overrides the ++value of $home that came from check_local_user. ++ ++When a router accepts an address and assigns it to a local transport (including ++the cases when a redirect router generates a pipe, file, or autoreply ++delivery), the home directory setting for the transport is taken from the first ++of these values that is set: ++ ++ * The home_directory option on the transport; ++ ++ * The transport_home_directory option on the router; ++ ++ * The password data if check_local_user is set on the router; ++ ++ * The router_home_directory option on the router. ++ ++In other words, router_home_directory overrides the password data for the ++router, but not for the transport. ++ +++----------------------------------------------+ ++|self|Use: routers|Type: string|Default: freeze| +++----------------------------------------------+ ++ ++This option applies to those routers that use a recipient address to find a ++list of remote hosts. Currently, these are the dnslookup, ipliteral, and ++manualroute routers. Certain configurations of the queryprogram router can also ++specify a list of remote hosts. Usually such routers are configured to send the ++message to a remote host via an smtp transport. The self option specifies what ++happens when the first host on the list turns out to be the local host. The way ++in which Exim checks for the local host is described in section 13.8. ++ ++Normally this situation indicates either an error in Exim's configuration (for ++example, the router should be configured not to process this domain), or an ++error in the DNS (for example, the MX should not point to this host). For this ++reason, the default action is to log the incident, defer the address, and ++freeze the message. The following alternatives are provided for use in special ++cases: ++ ++defer ++ ++ Delivery of the message is tried again later, but the message is not ++ frozen. ++ ++reroute: <domain> ++ ++ The domain is changed to the given domain, and the address is passed back ++ to be reprocessed by the routers. No rewriting of headers takes place. This ++ behaviour is essentially a redirection. ++ ++reroute: rewrite: <domain> ++ ++ The domain is changed to the given domain, and the address is passed back ++ to be reprocessed by the routers. Any headers that contain the original ++ domain are rewritten. ++ ++pass ++ ++ The router passes the address to the next router, or to the router named in ++ the pass_router option if it is set. This overrides no_more. During ++ subsequent routing and delivery, the variable $self_hostname contains the ++ name of the local host that the router encountered. This can be used to ++ distinguish between different cases for hosts with multiple names. The ++ combination ++ ++ self = pass ++ no_more ++ ++ ensures that only those addresses that routed to the local host are passed ++ on. Without no_more, addresses that were declined for other reasons would ++ also be passed to the next router. ++ ++fail ++ ++ Delivery fails and an error report is generated. ++ ++send ++ ++ The anomaly is ignored and the address is queued for the transport. This ++ setting should be used with extreme caution. For an smtp transport, it ++ makes sense only in cases where the program that is listening on the SMTP ++ port is not this version of Exim. That is, it must be some other MTA, or ++ Exim with a different configuration file that handles the domain in another ++ way. ++ +++---------------------------------------------------------+ ++|senders|Use: routers**|Type: address list*|Default: unset| +++---------------------------------------------------------+ ++ ++If this option is set, the router is skipped unless the message's sender ++address matches something on the list. See section 3.12 for a list of the order ++in which preconditions are evaluated. ++ ++There are issues concerning verification when the running of routers is ++dependent on the sender. When Exim is verifying the address in an errors_to ++setting, it sets the sender to the null string. When using the -bt option to ++check a configuration file, it is necessary also to use the -f option to set an ++appropriate sender. For incoming mail, the sender is unset when verifying the ++sender, but is available when verifying any recipients. If the SMTP VRFY ++command is enabled, it must be used after MAIL if the sender address matters. ++ +++--------------------------------------------------------------+ ++|translate_ip_address|Use: routers|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++There exist some rare networking situations (for example, packet radio) where ++it is helpful to be able to translate IP addresses generated by normal routing ++mechanisms into other IP addresses, thus performing a kind of manual IP ++routing. This should be done only if the normal IP routing of the TCP/IP stack ++is inadequate or broken. Because this is an extremely uncommon requirement, the ++code to support this option is not included in the Exim binary unless ++SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in Local/Makefile. ++ ++The translate_ip_address string is expanded for every IP address generated by ++the router, with the generated address set in $host_address. If the expansion ++is forced to fail, no action is taken. For any other expansion error, delivery ++of the message is deferred. If the result of the expansion is an IP address, ++that replaces the original address; otherwise the result is assumed to be a ++host name - this is looked up using gethostbyname() (or getipnodebyname() when ++available) to produce one or more replacement IP addresses. For example, to ++subvert all IP addresses in some specific networks, this could be added to a ++router: ++ ++translate_ip_address = \ ++ ${lookup{${mask:$host_address/26}}lsearch{/some/file}\ ++ {$value}fail}} ++ ++The file would contain lines like ++ ++10.2.3.128/26 some.host ++10.8.4.34/26 10.44.8.15 ++ ++You should not make use of this facility unless you really understand what you ++are doing. ++ +++---------------------------------------------------+ ++|transport|Use: routers|Type: string*|Default: unset| +++---------------------------------------------------+ ++ ++This option specifies the transport to be used when a router accepts an address ++and sets it up for delivery. A transport is never needed if a router is used ++only for verification. The value of the option is expanded at routing time, ++after the expansion of errors_to, headers_add, and headers_remove, and result ++must be the name of one of the configured transports. If it is not, delivery is ++deferred. ++ ++The transport option is not used by the redirect router, but it does have some ++private options that set up transports for pipe and file deliveries (see ++chapter 22). ++ +++---------------------------------------------------------------------+ ++|transport_current_directory|Use: routers|Type: string*|Default: unset| +++---------------------------------------------------------------------+ ++ ++This option associates a current directory with any address that is routed to a ++local transport. This can happen either because a transport is explicitly ++configured for the router, or because it generates a delivery to a file or a ++pipe. During the delivery process (that is, at transport time), this option ++string is expanded and is set as the current directory, unless overridden by a ++setting on the transport. If the expansion fails for any reason, including ++forced failure, an error is logged, and delivery is deferred. See chapter 23 ++for details of the local delivery environment. ++ +++----------------------------------------------------------------------+ ++|transport_home_directory|Use: routers|Type: string*|Default: see below| +++----------------------------------------------------------------------+ ++ ++This option associates a home directory with any address that is routed to a ++local transport. This can happen either because a transport is explicitly ++configured for the router, or because it generates a delivery to a file or a ++pipe. During the delivery process (that is, at transport time), the option ++string is expanded and is set as the home directory, unless overridden by a ++setting of home_directory on the transport. If the expansion fails for any ++reason, including forced failure, an error is logged, and delivery is deferred. ++ ++If the transport does not specify a home directory, and ++transport_home_directory is not set for the router, the home directory for the ++transport is taken from the password data if check_local_user is set for the ++router. Otherwise it is taken from router_home_directory if that option is set; ++if not, no home directory is set for the transport. ++ ++See chapter 23 for further details of the local delivery environment. ++ +++-------------------------------------------------+ ++|unseen|Use: routers|Type: boolean*|Default: false| +++-------------------------------------------------+ ++ ++The result of string expansion for this option must be a valid boolean value, ++that is, one of the strings "yes", "no", "true", or "false". Any other result ++causes an error, and delivery is deferred. If the expansion is forced to fail, ++the default value for the option (false) is used. Other failures cause delivery ++to be deferred. ++ ++When this option is set true, routing does not cease if the router accepts the ++address. Instead, a copy of the incoming address is passed to the next router, ++overriding a false setting of more. There is little point in setting more false ++if unseen is always true, but it may be useful in cases when the value of ++unseen contains expansion items (and therefore, presumably, is sometimes true ++and sometimes false). ++ ++Setting the unseen option has a similar effect to the unseen command qualifier ++in filter files. It can be used to cause copies of messages to be delivered to ++some other destination, while also carrying out a normal delivery. In effect, ++the current address is made into a "parent" that has two children - one that is ++delivered as specified by this router, and a clone that goes on to be routed ++further. For this reason, unseen may not be combined with the one_time option ++in a redirect router. ++ ++Warning: Header lines added to the address (or specified for removal) by this ++router or by previous routers affect the "unseen" copy of the message only. The ++clone that continues to be processed by further routers starts with no added ++headers and none specified for removal. For a redirect router, if a generated ++address is the same as the incoming address, this can lead to duplicate ++addresses with different header modifications. Exim does not do duplicate ++deliveries (except, in certain circumstances, to pipes -- see section 22.7), ++but it is undefined which of the duplicates is discarded, so this ambiguous ++situation should be avoided. The repeat_use option of the redirect router may ++be of help. ++ ++Unlike the handling of header modifications, any data that was set by the ++address_data option in the current or previous routers is passed on to ++subsequent routers. ++ +++--------------------------------------------------+ ++|user|Use: routers|Type: string*|Default: see below| +++--------------------------------------------------+ ++ ++When a router queues an address for a transport, and the transport does not ++specify a user, the user given here is used when running the delivery process. ++The user may be specified numerically or by name. If expansion fails, the error ++is logged and delivery is deferred. This user is also used by the redirect ++router when running a filter file. The default is unset, except when ++check_local_user is set. In this case, the default is taken from the password ++information. If the user is specified as a name, and group is not set, the ++group associated with the user is used. See also initgroups and group and the ++discussion in chapter 23. ++ +++-------------------------------------------------+ ++|verify|Use: routers**|Type: boolean|Default: true| +++-------------------------------------------------+ ++ ++Setting this option has the effect of setting verify_sender and ++verify_recipient to the same value. ++ +++-------------------------------------------------------+ ++|verify_only|Use: routers**|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++If this option is set, the router is used only when verifying an address, ++delivering in cutthrough mode or testing with the -bv option, not when actually ++doing a delivery, testing with the -bt option, or running the SMTP EXPN ++command. It can be further restricted to verifying only senders or recipients ++by means of verify_sender and verify_recipient. ++ ++Warning: When the router is being run to verify addresses for an incoming SMTP ++message, Exim is not running as root, but under its own uid. If the router ++accesses any files, you need to make sure that they are accessible to the Exim ++user or group. ++ +++-----------------------------------------------------------+ ++|verify_recipient|Use: routers**|Type: boolean|Default: true| +++-----------------------------------------------------------+ ++ ++If this option is false, the router is skipped when verifying recipient ++addresses, delivering in cutthrough mode or testing recipient verification ++using -bv. See section 3.12 for a list of the order in which preconditions are ++evaluated. ++ +++--------------------------------------------------------+ ++|verify_sender|Use: routers**|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++If this option is false, the router is skipped when verifying sender addresses ++or testing sender verification using -bvs. See section 3.12 for a list of the ++order in which preconditions are evaluated. ++ ++ ++ ++=============================================================================== ++16. THE ACCEPT ROUTER ++ ++The accept router has no private options of its own. Unless it is being used ++purely for verification (see verify_only) a transport is required to be defined ++by the generic transport option. If the preconditions that are specified by ++generic options are met, the router accepts the address and queues it for the ++given transport. The most common use of this router is for setting up ++deliveries to local mailboxes. For example: ++ ++localusers: ++ driver = accept ++ domains = mydomain.example ++ check_local_user ++ transport = local_delivery ++ ++The domains condition in this example checks the domain of the address, and ++check_local_user checks that the local part is the login of a local user. When ++both preconditions are met, the accept router runs, and queues the address for ++the local_delivery transport. ++ ++ ++ ++=============================================================================== ++17. THE DNSLOOKUP ROUTER ++ ++The dnslookup router looks up the hosts that handle mail for the recipient's ++domain in the DNS. A transport must always be set for this router, unless ++verify_only is set. ++ ++If SRV support is configured (see check_srv below), Exim first searches for SRV ++records. If none are found, or if SRV support is not configured, MX records are ++looked up. If no MX records exist, address records are sought. However, ++mx_domains can be set to disable the direct use of address records. ++ ++MX records of equal priority are sorted by Exim into a random order. Exim then ++looks for address records for the host names obtained from MX or SRV records. ++When a host has more than one IP address, they are sorted into a random order, ++except that IPv6 addresses are always sorted before IPv4 addresses. If all the ++IP addresses found are discarded by a setting of the ignore_target_hosts ++generic option, the router declines. ++ ++Unless they have the highest priority (lowest MX value), MX records that point ++to the local host, or to any host name that matches hosts_treat_as_local, are ++discarded, together with any other MX records of equal or lower priority. ++ ++If the host pointed to by the highest priority MX record, or looked up as an ++address record, is the local host, or matches hosts_treat_as_local, what ++happens is controlled by the generic self option. ++ ++ ++17.1 Problems with DNS lookups ++------------------------------ ++ ++There have been problems with DNS servers when SRV records are looked up. Some ++mis-behaving servers return a DNS error or timeout when a non-existent SRV ++record is sought. Similar problems have in the past been reported for MX ++records. The global dns_again_means_nonexist option can help with this problem, ++but it is heavy-handed because it is a global option. ++ ++For this reason, there are two options, srv_fail_domains and mx_fail_domains, ++that control what happens when a DNS lookup in a dnslookup router results in a ++DNS failure or a "try again" response. If an attempt to look up an SRV or MX ++record causes one of these results, and the domain matches the relevant list, ++Exim behaves as if the DNS had responded "no such record". In the case of an ++SRV lookup, this means that the router proceeds to look for MX records; in the ++case of an MX lookup, it proceeds to look for A or AAAA records, unless the ++domain matches mx_domains, in which case routing fails. ++ ++ ++17.2 Declining addresses by dnslookup ++------------------------------------- ++ ++There are a few cases where a dnslookup router will decline to accept an ++address; if such a router is expected to handle "all remaining non-local ++domains", then it is important to set no_more. ++ ++Reasons for a dnslookup router to decline currently include: ++ ++ * The domain does not exist in DNS ++ ++ * The domain exists but the MX record's host part is just "."; this is a ++ common convention (borrowed from SRV) used to indicate that there is no ++ such service for this domain and to not fall back to trying A/AAAA records. ++ ++ * Ditto, but for SRV records, when check_srv is set on this router. ++ ++ * MX record points to a non-existent host. ++ ++ * MX record points to an IP address and the main section option ++ allow_mx_to_ip is not set. ++ ++ * MX records exist and point to valid hosts, but all hosts resolve only to ++ addresses blocked by the ignore_target_hosts generic option on this router. ++ ++ * The domain is not syntactically valid (see also allow_utf8_domains and ++ dns_check_names_pattern for handling one variant of this) ++ ++ * check_secondary_mx is set on this router but the local host can not be ++ found in the MX records (see below) ++ ++ ++17.3 Private options for dnslookup ++---------------------------------- ++ ++The private options for the dnslookup router are as follows: ++ +++--------------------------------------------------------------+ ++|check_secondary_mx|Use: dnslookup|Type: boolean|Default: false| +++--------------------------------------------------------------+ ++ ++If this option is set, the router declines unless the local host is found in ++(and removed from) the list of hosts obtained by MX lookup. This can be used to ++process domains for which the local host is a secondary mail exchanger ++differently to other domains. The way in which Exim decides whether a host is ++the local host is described in section 13.8. ++ +++-----------------------------------------------------+ ++|check_srv|Use: dnslookup|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++The dnslookup router supports the use of SRV records (see RFC 2782) in addition ++to MX and address records. The support is disabled by default. To enable SRV ++support, set the check_srv option to the name of the service required. For ++example, ++ ++check_srv = smtp ++ ++looks for SRV records that refer to the normal smtp service. The option is ++expanded, so the service name can vary from message to message or address to ++address. This might be helpful if SRV records are being used for a submission ++service. If the expansion is forced to fail, the check_srv option is ignored, ++and the router proceeds to look for MX records in the normal way. ++ ++When the expansion succeeds, the router searches first for SRV records for the ++given service (it assumes TCP protocol). A single SRV record with a host name ++that consists of just a single dot indicates "no such service for this domain"; ++if this is encountered, the router declines. If other kinds of SRV record are ++found, they are used to construct a host list for delivery according to the ++rules of RFC 2782. MX records are not sought in this case. ++ ++When no SRV records are found, MX records (and address records) are sought in ++the traditional way. In other words, SRV records take precedence over MX ++records, just as MX records take precedence over address records. Note that ++this behaviour is not sanctioned by RFC 2782, though a previous draft RFC ++defined it. It is apparently believed that MX records are sufficient for email ++and that SRV records should not be used for this purpose. However, SRV records ++have an additional "weight" feature which some people might find useful when ++trying to split an SMTP load between hosts of different power. ++ ++See section 17.1 above for a discussion of Exim's behaviour when there is a DNS ++lookup error. ++ +++-----------------------------------------------------------+ ++|mx_domains|Use: dnslookup|Type: domain list*|Default: unset| +++-----------------------------------------------------------+ ++ ++A domain that matches mx_domains is required to have either an MX or an SRV ++record in order to be recognized. (The name of this option could be improved.) ++For example, if all the mail hosts in fict.example are known to have MX ++records, except for those in discworld.fict.example, you could use this ++setting: ++ ++mx_domains = ! *.discworld.fict.example : *.fict.example ++ ++This specifies that messages addressed to a domain that matches the list but ++has no MX record should be bounced immediately instead of being routed using ++the address record. ++ +++----------------------------------------------------------------+ ++|mx_fail_domains|Use: dnslookup|Type: domain list*|Default: unset| +++----------------------------------------------------------------+ ++ ++If the DNS lookup for MX records for one of the domains in this list causes a ++DNS lookup error, Exim behaves as if no MX records were found. See section 17.1 ++for more discussion. ++ +++---------------------------------------------------------+ ++|qualify_single|Use: dnslookup|Type: boolean|Default: true| +++---------------------------------------------------------+ ++ ++When this option is true, the resolver option RES_DEFNAMES is set for DNS ++lookups. Typically, but not standardly, this causes the resolver to qualify ++single-component names with the default domain. For example, on a machine ++called dictionary.ref.example, the domain thesaurus would be changed to ++thesaurus.ref.example inside the resolver. For details of what your resolver ++actually does, consult your man pages for resolver and resolv.conf. ++ +++----------------------------------------------------------+ ++|rewrite_headers|Use: dnslookup|Type: boolean|Default: true| +++----------------------------------------------------------+ ++ ++If the domain name in the address that is being processed is not fully ++qualified, it may be expanded to its full form by a DNS lookup. For example, if ++an address is specified as dormouse@teaparty, the domain might be expanded to ++teaparty.wonderland.fict.example. Domain expansion can also occur as a result ++of setting the widen_domains option. If rewrite_headers is true, all ++occurrences of the abbreviated domain name in any Bcc:, Cc:, From:, Reply-to:, ++Sender:, and To: header lines of the message are rewritten with the full domain ++name. ++ ++This option should be turned off only when it is known that no message is ever ++going to be sent outside an environment where the abbreviation makes sense. ++ ++When an MX record is looked up in the DNS and matches a wildcard record, name ++servers normally return a record containing the name that has been looked up, ++making it impossible to detect whether a wildcard was present or not. However, ++some name servers have recently been seen to return the wildcard entry. If the ++name returned by a DNS lookup begins with an asterisk, it is not used for ++header rewriting. ++ +++--------------------------------------------------------------------+ ++|same_domain_copy_routing|Use: dnslookup|Type: boolean|Default: false| +++--------------------------------------------------------------------+ ++ ++Addresses with the same domain are normally routed by the dnslookup router to ++the same list of hosts. However, this cannot be presumed, because the router ++options and preconditions may refer to the local part of the address. By ++default, therefore, Exim routes each address in a message independently. DNS ++servers run caches, so repeated DNS lookups are not normally expensive, and in ++any case, personal messages rarely have more than a few recipients. ++ ++If you are running mailing lists with large numbers of subscribers at the same ++domain, and you are using a dnslookup router which is independent of the local ++part, you can set same_domain_copy_routing to bypass repeated DNS lookups for ++identical domains in one message. In this case, when dnslookup routes an ++address to a remote transport, any other unrouted addresses in the message that ++have the same domain are automatically given the same routing without ++processing them independently, provided the following conditions are met: ++ ++ * No router that processed the address specified headers_add or ++ headers_remove. ++ ++ * The router did not change the address in any way, for example, by ++ "widening" the domain. ++ +++----------------------------------------------------------+ ++|search_parents|Use: dnslookup|Type: boolean|Default: false| +++----------------------------------------------------------+ ++ ++When this option is true, the resolver option RES_DNSRCH is set for DNS ++lookups. This is different from the qualify_single option in that it applies to ++domains containing dots. Typically, but not standardly, it causes the resolver ++to search for the name in the current domain and in parent domains. For ++example, on a machine in the fict.example domain, if looking up ++teaparty.wonderland failed, the resolver would try ++teaparty.wonderland.fict.example. For details of what your resolver actually ++does, consult your man pages for resolver and resolv.conf. ++ ++Setting this option true can cause problems in domains that have a wildcard MX ++record, because any domain that does not have its own MX record matches the ++local wildcard. ++ +++-----------------------------------------------------------------+ ++|srv_fail_domains|Use: dnslookup|Type: domain list*|Default: unset| +++-----------------------------------------------------------------+ ++ ++If the DNS lookup for SRV records for one of the domains in this list causes a ++DNS lookup error, Exim behaves as if no SRV records were found. See section ++17.1 for more discussion. ++ +++-------------------------------------------------------------+ ++|widen_domains|Use: dnslookup|Type: string list|Default: unset| +++-------------------------------------------------------------+ ++ ++If a DNS lookup fails and this option is set, each of its strings in turn is ++added onto the end of the domain, and the lookup is tried again. For example, ++if ++ ++widen_domains = fict.example:ref.example ++ ++is set and a lookup of klingon.dictionary fails, ++klingon.dictionary.fict.example is looked up, and if this fails, ++klingon.dictionary.ref.example is tried. Note that the qualify_single and ++search_parents options can cause some widening to be undertaken inside the DNS ++resolver. widen_domains is not applied to sender addresses when verifying, ++unless rewrite_headers is false (not the default). ++ ++ ++17.4 Effect of qualify_single and search_parents ++------------------------------------------------ ++ ++When a domain from an envelope recipient is changed by the resolver as a result ++of the qualify_single or search_parents options, Exim rewrites the ++corresponding address in the message's header lines unless rewrite_headers is ++set false. Exim then re-routes the address, using the full domain. ++ ++These two options affect only the DNS lookup that takes place inside the router ++for the domain of the address that is being routed. They do not affect lookups ++such as that implied by ++ ++domains = @mx_any ++ ++that may happen while processing a router precondition before the router is ++entered. No widening ever takes place for these lookups. ++ ++ ++ ++=============================================================================== ++18. THE IPLITERAL ROUTER ++ ++This router has no private options. Unless it is being used purely for ++verification (see verify_only) a transport is required to be defined by the ++generic transport option. The router accepts the address if its domain part ++takes the form of an RFC 2822 domain literal. For example, the ipliteral router ++handles the address ++ ++root@[192.168.1.1] ++ ++by setting up delivery to the host with that IP address. IPv4 domain literals ++consist of an IPv4 address enclosed in square brackets. IPv6 domain literals ++are similar, but the address is preceded by "ipv6:". For example: ++ ++postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678] ++ ++Exim allows "ipv4:" before IPv4 addresses, for consistency, and on the grounds ++that sooner or later somebody will try it. ++ ++If the IP address matches something in ignore_target_hosts, the router ++declines. If an IP literal turns out to refer to the local host, the generic ++self option determines what happens. ++ ++The RFCs require support for domain literals; however, their use is ++controversial in today's Internet. If you want to use this router, you must ++also set the main configuration option allow_domain_literals. Otherwise, Exim ++will not recognize the domain literal syntax in addresses. ++ ++ ++ ++=============================================================================== ++19. THE IPLOOKUP ROUTER ++ ++The iplookup router was written to fulfil a specific requirement in Cambridge ++University (which in fact no longer exists). For this reason, it is not ++included in the binary of Exim by default. If you want to include it, you must ++set ++ ++ROUTER_IPLOOKUP=yes ++ ++in your Local/Makefile configuration file. ++ ++The iplookup router routes an address by sending it over a TCP or UDP ++connection to one or more specific hosts. The host can then return the same or ++a different address - in effect rewriting the recipient address in the ++message's envelope. The new address is then passed on to subsequent routers. If ++this process fails, the address can be passed on to other routers, or delivery ++can be deferred. Since iplookup is just a rewriting router, a transport must ++not be specified for it. ++ +++-----------------------------------------------+ ++|hosts|Use: iplookup|Type: string|Default: unset| +++-----------------------------------------------+ ++ ++This option must be supplied. Its value is a colon-separated list of host ++names. The hosts are looked up using gethostbyname() (or getipnodebyname() when ++available) and are tried in order until one responds to the query. If none ++respond, what happens is controlled by optional. ++ +++---------------------------------------------------+ ++|optional|Use: iplookup|Type: boolean|Default: false| +++---------------------------------------------------+ ++ ++If optional is true, if no response is obtained from any host, the address is ++passed to the next router, overriding no_more. If optional is false, delivery ++to the address is deferred. ++ +++-------------------------------------------+ ++|port|Use: iplookup|Type: integer|Default: 0| +++-------------------------------------------+ ++ ++This option must be supplied. It specifies the port number for the TCP or UDP ++call. ++ +++------------------------------------------------+ ++|protocol|Use: iplookup|Type: string|Default: udp| +++------------------------------------------------+ ++ ++This option can be set to "udp" or "tcp" to specify which of the two protocols ++is to be used. ++ +++----------------------------------------------------+ ++|query|Use: iplookup|Type: string*|Default: see below| +++----------------------------------------------------+ ++ ++This defines the content of the query that is sent to the remote hosts. The ++default value is: ++ ++$local_part@$domain $local_part@$domain ++ ++The repetition serves as a way of checking that a response is to the correct ++query in the default case (see response_pattern below). ++ +++--------------------------------------------------+ ++|reroute|Use: iplookup|Type: string*|Default: unset| +++--------------------------------------------------+ ++ ++If this option is not set, the rerouted address is precisely the byte string ++returned by the remote host, up to the first white space, if any. If set, the ++string is expanded to form the rerouted address. It can include parts matched ++in the response by response_pattern by means of numeric variables such as $1, ++$2, etc. The variable $0 refers to the entire input string, whether or not a ++pattern is in use. In all cases, the rerouted address must end up in the form ++local_part@domain. ++ +++----------------------------------------------------------+ ++|response_pattern|Use: iplookup|Type: string|Default: unset| +++----------------------------------------------------------+ ++ ++This option can be set to a regular expression that is applied to the string ++returned from the remote host. If the pattern does not match the response, the ++router declines. If response_pattern is not set, no checking of the response is ++done, unless the query was defaulted, in which case there is a check that the ++text returned after the first white space is the original address. This checks ++that the answer that has been received is in response to the correct question. ++For example, if the response is just a new domain, the following could be used: ++ ++response_pattern = ^([^@]+)$ ++reroute = $local_part@$1 ++ +++--------------------------------------------+ ++|timeout|Use: iplookup|Type: time|Default: 5s| +++--------------------------------------------+ ++ ++This specifies the amount of time to wait for a response from the remote ++machine. The same timeout is used for the connect() function for a TCP call. It ++does not apply to UDP. ++ ++ ++ ++=============================================================================== ++20. THE MANUALROUTE ROUTER ++ ++The manualroute router is so-called because it provides a way of manually ++routing an address according to its domain. It is mainly used when you want to ++route addresses to remote hosts according to your own rules, bypassing the ++normal DNS routing that looks up MX records. However, manualroute can also ++route to local transports, a facility that may be useful if you want to save ++messages for dial-in hosts in local files. ++ ++The manualroute router compares a list of domain patterns with the domain it is ++trying to route. If there is no match, the router declines. Each pattern has ++associated with it a list of hosts and some other optional data, which may ++include a transport. The combination of a pattern and its data is called a ++"routing rule". For patterns that do not have an associated transport, the ++generic transport option must specify a transport, unless the router is being ++used purely for verification (see verify_only). ++ ++In the case of verification, matching the domain pattern is sufficient for the ++router to accept the address. When actually routing an address for delivery, an ++address that matches a domain pattern is queued for the associated transport. ++If the transport is not a local one, a host list must be associated with the ++pattern; IP addresses are looked up for the hosts, and these are passed to the ++transport along with the mail address. For local transports, a host list is ++optional. If it is present, it is passed in $host as a single text string. ++ ++The list of routing rules can be provided as an inline string in route_list, or ++the data can be obtained by looking up the domain in a file or database by ++setting route_data. Only one of these settings may appear in any one instance ++of manualroute. The format of routing rules is described below, following the ++list of private options. ++ ++ ++20.1 Private options for manualroute ++------------------------------------ ++ ++The private options for the manualroute router are as follows: ++ +++-------------------------------------------------------------+ ++|host_all_ignored|Use: manualroute|Type: string|Default: defer| +++-------------------------------------------------------------+ ++ ++See host_find_failed. ++ +++--------------------------------------------------------------+ ++|host_find_failed|Use: manualroute|Type: string|Default: freeze| +++--------------------------------------------------------------+ ++ ++This option controls what happens when manualroute tries to find an IP address ++for a host, and the host does not exist. The option can be set to one of the ++following values: ++ ++decline ++defer ++fail ++freeze ++ignore ++pass ++ ++The default ("freeze") assumes that this state is a serious configuration ++error. The difference between "pass" and "decline" is that the former forces ++the address to be passed to the next router (or the router defined by ++pass_router), overriding no_more, whereas the latter passes the address to the ++next router only if more is true. ++ ++The value "ignore" causes Exim to completely ignore a host whose IP address ++cannot be found. If all the hosts in the list are ignored, the behaviour is ++controlled by the host_all_ignored option. This takes the same values as ++host_find_failed, except that it cannot be set to "ignore". ++ ++The host_find_failed option applies only to a definite "does not exist" state; ++if a host lookup gets a temporary error, delivery is deferred unless the ++generic pass_on_timeout option is set. ++ +++-------------------------------------------------------------+ ++|hosts_randomize|Use: manualroute|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++If this option is set, the order of the items in a host list in a routing rule ++is randomized each time the list is used, unless an option in the routing rule ++overrides (see below). Randomizing the order of a host list can be used to do ++crude load sharing. However, if more than one mail address is routed by the ++same router to the same host list, the host lists are considered to be the same ++(even though they may be randomized into different orders) for the purpose of ++deciding whether to batch the deliveries into a single SMTP transaction. ++ ++When hosts_randomize is true, a host list may be split into groups whose order ++is separately randomized. This makes it possible to set up MX-like behaviour. ++The boundaries between groups are indicated by an item that is just "+" in the ++host list. For example: ++ ++route_list = * host1:host2:host3:+:host4:host5 ++ ++The order of the first three hosts and the order of the last two hosts is ++randomized for each use, but the first three always end up before the last two. ++If hosts_randomize is not set, a "+" item in the list is ignored. If a ++randomized host list is passed to an smtp transport that also has ++hosts_randomize set, the list is not re-randomized. ++ +++--------------------------------------------------------+ ++|route_data|Use: manualroute|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++If this option is set, it must expand to yield the data part of a routing rule. ++Typically, the expansion string includes a lookup based on the domain. For ++example: ++ ++route_data = ${lookup{$domain}dbm{/etc/routes}} ++ ++If the expansion is forced to fail, or the result is an empty string, the ++router declines. Other kinds of expansion failure cause delivery to be ++deferred. ++ +++------------------------------------------------------------+ ++|route_list|Use: manualroute|Type: string list|Default: unset| +++------------------------------------------------------------+ ++ ++This string is a list of routing rules, in the form defined below. Note that, ++unlike most string lists, the items are separated by semicolons. This is so ++that they may contain colon-separated host lists. ++ +++----------------------------------------------------------------------+ ++|same_domain_copy_routing|Use: manualroute|Type: boolean|Default: false| +++----------------------------------------------------------------------+ ++ ++Addresses with the same domain are normally routed by the manualroute router to ++the same list of hosts. However, this cannot be presumed, because the router ++options and preconditions may refer to the local part of the address. By ++default, therefore, Exim routes each address in a message independently. DNS ++servers run caches, so repeated DNS lookups are not normally expensive, and in ++any case, personal messages rarely have more than a few recipients. ++ ++If you are running mailing lists with large numbers of subscribers at the same ++domain, and you are using a manualroute router which is independent of the ++local part, you can set same_domain_copy_routing to bypass repeated DNS lookups ++for identical domains in one message. In this case, when manualroute routes an ++address to a remote transport, any other unrouted addresses in the message that ++have the same domain are automatically given the same routing without ++processing them independently. However, this is only done if headers_add and ++headers_remove are unset. ++ ++ ++20.2 Routing rules in route_list ++-------------------------------- ++ ++The value of route_list is a string consisting of a sequence of routing rules, ++separated by semicolons. If a semicolon is needed in a rule, it can be entered ++as two semicolons. Alternatively, the list separator can be changed as ++described (for colon-separated lists) in section 6.19. Empty rules are ignored. ++The format of each rule is ++ ++<domain pattern> <list of hosts> <options> ++ ++The following example contains two rules, each with a simple domain pattern and ++no options: ++ ++route_list = \ ++ dict.ref.example mail-1.ref.example:mail-2.ref.example ; \ ++ thes.ref.example mail-3.ref.example:mail-4.ref.example ++ ++The three parts of a rule are separated by white space. The pattern and the ++list of hosts can be enclosed in quotes if necessary, and if they are, the ++usual quoting rules apply. Each rule in a route_list must start with a single ++domain pattern, which is the only mandatory item in the rule. The pattern is in ++the same format as one item in a domain list (see section 10.8), except that it ++may not be the name of an interpolated file. That is, it may be wildcarded, or ++a regular expression, or a file or database lookup (with semicolons doubled, ++because of the use of semicolon as a separator in a route_list). ++ ++The rules in route_list are searched in order until one of the patterns matches ++the domain that is being routed. The list of hosts and then options are then ++used as described below. If there is no match, the router declines. When ++route_list is set, route_data must not be set. ++ ++ ++20.3 Routing rules in route_data ++-------------------------------- ++ ++The use of route_list is convenient when there are only a small number of ++routing rules. For larger numbers, it is easier to use a file or database to ++hold the routing information, and use the route_data option instead. The value ++of route_data is a list of hosts, followed by (optional) options. Most ++commonly, route_data is set as a string that contains an expansion lookup. For ++example, suppose we place two routing rules in a file like this: ++ ++dict.ref.example: mail-1.ref.example:mail-2.ref.example ++thes.ref.example: mail-3.ref.example:mail-4.ref.example ++ ++This data can be accessed by setting ++ ++route_data = ${lookup{$domain}lsearch{/the/file/name}} ++ ++Failure of the lookup results in an empty string, causing the router to ++decline. However, you do not have to use a lookup in route_data. The only ++requirement is that the result of expanding the string is a list of hosts, ++possibly followed by options, separated by white space. The list of hosts must ++be enclosed in quotes if it contains white space. ++ ++ ++20.4 Format of the list of hosts ++-------------------------------- ++ ++A list of hosts, whether obtained via route_data or route_list, is always ++separately expanded before use. If the expansion fails, the router declines. ++The result of the expansion must be a colon-separated list of names and/or IP ++addresses, optionally also including ports. The format of each item in the list ++is described in the next section. The list separator can be changed as ++described in section 6.19. ++ ++If the list of hosts was obtained from a route_list item, the following ++variables are set during its expansion: ++ ++ * If the domain was matched against a regular expression, the numeric ++ variables $1, $2, etc. may be set. For example: ++ ++ route_list = ^domain(\d+) host-$1.text.example ++ ++ * $0 is always set to the entire domain. ++ ++ * $1 is also set when partial matching is done in a file lookup. ++ ++ * If the pattern that matched the domain was a lookup item, the data that was ++ looked up is available in the expansion variable $value. For example: ++ ++ route_list = lsearch;;/some/file.routes $value ++ ++Note the doubling of the semicolon in the pattern that is necessary because ++semicolon is the default route list separator. ++ ++ ++20.5 Format of one host item ++---------------------------- ++ ++Each item in the list of hosts is either a host name or an IP address, ++optionally with an attached port number. When no port is given, an IP address ++is not enclosed in brackets. When a port is specified, it overrides the port ++specification on the transport. The port is separated from the name or address ++by a colon. This leads to some complications: ++ ++ * Because colon is the default separator for the list of hosts, either the ++ colon that specifies a port must be doubled, or the list separator must be ++ changed. The following two examples have the same effect: ++ ++ route_list = * "host1.tld::1225 : host2.tld::1226" ++ route_list = * "<+ host1.tld:1225 + host2.tld:1226" ++ ++ * When IPv6 addresses are involved, it gets worse, because they contain ++ colons of their own. To make this case easier, it is permitted to enclose ++ an IP address (either v4 or v6) in square brackets if a port number ++ follows. For example: ++ ++ route_list = * "</ [10.1.1.1]:1225 / [::1]:1226" ++ ++ ++20.6 How the list of hosts is used ++---------------------------------- ++ ++When an address is routed to an smtp transport by manualroute, each of the ++hosts is tried, in the order specified, when carrying out the SMTP delivery. ++However, the order can be changed by setting the hosts_randomize option, either ++on the router (see section 20.1 above), or on the transport. ++ ++Hosts may be listed by name or by IP address. An unadorned name in the list of ++hosts is interpreted as a host name. A name that is followed by "/MX" is ++interpreted as an indirection to a sublist of hosts obtained by looking up MX ++records in the DNS. For example: ++ ++route_list = * x.y.z:p.q.r/MX:e.f.g ++ ++If this feature is used with a port specifier, the port must come last. For ++example: ++ ++route_list = * dom1.tld/mx::1225 ++ ++If the hosts_randomize option is set, the order of the items in the list is ++randomized before any lookups are done. Exim then scans the list; for any name ++that is not followed by "/MX" it looks up an IP address. If this turns out to ++be an interface on the local host and the item is not the first in the list, ++Exim discards it and any subsequent items. If it is the first item, what ++happens is controlled by the self option of the router. ++ ++A name on the list that is followed by "/MX" is replaced with the list of hosts ++obtained by looking up MX records for the name. This is always a DNS lookup; ++the bydns and byname options (see section 20.7 below) are not relevant here. ++The order of these hosts is determined by the preference values in the MX ++records, according to the usual rules. Because randomizing happens before the ++MX lookup, it does not affect the order that is defined by MX preferences. ++ ++If the local host is present in the sublist obtained from MX records, but is ++not the most preferred host in that list, it and any equally or less preferred ++hosts are removed before the sublist is inserted into the main list. ++ ++If the local host is the most preferred host in the MX list, what happens ++depends on where in the original list of hosts the "/MX" item appears. If it is ++not the first item (that is, there are previous hosts in the main list), Exim ++discards this name and any subsequent items in the main list. ++ ++If the MX item is first in the list of hosts, and the local host is the most ++preferred host, what happens is controlled by the self option of the router. ++ ++DNS failures when lookup up the MX records are treated in the same way as DNS ++failures when looking up IP addresses: pass_on_timeout and host_find_failed are ++used when relevant. ++ ++The generic ignore_target_hosts option applies to all hosts in the list, ++whether obtained from an MX lookup or not. ++ ++ ++20.7 How the options are used ++----------------------------- ++ ++The options are a sequence of words; in practice no more than three are ever ++present. One of the words can be the name of a transport; this overrides the ++transport option on the router for this particular routing rule only. The other ++words (if present) control randomization of the list of hosts on a per-rule ++basis, and how the IP addresses of the hosts are to be found when routing to a ++remote transport. These options are as follows: ++ ++ * randomize: randomize the order of the hosts in this list, overriding the ++ setting of hosts_randomize for this routing rule only. ++ ++ * no_randomize: do not randomize the order of the hosts in this list, ++ overriding the setting of hosts_randomize for this routing rule only. ++ ++ * byname: use getipnodebyname() (gethostbyname() on older systems) to find IP ++ addresses. This function may ultimately cause a DNS lookup, but it may also ++ look in /etc/hosts or other sources of information. ++ ++ * bydns: look up address records for the hosts directly in the DNS; fail if ++ no address records are found. If there is a temporary DNS error (such as a ++ timeout), delivery is deferred. ++ ++For example: ++ ++route_list = domain1 host1:host2:host3 randomize bydns;\ ++ domain2 host4:host5 ++ ++If neither byname nor bydns is given, Exim behaves as follows: First, a DNS ++lookup is done. If this yields anything other than HOST_NOT_FOUND, that result ++is used. Otherwise, Exim goes on to try a call to getipnodebyname() or ++gethostbyname(), and the result of the lookup is the result of that call. ++ ++Warning: It has been discovered that on some systems, if a DNS lookup called ++via getipnodebyname() times out, HOST_NOT_FOUND is returned instead of ++TRY_AGAIN. That is why the default action is to try a DNS lookup first. Only if ++that gives a definite "no such host" is the local function called. ++ ++If no IP address for a host can be found, what happens is controlled by the ++host_find_failed option. ++ ++When an address is routed to a local transport, IP addresses are not looked up. ++The host list is passed to the transport in the $host variable. ++ ++ ++20.8 Manualroute examples ++------------------------- ++ ++In some of the examples that follow, the presence of the remote_smtp transport, ++as defined in the default configuration file, is assumed: ++ ++ * The manualroute router can be used to forward all external mail to a smart ++ host. If you have set up, in the main part of the configuration, a named ++ domain list that contains your local domains, for example: ++ ++ domainlist local_domains = my.domain.example ++ ++ You can arrange for all other domains to be routed to a smart host by ++ making your first router something like this: ++ ++ smart_route: ++ driver = manualroute ++ domains = !+local_domains ++ transport = remote_smtp ++ route_list = * smarthost.ref.example ++ ++ This causes all non-local addresses to be sent to the single host ++ smarthost.ref.example. If a colon-separated list of smart hosts is given, ++ they are tried in order (but you can use hosts_randomize to vary the order ++ each time). Another way of configuring the same thing is this: ++ ++ smart_route: ++ driver = manualroute ++ transport = remote_smtp ++ route_list = !+local_domains smarthost.ref.example ++ ++ There is no difference in behaviour between these two routers as they ++ stand. However, they behave differently if no_more is added to them. In the ++ first example, the router is skipped if the domain does not match the ++ domains precondition; the following router is always tried. If the router ++ runs, it always matches the domain and so can never decline. Therefore, ++ no_more would have no effect. In the second case, the router is never ++ skipped; it always runs. However, if it doesn't match the domain, it ++ declines. In this case no_more would prevent subsequent routers from ++ running. ++ ++ * A mail hub is a host which receives mail for a number of domains via MX ++ records in the DNS and delivers it via its own private routing mechanism. ++ Often the final destinations are behind a firewall, with the mail hub being ++ the one machine that can connect to machines both inside and outside the ++ firewall. The manualroute router is usually used on a mail hub to route ++ incoming messages to the correct hosts. For a small number of domains, the ++ routing can be inline, using the route_list option, but for a larger number ++ a file or database lookup is easier to manage. ++ ++ If the domain names are in fact the names of the machines to which the mail ++ is to be sent by the mail hub, the configuration can be quite simple. For ++ example: ++ ++ hub_route: ++ driver = manualroute ++ transport = remote_smtp ++ route_list = *.rhodes.tvs.example $domain ++ ++ This configuration routes domains that match "*.rhodes.tvs.example" to ++ hosts whose names are the same as the mail domains. A similar approach can ++ be taken if the host name can be obtained from the domain name by a string ++ manipulation that the expansion facilities can handle. Otherwise, a lookup ++ based on the domain can be used to find the host: ++ ++ through_firewall: ++ driver = manualroute ++ transport = remote_smtp ++ route_data = ${lookup {$domain} cdb {/internal/host/routes}} ++ ++ The result of the lookup must be the name or IP address of the host (or ++ hosts) to which the address is to be routed. If the lookup fails, the route ++ data is empty, causing the router to decline. The address then passes to ++ the next router. ++ ++ * You can use manualroute to deliver messages to pipes or files in batched ++ SMTP format for onward transportation by some other means. This is one way ++ of storing mail for a dial-up host when it is not connected. The route list ++ entry can be as simple as a single domain name in a configuration like ++ this: ++ ++ save_in_file: ++ driver = manualroute ++ transport = batchsmtp_appendfile ++ route_list = saved.domain.example ++ ++ though often a pattern is used to pick up more than one domain. If there ++ are several domains or groups of domains with different transport ++ requirements, different transports can be listed in the routing ++ information: ++ ++ save_in_file: ++ driver = manualroute ++ route_list = \ ++ *.saved.domain1.example $domain batch_appendfile; \ ++ *.saved.domain2.example \ ++ ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \ ++ batch_pipe ++ ++ The first of these just passes the domain in the $host variable, which ++ doesn't achieve much (since it is also in $domain), but the second does a ++ file lookup to find a value to pass, causing the router to decline to ++ handle the address if the lookup fails. ++ ++ * Routing mail directly to UUCP software is a specific case of the use of ++ manualroute in a gateway to another mail environment. This is an example of ++ one way it can be done: ++ ++ # Transport ++ uucp: ++ driver = pipe ++ user = nobody ++ command = /usr/local/bin/uux -r - \ ++ ${substr_-5:$host}!rmail ${local_part} ++ return_fail_output = true ++ ++ # Router ++ uucphost: ++ transport = uucp ++ driver = manualroute ++ route_data = \ ++ ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}} ++ ++ The file /usr/local/exim/uucphosts contains entries like ++ ++ darksite.ethereal.example: darksite.UUCP ++ ++ It can be set up more simply without adding and removing ".UUCP" but this ++ way makes clear the distinction between the domain name ++ darksite.ethereal.example and the UUCP host name darksite. ++ ++ ++ ++=============================================================================== ++21. THE QUERYPROGRAM ROUTER ++ ++The queryprogram router routes an address by running an external command and ++acting on its output. This is an expensive way to route, and is intended mainly ++for use in lightly-loaded systems, or for performing experiments. However, if ++it is possible to use the precondition options (domains, local_parts, etc) to ++skip this router for most addresses, it could sensibly be used in special ++cases, even on a busy host. There are the following private options: ++ +++------------------------------------------------------+ ++|command|Use: queryprogram|Type: string*|Default: unset| +++------------------------------------------------------+ ++ ++This option must be set. It specifies the command that is to be run. The ++command is split up into a command name and arguments, and then each is ++expanded separately (exactly as for a pipe transport, described in chapter 29). ++ +++-----------------------------------------------------------+ ++|command_group|Use: queryprogram|Type: string|Default: unset| +++-----------------------------------------------------------+ ++ ++This option specifies a gid to be set when running the command while routing an ++address for deliver. It must be set if command_user specifies a numerical uid. ++If it begins with a digit, it is interpreted as the numerical value of the gid. ++Otherwise it is looked up using getgrnam(). ++ +++----------------------------------------------------------+ ++|command_user|Use: queryprogram|Type: string|Default: unset| +++----------------------------------------------------------+ ++ ++This option must be set. It specifies the uid which is set when running the ++command while routing an address for delivery. If the value begins with a ++digit, it is interpreted as the numerical value of the uid. Otherwise, it is ++looked up using getpwnam() to obtain a value for the uid and, if command_group ++is not set, a value for the gid also. ++ ++Warning: Changing uid and gid is possible only when Exim is running as root, ++which it does during a normal delivery in a conventional configuration. ++However, when an address is being verified during message reception, Exim is ++usually running as the Exim user, not as root. If the queryprogram router is ++called from a non-root process, Exim cannot change uid or gid before running ++the command. In this circumstance the command runs under the current uid and ++gid. ++ +++-----------------------------------------------------------+ ++|current_directory|Use: queryprogram|Type: string|Default: /| +++-----------------------------------------------------------+ ++ ++This option specifies an absolute path which is made the current directory ++before running the command. ++ +++------------------------------------------------+ ++|timeout|Use: queryprogram|Type: time|Default: 1h| +++------------------------------------------------+ ++ ++If the command does not complete within the timeout period, its process group ++is killed and the message is frozen. A value of zero time specifies no timeout. ++ ++The standard output of the command is connected to a pipe, which is read when ++the command terminates. It should consist of a single line of output, ++containing up to five fields, separated by white space. The maximum length of ++the line is 1023 characters. Longer lines are silently truncated. The first ++field is one of the following words (case-insensitive): ++ ++ * Accept: routing succeeded; the remaining fields specify what to do (see ++ below). ++ ++ * Decline: the router declines; pass the address to the next router, unless ++ no_more is set. ++ ++ * Fail: routing failed; do not pass the address to any more routers. Any ++ subsequent text on the line is an error message. If the router is run as ++ part of address verification during an incoming SMTP message, the message ++ is included in the SMTP response. ++ ++ * Defer: routing could not be completed at this time; try again later. Any ++ subsequent text on the line is an error message which is logged. It is not ++ included in any SMTP response. ++ ++ * Freeze: the same as defer, except that the message is frozen. ++ ++ * Pass: pass the address to the next router (or the router specified by ++ pass_router), overriding no_more. ++ ++ * Redirect: the message is redirected. The remainder of the line is a list of ++ new addresses, which are routed independently, starting with the first ++ router, or the router specified by redirect_router, if set. ++ ++When the first word is accept, the remainder of the line consists of a number ++of keyed data values, as follows (split into two lines here, to fit on the ++page): ++ ++ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts> ++LOOKUP=byname|bydns DATA=<text> ++ ++The data items can be given in any order, and all are optional. If no transport ++is included, the transport specified by the generic transport option is used. ++The list of hosts and the lookup type are needed only if the transport is an ++smtp transport that does not itself supply a list of hosts. ++ ++The format of the list of hosts is the same as for the manualroute router. As ++well as host names and IP addresses with optional port numbers, as described in ++section 20.5, it may contain names followed by "/MX" to specify sublists of ++hosts that are obtained by looking up MX records (see section 20.6). ++ ++If the lookup type is not specified, Exim behaves as follows when trying to ++find an IP address for each host: First, a DNS lookup is done. If this yields ++anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim goes ++on to try a call to getipnodebyname() or gethostbyname(), and the result of the ++lookup is the result of that call. ++ ++If the DATA field is set, its value is placed in the $address_data variable. ++For example, this return line ++ ++accept hosts=x1.y.example:x2.y.example data="rule1" ++ ++routes the address to the default transport, passing a list of two hosts. When ++the transport runs, the string "rule1" is in $address_data. ++ ++ ++ ++=============================================================================== ++22. THE REDIRECT ROUTER ++ ++The redirect router handles several kinds of address redirection. Its most ++common uses are for resolving local part aliases from a central alias file ++(usually called /etc/aliases) and for handling users' personal .forward files, ++but it has many other potential uses. The incoming address can be redirected in ++several different ways: ++ ++ * It can be replaced by one or more new addresses which are themselves routed ++ independently. ++ ++ * It can be routed to be delivered to a given file or directory. ++ ++ * It can be routed to be delivered to a specified pipe command. ++ ++ * It can cause an automatic reply to be generated. ++ ++ * It can be forced to fail, optionally with a custom error message. ++ ++ * It can be temporarily deferred, optionally with a custom message. ++ ++ * It can be discarded. ++ ++The generic transport option must not be set for redirect routers. However, ++there are some private options which define transports for delivery to files ++and pipes, and for generating autoreplies. See the file_transport, ++pipe_transport and reply_transport descriptions below. ++ ++ ++22.1 Redirection data ++--------------------- ++ ++The router operates by interpreting a text string which it obtains either by ++expanding the contents of the data option, or by reading the entire contents of ++a file whose name is given in the file option. These two options are mutually ++exclusive. The first is commonly used for handling system aliases, in a ++configuration like this: ++ ++system_aliases: ++ driver = redirect ++ data = ${lookup{$local_part}lsearch{/etc/aliases}} ++ ++If the lookup fails, the expanded string in this example is empty. When the ++expansion of data results in an empty string, the router declines. A forced ++expansion failure also causes the router to decline; other expansion failures ++cause delivery to be deferred. ++ ++A configuration using file is commonly used for handling users' .forward files, ++like this: ++ ++userforward: ++ driver = redirect ++ check_local_user ++ file = $home/.forward ++ no_verify ++ ++If the file does not exist, or causes no action to be taken (for example, it is ++empty or consists only of comments), the router declines. Warning: This is not ++the case when the file contains syntactically valid items that happen to yield ++empty addresses, for example, items containing only RFC 2822 address comments. ++ ++ ++22.2 Forward files and address verification ++------------------------------------------- ++ ++It is usual to set no_verify on redirect routers which handle users' .forward ++files, as in the example above. There are two reasons for this: ++ ++ * When Exim is receiving an incoming SMTP message from a remote host, it is ++ running under the Exim uid, not as root. Exim is unable to change uid to ++ read the file as the user, and it may not be able to read it as the Exim ++ user. So in practice the router may not be able to operate. ++ ++ * However, even when the router can operate, the existence of a .forward file ++ is unimportant when verifying an address. What should be checked is whether ++ the local part is a valid user name or not. Cutting out the redirection ++ processing saves some resources. ++ ++ ++22.3 Interpreting redirection data ++---------------------------------- ++ ++The contents of the data string, whether obtained from data or file, can be ++interpreted in two different ways: ++ ++ * If the allow_filter option is set true, and the data begins with the text " ++ #Exim filter" or "#Sieve filter", it is interpreted as a list of filtering ++ instructions in the form of an Exim or Sieve filter file, respectively. ++ Details of the syntax and semantics of filter files are described in a ++ separate document entitled Exim's interfaces to mail filtering; this ++ document is intended for use by end users. ++ ++ * Otherwise, the data must be a comma-separated list of redirection items, as ++ described in the next section. ++ ++When a message is redirected to a file (a "mail folder"), the file name given ++in a non-filter redirection list must always be an absolute path. A filter may ++generate a relative path - how this is handled depends on the transport's ++configuration. See section 26.1 for a discussion of this issue for the ++appendfile transport. ++ ++ ++22.4 Items in a non-filter redirection list ++------------------------------------------- ++ ++When the redirection data is not an Exim or Sieve filter, for example, if it ++comes from a conventional alias or forward file, it consists of a list of ++addresses, file names, pipe commands, or certain special items (see section ++22.6 below). The special items can be individually enabled or disabled by means ++of options whose names begin with allow_ or forbid_, depending on their default ++values. The items in the list are separated by commas or newlines. If a comma ++is required in an item, the entire item must be enclosed in double quotes. ++ ++Lines starting with a # character are comments, and are ignored, and # may also ++appear following a comma, in which case everything between the # and the next ++newline character is ignored. ++ ++If an item is entirely enclosed in double quotes, these are removed. Otherwise ++double quotes are retained because some forms of mail address require their use ++(but never to enclose the entire address). In the following description, "item" ++refers to what remains after any surrounding double quotes have been removed. ++ ++Warning: If you use an Exim expansion to construct a redirection address, and ++the expansion contains a reference to $local_part, you should make use of the ++quote_local_part expansion operator, in case the local part contains special ++characters. For example, to redirect all mail for the domain obsolete.example, ++retaining the existing local part, you could use this setting: ++ ++data = ${quote_local_part:$local_part}@newdomain.example ++ ++ ++22.5 Redirecting to a local mailbox ++----------------------------------- ++ ++A redirection item may safely be the same as the address currently under ++consideration. This does not cause a routing loop, because a router is ++automatically skipped if any ancestor of the address that is being processed is ++the same as the current address and was processed by the current router. Such ++an address is therefore passed to the following routers, so it is handled as if ++there were no redirection. When making this loop-avoidance test, the complete ++local part, including any prefix or suffix, is used. ++ ++Specifying the same local part without a domain is a common usage in personal ++filter files when the user wants to have messages delivered to the local ++mailbox and also forwarded elsewhere. For example, the user whose login is cleo ++might have a .forward file containing this: ++ ++cleo, cleopatra@egypt.example ++ ++For compatibility with other MTAs, such unqualified local parts may be preceded ++by "\", but this is not a requirement for loop prevention. However, it does ++make a difference if more than one domain is being handled synonymously. ++ ++If an item begins with "\" and the rest of the item parses as a valid RFC 2822 ++address that does not include a domain, the item is qualified using the domain ++of the incoming address. In the absence of a leading "\", unqualified addresses ++are qualified using the value in qualify_recipient, but you can force the ++incoming domain to be used by setting qualify_preserve_domain. ++ ++Care must be taken if there are alias names for local users. Consider an MTA ++handling a single local domain where the system alias file contains: ++ ++Sam.Reman: spqr ++ ++Now suppose that Sam (whose login id is spqr) wants to save copies of messages ++in the local mailbox, and also forward copies elsewhere. He creates this ++forward file: ++ ++Sam.Reman, spqr@reme.elsewhere.example ++ ++With these settings, an incoming message addressed to Sam.Reman fails. The ++redirect router for system aliases does not process Sam.Reman the second time ++round, because it has previously routed it, and the following routers ++presumably cannot handle the alias. The forward file should really contain ++ ++spqr, spqr@reme.elsewhere.example ++ ++but because this is such a common error, the check_ancestor option (see below) ++exists to provide a way to get round it. This is normally set on a redirect ++router that is handling users' .forward files. ++ ++ ++22.6 Special items in redirection lists ++--------------------------------------- ++ ++In addition to addresses, the following types of item may appear in redirection ++lists (that is, in non-filter redirection data): ++ ++ * An item is treated as a pipe command if it begins with "|" and does not ++ parse as a valid RFC 2822 address that includes a domain. A transport for ++ running the command must be specified by the pipe_transport option. ++ Normally, either the router or the transport specifies a user and a group ++ under which to run the delivery. The default is to use the Exim user and ++ group. ++ ++ Single or double quotes can be used for enclosing the individual arguments ++ of the pipe command; no interpretation of escapes is done for single ++ quotes. If the command contains a comma character, it is necessary to put ++ the whole item in double quotes, for example: ++ ++ "|/some/command ready,steady,go" ++ ++ since items in redirection lists are terminated by commas. Do not, however, ++ quote just the command. An item such as ++ ++ |"/some/command ready,steady,go" ++ ++ is interpreted as a pipe with a rather strange command name, and no ++ arguments. ++ ++ Note that the above example assumes that the text comes from a lookup ++ source of some sort, so that the quotes are part of the data. If composing ++ a redirect router with a data option directly specifying this command, the ++ quotes will be used by the configuration parser to define the extent of one ++ string, but will not be passed down into the redirect router itself. There ++ are two main approaches to get around this: escape quotes to be part of the ++ data itself, or avoid using this mechanism and instead create a custom ++ transport with the command option set and reference that transport from an ++ accept router. ++ ++ * An item is interpreted as a path name if it begins with "/" and does not ++ parse as a valid RFC 2822 address that includes a domain. For example, ++ ++ /home/world/minbari ++ ++ is treated as a file name, but ++ ++ /s=molari/o=babylon/@x400gate.way ++ ++ is treated as an address. For a file name, a transport must be specified ++ using the file_transport option. However, if the generated path name ends ++ with a forward slash character, it is interpreted as a directory name ++ rather than a file name, and directory_transport is used instead. ++ ++ Normally, either the router or the transport specifies a user and a group ++ under which to run the delivery. The default is to use the Exim user and ++ group. ++ ++ However, if a redirection item is the path /dev/null, delivery to it is ++ bypassed at a high level, and the log entry shows "**bypassed**" instead of ++ a transport name. In this case the user and group are not used. ++ ++ * If an item is of the form ++ ++ :include:<path name> ++ ++ a list of further items is taken from the given file and included at that ++ point. Note: Such a file can not be a filter file; it is just an ++ out-of-line addition to the list. The items in the included list are ++ separated by commas or newlines and are not subject to expansion. If this ++ is the first item in an alias list in an lsearch file, a colon must be used ++ to terminate the alias name. This example is incorrect: ++ ++ list1 :include:/opt/lists/list1 ++ ++ It must be given as ++ ++ list1: :include:/opt/lists/list1 ++ ++ * Sometimes you want to throw away mail to a particular local part. Making ++ the data option expand to an empty string does not work, because that ++ causes the router to decline. Instead, the alias item :blackhole: can be ++ used. It does what its name implies. No delivery is done, and no error ++ message is generated. This has the same effect as specifing /dev/null as a ++ destination, but it can be independently disabled. ++ ++ Warning: If :blackhole: appears anywhere in a redirection list, no delivery ++ is done for the original local part, even if other redirection items are ++ present. If you are generating a multi-item list (for example, by reading a ++ database) and need the ability to provide a no-op item, you must use /dev/ ++ null. ++ ++ * An attempt to deliver a particular address can be deferred or forced to ++ fail by redirection items of the form ++ ++ :defer: ++ :fail: ++ ++ respectively. When a redirection list contains such an item, it applies to ++ the entire redirection; any other items in the list are ignored. Any text ++ following :fail: or :defer: is placed in the error text associated with the ++ failure. For example, an alias file might contain: ++ ++ X.Employee: :fail: Gone away, no forwarding address ++ ++ In the case of an address that is being verified from an ACL or as the ++ subject of a VRFY command, the text is included in the SMTP error response ++ by default. The text is not included in the response to an EXPN command. In ++ non-SMTP cases the text is included in the error message that Exim ++ generates. ++ ++ By default, Exim sends a 451 SMTP code for a :defer:, and 550 for :fail:. ++ However, if the message starts with three digits followed by a space, ++ optionally followed by an extended code of the form n.n.n, also followed by ++ a space, and the very first digit is the same as the default error code, ++ the code from the message is used instead. If the very first digit is ++ incorrect, a panic error is logged, and the default code is used. You can ++ suppress the use of the supplied code in a redirect router by setting the ++ forbid_smtp_code option true. In this case, any SMTP code is quietly ++ ignored. ++ ++ In an ACL, an explicitly provided message overrides the default, but the ++ default message is available in the variable $acl_verify_message and can ++ therefore be included in a custom message if this is desired. ++ ++ Normally the error text is the rest of the redirection list - a comma does ++ not terminate it - but a newline does act as a terminator. Newlines are not ++ normally present in alias expansions. In lsearch lookups they are removed ++ as part of the continuation process, but they may exist in other kinds of ++ lookup and in :include: files. ++ ++ During routing for message delivery (as opposed to verification), a ++ redirection containing :fail: causes an immediate failure of the incoming ++ address, whereas :defer: causes the message to remain on the queue so that ++ a subsequent delivery attempt can happen at a later time. If an address is ++ deferred for too long, it will ultimately fail, because the normal retry ++ rules still apply. ++ ++ * Sometimes it is useful to use a single-key search type with a default (see ++ chapter 9) to look up aliases. However, there may be a need for exceptions ++ to the default. These can be handled by aliasing them to :unknown:. This ++ differs from :fail: in that it causes the redirect router to decline, ++ whereas :fail: forces routing to fail. A lookup which results in an empty ++ redirection list has the same effect. ++ ++ ++22.7 Duplicate addresses ++------------------------ ++ ++Exim removes duplicate addresses from the list to which it is delivering, so as ++to deliver just one copy to each address. This does not apply to deliveries ++routed to pipes by different immediate parent addresses, but an indirect ++aliasing scheme of the type ++ ++pipe: |/some/command $local_part ++localpart1: pipe ++localpart2: pipe ++ ++does not work with a message that is addressed to both local parts, because ++when the second is aliased to the intermediate local part "pipe" it gets ++discarded as being the same as a previously handled address. However, a scheme ++such as ++ ++localpart1: |/some/command $local_part ++localpart2: |/some/command $local_part ++ ++does result in two different pipe deliveries, because the immediate parents of ++the pipes are distinct. ++ ++ ++22.8 Repeated redirection expansion ++----------------------------------- ++ ++When a message cannot be delivered to all of its recipients immediately, ++leading to two or more delivery attempts, redirection expansion is carried out ++afresh each time for those addresses whose children were not all previously ++delivered. If redirection is being used as a mailing list, this can lead to new ++members of the list receiving copies of old messages. The one_time option can ++be used to avoid this. ++ ++ ++22.9 Errors in redirection lists ++-------------------------------- ++ ++If skip_syntax_errors is set, a malformed address that causes a parsing error ++is skipped, and an entry is written to the main log. This may be useful for ++mailing lists that are automatically managed. Otherwise, if an error is ++detected while generating the list of new addresses, the original address is ++deferred. See also syntax_errors_to. ++ ++ ++22.10 Private options for the redirect router ++--------------------------------------------- ++ ++The private options for the redirect router are as follows: ++ +++------------------------------------------------------+ ++|allow_defer|Use: redirect|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++Setting this option allows the use of :defer: in non-filter redirection data, ++or the defer command in an Exim filter file. ++ +++-----------------------------------------------------+ ++|allow_fail|Use: redirect|Type: boolean|Default: false| +++-----------------------------------------------------+ ++ ++If this option is true, the :fail: item can be used in a redirection list, and ++the fail command may be used in an Exim filter file. ++ +++-------------------------------------------------------+ ++|allow_filter|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++Setting this option allows Exim to interpret redirection data that starts with ++"#Exim filter" or "#Sieve filter" as a set of filtering instructions. There are ++some features of Exim filter files that some administrators may wish to lock ++out; see the forbid_filter_xxx options below. ++ ++It is also possible to lock out Exim filters or Sieve filters while allowing ++the other type; see forbid_exim_filter and forbid_sieve_filter. ++ ++The filter is run using the uid and gid set by the generic user and group ++options. These take their defaults from the password data if check_local_user ++is set, so in the normal case of users' personal filter files, the filter is ++run as the relevant user. When allow_filter is set true, Exim insists that ++either check_local_user or user is set. ++ +++-------------------------------------------------------+ ++|allow_freeze|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++Setting this option allows the use of the freeze command in an Exim filter. ++This command is more normally encountered in system filters, and is disabled by ++default for redirection filters because it isn't something you usually want to ++let ordinary users do. ++ +++---------------------------------------------------------+ ++|check_ancestor|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++This option is concerned with handling generated addresses that are the same as ++some address in the list of redirection ancestors of the current address. ++Although it is turned off by default in the code, it is set in the default ++configuration file for handling users' .forward files. It is recommended for ++this use of the redirect router. ++ ++When check_ancestor is set, if a generated address (including the domain) is ++the same as any ancestor of the current address, it is replaced by a copy of ++the current address. This helps in the case where local part A is aliased to B, ++and B has a .forward file pointing back to A. For example, within a single ++domain, the local part "Joe.Bloggs" is aliased to "jb" and jb/.forward ++contains: ++ ++\Joe.Bloggs, <other item(s)> ++ ++Without the check_ancestor setting, either local part ("jb" or "joe.bloggs") ++gets processed once by each router and so ends up as it was originally. If "jb" ++is the real mailbox name, mail to "jb" gets delivered (having been turned into ++"joe.bloggs" by the .forward file and back to "jb" by the alias), but mail to ++"joe.bloggs" fails. Setting check_ancestor on the redirect router that handles ++the .forward file prevents it from turning "jb" back into "joe.bloggs" when ++that was the original address. See also the repeat_use option below. ++ +++----------------------------------------------------------+ ++|check_group|Use: redirect|Type: boolean|Default: see below| +++----------------------------------------------------------+ ++ ++When the file option is used, the group owner of the file is checked only when ++this option is set. The permitted groups are those listed in the owngroups ++option, together with the user's default group if check_local_user is set. If ++the file has the wrong group, routing is deferred. The default setting for this ++option is true if check_local_user is set and the modemask option permits the ++group write bit, or if the owngroups option is set. Otherwise it is false, and ++no group check occurs. ++ +++----------------------------------------------------------+ ++|check_owner|Use: redirect|Type: boolean|Default: see below| +++----------------------------------------------------------+ ++ ++When the file option is used, the owner of the file is checked only when this ++option is set. If check_local_user is set, the local user is permitted; ++otherwise the owner must be one of those listed in the owners option. The ++default value for this option is true if check_local_user or owners is set. ++Otherwise the default is false, and no owner check occurs. ++ +++-----------------------------------------------+ ++|data|Use: redirect|Type: string*|Default: unset| +++-----------------------------------------------+ ++ ++This option is mutually exclusive with file. One or other of them must be set, ++but not both. The contents of data are expanded, and then used as the list of ++forwarding items, or as a set of filtering instructions. If the expansion is ++forced to fail, or the result is an empty string or a string that has no effect ++(consists entirely of comments), the router declines. ++ ++When filtering instructions are used, the string must begin with "#Exim ++filter", and all comments in the string, including this initial one, must be ++terminated with newline characters. For example: ++ ++data = #Exim filter\n\ ++ if $h_to: contains Exim then save $home/mail/exim endif ++ ++If you are reading the data from a database where newlines cannot be included, ++you can use the ${sg} expansion item to turn the escape string of your choice ++into a newline. ++ +++--------------------------------------------------------------+ ++|directory_transport|Use: redirect|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++A redirect router sets up a direct delivery to a directory when a path name ++ending with a slash is specified as a new "address". The transport used is ++specified by this option, which, after expansion, must be the name of a ++configured transport. This should normally be an appendfile transport. ++ +++-----------------------------------------------+ ++|file|Use: redirect|Type: string*|Default: unset| +++-----------------------------------------------+ ++ ++This option specifies the name of a file that contains the redirection data. It ++is mutually exclusive with the data option. The string is expanded before use; ++if the expansion is forced to fail, the router declines. Other expansion ++failures cause delivery to be deferred. The result of a successful expansion ++must be an absolute path. The entire file is read and used as the redirection ++data. If the data is an empty string or a string that has no effect (consists ++entirely of comments), the router declines. ++ ++If the attempt to open the file fails with a "does not exist" error, Exim runs ++a check on the containing directory, unless ignore_enotdir is true (see below). ++If the directory does not appear to exist, delivery is deferred. This can ++happen when users' .forward files are in NFS-mounted directories, and there is ++a mount problem. If the containing directory does exist, but the file does not, ++the router declines. ++ +++---------------------------------------------------------+ ++|file_transport|Use: redirect|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++A redirect router sets up a direct delivery to a file when a path name not ++ending in a slash is specified as a new "address". The transport used is ++specified by this option, which, after expansion, must be the name of a ++configured transport. This should normally be an appendfile transport. When it ++is running, the file name is in $address_file. ++ +++-------------------------------------------------------------+ ++|filter_prepend_home|Use: redirect|Type: boolean|Default: true| +++-------------------------------------------------------------+ ++ ++When this option is true, if a save command in an Exim filter specifies a ++relative path, and $home is defined, it is automatically prepended to the ++relative path. If this option is set false, this action does not happen. The ++relative path is then passed to the transport unmodified. ++ +++-----------------------------------------------------------+ ++|forbid_blackhole|Use: redirect|Type: boolean|Default: false| +++-----------------------------------------------------------+ ++ ++If this option is true, the :blackhole: item may not appear in a redirection ++list. ++ +++-------------------------------------------------------------+ ++|forbid_exim_filter|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++If this option is set true, only Sieve filters are permitted when allow_filter ++is true. ++ +++------------------------------------------------------+ ++|forbid_file|Use: redirect|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If this option is true, this router may not generate a new address that ++specifies delivery to a local file or directory, either from a filter or from a ++conventional forward file. This option is forced to be true if one_time is set. ++It applies to Sieve filters as well as to Exim filters, but if true, it locks ++out the Sieve's "keep" facility. ++ +++---------------------------------------------------------------+ ++|forbid_filter_dlfunc|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------------------+ ++ ++If this option is true, string expansions in Exim filters are not allowed to ++make use of the dlfunc expansion facility to run dynamically loaded functions. ++ +++-------------------------------------------------------------------+ ++|forbid_filter_existstest|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------------------+ ++ ++If this option is true, string expansions in Exim filters are not allowed to ++make use of the exists condition or the stat expansion item. ++ +++-----------------------------------------------------------------+ ++|forbid_filter_logwrite|Use: redirect|Type: boolean|Default: false| +++-----------------------------------------------------------------+ ++ ++If this option is true, use of the logging facility in Exim filters is not ++permitted. Logging is in any case available only if the filter is being run ++under some unprivileged uid (which is normally the case for ordinary users' ++.forward files). ++ +++---------------------------------------------------------------+ ++|forbid_filter_lookup|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------------------+ ++ ++If this option is true, string expansions in Exim filter files are not allowed ++to make use of lookup items. ++ +++-------------------------------------------------------------+ ++|forbid_filter_perl|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++This option has an effect only if Exim is built with embedded Perl support. If ++it is true, string expansions in Exim filter files are not allowed to make use ++of the embedded Perl support. ++ +++-----------------------------------------------------------------+ ++|forbid_filter_readfile|Use: redirect|Type: boolean|Default: false| +++-----------------------------------------------------------------+ ++ ++If this option is true, string expansions in Exim filter files are not allowed ++to make use of readfile items. ++ +++-------------------------------------------------------------------+ ++|forbid_filter_readsocket|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------------------+ ++ ++If this option is true, string expansions in Exim filter files are not allowed ++to make use of readsocket items. ++ +++--------------------------------------------------------------+ ++|forbid_filter_reply|Use: redirect|Type: boolean|Default: false| +++--------------------------------------------------------------+ ++ ++If this option is true, this router may not generate an automatic reply ++message. Automatic replies can be generated only from Exim or Sieve filter ++files, not from traditional forward files. This option is forced to be true if ++one_time is set. ++ +++------------------------------------------------------------+ ++|forbid_filter_run|Use: redirect|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is true, string expansions in Exim filter files are not allowed ++to make use of run items. ++ +++---------------------------------------------------------+ ++|forbid_include|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is true, items of the form ++ ++:include:<path name> ++ ++are not permitted in non-filter redirection lists. ++ +++------------------------------------------------------+ ++|forbid_pipe|Use: redirect|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If this option is true, this router may not generate a new address which ++specifies delivery to a pipe, either from an Exim filter or from a conventional ++forward file. This option is forced to be true if one_time is set. ++ +++--------------------------------------------------------------+ ++|forbid_sieve_filter|Use: redirect|Type: boolean|Default: false| +++--------------------------------------------------------------+ ++ ++If this option is set true, only Exim filters are permitted when allow_filter ++is true. ++ +++-----------------------------------------------------------+ ++|forbid_smtp_code|Use: redirect|Type: boolean|Default: false| +++-----------------------------------------------------------+ ++ ++If this option is set true, any SMTP error codes that are present at the start ++of messages specified for ":defer:" or ":fail:" are quietly ignored, and the ++default codes (451 and 550, respectively) are always used. ++ +++---------------------------------------------------------------+ ++|hide_child_in_errmsg|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------------------+ ++ ++If this option is true, it prevents Exim from quoting a child address if it ++generates a bounce or delay message for it. Instead it says "an address ++generated from <the top level address>". Of course, this applies only to ++bounces generated locally. If a message is forwarded to another host, its ++bounce may well quote the generated address. ++ +++--------------------------------------------------------+ ++|ignore_eacces|Use: redirect|Type: boolean|Default: false| +++--------------------------------------------------------+ ++ ++If this option is set and an attempt to open a redirection file yields the ++EACCES error (permission denied), the redirect router behaves as if the file ++did not exist. ++ +++---------------------------------------------------------+ ++|ignore_enotdir|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is set and an attempt to open a redirection file yields the ++ENOTDIR error (something on the path is not a directory), the redirect router ++behaves as if the file did not exist. ++ ++Setting ignore_enotdir has another effect as well: When a redirect router that ++has the file option set discovers that the file does not exist (the ENOENT ++error), it tries to stat() the parent directory, as a check against unmounted ++NFS directories. If the parent can not be statted, delivery is deferred. ++However, it seems wrong to do this check when ignore_enotdir is set, because ++that option tells Exim to ignore "something on the path is not a directory" ++(the ENOTDIR error). This is a confusing area, because it seems that some ++operating systems give ENOENT where others give ENOTDIR. ++ +++-----------------------------------------------------------+ ++|include_directory|Use: redirect|Type: string|Default: unset| +++-----------------------------------------------------------+ ++ ++If this option is set, the path names of any :include: items in a redirection ++list must start with this directory. ++ +++-------------------------------------------------------+ ++|modemask|Use: redirect|Type: octal integer|Default: 022| +++-------------------------------------------------------+ ++ ++This specifies mode bits which must not be set for a file specified by the file ++option. If any of the forbidden bits are set, delivery is deferred. ++ +++---------------------------------------------------+ ++|one_time|Use: redirect|Type: boolean|Default: false| +++---------------------------------------------------+ ++ ++Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection ++files each time it tries to deliver a message causes a problem when one or more ++of the generated addresses fails be delivered at the first attempt. The problem ++is not one of duplicate delivery - Exim is clever enough to handle that - but ++of what happens when the redirection list changes during the time that the ++message is on Exim's queue. This is particularly true in the case of mailing ++lists, where new subscribers might receive copies of messages that were posted ++before they subscribed. ++ ++If one_time is set and any addresses generated by the router fail to deliver at ++the first attempt, the failing addresses are added to the message as "top ++level" addresses, and the parent address that generated them is marked ++"delivered". Thus, redirection does not happen again at the next delivery ++attempt. ++ ++Warning 1: Any header line addition or removal that is specified by this router ++would be lost if delivery did not succeed at the first attempt. For this ++reason, the headers_add and headers_remove generic options are not permitted ++when one_time is set. ++ ++Warning 2: To ensure that the router generates only addresses (as opposed to ++pipe or file deliveries or auto-replies) forbid_file, forbid_pipe, and ++forbid_filter_reply are forced to be true when one_time is set. ++ ++Warning 3: The unseen generic router option may not be set with one_time. ++ ++The original top-level address is remembered with each of the generated ++addresses, and is output in any log messages. However, any intermediate parent ++addresses are not recorded. This makes a difference to the log only if ++all_parents log selector is set. It is expected that one_time will typically be ++used for mailing lists, where there is normally just one level of expansion. ++ +++-----------------------------------------------------+ ++|owners|Use: redirect|Type: string list|Default: unset| +++-----------------------------------------------------+ ++ ++This specifies a list of permitted owners for the file specified by file. This ++list is in addition to the local user when check_local_user is set. See ++check_owner above. ++ +++--------------------------------------------------------+ ++|owngroups|Use: redirect|Type: string list|Default: unset| +++--------------------------------------------------------+ ++ ++This specifies a list of permitted groups for the file specified by file. The ++list is in addition to the local user's primary group when check_local_user is ++set. See check_group above. ++ +++---------------------------------------------------------+ ++|pipe_transport|Use: redirect|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++A redirect router sets up a direct delivery to a pipe when a string starting ++with a vertical bar character is specified as a new "address". The transport ++used is specified by this option, which, after expansion, must be the name of a ++configured transport. This should normally be a pipe transport. When the ++transport is run, the pipe command is in $address_pipe. ++ +++---------------------------------------------------------+ ++|qualify_domain|Use: redirect|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++If this option is set, and an unqualified address (one without a domain) is ++generated, and that address would normally be qualified by the global setting ++in qualify_recipient, it is instead qualified with the domain specified by ++expanding this string. If the expansion fails, the router declines. If you want ++to revert to the default, you can have the expansion generate ++$qualify_recipient. ++ ++This option applies to all unqualified addresses generated by Exim filters, but ++for traditional .forward files, it applies only to addresses that are not ++preceded by a backslash. Sieve filters cannot generate unqualified addresses. ++ +++------------------------------------------------------------------+ ++|qualify_preserve_domain|Use: redirect|Type: boolean|Default: false| +++------------------------------------------------------------------+ ++ ++If this option is set, the router's local qualify_domain option must not be set ++(a configuration error occurs if it is). If an unqualified address (one without ++a domain) is generated, it is qualified with the domain of the parent address ++(the immediately preceding ancestor) instead of the global qualify_recipient ++value. In the case of a traditional .forward file, this applies whether or not ++the address is preceded by a backslash. ++ +++----------------------------------------------------+ ++|repeat_use|Use: redirect|Type: boolean|Default: true| +++----------------------------------------------------+ ++ ++If this option is set false, the router is skipped for a child address that has ++any ancestor that was routed by this router. This test happens before any of ++the other preconditions are tested. Exim's default anti-looping rules skip only ++when the ancestor is the same as the current address. See also check_ancestor ++above and the generic redirect_router option. ++ +++----------------------------------------------------------+ ++|reply_transport|Use: redirect|Type: string*|Default: unset| +++----------------------------------------------------------+ ++ ++A redirect router sets up an automatic reply when a mail or vacation command is ++used in a filter file. The transport used is specified by this option, which, ++after expansion, must be the name of a configured transport. This should ++normally be an autoreply transport. Other transports are unlikely to do ++anything sensible or useful. ++ +++-------------------------------------------------+ ++|rewrite|Use: redirect|Type: boolean|Default: true| +++-------------------------------------------------+ ++ ++If this option is set false, addresses generated by the router are not subject ++to address rewriting. Otherwise, they are treated like new addresses and are ++rewritten according to the global rewriting rules. ++ +++-----------------------------------------------------------+ ++|sieve_subaddress|Use: redirect|Type: string*|Default: unset| +++-----------------------------------------------------------+ ++ ++The value of this option is passed to a Sieve filter to specify the :subaddress ++part of an address. ++ +++------------------------------------------------------------+ ++|sieve_useraddress|Use: redirect|Type: string*|Default: unset| +++------------------------------------------------------------+ ++ ++The value of this option is passed to a Sieve filter to specify the :user part ++of an address. However, if it is unset, the entire original local part ++(including any prefix or suffix) is used for :user. ++ +++-------------------------------------------------------------------+ ++|sieve_vacation_directory|Use: redirect|Type: string*|Default: unset| +++-------------------------------------------------------------------+ ++ ++To enable the "vacation" extension for Sieve filters, you must set ++sieve_vacation_directory to the directory where vacation databases are held (do ++not put anything else in that directory), and ensure that the reply_transport ++option refers to an autoreply transport. Each user needs their own directory; ++Exim will create it if necessary. ++ +++-------------------------------------------------------------+ ++|skip_syntax_errors|Use: redirect|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++If skip_syntax_errors is set, syntactically malformed addresses in non-filter ++redirection data are skipped, and each failing address is logged. If ++syntax_errors_to is set, a message is sent to the address it defines, giving ++details of the failures. If syntax_errors_text is set, its contents are ++expanded and placed at the head of the error message generated by ++syntax_errors_to. Usually it is appropriate to set syntax_errors_to to be the ++same address as the generic errors_to option. The skip_syntax_errors option is ++often used when handling mailing lists. ++ ++If all the addresses in a redirection list are skipped because of syntax ++errors, the router declines to handle the original address, and it is passed to ++the following routers. ++ ++If skip_syntax_errors is set when an Exim filter is interpreted, any syntax ++error in the filter causes filtering to be abandoned without any action being ++taken. The incident is logged, and the router declines to handle the address, ++so it is passed to the following routers. ++ ++Syntax errors in a Sieve filter file cause the "keep" action to occur. This ++action is specified by RFC 3028. The values of skip_syntax_errors, ++syntax_errors_to, and syntax_errors_text are not used. ++ ++skip_syntax_errors can be used to specify that errors in users' forward lists ++or filter files should not prevent delivery. The syntax_errors_to option, used ++with an address that does not get redirected, can be used to notify users of ++these errors, by means of a router like this: ++ ++userforward: ++ driver = redirect ++ allow_filter ++ check_local_user ++ file = $home/.forward ++ file_transport = address_file ++ pipe_transport = address_pipe ++ reply_transport = address_reply ++ no_verify ++ skip_syntax_errors ++ syntax_errors_to = real-$local_part@$domain ++ syntax_errors_text = \ ++ This is an automatically generated message. An error has\n\ ++ been found in your .forward file. Details of the error are\n\ ++ reported below. While this error persists, you will receive\n\ ++ a copy of this message for every message that is addressed\n\ ++ to you. If your .forward file is a filter file, or if it is\n\ ++ a non-filter file containing no valid forwarding addresses,\n\ ++ a copy of each incoming message will be put in your normal\n\ ++ mailbox. If a non-filter file contains at least one valid\n\ ++ forwarding address, forwarding to the valid addresses will\n\ ++ happen, and those will be the only deliveries that occur. ++ ++You also need a router to ensure that local addresses that are prefixed by ++"real-" are recognized, but not forwarded or filtered. For example, you could ++put this immediately before the userforward router: ++ ++real_localuser: ++ driver = accept ++ check_local_user ++ local_part_prefix = real- ++ transport = local_delivery ++ ++For security, it would probably be a good idea to restrict the use of this ++router to locally-generated messages, using a condition such as this: ++ ++ condition = ${if match {$sender_host_address}\ ++ {\N^(|127\.0\.0\.1)$\N}} ++ +++-------------------------------------------------------------+ ++|syntax_errors_text|Use: redirect|Type: string*|Default: unset| +++-------------------------------------------------------------+ ++ ++See skip_syntax_errors above. ++ +++----------------------------------------------------------+ ++|syntax_errors_to|Use: redirect|Type: string|Default: unset| +++----------------------------------------------------------+ ++ ++See skip_syntax_errors above. ++ ++ ++ ++=============================================================================== ++23. ENVIRONMENT FOR RUNNING LOCAL TRANSPORTS ++ ++Local transports handle deliveries to files and pipes. (The autoreply transport ++can be thought of as similar to a pipe.) Exim always runs transports in ++subprocesses, under specified uids and gids. Typical deliveries to local ++mailboxes run under the uid and gid of the local user. ++ ++Exim also sets a specific current directory while running the transport; for ++some transports a home directory setting is also relevant. The pipe transport ++is the only one that sets up environment variables; see section 29.4 for ++details. ++ ++The values used for the uid, gid, and the directories may come from several ++different places. In many cases, the router that handles the address associates ++settings with that address as a result of its check_local_user, group, or user ++options. However, values may also be given in the transport's own ++configuration, and these override anything that comes from the router. ++ ++ ++23.1 Concurrent deliveries ++-------------------------- ++ ++If two different messages for the same local recipient arrive more or less ++simultaneously, the two delivery processes are likely to run concurrently. When ++the appendfile transport is used to write to a file, Exim applies locking rules ++to stop concurrent processes from writing to the same file at the same time. ++ ++However, when you use a pipe transport, it is up to you to arrange any locking ++that is needed. Here is a silly example: ++ ++my_transport: ++ driver = pipe ++ command = /bin/sh -c 'cat >>/some/file' ++ ++This is supposed to write the message at the end of the file. However, if two ++messages arrive at the same time, the file will be scrambled. You can use the ++exim_lock utility program (see section 52.15) to lock a file using the same ++algorithm that Exim itself uses. ++ ++ ++23.2 Uids and gids ++------------------ ++ ++All transports have the options group and user. If group is set, it overrides ++any group that the router set in the address, even if user is not set for the ++transport. This makes it possible, for example, to run local mail delivery ++under the uid of the recipient (set by the router), but in a special group (set ++by the transport). For example: ++ ++# Routers ... ++# User/group are set by check_local_user in this router ++local_users: ++ driver = accept ++ check_local_user ++ transport = group_delivery ++ ++# Transports ... ++# This transport overrides the group ++group_delivery: ++ driver = appendfile ++ file = /var/spool/mail/$local_part ++ group = mail ++ ++If user is set for a transport, its value overrides what is set in the address ++by the router. If user is non-numeric and group is not set, the gid associated ++with the user is used. If user is numeric, group must be set. ++ ++When the uid is taken from the transport's configuration, the initgroups() ++function is called for the groups associated with that uid if the initgroups ++option is set for the transport. When the uid is not specified by the ++transport, but is associated with the address by a router, the option for ++calling initgroups() is taken from the router configuration. ++ ++The pipe transport contains the special option pipe_as_creator. If this is set ++and user is not set, the uid of the process that called Exim to receive the ++message is used, and if group is not set, the corresponding original gid is ++also used. ++ ++This is the detailed preference order for obtaining a gid; the first of the ++following that is set is used: ++ ++ * A group setting of the transport; ++ ++ * A group setting of the router; ++ ++ * A gid associated with a user setting of the router, either as a result of ++ check_local_user or an explicit non-numeric user setting; ++ ++ * The group associated with a non-numeric user setting of the transport; ++ ++ * In a pipe transport, the creator's gid if deliver_as_creator is set and the ++ uid is the creator's uid; ++ ++ * The Exim gid if the Exim uid is being used as a default. ++ ++If, for example, the user is specified numerically on the router and there are ++no group settings, no gid is available. In this situation, an error occurs. ++This is different for the uid, for which there always is an ultimate default. ++The first of the following that is set is used: ++ ++ * A user setting of the transport; ++ ++ * In a pipe transport, the creator's uid if deliver_as_creator is set; ++ ++ * A user setting of the router; ++ ++ * A check_local_user setting of the router; ++ ++ * The Exim uid. ++ ++Of course, an error will still occur if the uid that is chosen is on the ++never_users list. ++ ++ ++23.3 Current and home directories ++--------------------------------- ++ ++Routers may set current and home directories for local transports by means of ++the transport_current_directory and transport_home_directory options. However, ++if the transport's current_directory or home_directory options are set, they ++override the router's values. In detail, the home directory for a local ++transport is taken from the first of these values that is set: ++ ++ * The home_directory option on the transport; ++ ++ * The transport_home_directory option on the router; ++ ++ * The password data if check_local_user is set on the router; ++ ++ * The router_home_directory option on the router. ++ ++The current directory is taken from the first of these values that is set: ++ ++ * The current_directory option on the transport; ++ ++ * The transport_current_directory option on the router. ++ ++If neither the router nor the transport sets a current directory, Exim uses the ++value of the home directory, if it is set. Otherwise it sets the current ++directory to / before running a local transport. ++ ++ ++23.4 Expansion variables derived from the address ++------------------------------------------------- ++ ++Normally a local delivery is handling a single address, and in that case the ++variables such as $domain and $local_part are set during local deliveries. ++However, in some circumstances more than one address may be handled at once ++(for example, while writing batch SMTP for onward transmission by some other ++means). In this case, the variables associated with the local part are never ++set, $domain is set only if all the addresses have the same domain, and ++$original_domain is never set. ++ ++ ++ ++=============================================================================== ++24. GENERIC OPTIONS FOR TRANSPORTS ++ ++The following generic options apply to all transports: ++ +++------------------------------------------------------+ ++|body_only|Use: transports|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If this option is set, the message's headers are not transported. It is ++mutually exclusive with headers_only. If it is used with the appendfile or pipe ++transports, the settings of message_prefix and message_suffix should be ++checked, because this option does not automatically suppress them. ++ +++--------------------------------------------------------------+ ++|current_directory|Use: transports|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++This specifies the current directory that is to be set while running the ++transport, overriding any value that may have been set by the router. If the ++expansion fails for any reason, including forced failure, an error is logged, ++and delivery is deferred. ++ +++------------------------------------------------------------+ ++|disable_logging|Use: transports|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is set true, nothing is logged for any deliveries by the ++transport or for any transport errors. You should not set this option unless ++you really, really know what you are doing. ++ +++--------------------------------------------------------+ ++|debug_print|Use: transports|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++If this option is set and debugging is enabled (see the -d command line ++option), the string is expanded and included in the debugging output when the ++transport is run. If expansion of the string fails, the error message is ++written to the debugging output, and Exim carries on processing. This facility ++is provided to help with checking out the values of variables and so on when ++debugging driver configurations. For example, if a headers_add option is not ++working properly, debug_print could be used to output the variables it ++references. A newline is added to the text if it does not end with one. The ++variables $transport_name and $router_name contain the name of the transport ++and the router that called it. ++ +++--------------------------------------------------------------+ ++|delivery_date_add|Use: transports|Type: boolean|Default: false| +++--------------------------------------------------------------+ ++ ++If this option is true, a Delivery-date: header is added to the message. This ++gives the actual time the delivery was made. As this is not a standard header, ++Exim has a configuration option (delivery_date_remove) which requests its ++removal from incoming messages, so that delivered messages can safely be resent ++to other recipients. ++ +++--------------------------------------------------+ ++|driver|Use: transports|Type: string|Default: unset| +++--------------------------------------------------+ ++ ++This specifies which of the available transport drivers is to be used. There is ++no default, and this option must be set for every transport. ++ +++------------------------------------------------------------+ ++|envelope_to_add|Use: transports|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is true, an Envelope-to: header is added to the message. This ++gives the original address(es) in the incoming envelope that caused this ++delivery to happen. More than one address may be present if the transport is ++configured to handle several addresses at once, or if more than one original ++address was redirected to the same final address. As this is not a standard ++header, Exim has a configuration option (envelope_to_remove) which requests its ++removal from incoming messages, so that delivered messages can safely be resent ++to other recipients. ++ +++-------------------------------------------------------+ ++|group|Use: transports|Type: string*|Default: Exim group| +++-------------------------------------------------------+ ++ ++This option specifies a gid for running the transport process, overriding any ++value that the router supplies, and also overriding any value associated with ++user (see below). ++ +++--------------------------------------------------------+ ++|headers_add|Use: transports|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option specifies a string of text that is expanded and added to the header ++portion of a message as it is transported, as described in section 46.17. ++Additional header lines can also be specified by routers. If the result of the ++expansion is an empty string, or if the expansion is forced to fail, no action ++is taken. Other expansion failures are treated as errors and cause the delivery ++to be deferred. ++ ++Unlike most options, headers_add can be specified multiple times for a ++transport; all listed headers are added. ++ +++---------------------------------------------------------+ ++|headers_only|Use: transports|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is set, the message's body is not transported. It is mutually ++exclusive with body_only. If it is used with the appendfile or pipe transports, ++the settings of message_prefix and message_suffix should be checked, since this ++option does not automatically suppress them. ++ +++-----------------------------------------------------------+ ++|headers_remove|Use: transports|Type: string*|Default: unset| +++-----------------------------------------------------------+ ++ ++This option specifies a string that is expanded into a list of header names; ++these headers are omitted from the message as it is transported, as described ++in section 46.17. Header removal can also be specified by routers. If the ++result of the expansion is an empty string, or if the expansion is forced to ++fail, no action is taken. Other expansion failures are treated as errors and ++cause the delivery to be deferred. ++ ++Unlike most options, headers_remove can be specified multiple times for a ++router; all listed headers are added. ++ +++-----------------------------------------------------------+ ++|headers_rewrite|Use: transports|Type: string|Default: unset| +++-----------------------------------------------------------+ ++ ++This option allows addresses in header lines to be rewritten at transport time, ++that is, as the message is being copied to its destination. The contents of the ++option are a colon-separated list of rewriting rules. Each rule is in exactly ++the same form as one of the general rewriting rules that are applied when a ++message is received. These are described in chapter 31. For example, ++ ++headers_rewrite = a@b c@d f : \ ++ x@y w@z ++ ++changes a@b into c@d in From: header lines, and x@y into w@z in all ++address-bearing header lines. The rules are applied to the header lines just ++before they are written out at transport time, so they affect only those copies ++of the message that pass through the transport. However, only the message's ++original header lines, and any that were added by a system filter, are ++rewritten. If a router or transport adds header lines, they are not affected by ++this option. These rewriting rules are not applied to the envelope. You can ++change the return path using return_path, but you cannot change envelope ++recipients at this time. ++ +++-----------------------------------------------------------+ ++|home_directory|Use: transports|Type: string*|Default: unset| +++-----------------------------------------------------------+ ++ ++This option specifies a home directory setting for a local transport, ++overriding any value that may be set by the router. The home directory is ++placed in $home while expanding the transport's private options. It is also ++used as the current directory if no current directory is set by the ++current_directory option on the transport or the transport_current_directory ++option on the router. If the expansion fails for any reason, including forced ++failure, an error is logged, and delivery is deferred. ++ +++-------------------------------------------------------+ ++|initgroups|Use: transports|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++If this option is true and the uid for the delivery process is provided by the ++transport, the initgroups() function is called when running the transport to ++ensure that any additional groups associated with the uid are set up. ++ +++-----------------------------------------------------------+ ++|message_size_limit|Use: transports|Type: string*|Default: 0| +++-----------------------------------------------------------+ ++ ++This option controls the size of messages passed through the transport. It is ++expanded before use; the result of the expansion must be a sequence of decimal ++digits, optionally followed by K or M. If the expansion fails for any reason, ++including forced failure, or if the result is not of the required form, ++delivery is deferred. If the value is greater than zero and the size of a ++message exceeds this limit, the address is failed. If there is any chance that ++the resulting bounce message could be routed to the same transport, you should ++ensure that return_size_limit is less than the transport's message_size_limit, ++as otherwise the bounce message will fail to get delivered. ++ +++-----------------------------------------------------------------+ ++|rcpt_include_affixes|Use: transports|Type: boolean|Default: false| +++-----------------------------------------------------------------+ ++ ++When this option is false (the default), and an address that has had any ++affixes (prefixes or suffixes) removed from the local part is delivered by any ++form of SMTP or LMTP, the affixes are not included. For example, if a router ++that contains ++ ++local_part_prefix = *- ++ ++routes the address abc-xyz@some.domain to an SMTP transport, the envelope is ++delivered with ++ ++RCPT TO:<xyz@some.domain> ++ ++This is also the case when an ACL-time callout is being used to verify a ++recipient address. However, if rcpt_include_affixes is set true, the whole ++local part is included in the RCPT command. This option applies to BSMTP ++deliveries by the appendfile and pipe transports as well as to the lmtp and ++smtp transports. ++ +++---------------------------------------------------------------------+ ++|retry_use_local_part|Use: transports|Type: boolean|Default: see below| +++---------------------------------------------------------------------+ ++ ++When a delivery suffers a temporary failure, a retry record is created in ++Exim's hints database. For remote deliveries, the key for the retry record is ++based on the name and/or IP address of the failing remote host. For local ++deliveries, the key is normally the entire address, including both the local ++part and the domain. This is suitable for most common cases of local delivery ++temporary failure - for example, exceeding a mailbox quota should delay only ++deliveries to that mailbox, not to the whole domain. ++ ++However, in some special cases you may want to treat a temporary local delivery ++as a failure associated with the domain, and not with a particular local part. ++(For example, if you are storing all mail for some domain in files.) You can do ++this by setting retry_use_local_part false. ++ ++For all the local transports, its default value is true. For remote transports, ++the default value is false for tidiness, but changing the value has no effect ++on a remote transport in the current implementation. ++ +++--------------------------------------------------------+ ++|return_path|Use: transports|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++If this option is set, the string is expanded at transport time and replaces ++the existing return path (envelope sender) value in the copy of the message ++that is being delivered. An empty return path is permitted. This feature is ++designed for remote deliveries, where the value of this option is used in the ++SMTP MAIL command. If you set return_path for a local transport, the only ++effect is to change the address that is placed in the Return-path: header line, ++if one is added to the message (see the next option). ++ ++Note: A changed return path is not logged unless you add ++return_path_on_delivery to the log selector. ++ ++The expansion can refer to the existing value via $return_path. This is either ++the message's envelope sender, or an address set by the errors_to option on a ++router. If the expansion is forced to fail, no replacement occurs; if it fails ++for another reason, delivery is deferred. This option can be used to support ++VERP (Variable Envelope Return Paths) - see section 49.6. ++ ++Note: If a delivery error is detected locally, including the case when a remote ++server rejects a message at SMTP time, the bounce message is not sent to the ++value of this option. It is sent to the previously set errors address. This ++defaults to the incoming sender address, but can be changed by setting ++errors_to in a router. ++ +++------------------------------------------------------------+ ++|return_path_add|Use: transports|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is true, a Return-path: header is added to the message. Although ++the return path is normally available in the prefix line of BSD mailboxes, this ++is commonly not displayed by MUAs, and so the user does not have easy access to ++it. ++ ++RFC 2821 states that the Return-path: header is added to a message "when the ++delivery SMTP server makes the final delivery". This implies that this header ++should not be present in incoming messages. Exim has a configuration option, ++return_path_remove, which requests removal of this header from incoming ++messages, so that delivered messages can safely be resent to other recipients. ++ +++-------------------------------------------------------------+ ++|shadow_condition|Use: transports|Type: string*|Default: unset| +++-------------------------------------------------------------+ ++ ++See shadow_transport below. ++ +++------------------------------------------------------------+ ++|shadow_transport|Use: transports|Type: string|Default: unset| +++------------------------------------------------------------+ ++ ++A local transport may set the shadow_transport option to the name of another ++local transport. Shadow remote transports are not supported. ++ ++Whenever a delivery to the main transport succeeds, and either shadow_condition ++is unset, or its expansion does not result in the empty string or one of the ++strings "0" or "no" or "false", the message is also passed to the shadow ++transport, with the same delivery address or addresses. If expansion fails, no ++action is taken except that non-forced expansion failures cause a log line to ++be written. ++ ++The result of the shadow transport is discarded and does not affect the ++subsequent processing of the message. Only a single level of shadowing is ++provided; the shadow_transport option is ignored on any transport when it is ++running as a shadow. Options concerned with output from pipes are also ignored. ++The log line for the successful delivery has an item added on the end, of the ++form ++ ++ST=<shadow transport name> ++ ++If the shadow transport did not succeed, the error message is put in ++parentheses afterwards. Shadow transports can be used for a number of different ++purposes, including keeping more detailed log information than Exim normally ++provides, and implementing automatic acknowledgment policies based on message ++headers that some sites insist on. ++ +++-------------------------------------------------------------+ ++|transport_filter|Use: transports|Type: string*|Default: unset| +++-------------------------------------------------------------+ ++ ++This option sets up a filtering (in the Unix shell sense) process for messages ++at transport time. It should not be confused with mail filtering as set up by ++individual users or via a system filter. ++ ++When the message is about to be written out, the command specified by ++transport_filter is started up in a separate, parallel process, and the entire ++message, including the header lines, is passed to it on its standard input ++(this in fact is done from a third process, to avoid deadlock). The command ++must be specified as an absolute path. ++ ++The lines of the message that are written to the transport filter are ++terminated by newline ("\n"). The message is passed to the filter before any ++SMTP-specific processing, such as turning "\n" into "\r\n" and escaping lines ++beginning with a dot, and also before any processing implied by the settings of ++check_string and escape_string in the appendfile or pipe transports. ++ ++The standard error for the filter process is set to the same destination as its ++standard output; this is read and written to the message's ultimate ++destination. The process that writes the message to the filter, the filter ++itself, and the original process that reads the result and delivers it are all ++run in parallel, like a shell pipeline. ++ ++The filter can perform any transformations it likes, but of course should take ++care not to break RFC 2822 syntax. Exim does not check the result, except to ++test for a final newline when SMTP is in use. All messages transmitted over ++SMTP must end with a newline, so Exim supplies one if it is missing. ++ ++A transport filter can be used to provide content-scanning on a per-user basis ++at delivery time if the only required effect of the scan is to modify the ++message. For example, a content scan could insert a new header line containing ++a spam score. This could be interpreted by a filter in the user's MUA. It is ++not possible to discard a message at this stage. ++ ++A problem might arise if the filter increases the size of a message that is ++being sent down an SMTP connection. If the receiving SMTP server has indicated ++support for the SIZE parameter, Exim will have sent the size of the message at ++the start of the SMTP session. If what is actually sent is substantially more, ++the server might reject the message. This can be worked round by setting the ++size_addition option on the smtp transport, either to allow for additions to ++the message, or to disable the use of SIZE altogether. ++ ++The value of the transport_filter option is the command string for starting the ++filter, which is run directly from Exim, not under a shell. The string is ++parsed by Exim in the same way as a command string for the pipe transport: Exim ++breaks it up into arguments and then expands each argument separately (see ++section 29.3). Any kind of expansion failure causes delivery to be deferred. ++The special argument $pipe_addresses is replaced by a number of arguments, one ++for each address that applies to this delivery. (This isn't an ideal name for ++this feature here, but as it was already implemented for the pipe transport, it ++seemed sensible not to change it.) ++ ++The expansion variables $host and $host_address are available when the ++transport is a remote one. They contain the name and IP address of the host to ++which the message is being sent. For example: ++ ++transport_filter = /some/directory/transport-filter.pl \ ++ $host $host_address $sender_address $pipe_addresses ++ ++Two problems arise if you want to use more complicated expansion items to ++generate transport filter commands, both of which due to the fact that the ++command is split up before expansion. ++ ++ * If an expansion item contains white space, you must quote it, so that it is ++ all part of the same command item. If the entire option setting is one such ++ expansion item, you have to take care what kind of quoting you use. For ++ example: ++ ++ transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}' ++ ++ This runs the command /bin/cmd1 if the host name is a.b.c, and /bin/cmd2 ++ otherwise. If double quotes had been used, they would have been stripped by ++ Exim when it read the option's value. When the value is used, if the single ++ quotes were missing, the line would be split into two items, "/bin/cmd${if" ++ and "eq{$host}{a.b.c}{1}{2}", and an error would occur when Exim tried to ++ expand the first one. ++ ++ * Except for the special case of $pipe_addresses that is mentioned above, an ++ expansion cannot generate multiple arguments, or a command name followed by ++ arguments. Consider this example: ++ ++ transport_filter = ${lookup{$host}lsearch{/a/file}\ ++ {$value}{/bin/cat}} ++ ++ The result of the lookup is interpreted as the name of the command, even if ++ it contains white space. The simplest way round this is to use a shell: ++ ++ transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\ ++ {$value}{/bin/cat}} ++ ++The filter process is run under the same uid and gid as the normal delivery. ++For remote deliveries this is the Exim uid/gid by default. The command should ++normally yield a zero return code. Transport filters are not supposed to fail. ++A non-zero code is taken to mean that the transport filter encountered some ++serious problem. Delivery of the message is deferred; the message remains on ++the queue and is tried again later. It is not possible to cause a message to be ++bounced from a transport filter. ++ ++If a transport filter is set on an autoreply transport, the original message is ++passed through the filter as it is being copied into the newly generated ++message, which happens if the return_message option is set. ++ +++---------------------------------------------------------------+ ++|transport_filter_timeout|Use: transports|Type: time|Default: 5m| +++---------------------------------------------------------------+ ++ ++When Exim is reading the output of a transport filter, it applies a timeout ++that can be set by this option. Exceeding the timeout is normally treated as a ++temporary delivery failure. However, if a transport filter is used with a pipe ++transport, a timeout in the transport filter is treated in the same way as a ++timeout in the pipe command itself. By default, a timeout is a hard error, but ++if the pipe transport's timeout_defer option is set true, it becomes a ++temporary error. ++ +++-----------------------------------------------------+ ++|user|Use: transports|Type: string*|Default: Exim user| +++-----------------------------------------------------+ ++ ++This option specifies the user under whose uid the delivery process is to be ++run, overriding any uid that may have been set by the router. If the user is ++given as a name, the uid is looked up from the password data, and the ++associated group is taken as the value of the gid to be used if the group ++option is not set. ++ ++For deliveries that use local transports, a user and group are normally ++specified explicitly or implicitly (for example, as a result of ++check_local_user) by the router or transport. ++ ++For remote transports, you should leave this option unset unless you really are ++sure you know what you are doing. When a remote transport is running, it needs ++to be able to access Exim's hints databases, because each host may have its own ++retry data. ++ ++ ++ ++=============================================================================== ++25. ADDRESS BATCHING IN LOCAL TRANSPORTS ++ ++The only remote transport (smtp) is normally configured to handle more than one ++address at a time, so that when several addresses are routed to the same remote ++host, just one copy of the message is sent. Local transports, however, normally ++handle one address at a time. That is, a separate instance of the transport is ++run for each address that is routed to the transport. A separate copy of the ++message is delivered each time. ++ ++In special cases, it may be desirable to handle several addresses at once in a ++local transport, for example: ++ ++ * In an appendfile transport, when storing messages in files for later ++ delivery by some other means, a single copy of the message with multiple ++ recipients saves space. ++ ++ * In an lmtp transport, when delivering over "local SMTP" to some process, a ++ single copy saves time, and is the normal way LMTP is expected to work. ++ ++ * In a pipe transport, when passing the message to a scanner program or to ++ some other delivery mechanism such as UUCP, multiple recipients may be ++ acceptable. ++ ++These three local transports all have the same options for controlling multiple ++("batched") deliveries, namely batch_max and batch_id. To save repeating the ++information for each transport, these options are described here. ++ ++The batch_max option specifies the maximum number of addresses that can be ++delivered together in a single run of the transport. Its default value is one ++(no batching). When more than one address is routed to a transport that has a ++batch_max value greater than one, the addresses are delivered in a batch (that ++is, in a single run of the transport with multiple recipients), subject to ++certain conditions: ++ ++ * If any of the transport's options contain a reference to $local_part, no ++ batching is possible. ++ ++ * If any of the transport's options contain a reference to $domain, only ++ addresses with the same domain are batched. ++ ++ * If batch_id is set, it is expanded for each address, and only those ++ addresses with the same expanded value are batched. This allows you to ++ specify customized batching conditions. Failure of the expansion for any ++ reason, including forced failure, disables batching, but it does not stop ++ the delivery from taking place. ++ ++ * Batched addresses must also have the same errors address (where to send ++ delivery errors), the same header additions and removals, the same user and ++ group for the transport, and if a host list is present, the first host must ++ be the same. ++ ++In the case of the appendfile and pipe transports, batching applies both when ++the file or pipe command is specified in the transport, and when it is ++specified by a redirect router, but all the batched addresses must of course be ++routed to the same file or pipe command. These two transports have an option ++called use_bsmtp, which causes them to deliver the message in "batched SMTP" ++format, with the envelope represented as SMTP commands. The check_string and ++escape_string options are forced to the values ++ ++check_string = "." ++escape_string = ".." ++ ++when batched SMTP is in use. A full description of the batch SMTP mechanism is ++given in section 47.10. The lmtp transport does not have a use_bsmtp option, ++because it always delivers using the SMTP protocol. ++ ++If the generic envelope_to_add option is set for a batching transport, the ++Envelope-to: header that is added to the message contains all the addresses ++that are being processed together. If you are using a batching appendfile ++transport without use_bsmtp, the only way to preserve the recipient addresses ++is to set the envelope_to_add option. ++ ++If you are using a pipe transport without BSMTP, and setting the transport's ++command option, you can include $pipe_addresses as part of the command. This is ++not a true variable; it is a bit of magic that causes each of the recipient ++addresses to be inserted into the command as a separate argument. This provides ++a way of accessing all the addresses that are being delivered in the batch. ++Note: This is not possible for pipe commands that are specified by a redirect ++router. ++ ++ ++ ++=============================================================================== ++26. THE APPENDFILE TRANSPORT ++ ++The appendfile transport delivers a message by appending it to an existing ++file, or by creating an entirely new file in a specified directory. Single ++files to which messages are appended can be in the traditional Unix mailbox ++format, or optionally in the MBX format supported by the Pine MUA and ++University of Washington IMAP daemon, inter alia. When each message is being ++delivered as a separate file, "maildir" format can optionally be used to give ++added protection against failures that happen part-way through the delivery. A ++third form of separate-file delivery known as "mailstore" is also supported. ++For all file formats, Exim attempts to create as many levels of directory as ++necessary, provided that create_directory is set. ++ ++The code for the optional formats is not included in the Exim binary by ++default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or ++SUPPORT_MAILSTORE in Local/Makefile to have the appropriate code included. ++ ++Exim recognizes system quota errors, and generates an appropriate message. Exim ++also supports its own quota control within the transport, for use when the ++system facility is unavailable or cannot be used for some reason. ++ ++If there is an error while appending to a file (for example, quota exceeded or ++partition filled), Exim attempts to reset the file's length and last ++modification time back to what they were before. If there is an error while ++creating an entirely new file, the new file is removed. ++ ++Before appending to a file, a number of security checks are made, and the file ++is locked. A detailed description is given below, after the list of private ++options. ++ ++The appendfile transport is most commonly used for local deliveries to users' ++mailboxes. However, it can also be used as a pseudo-remote transport for ++putting messages into files for remote delivery by some means other than Exim. ++"Batch SMTP" format is often used in this case (see the use_bsmtp option). ++ ++ ++26.1 The file and directory options ++----------------------------------- ++ ++The file option specifies a single file, to which the message is appended; the ++directory option specifies a directory, in which a new file containing the ++message is created. Only one of these two options can be set, and for normal ++deliveries to mailboxes, one of them must be set. ++ ++However, appendfile is also used for delivering messages to files or ++directories whose names (or parts of names) are obtained from alias, ++forwarding, or filtering operations (for example, a save command in a user's ++Exim filter). When such a transport is running, $local_part contains the local ++part that was aliased or forwarded, and $address_file contains the name (or ++partial name) of the file or directory generated by the redirection operation. ++There are two cases: ++ ++ * If neither file nor directory is set, the redirection operation must ++ specify an absolute path (one that begins with "/"). This is the most ++ common case when users with local accounts use filtering to sort mail into ++ different folders. See for example, the address_file transport in the ++ default configuration. If the path ends with a slash, it is assumed to be ++ the name of a directory. A delivery to a directory can also be forced by ++ setting maildir_format or mailstore_format. ++ ++ * If file or directory is set for a delivery from a redirection, it is used ++ to determine the file or directory name for the delivery. Normally, the ++ contents of $address_file are used in some way in the string expansion. ++ ++As an example of the second case, consider an environment where users do not ++have home directories. They may be permitted to use Exim filter commands of the ++form: ++ ++save folder23 ++ ++or Sieve filter commands of the form: ++ ++require "fileinto"; ++fileinto "folder23"; ++ ++In this situation, the expansion of file or directory in the transport must ++transform the relative path into an appropriate absolute file name. In the case ++of Sieve filters, the name inbox must be handled. It is the name that is used ++as a result of a "keep" action in the filter. This example shows one way of ++handling this requirement: ++ ++file = ${if eq{$address_file}{inbox} \ ++ {/var/mail/$local_part} \ ++ {${if eq{${substr_0_1:$address_file}}{/} \ ++ {$address_file} \ ++ {$home/mail/$address_file} \ ++ }} \ ++ } ++ ++With this setting of file, inbox refers to the standard mailbox location, ++absolute paths are used without change, and other folders are in the mail ++directory within the home directory. ++ ++Note 1: While processing an Exim filter, a relative path such as folder23 is ++turned into an absolute path if a home directory is known to the router. In ++particular, this is the case if check_local_user is set. If you want to prevent ++this happening at routing time, you can set router_home_directory empty. This ++forces the router to pass the relative path to the transport. ++ ++Note 2: An absolute path in $address_file is not treated specially; the file or ++directory option is still used if it is set. ++ ++ ++26.2 Private options for appendfile ++----------------------------------- ++ +++-------------------------------------------------------+ ++|allow_fifo|Use: appendfile|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++Setting this option permits delivery to named pipes (FIFOs) as well as to ++regular files. If no process is reading the named pipe at delivery time, the ++delivery is deferred. ++ +++----------------------------------------------------------+ ++|allow_symlink|Use: appendfile|Type: boolean|Default: false| +++----------------------------------------------------------+ ++ ++By default, appendfile will not deliver if the path name for the file is that ++of a symbolic link. Setting this option relaxes that constraint, but there are ++security issues involved in the use of symbolic links. Be sure you know what ++you are doing if you set this. Details of exactly what this option affects are ++included in the discussion which follows this list of options. ++ +++-----------------------------------------------------+ ++|batch_id|Use: appendfile|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++See the description of local delivery batching in chapter 25. However, batching ++is automatically disabled for appendfile deliveries that happen as a result of ++forwarding or aliasing or other redirection directly to a file. ++ +++--------------------------------------------------+ ++|batch_max|Use: appendfile|Type: integer|Default: 1| +++--------------------------------------------------+ ++ ++See the description of local delivery batching in chapter 25. ++ +++--------------------------------------------------------+ ++|check_group|Use: appendfile|Type: boolean|Default: false| +++--------------------------------------------------------+ ++ ++When this option is set, the group owner of the file defined by the file option ++is checked to see that it is the same as the group under which the delivery ++process is running. The default setting is false because the default file mode ++is 0600, which means that the group is irrelevant. ++ +++-------------------------------------------------------+ ++|check_owner|Use: appendfile|Type: boolean|Default: true| +++-------------------------------------------------------+ ++ ++When this option is set, the owner of the file defined by the file option is ++checked to ensure that it is the same as the user under which the delivery ++process is running. ++ +++------------------------------------------------------------+ ++|check_string|Use: appendfile|Type: string|Default: see below| +++------------------------------------------------------------+ ++ ++As appendfile writes the message, the start of each line is tested for matching ++check_string, and if it does, the initial matching characters are replaced by ++the contents of escape_string. The value of check_string is a literal string, ++not a regular expression, and the case of any letters it contains is ++significant. ++ ++If use_bsmtp is set the values of check_string and escape_string are forced to ++"." and ".." respectively, and any settings in the configuration are ignored. ++Otherwise, they default to "From " and ">From " when the file option is set, ++and unset when any of the directory, maildir, or mailstore options are set. ++ ++The default settings, along with message_prefix and message_suffix, are ++suitable for traditional "BSD" mailboxes, where a line beginning with "From " ++indicates the start of a new message. All four options need changing if another ++format is used. For example, to deliver to mailboxes in MMDF format: ++ ++check_string = "\1\1\1\1\n" ++escape_string = "\1\1\1\1 \n" ++message_prefix = "\1\1\1\1\n" ++message_suffix = "\1\1\1\1\n" ++ +++------------------------------------------------------------+ ++|create_directory|Use: appendfile|Type: boolean|Default: true| +++------------------------------------------------------------+ ++ ++When this option is true, Exim attempts to create any missing superior ++directories for the file that it is about to write. A created directory's mode ++is given by the directory_mode option. ++ ++The group ownership of a newly created directory is highly dependent on the ++operating system (and possibly the file system) that is being used. For ++example, in Solaris, if the parent directory has the setgid bit set, its group ++is propagated to the child; if not, the currently set group is used. However, ++in FreeBSD, the parent's group is always used. ++ +++----------------------------------------------------------+ ++|create_file|Use: appendfile|Type: string|Default: anywhere| +++----------------------------------------------------------+ ++ ++This option constrains the location of files and directories that are created ++by this transport. It applies to files defined by the file option and ++directories defined by the directory option. In the case of maildir delivery, ++it applies to the top level directory, not the maildir directories beneath. ++ ++The option must be set to one of the words "anywhere", "inhome", or ++"belowhome". In the second and third cases, a home directory must have been set ++for the transport. This option is not useful when an explicit file name is ++given for normal mailbox deliveries. It is intended for the case when file ++names are generated from users' .forward files. These are usually handled by an ++appendfile transport called address_file. See also file_must_exist. ++ +++------------------------------------------------------+ ++|directory|Use: appendfile|Type: string*|Default: unset| +++------------------------------------------------------+ ++ ++This option is mutually exclusive with the file option, but one of file or ++directory must be set, unless the delivery is the direct result of a ++redirection (see section 26.1). ++ ++When directory is set, the string is expanded, and the message is delivered ++into a new file or files in or below the given directory, instead of being ++appended to a single mailbox file. A number of different formats are provided ++(see maildir_format and mailstore_format), and see section 26.4 for further ++details of this form of delivery. ++ +++---------------------------------------------------------------+ ++|directory_file|Use: appendfile|Type: string*|Default: see below| +++---------------------------------------------------------------+ ++ ++When directory is set, but neither maildir_format nor mailstore_format is set, ++appendfile delivers each message into a file whose name is obtained by ++expanding this string. The default value is: ++ ++q${base62:$tod_epoch}-$inode ++ ++This generates a unique name from the current time, in base 62 form, and the ++inode of the file. The variable $inode is available only when expanding this ++option. ++ +++----------------------------------------------------------------+ ++|directory_mode|Use: appendfile|Type: octal integer|Default: 0700| +++----------------------------------------------------------------+ ++ ++If appendfile creates any directories as a result of the create_directory ++option, their mode is specified by this option. ++ +++-------------------------------------------------------------------+ ++|escape_string|Use: appendfile|Type: string|Default: see description| +++-------------------------------------------------------------------+ ++ ++See check_string above. ++ +++-------------------------------------------------+ ++|file|Use: appendfile|Type: string*|Default: unset| +++-------------------------------------------------+ ++ ++This option is mutually exclusive with the directory option, but one of file or ++directory must be set, unless the delivery is the direct result of a ++redirection (see section 26.1). The file option specifies a single file, to ++which the message is appended. One or more of use_fcntl_lock, use_flock_lock, ++or use_lockfile must be set with file. ++ ++If you are using more than one host to deliver over NFS into the same ++mailboxes, you should always use lock files. ++ ++The string value is expanded for each delivery, and must yield an absolute ++path. The most common settings of this option are variations on one of these ++examples: ++ ++file = /var/spool/mail/$local_part ++file = /home/$local_part/inbox ++file = $home/inbox ++ ++In the first example, all deliveries are done into the same directory. If Exim ++is configured to use lock files (see use_lockfile below) it must be able to ++create a file in the directory, so the "sticky" bit must be turned on for ++deliveries to be possible, or alternatively the group option can be used to run ++the delivery under a group id which has write access to the directory. ++ +++-------------------------------------------------------+ ++|file_format|Use: appendfile|Type: string|Default: unset| +++-------------------------------------------------------+ ++ ++This option requests the transport to check the format of an existing file ++before adding to it. The check consists of matching a specific string at the ++start of the file. The value of the option consists of an even number of ++colon-separated strings. The first of each pair is the test string, and the ++second is the name of a transport. If the transport associated with a matched ++string is not the current transport, control is passed over to the other ++transport. For example, suppose the standard local_delivery transport has this ++added to it: ++ ++file_format = "From : local_delivery :\ ++ \1\1\1\1\n : local_mmdf_delivery" ++ ++Mailboxes that begin with "From" are still handled by this transport, but if a ++mailbox begins with four binary ones followed by a newline, control is passed ++to a transport called local_mmdf_delivery, which presumably is configured to do ++the delivery in MMDF format. If a mailbox does not exist or is empty, it is ++assumed to match the current transport. If the start of a mailbox doesn't match ++any string, or if the transport named for a given string is not defined, ++delivery is deferred. ++ +++------------------------------------------------------------+ ++|file_must_exist|Use: appendfile|Type: boolean|Default: false| +++------------------------------------------------------------+ ++ ++If this option is true, the file specified by the file option must exist. A ++temporary error occurs if it does not, causing delivery to be deferred. If this ++option is false, the file is created if it does not exist. ++ +++---------------------------------------------------------+ ++|lock_fcntl_timeout|Use: appendfile|Type: time|Default: 0s| +++---------------------------------------------------------+ ++ ++By default, the appendfile transport uses non-blocking calls to fcntl() when ++locking an open mailbox file. If the call fails, the delivery process sleeps ++for lock_interval and tries again, up to lock_retries times. Non-blocking calls ++are used so that the file is not kept open during the wait for the lock; the ++reason for this is to make it as safe as possible for deliveries over NFS in ++the case when processes might be accessing an NFS mailbox without using a lock ++file. This should not be done, but misunderstandings and hence ++misconfigurations are not unknown. ++ ++On a busy system, however, the performance of a non-blocking lock approach is ++not as good as using a blocking lock with a timeout. In this case, the waiting ++is done inside the system call, and Exim's delivery process acquires the lock ++and can proceed as soon as the previous lock holder releases it. ++ ++If lock_fcntl_timeout is set to a non-zero time, blocking locks, with that ++timeout, are used. There may still be some retrying: the maximum number of ++retries is ++ ++(lock_retries * lock_interval) / lock_fcntl_timeout ++ ++rounded up to the next whole number. In other words, the total time during ++which appendfile is trying to get a lock is roughly the same, unless ++lock_fcntl_timeout is set very large. ++ ++You should consider setting this option if you are getting a lot of delayed ++local deliveries because of errors of the form ++ ++failed to lock mailbox /some/file (fcntl) ++ +++---------------------------------------------------------+ ++|lock_flock_timeout|Use: appendfile|Type: time|Default: 0s| +++---------------------------------------------------------+ ++ ++This timeout applies to file locking when using flock() (see use_flock); the ++timeout operates in a similar manner to lock_fcntl_timeout. ++ +++----------------------------------------------------+ ++|lock_interval|Use: appendfile|Type: time|Default: 3s| +++----------------------------------------------------+ ++ ++This specifies the time to wait between attempts to lock the file. See below ++for details of locking. ++ +++------------------------------------------------------+ ++|lock_retries|Use: appendfile|Type: integer|Default: 10| +++------------------------------------------------------+ ++ ++This specifies the maximum number of attempts to lock the file. A value of zero ++is treated as 1. See below for details of locking. ++ +++---------------------------------------------------------------+ ++|lockfile_mode|Use: appendfile|Type: octal integer|Default: 0600| +++---------------------------------------------------------------+ ++ ++This specifies the mode of the created lock file, when a lock file is being ++used (see use_lockfile and use_mbx_lock). ++ +++--------------------------------------------------------+ ++|lockfile_timeout|Use: appendfile|Type: time|Default: 30m| +++--------------------------------------------------------+ ++ ++When a lock file is being used (see use_lockfile), if a lock file already ++exists and is older than this value, it is assumed to have been left behind by ++accident, and Exim attempts to remove it. ++ +++--------------------------------------------------------------+ ++|mailbox_filecount|Use: appendfile|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++If this option is set, it is expanded, and the result is taken as the current ++number of files in the mailbox. It must be a decimal number, optionally ++followed by K or M. This provides a way of obtaining this information from an ++external source that maintains the data. ++ +++---------------------------------------------------------+ ++|mailbox_size|Use: appendfile|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++If this option is set, it is expanded, and the result is taken as the current ++size the mailbox. It must be a decimal number, optionally followed by K or M. ++This provides a way of obtaining this information from an external source that ++maintains the data. This is likely to be helpful for maildir deliveries where ++it is computationally expensive to compute the size of a mailbox. ++ +++-----------------------------------------------------------+ ++|maildir_format|Use: appendfile|Type: boolean|Default: false| +++-----------------------------------------------------------+ ++ ++If this option is set with the directory option, the delivery is into a new ++file, in the "maildir" format that is used by other mail software. When the ++transport is activated directly from a redirect router (for example, the ++address_file transport in the default configuration), setting maildir_format ++causes the path received from the router to be treated as a directory, whether ++or not it ends with "/". This option is available only if SUPPORT_MAILDIR is ++present in Local/Makefile. See section 26.5 below for further details. ++ +++-----------------------------------------------------------------------------+ ++|maildir_quota_directory_regex|Use: appendfile|Type: string|Default: See below| +++-----------------------------------------------------------------------------+ ++ ++This option is relevant only when maildir_use_size_file is set. It defines a ++regular expression for specifying directories, relative to the quota directory ++(see quota_directory), that should be included in the quota calculation. The ++default value is: ++ ++maildir_quota_directory_regex = ^(?:cur|new|\..*)$ ++ ++This includes the cur and new directories, and any maildir++ folders ++(directories whose names begin with a dot). If you want to exclude the Trash ++folder from the count (as some sites do), you need to change this setting to ++ ++maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$ ++ ++This uses a negative lookahead in the regular expression to exclude the ++directory whose name is .Trash. When a directory is excluded from quota ++calculations, quota processing is bypassed for any messages that are delivered ++directly into that directory. ++ +++---------------------------------------------------------+ ++|maildir_retries|Use: appendfile|Type: integer|Default: 10| +++---------------------------------------------------------+ ++ ++This option specifies the number of times to retry when writing a file in ++"maildir" format. See section 26.5 below. ++ +++--------------------------------------------------------+ ++|maildir_tag|Use: appendfile|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option applies only to deliveries in maildir format, and is described in ++section 26.5 below. ++ +++-------------------------------------------------------------------+ ++|maildir_use_size_file|Use: appendfile*|Type: boolean|Default: false| +++-------------------------------------------------------------------+ ++ ++The result of string expansion for this option must be a valid boolean value. ++If it is true, it enables support for maildirsize files. Exim creates a ++maildirsize file in a maildir if one does not exist, taking the quota from the ++quota option of the transport. If quota is unset, the value is zero. See ++maildir_quota_directory_regex above and section 26.5 below for further details. ++ +++----------------------------------------------------------------------+ ++|maildirfolder_create_regex|Use: appendfile|Type: string|Default: unset| +++----------------------------------------------------------------------+ ++ ++The value of this option is a regular expression. If it is unset, it has no ++effect. Otherwise, before a maildir delivery takes place, the pattern is ++matched against the name of the maildir directory, that is, the directory ++containing the new and tmp subdirectories that will be used for the delivery. ++If there is a match, Exim checks for the existence of a file called ++maildirfolder in the directory, and creates it if it does not exist. See ++section 26.5 for more details. ++ +++-------------------------------------------------------------+ ++|mailstore_format|Use: appendfile|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++If this option is set with the directory option, the delivery is into two new ++files in "mailstore" format. The option is available only if SUPPORT_MAILSTORE ++is present in Local/Makefile. See section 26.4 below for further details. ++ +++-------------------------------------------------------------+ ++|mailstore_prefix|Use: appendfile|Type: string*|Default: unset| +++-------------------------------------------------------------+ ++ ++This option applies only to deliveries in mailstore format, and is described in ++section 26.4 below. ++ +++-------------------------------------------------------------+ ++|mailstore_suffix|Use: appendfile|Type: string*|Default: unset| +++-------------------------------------------------------------+ ++ ++This option applies only to deliveries in mailstore format, and is described in ++section 26.4 below. ++ +++-------------------------------------------------------+ ++|mbx_format|Use: appendfile|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++This option is available only if Exim has been compiled with SUPPORT_MBX set in ++Local/Makefile. If mbx_format is set with the file option, the message is ++appended to the mailbox file in MBX format instead of traditional Unix format. ++This format is supported by Pine4 and its associated IMAP and POP daemons, by ++means of the c-client library that they all use. ++ ++Note: The message_prefix and message_suffix options are not automatically ++changed by the use of mbx_format. They should normally be set empty when using ++MBX format, so this option almost always appears in this combination: ++ ++mbx_format = true ++message_prefix = ++message_suffix = ++ ++If none of the locking options are mentioned in the configuration, use_mbx_lock ++is assumed and the other locking options default to false. It is possible to ++specify the other kinds of locking with mbx_format, but use_fcntl_lock and ++use_mbx_lock are mutually exclusive. MBX locking interworks with c-client, ++providing for shared access to the mailbox. It should not be used if any ++program that does not use this form of locking is going to access the mailbox, ++nor should it be used if the mailbox file is NFS mounted, because it works only ++when the mailbox is accessed from a single host. ++ ++If you set use_fcntl_lock with an MBX-format mailbox, you cannot use the ++standard version of c-client, because as long as it has a mailbox open (this ++means for the whole of a Pine or IMAP session), Exim will not be able to append ++messages to it. ++ +++---------------------------------------------------------------+ ++|message_prefix|Use: appendfile|Type: string*|Default: see below| +++---------------------------------------------------------------+ ++ ++The string specified here is expanded and output at the start of every message. ++The default is unset unless file is specified and use_bsmtp is not set, in ++which case it is: ++ ++message_prefix = "From ${if def:return_path{$return_path}\ ++ {MAILER-DAEMON}} $tod_bsdinbox\n" ++ ++Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ ++n" in message_prefix. ++ +++---------------------------------------------------------------+ ++|message_suffix|Use: appendfile|Type: string*|Default: see below| +++---------------------------------------------------------------+ ++ ++The string specified here is expanded and output at the end of every message. ++The default is unset unless file is specified and use_bsmtp is not set, in ++which case it is a single newline character. The suffix can be suppressed by ++setting ++ ++message_suffix = ++ ++Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ ++n" in message_suffix. ++ +++------------------------------------------------------+ ++|mode|Use: appendfile|Type: octal integer|Default: 0600| +++------------------------------------------------------+ ++ ++If the output file is created, it is given this mode. If it already exists and ++has wider permissions, they are reduced to this mode. If it has narrower ++permissions, an error occurs unless mode_fail_narrower is false. However, if ++the delivery is the result of a save command in a filter file specifying a ++particular mode, the mode of the output file is always forced to take that ++value, and this option is ignored. ++ +++--------------------------------------------------------------+ ++|mode_fail_narrower|Use: appendfile|Type: boolean|Default: true| +++--------------------------------------------------------------+ ++ ++This option applies in the case when an existing mailbox file has a narrower ++mode than that specified by the mode option. If mode_fail_narrower is true, the ++delivery is deferred ("mailbox has the wrong mode"); otherwise Exim continues ++with the delivery attempt, using the existing mode of the file. ++ +++----------------------------------------------------------+ ++|notify_comsat|Use: appendfile|Type: boolean|Default: false| +++----------------------------------------------------------+ ++ ++If this option is true, the comsat daemon is notified after every successful ++delivery to a user mailbox. This is the daemon that notifies logged on users ++about incoming mail. ++ +++--------------------------------------------------+ ++|quota|Use: appendfile|Type: string*|Default: unset| +++--------------------------------------------------+ ++ ++This option imposes a limit on the size of the file to which Exim is appending, ++or to the total space used in the directory tree when the directory option is ++set. In the latter case, computation of the space used is expensive, because ++all the files in the directory (and any sub-directories) have to be ++individually inspected and their sizes summed. (See quota_size_regex and ++maildir_use_size_file for ways to avoid this in environments where users have ++no shell access to their mailboxes). ++ ++As there is no interlock against two simultaneous deliveries into a multi-file ++mailbox, it is possible for the quota to be overrun in this case. For ++single-file mailboxes, of course, an interlock is a necessity. ++ ++A file's size is taken as its used value. Because of blocking effects, this may ++be a lot less than the actual amount of disk space allocated to the file. If ++the sizes of a number of files are being added up, the rounding effect can ++become quite noticeable, especially on systems that have large block sizes. ++Nevertheless, it seems best to stick to the used figure, because this is the ++obvious value which users understand most easily. ++ ++The value of the option is expanded, and must then be a numerical value ++(decimal point allowed), optionally followed by one of the letters K, M, or G, ++for kilobytes, megabytes, or gigabytes. If Exim is running on a system with ++large file support (Linux and FreeBSD have this), mailboxes larger than 2G can ++be handled. ++ ++Note: A value of zero is interpreted as "no quota". ++ ++The expansion happens while Exim is running as root, before it changes uid for ++the delivery. This means that files that are inaccessible to the end user can ++be used to hold quota values that are looked up in the expansion. When delivery ++fails because this quota is exceeded, the handling of the error is as for ++system quota failures. ++ ++By default, Exim's quota checking mimics system quotas, and restricts the ++mailbox to the specified maximum size, though the value is not accurate to the ++last byte, owing to separator lines and additional headers that may get added ++during message delivery. When a mailbox is nearly full, large messages may get ++refused even though small ones are accepted, because the size of the current ++message is added to the quota when the check is made. This behaviour can be ++changed by setting quota_is_inclusive false. When this is done, the check for ++exceeding the quota does not include the current message. Thus, deliveries ++continue until the quota has been exceeded; thereafter, no further messages are ++delivered. See also quota_warn_threshold. ++ +++------------------------------------------------------------+ ++|quota_directory|Use: appendfile|Type: string*|Default: unset| +++------------------------------------------------------------+ ++ ++This option defines the directory to check for quota purposes when delivering ++into individual files. The default is the delivery directory, or, if a file ++called maildirfolder exists in a maildir directory, the parent of the delivery ++directory. ++ +++--------------------------------------------------------+ ++|quota_filecount|Use: appendfile|Type: string*|Default: 0| +++--------------------------------------------------------+ ++ ++This option applies when the directory option is set. It limits the total ++number of files in the directory (compare the inode limit in system quotas). It ++can only be used if quota is also set. The value is expanded; an expansion ++failure causes delivery to be deferred. A value of zero is interpreted as "no ++quota". ++ +++--------------------------------------------------------------+ ++|quota_is_inclusive|Use: appendfile|Type: boolean|Default: true| +++--------------------------------------------------------------+ ++ ++See quota above. ++ +++------------------------------------------------------------+ ++|quota_size_regex|Use: appendfile|Type: string|Default: unset| +++------------------------------------------------------------+ ++ ++This option applies when one of the delivery modes that writes a separate file ++for each message is being used. When Exim wants to find the size of one of ++these files in order to test the quota, it first checks quota_size_regex. If ++this is set to a regular expression that matches the file name, and it captures ++one string, that string is interpreted as a representation of the file's size. ++The value of quota_size_regex is not expanded. ++ ++This feature is useful only when users have no shell access to their mailboxes ++- otherwise they could defeat the quota simply by renaming the files. This ++facility can be used with maildir deliveries, by setting maildir_tag to add the ++file length to the file name. For example: ++ ++maildir_tag = ,S=$message_size ++quota_size_regex = ,S=(\d+) ++ ++An alternative to $message_size is $message_linecount, which contains the ++number of lines in the message. ++ ++The regular expression should not assume that the length is at the end of the ++file name (even though maildir_tag puts it there) because maildir MUAs ++sometimes add other information onto the ends of message file names. ++ ++Section 26.7 contains further information. ++ +++-------------------------------------------------------------------+ ++|quota_warn_message|Use: appendfile|Type: string*|Default: see below| +++-------------------------------------------------------------------+ ++ ++See below for the use of this option. If it is not set when ++quota_warn_threshold is set, it defaults to ++ ++quota_warn_message = "\ ++ To: $local_part@$domain\n\ ++ Subject: Your mailbox\n\n\ ++ This message is automatically created \ ++ by mail delivery software.\n\n\ ++ The size of your mailbox has exceeded \ ++ a warning threshold that is\n\ ++ set by the system administrator.\n" ++ +++-------------------------------------------------------------+ ++|quota_warn_threshold|Use: appendfile|Type: string*|Default: 0| +++-------------------------------------------------------------+ ++ ++This option is expanded in the same way as quota (see above). If the resulting ++value is greater than zero, and delivery of the message causes the size of the ++file or total space in the directory tree to cross the given threshold, a ++warning message is sent. If quota is also set, the threshold may be specified ++as a percentage of it by following the value with a percent sign. For example: ++ ++quota = 10M ++quota_warn_threshold = 75% ++ ++If quota is not set, a setting of quota_warn_threshold that ends with a percent ++sign is ignored. ++ ++The warning message itself is specified by the quota_warn_message option, and ++it must start with a To: header line containing the recipient(s) of the warning ++message. These do not necessarily have to include the recipient(s) of the ++original message. A Subject: line should also normally be supplied. You can ++include any other header lines that you want. If you do not include a From: ++line, the default is: ++ ++From: Mail Delivery System <mailer-daemon@$qualify_domain_sender> ++ ++If you supply a Reply-To: line, it overrides the global errors_reply_to option. ++ ++The quota option does not have to be set in order to use this option; they are ++independent of one another except when the threshold is specified as a ++percentage. ++ +++------------------------------------------------------+ ++|use_bsmtp|Use: appendfile|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If this option is set true, appendfile writes messages in "batch SMTP" format, ++with the envelope sender and recipient(s) included as SMTP commands. If you ++want to include a leading HELO command with such messages, you can do so by ++setting the message_prefix option. See section 47.10 for details of batch SMTP. ++ +++-----------------------------------------------------+ ++|use_crlf|Use: appendfile|Type: boolean|Default: false| +++-----------------------------------------------------+ ++ ++This option causes lines to be terminated with the two-character CRLF sequence ++(carriage return, linefeed) instead of just a linefeed character. In the case ++of batched SMTP, the byte sequence written to the file is then an exact image ++of what would be sent down a real SMTP connection. ++ ++Note: The contents of the message_prefix and message_suffix options (which are ++used to supply the traditional "From " and blank line separators in ++Berkeley-style mailboxes) are written verbatim, so must contain their own ++carriage return characters if these are needed. In cases where these options ++have non-empty defaults, the values end with a single linefeed, so they must be ++changed to end with "\r\n" if use_crlf is set. ++ +++---------------------------------------------------------------+ ++|use_fcntl_lock|Use: appendfile|Type: boolean|Default: see below| +++---------------------------------------------------------------+ ++ ++This option controls the use of the fcntl() function to lock a file for ++exclusive use when a message is being appended. It is set by default unless ++use_flock_lock is set. Otherwise, it should be turned off only if you know that ++all your MUAs use lock file locking. When both use_fcntl_lock and ++use_flock_lock are unset, use_lockfile must be set. ++ +++-----------------------------------------------------------+ ++|use_flock_lock|Use: appendfile|Type: boolean|Default: false| +++-----------------------------------------------------------+ ++ ++This option is provided to support the use of flock() for file locking, for the ++few situations where it is needed. Most modern operating systems support fcntl ++() and lockf() locking, and these two functions interwork with each other. Exim ++uses fcntl() locking by default. ++ ++This option is required only if you are using an operating system where flock() ++is used by programs that access mailboxes (typically MUAs), and where flock() ++does not correctly interwork with fcntl(). You can use both fcntl() and flock() ++locking simultaneously if you want. ++ ++Not all operating systems provide flock(). Some versions of Solaris do not have ++it (and some, I think, provide a not quite right version built on top of lockf ++()). If the OS does not have flock(), Exim will be built without the ability to ++use it, and any attempt to do so will cause a configuration error. ++ ++Warning: flock() locks do not work on NFS files (unless flock() is just being ++mapped onto fcntl() by the OS). ++ +++-------------------------------------------------------------+ ++|use_lockfile|Use: appendfile|Type: boolean|Default: see below| +++-------------------------------------------------------------+ ++ ++If this option is turned off, Exim does not attempt to create a lock file when ++appending to a mailbox file. In this situation, the only locking is by fcntl(). ++You should only turn use_lockfile off if you are absolutely sure that every MUA ++that is ever going to look at your users' mailboxes uses fcntl() rather than a ++lock file, and even then only when you are not delivering over NFS from more ++than one host. ++ ++In order to append to an NFS file safely from more than one host, it is ++necessary to take out a lock before opening the file, and the lock file ++achieves this. Otherwise, even with fcntl() locking, there is a risk of file ++corruption. ++ ++The use_lockfile option is set by default unless use_mbx_lock is set. It is not ++possible to turn both use_lockfile and use_fcntl_lock off, except when ++mbx_format is set. ++ +++-------------------------------------------------------------+ ++|use_mbx_lock|Use: appendfile|Type: boolean|Default: see below| +++-------------------------------------------------------------+ ++ ++This option is available only if Exim has been compiled with SUPPORT_MBX set in ++Local/Makefile. Setting the option specifies that special MBX locking rules be ++used. It is set by default if mbx_format is set and none of the locking options ++are mentioned in the configuration. The locking rules are the same as are used ++by the c-client library that underlies Pine and the IMAP4 and POP daemons that ++come with it (see the discussion below). The rules allow for shared access to ++the mailbox. However, this kind of locking does not work when the mailbox is ++NFS mounted. ++ ++You can set use_mbx_lock with either (or both) of use_fcntl_lock and ++use_flock_lock to control what kind of locking is used in implementing the MBX ++locking rules. The default is to use fcntl() if use_mbx_lock is set without ++use_fcntl_lock or use_flock_lock. ++ ++ ++26.3 Operational details for appending ++-------------------------------------- ++ ++Before appending to a file, the following preparations are made: ++ ++ * If the name of the file is /dev/null, no action is taken, and a success ++ return is given. ++ ++ * If any directories on the file's path are missing, Exim creates them if the ++ create_directory option is set. A created directory's mode is given by the ++ directory_mode option. ++ ++ * If file_format is set, the format of an existing file is checked. If this ++ indicates that a different transport should be used, control is passed to ++ that transport. ++ ++ * If use_lockfile is set, a lock file is built in a way that will work ++ reliably over NFS, as follows: ++ ++ 1. Create a "hitching post" file whose name is that of the lock file with ++ the current time, primary host name, and process id added, by opening ++ for writing as a new file. If this fails with an access error, delivery ++ is deferred. ++ ++ 2. Close the hitching post file, and hard link it to the lock file name. ++ ++ 3. If the call to link() succeeds, creation of the lock file has ++ succeeded. Unlink the hitching post name. ++ ++ 4. Otherwise, use stat() to get information about the hitching post file, ++ and then unlink hitching post name. If the number of links is exactly ++ two, creation of the lock file succeeded but something (for example, an ++ NFS server crash and restart) caused this fact not to be communicated ++ to the link() call. ++ ++ 5. If creation of the lock file failed, wait for lock_interval and try ++ again, up to lock_retries times. However, since any program that writes ++ to a mailbox should complete its task very quickly, it is reasonable to ++ time out old lock files that are normally the result of user agent and ++ system crashes. If an existing lock file is older than lockfile_timeout ++ Exim attempts to unlink it before trying again. ++ ++ * A call is made to lstat() to discover whether the main file exists, and if ++ so, what its characteristics are. If lstat() fails for any reason other ++ than non-existence, delivery is deferred. ++ ++ * If the file does exist and is a symbolic link, delivery is deferred, unless ++ the allow_symlink option is set, in which case the ownership of the link is ++ checked, and then stat() is called to find out about the real file, which ++ is then subjected to the checks below. The check on the top-level link ++ ownership prevents one user creating a link for another's mailbox in a ++ sticky directory, though allowing symbolic links in this case is definitely ++ not a good idea. If there is a chain of symbolic links, the intermediate ++ ones are not checked. ++ ++ * If the file already exists but is not a regular file, or if the file's ++ owner and group (if the group is being checked - see check_group above) are ++ different from the user and group under which the delivery is running, ++ delivery is deferred. ++ ++ * If the file's permissions are more generous than specified, they are ++ reduced. If they are insufficient, delivery is deferred, unless ++ mode_fail_narrower is set false, in which case the delivery is tried using ++ the existing permissions. ++ ++ * The file's inode number is saved, and the file is then opened for ++ appending. If this fails because the file has vanished, appendfile behaves ++ as if it hadn't existed (see below). For any other failures, delivery is ++ deferred. ++ ++ * If the file is opened successfully, check that the inode number hasn't ++ changed, that it is still a regular file, and that the owner and ++ permissions have not changed. If anything is wrong, defer delivery and ++ freeze the message. ++ ++ * If the file did not exist originally, defer delivery if the file_must_exist ++ option is set. Otherwise, check that the file is being created in a ++ permitted directory if the create_file option is set (deferring on ++ failure), and then open for writing as a new file, with the O_EXCL and ++ O_CREAT options, except when dealing with a symbolic link (the ++ allow_symlink option must be set). In this case, which can happen if the ++ link points to a non-existent file, the file is opened for writing using ++ O_CREAT but not O_EXCL, because that prevents link following. ++ ++ * If opening fails because the file exists, obey the tests given above for ++ existing files. However, to avoid looping in a situation where the file is ++ being continuously created and destroyed, the exists/not-exists loop is ++ broken after 10 repetitions, and the message is then frozen. ++ ++ * If opening fails with any other error, defer delivery. ++ ++ * Once the file is open, unless both use_fcntl_lock and use_flock_lock are ++ false, it is locked using fcntl() or flock() or both. If use_mbx_lock is ++ false, an exclusive lock is requested in each case. However, if ++ use_mbx_lock is true, Exim takes out a shared lock on the open file, and an ++ exclusive lock on the file whose name is ++ ++ /tmp/.<device-number>.<inode-number> ++ ++ using the device and inode numbers of the open mailbox file, in accordance ++ with the MBX locking rules. This file is created with a mode that is ++ specified by the lockfile_mode option. ++ ++ If Exim fails to lock the file, there are two possible courses of action, ++ depending on the value of the locking timeout. This is obtained from ++ lock_fcntl_timeout or lock_flock_timeout, as appropriate. ++ ++ If the timeout value is zero, the file is closed, Exim waits for ++ lock_interval, and then goes back and re-opens the file as above and tries ++ to lock it again. This happens up to lock_retries times, after which the ++ delivery is deferred. ++ ++ If the timeout has a value greater than zero, blocking calls to fcntl() or ++ flock() are used (with the given timeout), so there has already been some ++ waiting involved by the time locking fails. Nevertheless, Exim does not ++ give up immediately. It retries up to ++ ++ (lock_retries * lock_interval) / <timeout> ++ ++ times (rounded up). ++ ++At the end of delivery, Exim closes the file (which releases the fcntl() and/or ++flock() locks) and then deletes the lock file if one was created. ++ ++ ++26.4 Operational details for delivery to a new file ++--------------------------------------------------- ++ ++When the directory option is set instead of file, each message is delivered ++into a newly-created file or set of files. When appendfile is activated ++directly from a redirect router, neither file nor directory is normally set, ++because the path for delivery is supplied by the router. (See for example, the ++address_file transport in the default configuration.) In this case, delivery is ++to a new file if either the path name ends in "/", or the maildir_format or ++mailstore_format option is set. ++ ++No locking is required while writing the message to a new file, so the various ++locking options of the transport are ignored. The "From" line that by default ++separates messages in a single file is not normally needed, nor is the escaping ++of message lines that start with "From", and there is no need to ensure a ++newline at the end of each message. Consequently, the default values for ++check_string, message_prefix, and message_suffix are all unset when any of ++directory, maildir_format, or mailstore_format is set. ++ ++If Exim is required to check a quota setting, it adds up the sizes of all the ++files in the delivery directory by default. However, you can specify a ++different directory by setting quota_directory. Also, for maildir deliveries ++(see below) the maildirfolder convention is honoured. ++ ++There are three different ways in which delivery to individual files can be ++done, controlled by the settings of the maildir_format and mailstore_format ++options. Note that code to support maildir or mailstore formats is not included ++in the binary unless SUPPORT_MAILDIR or SUPPORT_MAILSTORE, respectively, is set ++in Local/Makefile. ++ ++In all three cases an attempt is made to create the directory and any necessary ++sub-directories if they do not exist, provided that the create_directory option ++is set (the default). The location of a created directory can be constrained by ++setting create_file. A created directory's mode is given by the directory_mode ++option. If creation fails, or if the create_directory option is not set when ++creation is required, delivery is deferred. ++ ++ ++26.5 Maildir delivery ++--------------------- ++ ++If the maildir_format option is true, Exim delivers each message by writing it ++to a file whose name is tmp/<stime>.H<mtime>P<pid>.<host> in the directory that ++is defined by the directory option (the "delivery directory"). If the delivery ++is successful, the file is renamed into the new subdirectory. ++ ++In the file name, <stime> is the current time of day in seconds, and <mtime> is ++the microsecond fraction of the time. After a maildir delivery, Exim checks ++that the time-of-day clock has moved on by at least one microsecond before ++terminating the delivery process. This guarantees uniqueness for the file name. ++However, as a precaution, Exim calls stat() for the file before opening it. If ++any response other than ENOENT (does not exist) is given, Exim waits 2 seconds ++and tries again, up to maildir_retries times. ++ ++Before Exim carries out a maildir delivery, it ensures that subdirectories ++called new, cur, and tmp exist in the delivery directory. If they do not exist, ++Exim tries to create them and any superior directories in their path, subject ++to the create_directory and create_file options. If the ++maildirfolder_create_regex option is set, and the regular expression it ++contains matches the delivery directory, Exim also ensures that a file called ++maildirfolder exists in the delivery directory. If a missing directory or ++maildirfolder file cannot be created, delivery is deferred. ++ ++These features make it possible to use Exim to create all the necessary files ++and directories in a maildir mailbox, including subdirectories for maildir++ ++folders. Consider this example: ++ ++maildir_format = true ++directory = /var/mail/$local_part\ ++ ${if eq{$local_part_suffix}{}{}\ ++ {/.${substr_1:$local_part_suffix}}} ++maildirfolder_create_regex = /\.[^/]+$ ++ ++If $local_part_suffix is empty (there was no suffix for the local part), ++delivery is into a toplevel maildir with a name like /var/mail/pimbo (for the ++user called pimbo). The pattern in maildirfolder_create_regex does not match ++this name, so Exim will not look for or create the file /var/mail/pimbo/ ++maildirfolder, though it will create /var/mail/pimbo/{cur,new,tmp} if ++necessary. ++ ++However, if $local_part_suffix contains "-eximusers" (for example), delivery is ++into the maildir++ folder /var/mail/pimbo/.eximusers, which does match ++maildirfolder_create_regex. In this case, Exim will create /var/mail/pimbo ++/.eximusers/maildirfolder as well as the three maildir directories /var/mail/ ++pimbo/.eximusers/{cur,new,tmp}. ++ ++Warning: Take care when setting maildirfolder_create_regex that it does not ++inadvertently match the toplevel maildir directory, because a maildirfolder ++file at top level would completely break quota calculations. ++ ++If Exim is required to check a quota setting before a maildir delivery, and ++quota_directory is not set, it looks for a file called maildirfolder in the ++maildir directory (alongside new, cur, tmp). If this exists, Exim assumes the ++directory is a maildir++ folder directory, which is one level down from the ++user's top level mailbox directory. This causes it to start at the parent ++directory instead of the current directory when calculating the amount of space ++used. ++ ++One problem with delivering into a multi-file mailbox is that it is ++computationally expensive to compute the size of the mailbox for quota ++checking. Various approaches have been taken to reduce the amount of work ++needed. The next two sections describe two of them. A third alternative is to ++use some external process for maintaining the size data, and use the expansion ++of the mailbox_size option as a way of importing it into Exim. ++ ++ ++26.6 Using tags to record message sizes ++--------------------------------------- ++ ++If maildir_tag is set, the string is expanded for each delivery. When the ++maildir file is renamed into the new sub-directory, the tag is added to its ++name. However, if adding the tag takes the length of the name to the point ++where the test stat() call fails with ENAMETOOLONG, the tag is dropped and the ++maildir file is created with no tag. ++ ++Tags can be used to encode the size of files in their names; see ++quota_size_regex above for an example. The expansion of maildir_tag happens ++after the message has been written. The value of the $message_size variable is ++set to the number of bytes actually written. If the expansion is forced to ++fail, the tag is ignored, but a non-forced failure causes delivery to be ++deferred. The expanded tag may contain any printing characters except "/". ++Non-printing characters in the string are ignored; if the resulting string is ++empty, it is ignored. If it starts with an alphanumeric character, a leading ++colon is inserted; this default has not proven to be the path that popular ++maildir implementations have chosen (but changing it in Exim would break ++backwards compatibility). ++ ++For one common implementation, you might set: ++ ++maildir_tag = ,S=${message_size} ++ ++but you should check the documentation of the other software to be sure. ++ ++It is advisable to also set quota_size_regex when setting maildir_tag as this ++allows Exim to extract the size from your tag, instead of having to stat() each ++message file. ++ ++ ++26.7 Using a maildirsize file ++----------------------------- ++ ++If maildir_use_size_file is true, Exim implements the maildir++ rules for ++storing quota and message size information in a file called maildirsize within ++the toplevel maildir directory. If this file does not exist, Exim creates it, ++setting the quota from the quota option of the transport. If the maildir ++directory itself does not exist, it is created before any attempt to write a ++maildirsize file. ++ ++The maildirsize file is used to hold information about the sizes of messages in ++the maildir, thus speeding up quota calculations. The quota value in the file ++is just a cache; if the quota is changed in the transport, the new value ++overrides the cached value when the next message is delivered. The cache is ++maintained for the benefit of other programs that access the maildir and need ++to know the quota. ++ ++If the quota option in the transport is unset or zero, the maildirsize file is ++maintained (with a zero quota setting), but no quota is imposed. ++ ++A regular expression is available for controlling which directories in the ++maildir participate in quota calculations when a maildirsizefile is in use. See ++the description of the maildir_quota_directory_regex option above for details. ++ ++ ++26.8 Mailstore delivery ++----------------------- ++ ++If the mailstore_format option is true, each message is written as two files in ++the given directory. A unique base name is constructed from the message id and ++the current delivery process, and the files that are written use this base name ++plus the suffixes .env and .msg. The .env file contains the message's envelope, ++and the .msg file contains the message itself. The base name is placed in the ++variable $mailstore_basename. ++ ++During delivery, the envelope is first written to a file with the suffix .tmp. ++The .msg file is then written, and when it is complete, the .tmp file is ++renamed as the .env file. Programs that access messages in mailstore format ++should wait for the presence of both a .msg and a .env file before accessing ++either of them. An alternative approach is to wait for the absence of a .tmp ++file. ++ ++The envelope file starts with any text defined by the mailstore_prefix option, ++expanded and terminated by a newline if there isn't one. Then follows the ++sender address on one line, then all the recipient addresses, one per line. ++There can be more than one recipient only if the batch_max option is set ++greater than one. Finally, mailstore_suffix is expanded and the result appended ++to the file, followed by a newline if it does not end with one. ++ ++If expansion of mailstore_prefix or mailstore_suffix ends with a forced ++failure, it is ignored. Other expansion errors are treated as serious ++configuration errors, and delivery is deferred. The variable ++$mailstore_basename is available for use during these expansions. ++ ++ ++26.9 Non-special new file delivery ++---------------------------------- ++ ++If neither maildir_format nor mailstore_format is set, a single new file is ++created directly in the named directory. For example, when delivering messages ++into files in batched SMTP format for later delivery to some host (see section ++47.10), a setting such as ++ ++directory = /var/bsmtp/$host ++ ++might be used. A message is written to a file with a temporary name, which is ++then renamed when the delivery is complete. The final name is obtained by ++expanding the contents of the directory_file option. ++ ++ ++ ++=============================================================================== ++27. THE AUTOREPLY TRANSPORT ++ ++The autoreply transport is not a true transport in that it does not cause the ++message to be transmitted. Instead, it generates a new mail message as an ++automatic reply to the incoming message. References: and Auto-Submitted: header ++lines are included. These are constructed according to the rules in RFCs 2822 ++and 3834, respectively. ++ ++If the router that passes the message to this transport does not have the ++unseen option set, the original message (for the current recipient) is not ++delivered anywhere. However, when the unseen option is set on the router that ++passes the message to this transport, routing of the address continues, so ++another router can set up a normal message delivery. ++ ++The autoreply transport is usually run as the result of mail filtering, a ++"vacation" message being the standard example. However, it can also be run ++directly from a router like any other transport. To reduce the possibility of ++message cascades, messages created by the autoreply transport always have empty ++envelope sender addresses, like bounce messages. ++ ++The parameters of the message to be sent can be specified in the configuration ++by options described below. However, these are used only when the address ++passed to the transport does not contain its own reply information. When the ++transport is run as a consequence of a mail or vacation command in a filter ++file, the parameters of the message are supplied by the filter, and passed with ++the address. The transport's options that define the message are then ignored ++(so they are not usually set in this case). The message is specified entirely ++by the filter or by the transport; it is never built from a mixture of options. ++However, the file_optional, mode, and return_message options apply in all ++cases. ++ ++Autoreply is implemented as a local transport. When used as a result of a ++command in a user's filter file, autoreply normally runs under the uid and gid ++of the user, and with appropriate current and home directories (see chapter 23 ++). ++ ++There is a subtle difference between routing a message to a pipe transport that ++generates some text to be returned to the sender, and routing it to an ++autoreply transport. This difference is noticeable only if more than one ++address from the same message is so handled. In the case of a pipe, the ++separate outputs from the different addresses are gathered up and returned to ++the sender in a single message, whereas if autoreply is used, a separate ++message is generated for each address that is passed to it. ++ ++Non-printing characters are not permitted in the header lines generated for the ++message that autoreply creates, with the exception of newlines that are ++immediately followed by white space. If any non-printing characters are found, ++the transport defers. Whether characters with the top bit set count as printing ++characters or not is controlled by the print_topbitchars global option. ++ ++If any of the generic options for manipulating headers (for example, ++headers_add) are set on an autoreply transport, they apply to the copy of the ++original message that is included in the generated message when return_message ++is set. They do not apply to the generated message itself. ++ ++If the autoreply transport receives return code 2 from Exim when it submits the ++message, indicating that there were no recipients, it does not treat this as an ++error. This means that autoreplies sent to $sender_address when this is empty ++(because the incoming message is a bounce message) do not cause problems. They ++are just discarded. ++ ++ ++27.1 Private options for autoreply ++---------------------------------- ++ +++-----------------------------------------------+ ++|bcc|Use: autoreply|Type: string*|Default: unset| +++-----------------------------------------------+ ++ ++This specifies the addresses that are to receive "blind carbon copies" of the ++message when the message is specified by the transport. ++ +++----------------------------------------------+ ++|cc|Use: autoreply|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++This specifies recipients of the message and the contents of the Cc: header ++when the message is specified by the transport. ++ +++------------------------------------------------+ ++|file|Use: autoreply|Type: string*|Default: unset| +++------------------------------------------------+ ++ ++The contents of the file are sent as the body of the message when the message ++is specified by the transport. If both file and text are set, the text string ++comes first. ++ +++-------------------------------------------------------+ ++|file_expand|Use: autoreply|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++If this is set, the contents of the file named by the file option are subjected ++to string expansion as they are added to the message. ++ +++---------------------------------------------------------+ ++|file_optional|Use: autoreply|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is true, no error is generated if the file named by the file ++option or passed with the address does not exist or cannot be read. ++ +++------------------------------------------------+ ++|from|Use: autoreply|Type: string*|Default: unset| +++------------------------------------------------+ ++ ++This specifies the contents of the From: header when the message is specified ++by the transport. ++ +++---------------------------------------------------+ ++|headers|Use: autoreply|Type: string*|Default: unset| +++---------------------------------------------------+ ++ ++This specifies additional RFC 2822 headers that are to be added to the message ++when the message is specified by the transport. Several can be given by using " ++\n" to separate them. There is no check on the format. ++ +++-----------------------------------------------+ ++|log|Use: autoreply|Type: string*|Default: unset| +++-----------------------------------------------+ ++ ++This option names a file in which a record of every message sent is logged when ++the message is specified by the transport. ++ +++-----------------------------------------------------+ ++|mode|Use: autoreply|Type: octal integer|Default: 0600| +++-----------------------------------------------------+ ++ ++If either the log file or the "once" file has to be created, this mode is used. ++ +++------------------------------------------------------------+ ++|never_mail|Use: autoreply|Type: address list*|Default: unset| +++------------------------------------------------------------+ ++ ++If any run of the transport creates a message with a recipient that matches any ++item in the list, that recipient is quietly discarded. If all recipients are ++discarded, no message is created. This applies both when the recipients are ++generated by a filter and when they are specified in the transport. ++ +++------------------------------------------------+ ++|once|Use: autoreply|Type: string*|Default: unset| +++------------------------------------------------+ ++ ++This option names a file or DBM database in which a record of each To: ++recipient is kept when the message is specified by the transport. Note: This ++does not apply to Cc: or Bcc: recipients. ++ ++If once is unset, or is set to an empty string, the message is always sent. By ++default, if once is set to a non-empty file name, the message is not sent if a ++potential recipient is already listed in the database. However, if the ++once_repeat option specifies a time greater than zero, the message is sent if ++that much time has elapsed since a message was last sent to this recipient. A ++setting of zero time for once_repeat (the default) prevents a message from ++being sent a second time - in this case, zero means infinity. ++ ++If once_file_size is zero, a DBM database is used to remember recipients, and ++it is allowed to grow as large as necessary. If once_file_size is set greater ++than zero, it changes the way Exim implements the once option. Instead of using ++a DBM file to record every recipient it sends to, it uses a regular file, whose ++size will never get larger than the given value. ++ ++In the file, Exim keeps a linear list of recipient addresses and the times at ++which they were sent messages. If the file is full when a new address needs to ++be added, the oldest address is dropped. If once_repeat is not set, this means ++that a given recipient may receive multiple messages, but at unpredictable ++intervals that depend on the rate of turnover of addresses in the file. If ++once_repeat is set, it specifies a maximum time between repeats. ++ +++------------------------------------------------------+ ++|once_file_size|Use: autoreply|Type: integer|Default: 0| +++------------------------------------------------------+ ++ ++See once above. ++ +++--------------------------------------------------+ ++|once_repeat|Use: autoreply|Type: time*|Default: 0s| +++--------------------------------------------------+ ++ ++See once above. After expansion, the value of this option must be a valid time ++value. ++ +++----------------------------------------------------+ ++|reply_to|Use: autoreply|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This specifies the contents of the Reply-To: header when the message is ++specified by the transport. ++ +++----------------------------------------------------------+ ++|return_message|Use: autoreply|Type: boolean|Default: false| +++----------------------------------------------------------+ ++ ++If this is set, a copy of the original message is returned with the new ++message, subject to the maximum size set in the return_size_limit global ++configuration option. ++ +++---------------------------------------------------+ ++|subject|Use: autoreply|Type: string*|Default: unset| +++---------------------------------------------------+ ++ ++This specifies the contents of the Subject: header when the message is ++specified by the transport. It is tempting to quote the original subject in ++automatic responses. For example: ++ ++subject = Re: $h_subject: ++ ++There is a danger in doing this, however. It may allow a third party to ++subscribe your users to an opt-in mailing list, provided that the list accepts ++bounce messages as subscription confirmations. Well-managed lists require a ++non-bounce message to confirm a subscription, so the danger is relatively ++small. ++ +++------------------------------------------------+ ++|text|Use: autoreply|Type: string*|Default: unset| +++------------------------------------------------+ ++ ++This specifies a single string to be used as the body of the message when the ++message is specified by the transport. If both text and file are set, the text ++comes first. ++ +++----------------------------------------------+ ++|to|Use: autoreply|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++This specifies recipients of the message and the contents of the To: header ++when the message is specified by the transport. ++ ++ ++ ++=============================================================================== ++28. THE LMTP TRANSPORT ++ ++The lmtp transport runs the LMTP protocol (RFC 2033) over a pipe to a specified ++command or by interacting with a Unix domain socket. This transport is ++something of a cross between the pipe and smtp transports. Exim also has ++support for using LMTP over TCP/IP; this is implemented as an option for the ++smtp transport. Because LMTP is expected to be of minority interest, the ++default build-time configure in src/EDITME has it commented out. You need to ++ensure that ++ ++TRANSPORT_LMTP=yes ++ ++is present in your Local/Makefile in order to have the lmtp transport included ++in the Exim binary. The private options of the lmtp transport are as follows: ++ +++-----------------------------------------------+ ++|batch_id|Use: lmtp|Type: string*|Default: unset| +++-----------------------------------------------+ ++ ++See the description of local delivery batching in chapter 25. ++ +++--------------------------------------------+ ++|batch_max|Use: lmtp|Type: integer|Default: 1| +++--------------------------------------------+ ++ ++This limits the number of addresses that can be handled in a single delivery. ++Most LMTP servers can handle several addresses at once, so it is normally a ++good idea to increase this value. See the description of local delivery ++batching in chapter 25. ++ +++----------------------------------------------+ ++|command|Use: lmtp|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++This option must be set if socket is not set. The string is a command which is ++run in a separate process. It is split up into a command name and list of ++arguments, each of which is separately expanded (so expansion cannot change the ++number of arguments). The command is run directly, not via a shell. The message ++is passed to the new process using the standard input and output to operate the ++LMTP protocol. ++ +++---------------------------------------------------+ ++|ignore_quota|Use: lmtp|Type: boolean|Default: false| +++---------------------------------------------------+ ++ ++If this option is set true, the string "IGNOREQUOTA" is added to RCPT commands, ++provided that the LMTP server has advertised support for IGNOREQUOTA in its ++response to the LHLO command. ++ +++---------------------------------------------+ ++|socket|Use: lmtp|Type: string*|Default: unset| +++---------------------------------------------+ ++ ++This option must be set if command is not set. The result of expansion must be ++the name of a Unix domain socket. The transport connects to the socket and ++delivers the message to it using the LMTP protocol. ++ +++----------------------------------------+ ++|timeout|Use: lmtp|Type: time|Default: 5m| +++----------------------------------------+ ++ ++The transport is aborted if the created process or Unix domain socket does not ++respond to LMTP commands or message input within this timeout. Delivery is ++deferred, and will be tried again later. Here is an example of a typical LMTP ++transport: ++ ++lmtp: ++ driver = lmtp ++ command = /some/local/lmtp/delivery/program ++ batch_max = 20 ++ user = exim ++ ++This delivers up to 20 addresses at a time, in a mixture of domains if ++necessary, running as the user exim. ++ ++ ++ ++=============================================================================== ++29. THE PIPE TRANSPORT ++ ++The pipe transport is used to deliver messages via a pipe to a command running ++in another process. One example is the use of pipe as a pseudo-remote transport ++for passing messages to some other delivery mechanism (such as UUCP). Another ++is the use by individual users to automatically process their incoming ++messages. The pipe transport can be used in one of the following ways: ++ ++ * A router routes one address to a transport in the normal way, and the ++ transport is configured as a pipe transport. In this case, $local_part ++ contains the local part of the address (as usual), and the command that is ++ run is specified by the command option on the transport. ++ ++ * If the batch_max option is set greater than 1 (the default is 1), the ++ transport can handle more than one address in a single run. In this case, ++ when more than one address is routed to the transport, $local_part is not ++ set (because it is not unique). However, the pseudo-variable ++ $pipe_addresses (described in section 29.3 below) contains all the ++ addresses that are routed to the transport. ++ ++ * A router redirects an address directly to a pipe command (for example, from ++ an alias or forward file). In this case, $address_pipe contains the text of ++ the pipe command, and the command option on the transport is ignored unless ++ force_command is set. If only one address is being transported (batch_max ++ is not greater than one, or only one address was redirected to this pipe ++ command), $local_part contains the local part that was redirected. ++ ++The pipe transport is a non-interactive delivery method. Exim can also deliver ++messages over pipes using the LMTP interactive protocol. This is implemented by ++the lmtp transport. ++ ++In the case when pipe is run as a consequence of an entry in a local user's ++.forward file, the command runs under the uid and gid of that user. In other ++cases, the uid and gid have to be specified explicitly, either on the transport ++or on the router that handles the address. Current and "home" directories are ++also controllable. See chapter 23 for details of the local delivery environment ++and chapter 25 for a discussion of local delivery batching. ++ ++ ++29.1 Concurrent delivery ++------------------------ ++ ++If two messages arrive at almost the same time, and both are routed to a pipe ++delivery, the two pipe transports may be run concurrently. You must ensure that ++any pipe commands you set up are robust against this happening. If the commands ++write to a file, the exim_lock utility might be of use. ++ ++ ++29.2 Returned status and data ++----------------------------- ++ ++If the command exits with a non-zero return code, the delivery is deemed to ++have failed, unless either the ignore_status option is set (in which case the ++return code is treated as zero), or the return code is one of those listed in ++the temp_errors option, which are interpreted as meaning "try again later". In ++this case, delivery is deferred. Details of a permanent failure are logged, but ++are not included in the bounce message, which merely contains "local delivery ++failed". ++ ++If the command exits on a signal and the freeze_signal option is set then the ++message will be frozen in the queue. If that option is not set, a bounce will ++be sent as normal. ++ ++If the return code is greater than 128 and the command being run is a shell ++script, it normally means that the script was terminated by a signal whose ++value is the return code minus 128. The freeze_signal option does not apply in ++this case. ++ ++If Exim is unable to run the command (that is, if execve() fails), the return ++code is set to 127. This is the value that a shell returns if it is asked to ++run a non-existent command. The wording for the log line suggests that a ++non-existent command may be the problem. ++ ++The return_output option can affect the result of a pipe delivery. If it is set ++and the command produces any output on its standard output or standard error ++streams, the command is considered to have failed, even if it gave a zero ++return code or if ignore_status is set. The output from the command is included ++as part of the bounce message. The return_fail_output option is similar, except ++that output is returned only when the command exits with a failure return code, ++that is, a value other than zero or a code that matches temp_errors. ++ ++ ++29.3 How the command is run ++--------------------------- ++ ++The command line is (by default) broken down into a command name and arguments ++by the pipe transport itself. The allow_commands and restrict_to_path options ++can be used to restrict the commands that may be run. ++ ++Unquoted arguments are delimited by white space. If an argument appears in ++double quotes, backslash is interpreted as an escape character in the usual ++way. If an argument appears in single quotes, no escaping is done. ++ ++String expansion is applied to the command line except when it comes from a ++traditional .forward file (commands from a filter file are expanded). The ++expansion is applied to each argument in turn rather than to the whole line. ++For this reason, any string expansion item that contains white space must be ++quoted so as to be contained within a single argument. A setting such as ++ ++command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}} ++ ++will not work, because the expansion item gets split between several arguments. ++You have to write ++ ++command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}" ++ ++to ensure that it is all in one argument. The expansion is done in this way, ++argument by argument, so that the number of arguments cannot be changed as a ++result of expansion, and quotes or backslashes in inserted variables do not ++interact with external quoting. However, this leads to problems if you want to ++generate multiple arguments (or the command name plus arguments) from a single ++expansion. In this situation, the simplest solution is to use a shell. For ++example: ++ ++command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}} ++ ++Special handling takes place when an argument consists of precisely the text ++"$pipe_addresses". This is not a general expansion variable; the only place ++this string is recognized is when it appears as an argument for a pipe or ++transport filter command. It causes each address that is being handled to be ++inserted in the argument list at that point as a separate argument. This avoids ++any problems with spaces or shell metacharacters, and is of use when a pipe ++transport is handling groups of addresses in a batch. ++ ++If force_command is enabled on the transport, Special handling takes place for ++an argument that consists of precisely the text "$address_pipe". It is handled ++similarly to $pipe_addresses above. It is expanded and each argument is ++inserted in the argument list at that point as a separate argument. The ++"$address_pipe" item does not need to be the only item in the argument; in ++fact, if it were then force_command should behave as a no-op. Rather, it should ++be used to adjust the command run while preserving the argument vector ++separation. ++ ++After splitting up into arguments and expansion, the resulting command is run ++in a subprocess directly from the transport, not under a shell. The message ++that is being delivered is supplied on the standard input, and the standard ++output and standard error are both connected to a single pipe that is read by ++Exim. The max_output option controls how much output the command may produce, ++and the return_output and return_fail_output options control what is done with ++it. ++ ++Not running the command under a shell (by default) lessens the security risks ++in cases when a command from a user's filter file is built out of data that was ++taken from an incoming message. If a shell is required, it can of course be ++explicitly specified as the command to be run. However, there are circumstances ++where existing commands (for example, in .forward files) expect to be run under ++a shell and cannot easily be modified. To allow for these cases, there is an ++option called use_shell, which changes the way the pipe transport works. ++Instead of breaking up the command line as just described, it expands it as a ++single string and passes the result to /bin/sh. The restrict_to_path option and ++the $pipe_addresses facility cannot be used with use_shell, and the whole ++mechanism is inherently less secure. ++ ++ ++29.4 Environment variables ++-------------------------- ++ ++The environment variables listed below are set up when the command is invoked. ++This list is a compromise for maximum compatibility with other MTAs. Note that ++the environment option can be used to add additional variables to this ++environment. ++ ++DOMAIN the domain of the address ++HOME the home directory, if set ++HOST the host name when called from a router (see below) ++LOCAL_PART see below ++LOCAL_PART_PREFIX see below ++LOCAL_PART_SUFFIX see below ++LOGNAME see below ++MESSAGE_ID Exim's local ID for the message ++PATH as specified by the path option below ++QUALIFY_DOMAIN the sender qualification domain ++RECIPIENT the complete recipient address ++SENDER the sender of the message (empty if a bounce) ++SHELL /bin/sh ++TZ the value of the timezone option, if set ++USER see below ++ ++When a pipe transport is called directly from (for example) an accept router, ++LOCAL_PART is set to the local part of the address. When it is called as a ++result of a forward or alias expansion, LOCAL_PART is set to the local part of ++the address that was expanded. In both cases, any affixes are removed from the ++local part, and made available in LOCAL_PART_PREFIX and LOCAL_PART_SUFFIX, ++respectively. LOGNAME and USER are set to the same value as LOCAL_PART for ++compatibility with other MTAs. ++ ++HOST is set only when a pipe transport is called from a router that associates ++hosts with an address, typically when using pipe as a pseudo-remote transport. ++HOST is set to the first host name specified by the router. ++ ++If the transport's generic home_directory option is set, its value is used for ++the HOME environment variable. Otherwise, a home directory may be set by the ++router's transport_home_directory option, which defaults to the user's home ++directory if check_local_user is set. ++ ++ ++29.5 Private options for pipe ++----------------------------- ++ +++----------------------------------------------------------+ ++|allow_commands|Use: pipe|Type: string list*|Default: unset| +++----------------------------------------------------------+ ++ ++The string is expanded, and is then interpreted as a colon-separated list of ++permitted commands. If restrict_to_path is not set, the only commands permitted ++are those in the allow_commands list. They need not be absolute paths; the path ++option is still used for relative paths. If restrict_to_path is set with ++allow_commands, the command must either be in the allow_commands list, or a ++name without any slashes that is found on the path. In other words, if neither ++allow_commands nor restrict_to_path is set, there is no restriction on the ++command, but otherwise only commands that are permitted by one or the other are ++allowed. For example, if ++ ++allow_commands = /usr/bin/vacation ++ ++and restrict_to_path is not set, the only permitted command is /usr/bin/ ++vacation. The allow_commands option may not be set if use_shell is set. ++ +++-----------------------------------------------+ ++|batch_id|Use: pipe|Type: string*|Default: unset| +++-----------------------------------------------+ ++ ++See the description of local delivery batching in chapter 25. ++ +++--------------------------------------------+ ++|batch_max|Use: pipe|Type: integer|Default: 1| +++--------------------------------------------+ ++ ++This limits the number of addresses that can be handled in a single delivery. ++See the description of local delivery batching in chapter 25. ++ +++--------------------------------------------------+ ++|check_string|Use: pipe|Type: string|Default: unset| +++--------------------------------------------------+ ++ ++As pipe writes the message, the start of each line is tested for matching ++check_string, and if it does, the initial matching characters are replaced by ++the contents of escape_string, provided both are set. The value of check_string ++is a literal string, not a regular expression, and the case of any letters it ++contains is significant. When use_bsmtp is set, the contents of check_string ++and escape_string are forced to values that implement the SMTP escaping ++protocol. Any settings made in the configuration file are ignored. ++ +++----------------------------------------------+ ++|command|Use: pipe|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++This option need not be set when pipe is being used to deliver to pipes ++obtained directly from address redirections. In other cases, the option must be ++set, to provide a command to be run. It need not yield an absolute path (see ++the path option below). The command is split up into separate arguments by ++Exim, and each argument is separately expanded, as described in section 29.3 ++above. ++ +++--------------------------------------------------+ ++|environment|Use: pipe|Type: string*|Default: unset| +++--------------------------------------------------+ ++ ++This option is used to add additional variables to the environment in which the ++command runs (see section 29.4 for the default list). Its value is a string ++which is expanded, and then interpreted as a colon-separated list of ++environment settings of the form <name>=<value>. ++ +++---------------------------------------------------+ ++|escape_string|Use: pipe|Type: string|Default: unset| +++---------------------------------------------------+ ++ ++See check_string above. ++ +++-------------------------------------------------------+ ++|freeze_exec_fail|Use: pipe|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++Failure to exec the command in a pipe transport is by default treated like any ++other failure while running the command. However, if freeze_exec_fail is set, ++failure to exec is treated specially, and causes the message to be frozen, ++whatever the setting of ignore_status. ++ +++----------------------------------------------------+ ++|freeze_signal|Use: pipe|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++Normally if the process run by a command in a pipe transport exits on a signal, ++a bounce message is sent. If freeze_signal is set, the message will be frozen ++in Exim's queue instead. ++ +++----------------------------------------------------+ ++|force_command|Use: pipe|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++Normally when a router redirects an address directly to a pipe command the ++command option on the transport is ignored. If force_command is set, the ++command option will used. This is especially useful for forcing a wrapper or ++additional argument to be added to the command. For example: ++ ++command = /usr/bin/remote_exec myhost -- $address_pipe ++force_command ++ ++Note that $address_pipe is handled specially in command when force_command is ++set, expanding out to the original argument vector as separate items, similarly ++to a Unix shell ""$@"" construct. ++ +++----------------------------------------------------+ ++|ignore_status|Use: pipe|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++If this option is true, the status returned by the subprocess that is set up to ++run the command is ignored, and Exim behaves as if zero had been returned. ++Otherwise, a non-zero status or termination by signal causes an error return ++from the transport unless the status value is one of those listed in ++temp_errors; these cause the delivery to be deferred and tried again later. ++ ++Note: This option does not apply to timeouts, which do not return a status. See ++the timeout_defer option for how timeouts are handled. ++ +++-------------------------------------------------------+ ++|log_defer_output|Use: pipe|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++If this option is set, and the status returned by the command is one of the ++codes listed in temp_errors (that is, delivery was deferred), and any output ++was produced, the first line of it is written to the main log. ++ +++------------------------------------------------------+ ++|log_fail_output|Use: pipe|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If this option is set, and the command returns any output, and also ends with a ++return code that is neither zero nor one of the return codes listed in ++temp_errors (that is, the delivery failed), the first line of output is written ++to the main log. This option and log_output are mutually exclusive. Only one of ++them may be set. ++ +++-------------------------------------------------+ ++|log_output|Use: pipe|Type: boolean|Default: false| +++-------------------------------------------------+ ++ ++If this option is set and the command returns any output, the first line of ++output is written to the main log, whatever the return code. This option and ++log_fail_output are mutually exclusive. Only one of them may be set. ++ +++-----------------------------------------------+ ++|max_output|Use: pipe|Type: integer|Default: 20K| +++-----------------------------------------------+ ++ ++This specifies the maximum amount of output that the command may produce on its ++standard output and standard error file combined. If the limit is exceeded, the ++process running the command is killed. This is intended as a safety measure to ++catch runaway processes. The limit is applied independently of the settings of ++the options that control what is done with such output (for example, ++return_output). Because of buffering effects, the amount of output may exceed ++the limit by a small amount before Exim notices. ++ +++---------------------------------------------------------+ ++|message_prefix|Use: pipe|Type: string*|Default: see below| +++---------------------------------------------------------+ ++ ++The string specified here is expanded and output at the start of every message. ++The default is unset if use_bsmtp is set. Otherwise it is ++ ++message_prefix = \ ++ From ${if def:return_path{$return_path}{MAILER-DAEMON}}\ ++ ${tod_bsdinbox}\n ++ ++This is required by the commonly used /usr/bin/vacation program. However, it ++must not be present if delivery is to the Cyrus IMAP server, or to the tmail ++local delivery agent. The prefix can be suppressed by setting ++ ++message_prefix = ++ ++Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ ++n" in message_prefix. ++ +++---------------------------------------------------------+ ++|message_suffix|Use: pipe|Type: string*|Default: see below| +++---------------------------------------------------------+ ++ ++The string specified here is expanded and output at the end of every message. ++The default is unset if use_bsmtp is set. Otherwise it is a single newline. The ++suffix can be suppressed by setting ++ ++message_suffix = ++ ++Note: If you set use_crlf true, you must change any occurrences of "\n" to "\r\ ++n" in message_suffix. ++ +++----------------------------------------------+ ++|path|Use: pipe|Type: string|Default: see below| +++----------------------------------------------+ ++ ++This option specifies the string that is set up in the PATH environment ++variable of the subprocess. The default is: ++ ++/bin:/usr/bin ++ ++If the command option does not yield an absolute path name, the command is ++sought in the PATH directories, in the usual way. Warning: This does not apply ++to a command specified as a transport filter. ++ +++------------------------------------------------------+ ++|permit_coredump|Use: pipe|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++Normally Exim inhibits core-dumps during delivery. If you have a need to get a ++core-dump of a pipe command, enable this command. This enables core-dumps ++during delivery and affects both the Exim binary and the pipe command run. It ++is recommended that this option remain off unless and until you have a need for ++it and that this only be enabled when needed, as the risk of excessive resource ++consumption can be quite high. Note also that Exim is typically installed as a ++setuid binary and most operating systems will inhibit coredumps of these by ++default, so further OS-specific action may be required. ++ +++------------------------------------------------------+ ++|pipe_as_creator|Use: pipe|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If the generic user option is not set and this option is true, the delivery ++process is run under the uid that was in force when Exim was originally called ++to accept the message. If the group id is not otherwise set (via the generic ++group option), the gid that was in force when Exim was originally called to ++accept the message is used. ++ +++-------------------------------------------------------+ ++|restrict_to_path|Use: pipe|Type: boolean|Default: false| +++-------------------------------------------------------+ ++ ++When this option is set, any command name not listed in allow_commands must ++contain no slashes. The command is searched for only in the directories listed ++in the path option. This option is intended for use in the case when a pipe ++command has been generated from a user's .forward file. This is usually handled ++by a pipe transport called address_pipe. ++ +++---------------------------------------------------------+ ++|return_fail_output|Use: pipe|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If this option is true, and the command produced any output and ended with a ++return code other than zero or one of the codes listed in temp_errors (that is, ++the delivery failed), the output is returned in the bounce message. However, if ++the message has a null sender (that is, it is itself a bounce message), output ++from the command is discarded. This option and return_output are mutually ++exclusive. Only one of them may be set. ++ +++----------------------------------------------------+ ++|return_output|Use: pipe|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++If this option is true, and the command produced any output, the delivery is ++deemed to have failed whatever the return code from the command, and the output ++is returned in the bounce message. Otherwise, the output is just discarded. ++However, if the message has a null sender (that is, it is a bounce message), ++output from the command is always discarded, whatever the setting of this ++option. This option and return_fail_output are mutually exclusive. Only one of ++them may be set. ++ +++----------------------------------------------------------+ ++|temp_errors|Use: pipe|Type: string list|Default: see below| +++----------------------------------------------------------+ ++ ++This option contains either a colon-separated list of numbers, or a single ++asterisk. If ignore_status is false and return_output is not set, and the ++command exits with a non-zero return code, the failure is treated as temporary ++and the delivery is deferred if the return code matches one of the numbers, or ++if the setting is a single asterisk. Otherwise, non-zero return codes are ++treated as permanent errors. The default setting contains the codes defined by ++EX_TEMPFAIL and EX_CANTCREAT in sysexits.h. If Exim is compiled on a system ++that does not define these macros, it assumes values of 75 and 73, ++respectively. ++ +++----------------------------------------+ ++|timeout|Use: pipe|Type: time|Default: 1h| +++----------------------------------------+ ++ ++If the command fails to complete within this time, it is killed. This normally ++causes the delivery to fail (but see timeout_defer). A zero time interval ++specifies no timeout. In order to ensure that any subprocesses created by the ++command are also killed, Exim makes the initial process a process group leader, ++and kills the whole process group on a timeout. However, this can be defeated ++if one of the processes starts a new process group. ++ +++----------------------------------------------------+ ++|timeout_defer|Use: pipe|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++A timeout in a pipe transport, either in the command that the transport runs, ++or in a transport filter that is associated with it, is by default treated as a ++hard error, and the delivery fails. However, if timeout_defer is set true, both ++kinds of timeout become temporary errors, causing the delivery to be deferred. ++ +++------------------------------------------------+ ++|umask|Use: pipe|Type: octal integer|Default: 022| +++------------------------------------------------+ ++ ++This specifies the umask setting for the subprocess that runs the command. ++ +++------------------------------------------------+ ++|use_bsmtp|Use: pipe|Type: boolean|Default: false| +++------------------------------------------------+ ++ ++If this option is set true, the pipe transport writes messages in "batch SMTP" ++format, with the envelope sender and recipient(s) included as SMTP commands. If ++you want to include a leading HELO command with such messages, you can do so by ++setting the message_prefix option. See section 47.10 for details of batch SMTP. ++ +++---------------------------------------------------------+ ++|use_classresources|Use: pipe|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++This option is available only when Exim is running on FreeBSD, NetBSD, or BSD/ ++OS. If it is set true, the setclassresources() function is used to set resource ++limits when a pipe transport is run to perform a delivery. The limits for the ++uid under which the pipe is to run are obtained from the login class database. ++ +++-----------------------------------------------+ ++|use_crlf|Use: pipe|Type: boolean|Default: false| +++-----------------------------------------------+ ++ ++This option causes lines to be terminated with the two-character CRLF sequence ++(carriage return, linefeed) instead of just a linefeed character. In the case ++of batched SMTP, the byte sequence written to the pipe is then an exact image ++of what would be sent down a real SMTP connection. ++ ++The contents of the message_prefix and message_suffix options are written ++verbatim, so must contain their own carriage return characters if these are ++needed. When use_bsmtp is not set, the default values for both message_prefix ++and message_suffix end with a single linefeed, so their values must be changed ++to end with "\r\n" if use_crlf is set. ++ +++------------------------------------------------+ ++|use_shell|Use: pipe|Type: boolean|Default: false| +++------------------------------------------------+ ++ ++If this option is set, it causes the command to be passed to /bin/sh instead of ++being run directly from the transport, as described in section 29.3. This is ++less secure, but is needed in some situations where the command is expected to ++be run under a shell and cannot easily be modified. The allow_commands and ++restrict_to_path options, and the "$pipe_addresses" facility are incompatible ++with use_shell. The command is expanded as a single string, and handed to /bin/ ++sh as data for its -c option. ++ ++ ++29.6 Using an external local delivery agent ++------------------------------------------- ++ ++The pipe transport can be used to pass all messages that require local delivery ++to a separate local delivery agent such as procmail. When doing this, care must ++be taken to ensure that the pipe is run under an appropriate uid and gid. In ++some configurations one wants this to be a uid that is trusted by the delivery ++agent to supply the correct sender of the message. It may be necessary to ++recompile or reconfigure the delivery agent so that it trusts an appropriate ++user. The following is an example transport and router configuration for ++procmail: ++ ++# transport ++procmail_pipe: ++ driver = pipe ++ command = /usr/local/bin/procmail -d $local_part ++ return_path_add ++ delivery_date_add ++ envelope_to_add ++ check_string = "From " ++ escape_string = ">From " ++ umask = 077 ++ user = $local_part ++ group = mail ++ ++# router ++procmail: ++ driver = accept ++ check_local_user ++ transport = procmail_pipe ++ ++In this example, the pipe is run as the local user, but with the group set to ++mail. An alternative is to run the pipe as a specific user such as mail or exim ++, but in this case you must arrange for procmail to trust that user to supply a ++correct sender address. If you do not specify either a group or a user option, ++the pipe command is run as the local user. The home directory is the user's ++home directory by default. ++ ++Note: The command that the pipe transport runs does not begin with ++ ++IFS=" " ++ ++as shown in some procmail documentation, because Exim does not by default use a ++shell to run pipe commands. ++ ++The next example shows a transport and a router for a system where local ++deliveries are handled by the Cyrus IMAP server. ++ ++# transport ++local_delivery_cyrus: ++ driver = pipe ++ command = /usr/cyrus/bin/deliver \ ++ -m ${substr_1:$local_part_suffix} -- $local_part ++ user = cyrus ++ group = mail ++ return_output ++ log_output ++ message_prefix = ++ message_suffix = ++ ++# router ++local_user_cyrus: ++ driver = accept ++ check_local_user ++ local_part_suffix = .* ++ transport = local_delivery_cyrus ++ ++Note the unsetting of message_prefix and message_suffix, and the use of ++return_output to cause any text written by Cyrus to be returned to the sender. ++ ++ ++ ++=============================================================================== ++30. THE SMTP TRANSPORT ++ ++The smtp transport delivers messages over TCP/IP connections using the SMTP or ++LMTP protocol. The list of hosts to try can either be taken from the address ++that is being processed (having been set up by the router), or specified ++explicitly for the transport. Timeout and retry processing (see chapter 32) is ++applied to each IP address independently. ++ ++ ++30.1 Multiple messages on a single connection ++--------------------------------------------- ++ ++The sending of multiple messages over a single TCP/IP connection can arise in ++two ways: ++ ++ * If a message contains more than max_rcpt (see below) addresses that are ++ routed to the same host, more than one copy of the message has to be sent ++ to that host. In this situation, multiple copies may be sent in a single ++ run of the smtp transport over a single TCP/IP connection. (What Exim ++ actually does when it has too many addresses to send in one message also ++ depends on the value of the global remote_max_parallel option. Details are ++ given in section 47.1.) ++ ++ * When a message has been successfully delivered over a TCP/IP connection, ++ Exim looks in its hints database to see if there are any other messages ++ awaiting a connection to the same host. If there are, a new delivery ++ process is started for one of them, and the current TCP/IP connection is ++ passed on to it. The new process may in turn send multiple copies and ++ possibly create yet another process. ++ ++For each copy sent over the same TCP/IP connection, a sequence counter is ++incremented, and if it ever gets to the value of connection_max_messages, no ++further messages are sent over that connection. ++ ++ ++30.2 Use of the $host and $host_address variables ++------------------------------------------------- ++ ++At the start of a run of the smtp transport, the values of $host and ++$host_address are the name and IP address of the first host on the host list ++passed by the router. However, when the transport is about to connect to a ++specific host, and while it is connected to that host, $host and $host_address ++are set to the values for that host. These are the values that are in force ++when the helo_data, hosts_try_auth, interface, serialize_hosts, and the various ++TLS options are expanded. ++ ++ ++30.3 Use of $tls_cipher and $tls_peerdn ++--------------------------------------- ++ ++At the start of a run of the smtp transport, the values of $tls_bits, ++$tls_cipher, $tls_peerdn and $tls_sni are the values that were set when the ++message was received. These are the values that are used for options that are ++expanded before any SMTP connections are made. Just before each connection is ++made, these four variables are emptied. If TLS is subsequently started, they ++are set to the appropriate values for the outgoing connection, and these are ++the values that are in force when any authenticators are run and when the ++authenticated_sender option is expanded. ++ ++These variables are deprecated in favour of $tls_in_cipher et. al. and will be ++removed in a future release. ++ ++ ++30.4 Private options for smtp ++----------------------------- ++ ++The private options of the smtp transport are as follows: ++ +++------------------------------------------------------------------+ ++|address_retry_include_sender|Use: smtp|Type: boolean|Default: true| +++------------------------------------------------------------------+ ++ ++When an address is delayed because of a 4xx response to a RCPT command, it is ++the combination of sender and recipient that is delayed in subsequent queue ++runs until the retry time is reached. You can delay the recipient without ++reference to the sender (which is what earlier versions of Exim did), by ++setting address_retry_include_sender false. However, this can lead to problems ++with servers that regularly issue 4xx responses to RCPT commands. ++ +++------------------------------------------------------+ ++|allow_localhost|Use: smtp|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++When a host specified in hosts or fallback_hosts (see below) turns out to be ++the local host, or is listed in hosts_treat_as_local, delivery is deferred by ++default. However, if allow_localhost is set, Exim goes on to do the delivery ++anyway. This should be used only in special cases when the configuration ++ensures that no looping will result (for example, a differently configured Exim ++is listening on the port to which the message is sent). ++ +++-----------------------------------------------------------+ ++|authenticated_sender|Use: smtp|Type: string*|Default: unset| +++-----------------------------------------------------------+ ++ ++When Exim has authenticated as a client, or if authenticated_sender_force is ++true, this option sets a value for the AUTH= item on outgoing MAIL commands, ++overriding any existing authenticated sender value. If the string expansion is ++forced to fail, the option is ignored. Other expansion failures cause delivery ++to be deferred. If the result of expansion is an empty string, that is also ++ignored. ++ ++The expansion happens after the outgoing connection has been made and TLS ++started, if required. This means that the $host, $host_address, $tls_out_cipher ++, and $tls_out_peerdn variables are set according to the particular connection. ++ ++If the SMTP session is not authenticated, the expansion of authenticated_sender ++still happens (and can cause the delivery to be deferred if it fails), but no ++AUTH= item is added to MAIL commands unless authenticated_sender_force is true. ++ ++This option allows you to use the smtp transport in LMTP mode to deliver mail ++to Cyrus IMAP and provide the proper local part as the "authenticated sender", ++via a setting such as: ++ ++authenticated_sender = $local_part ++ ++This removes the need for IMAP subfolders to be assigned special ACLs to allow ++direct delivery to those subfolders. ++ ++Because of expected uses such as that just described for Cyrus (when no domain ++is involved), there is no checking on the syntax of the provided value. ++ +++-----------------------------------------------------------------+ ++|authenticated_sender_force|Use: smtp|Type: boolean|Default: false| +++-----------------------------------------------------------------+ ++ ++If this option is set true, the authenticated_sender option's value is used for ++the AUTH= item on outgoing MAIL commands, even if Exim has not authenticated as ++a client. ++ +++------------------------------------------------+ ++|command_timeout|Use: smtp|Type: time|Default: 5m| +++------------------------------------------------+ ++ ++This sets a timeout for receiving a response to an SMTP command that has been ++sent out. It is also used when waiting for the initial banner line from the ++remote host. Its value must not be zero. ++ +++------------------------------------------------+ ++|connect_timeout|Use: smtp|Type: time|Default: 5m| +++------------------------------------------------+ ++ ++This sets a timeout for the connect() function, which sets up a TCP/IP call to ++a remote host. A setting of zero allows the system timeout (typically several ++minutes) to act. To have any effect, the value of this option must be less than ++the system timeout. However, it has been observed that on some systems there is ++no system timeout, which is why the default value for this option is 5 minutes, ++a value recommended by RFC 1123. ++ +++------------------------------------------------------------+ ++|connection_max_messages|Use: smtp|Type: integer|Default: 500| +++------------------------------------------------------------+ ++ ++This controls the maximum number of separate message deliveries that are sent ++over a single TCP/IP connection. If the value is zero, there is no limit. For ++testing purposes, this value can be overridden by the -oB command line option. ++ +++---------------------------------------------+ ++|data_timeout|Use: smtp|Type: time|Default: 5m| +++---------------------------------------------+ ++ ++This sets a timeout for the transmission of each block in the data portion of ++the message. As a result, the overall timeout for a message depends on the size ++of the message. Its value must not be zero. See also final_timeout. ++ +++--------------------------------------------------------+ ++|delay_after_cutoff|Use: smtp|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++This option controls what happens when all remote IP addresses for a given ++domain have been inaccessible for so long that they have passed their retry ++cutoff times. ++ ++In the default state, if the next retry time has not been reached for any of ++them, the address is bounced without trying any deliveries. In other words, ++Exim delays retrying an IP address after the final cutoff time until a new ++retry time is reached, and can therefore bounce an address without ever trying ++a delivery, when machines have been down for a long time. Some people are ++unhappy at this prospect, so... ++ ++If delay_after_cutoff is set false, Exim behaves differently. If all IP ++addresses are past their final cutoff time, Exim tries to deliver to those IP ++addresses that have not been tried since the message arrived. If there are ++none, of if they all fail, the address is bounced. In other words, it does not ++delay when a new message arrives, but immediately tries those expired IP ++addresses that haven't been tried since the message arrived. If there is a ++continuous stream of messages for the dead hosts, unsetting delay_after_cutoff ++means that there will be many more attempts to deliver to them. ++ +++--------------------------------------------------------+ ++|dns_qualify_single|Use: smtp|Type: boolean|Default: true| +++--------------------------------------------------------+ ++ ++If the hosts or fallback_hosts option is being used, and the gethostbyname ++option is false, the RES_DEFNAMES resolver option is set. See the ++qualify_single option in chapter 17 for more details. ++ +++---------------------------------------------------------+ ++|dns_search_parents|Use: smtp|Type: boolean|Default: false| +++---------------------------------------------------------+ ++ ++If the hosts or fallback_hosts option is being used, and the gethostbyname ++option is false, the RES_DNSRCH resolver option is set. See the search_parents ++option in chapter 17 for more details. ++ +++-------------------------------------------+ ++|dscp|Use: smtp|Type: string*|Default: unset| +++-------------------------------------------+ ++ ++This option causes the DSCP value associated with a socket to be set to one of ++a number of fixed strings or to numeric value. The -bI:dscp option may be used ++to ask Exim which names it knows of. Common values include "throughput", ++"mincost", and on newer systems "ef", "af41", etc. Numeric values may be in the ++range 0 to 0x3F. ++ ++The outbound packets from Exim will be marked with this value in the header ++(for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee ++that these values will have any effect, not be stripped by networking ++equipment, or do much of anything without cooperation with your Network ++Engineer and those of all network operators between the source and destination. ++ +++---------------------------------------------------------+ ++|fallback_hosts|Use: smtp|Type: string list|Default: unset| +++---------------------------------------------------------+ ++ ++String expansion is not applied to this option. The argument must be a ++colon-separated list of host names or IP addresses, optionally also including ++port numbers, though the separator can be changed, as described in section 6.19 ++. Each individual item in the list is the same as an item in a route_list ++setting for the manualroute router, as described in section 20.5. ++ ++Fallback hosts can also be specified on routers, which associate them with the ++addresses they process. As for the hosts option without hosts_override, ++fallback_hosts specified on the transport is used only if the address does not ++have its own associated fallback host list. Unlike hosts, a setting of ++fallback_hosts on an address is not overridden by hosts_override. However, ++hosts_randomize does apply to fallback host lists. ++ ++If Exim is unable to deliver to any of the hosts for a particular address, and ++the errors are not permanent rejections, the address is put on a separate ++transport queue with its host list replaced by the fallback hosts, unless the ++address was routed via MX records and the current host was in the original MX ++list. In that situation, the fallback host list is not used. ++ ++Once normal deliveries are complete, the fallback queue is delivered by ++re-running the same transports with the new host lists. If several failing ++addresses have the same fallback hosts (and max_rcpt permits it), a single copy ++of the message is sent. ++ ++The resolution of the host names on the fallback list is controlled by the ++gethostbyname option, as for the hosts option. Fallback hosts apply both to ++cases when the host list comes with the address and when it is taken from hosts ++. This option provides a "use a smart host only if delivery fails" facility. ++ +++-----------------------------------------------+ ++|final_timeout|Use: smtp|Type: time|Default: 10m| +++-----------------------------------------------+ ++ ++This is the timeout that applies while waiting for the response to the final ++line containing just "." that terminates a message. Its value must not be zero. ++ +++----------------------------------------------------+ ++|gethostbyname|Use: smtp|Type: boolean|Default: false| +++----------------------------------------------------+ ++ ++If this option is true when the hosts and/or fallback_hosts options are being ++used, names are looked up using gethostbyname() (or getipnodebyname() when ++available) instead of using the DNS. Of course, that function may in fact use ++the DNS, but it may also consult other sources of information such as /etc/ ++hosts. ++ +++---------------------------------------------------------+ ++|gnutls_compat_mode|Use: smtp|Type: boolean|Default: unset| +++---------------------------------------------------------+ ++ ++This option controls whether GnuTLS is used in compatibility mode in an Exim ++server. This reduces security slightly, but improves interworking with older ++implementations of TLS. ++ +++----------------------------------------------------+ ++|helo_data|Use: smtp|Type: string*|Default: see below| +++----------------------------------------------------+ ++ ++The value of this option is expanded after a connection to a another host has ++been set up. The result is used as the argument for the EHLO, HELO, or LHLO ++command that starts the outgoing SMTP or LMTP session. The default value of the ++option is: ++ ++$primary_hostname ++ ++During the expansion, the variables $host and $host_address are set to the ++identity of the remote host, and the variables $sending_ip_address and ++$sending_port are set to the local IP address and port number that are being ++used. These variables can be used to generate different values for different ++servers or different local IP addresses. For example, if you want the string ++that is used for helo_data to be obtained by a DNS lookup of the outgoing ++interface address, you could use this: ++ ++helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\ ++ {$primary_hostname}} ++ ++The use of helo_data applies both to sending messages and when doing callouts. ++ +++-------------------------------------------------+ ++|hosts|Use: smtp|Type: string list*|Default: unset| +++-------------------------------------------------+ ++ ++Hosts are associated with an address by a router such as dnslookup, which finds ++the hosts by looking up the address domain in the DNS, or by manualroute, which ++has lists of hosts in its configuration. However, email addresses can be passed ++to the smtp transport by any router, and not all of them can provide an ++associated list of hosts. ++ ++The hosts option specifies a list of hosts to be used if the address being ++processed does not have any hosts associated with it. The hosts specified by ++hosts are also used, whether or not the address has its own hosts, if ++hosts_override is set. ++ ++The string is first expanded, before being interpreted as a colon-separated ++list of host names or IP addresses, possibly including port numbers. The ++separator may be changed to something other than colon, as described in section ++6.19. Each individual item in the list is the same as an item in a route_list ++setting for the manualroute router, as described in section 20.5. However, note ++that the "/MX" facility of the manualroute router is not available here. ++ ++If the expansion fails, delivery is deferred. Unless the failure was caused by ++the inability to complete a lookup, the error is logged to the panic log as ++well as the main log. Host names are looked up either by searching directly for ++address records in the DNS or by calling gethostbyname() (or getipnodebyname() ++when available), depending on the setting of the gethostbyname option. When ++Exim is compiled with IPv6 support, if a host that is looked up in the DNS has ++both IPv4 and IPv6 addresses, both types of address are used. ++ ++During delivery, the hosts are tried in order, subject to their retry status, ++unless hosts_randomize is set. ++ +++-----------------------------------------------------------+ ++|hosts_avoid_esmtp|Use: smtp|Type: host list*|Default: unset| +++-----------------------------------------------------------+ ++ ++This option is for use with broken hosts that announce ESMTP facilities (for ++example, PIPELINING) and then fail to implement them properly. When a host ++matches hosts_avoid_esmtp, Exim sends HELO rather than EHLO at the start of the ++SMTP session. This means that it cannot use any of the ESMTP facilities such as ++AUTH, PIPELINING, SIZE, and STARTTLS. ++ +++----------------------------------------------------------------+ ++|hosts_avoid_pipelining|Use: smtp|Type: host list*|Default: unset| +++----------------------------------------------------------------+ ++ ++Exim will not use the SMTP PIPELINING extension when delivering to any host ++that matches this list, even if the server host advertises PIPELINING support. ++ +++---------------------------------------------------------+ ++|hosts_avoid_tls|Use: smtp|Type: host list*|Default: unset| +++---------------------------------------------------------+ ++ ++Exim will not try to start a TLS session when delivering to any host that ++matches this list. See chapter 41 for details of TLS. ++ +++------------------------------------------------------------+ ++|hosts_verify_avoid_tls|Use: smtp|Type: host list*|Default: *| +++------------------------------------------------------------+ ++ ++Exim will not try to start a TLS session for a verify callout, or when ++delivering in cutthrough mode, to any host that matches this list. Note that ++the default is to not use TLS. ++ +++------------------------------------------------+ ++|hosts_max_try|Use: smtp|Type: integer|Default: 5| +++------------------------------------------------+ ++ ++This option limits the number of IP addresses that are tried for any one ++delivery in cases where there are temporary delivery errors. Section 30.5 ++describes in detail how the value of this option is used. ++ +++-----------------------------------------------------------+ ++|hosts_max_try_hardlimit|Use: smtp|Type: integer|Default: 50| +++-----------------------------------------------------------+ ++ ++This is an additional check on the maximum number of IP addresses that Exim ++tries for any one delivery. Section 30.5 describes its use and why it exists. ++ +++----------------------------------------------------------+ ++|hosts_nopass_tls|Use: smtp|Type: host list*|Default: unset| +++----------------------------------------------------------+ ++ ++For any host that matches this list, a connection on which a TLS session has ++been started will not be passed to a new delivery process for sending another ++message on the same connection. See section 41.11 for an explanation of when ++this might be needed. ++ +++-----------------------------------------------------+ ++|hosts_override|Use: smtp|Type: boolean|Default: false| +++-----------------------------------------------------+ ++ ++If this option is set and the hosts option is also set, any hosts that are ++attached to the address are ignored, and instead the hosts specified by the ++hosts option are always used. This option does not apply to fallback_hosts. ++ +++------------------------------------------------------+ ++|hosts_randomize|Use: smtp|Type: boolean|Default: false| +++------------------------------------------------------+ ++ ++If this option is set, and either the list of hosts is taken from the hosts or ++the fallback_hosts option, or the hosts supplied by the router were not ++obtained from MX records (this includes fallback hosts from the router), and ++were not randomized by the router, the order of trying the hosts is randomized ++each time the transport runs. Randomizing the order of a host list can be used ++to do crude load sharing. ++ ++When hosts_randomize is true, a host list may be split into groups whose order ++is separately randomized. This makes it possible to set up MX-like behaviour. ++The boundaries between groups are indicated by an item that is just "+" in the ++host list. For example: ++ ++hosts = host1:host2:host3:+:host4:host5 ++ ++The order of the first three hosts and the order of the last two hosts is ++randomized for each use, but the first three always end up before the last two. ++If hosts_randomize is not set, a "+" item in the list is ignored. ++ +++------------------------------------------------------------+ ++|hosts_require_auth|Use: smtp|Type: host list*|Default: unset| +++------------------------------------------------------------+ ++ ++This option provides a list of servers for which authentication must succeed ++before Exim will try to transfer a message. If authentication fails for servers ++which are not in this list, Exim tries to send unauthenticated. If ++authentication fails for one of these servers, delivery is deferred. This ++temporary error is detectable in the retry rules, so it can be turned into a ++hard failure if required. See also hosts_try_auth, and chapter 33 for details ++of authentication. ++ +++-----------------------------------------------------------+ ++|hosts_require_tls|Use: smtp|Type: host list*|Default: unset| +++-----------------------------------------------------------+ ++ ++Exim will insist on using a TLS session when delivering to any host that ++matches this list. See chapter 41 for details of TLS. Note: This option affects ++outgoing mail only. To insist on TLS for incoming messages, use an appropriate ++ACL. ++ +++--------------------------------------------------------+ ++|hosts_try_auth|Use: smtp|Type: host list*|Default: unset| +++--------------------------------------------------------+ ++ ++This option provides a list of servers to which, provided they announce ++authentication support, Exim will attempt to authenticate as a client when it ++connects. If authentication fails, Exim will try to transfer the message ++unauthenticated. See also hosts_require_auth, and chapter 33 for details of ++authentication. ++ +++-----------------------------------------------------+ ++|interface|Use: smtp|Type: string list*|Default: unset| +++-----------------------------------------------------+ ++ ++This option specifies which interface to bind to when making an outgoing SMTP ++call. The value is an IP address, not an interface name such as "eth0". Do not ++confuse this with the interface address that was used when a message was ++received, which is in $received_ip_address, formerly known as ++$interface_address. The name was changed to minimize confusion with the ++outgoing interface address. There is no variable that contains an outgoing ++interface address because, unless it is set by this option, its value is ++unknown. ++ ++During the expansion of the interface option the variables $host and ++$host_address refer to the host to which a connection is about to be made ++during the expansion of the string. Forced expansion failure, or an empty ++string result causes the option to be ignored. Otherwise, after expansion, the ++string must be a list of IP addresses, colon-separated by default, but the ++separator can be changed in the usual way. For example: ++ ++interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061 ++ ++The first interface of the correct type (IPv4 or IPv6) is used for the outgoing ++connection. If none of them are the correct type, the option is ignored. If ++interface is not set, or is ignored, the system's IP functions choose which ++interface to use if the host has more than one. ++ +++-----------------------------------------------+ ++|keepalive|Use: smtp|Type: boolean|Default: true| +++-----------------------------------------------+ ++ ++This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket ++connections. When set, it causes the kernel to probe idle connections ++periodically, by sending packets with "old" sequence numbers. The other end of ++the connection should send a acknowledgment if the connection is still okay or ++a reset if the connection has been aborted. The reason for doing this is that ++it has the beneficial effect of freeing up certain types of connection that can ++get stuck when the remote host is disconnected without tidying up the TCP/IP ++call properly. The keepalive mechanism takes several hours to detect ++unreachable hosts. ++ +++--------------------------------------------------------+ ++|lmtp_ignore_quota|Use: smtp|Type: boolean|Default: false| +++--------------------------------------------------------+ ++ ++If this option is set true when the protocol option is set to "lmtp", the ++string "IGNOREQUOTA" is added to RCPT commands, provided that the LMTP server ++has advertised support for IGNOREQUOTA in its response to the LHLO command. ++ +++---------------------------------------------+ ++|max_rcpt|Use: smtp|Type: integer|Default: 100| +++---------------------------------------------+ ++ ++This option limits the number of RCPT commands that are sent in a single SMTP ++message transaction. Each set of addresses is treated independently, and so can ++cause parallel connections to the same host if remote_max_parallel permits ++this. ++ +++--------------------------------------------------+ ++|multi_domain|Use: smtp|Type: boolean|Default: true| +++--------------------------------------------------+ ++ ++When this option is set, the smtp transport can handle a number of addresses ++containing a mixture of different domains provided they all resolve to the same ++list of hosts. Turning the option off restricts the transport to handling only ++one domain at a time. This is useful if you want to use $domain in an expansion ++for the transport, because it is set only when there is a single domain ++involved in a remote delivery. ++ +++-----------------------------------------------+ ++|port|Use: smtp|Type: string*|Default: see below| +++-----------------------------------------------+ ++ ++This option specifies the TCP/IP port on the server to which Exim connects. ++Note: Do not confuse this with the port that was used when a message was ++received, which is in $received_port, formerly known as $interface_port. The ++name was changed to minimize confusion with the outgoing port. There is no ++variable that contains an outgoing port. ++ ++If the value of this option begins with a digit it is taken as a port number; ++otherwise it is looked up using getservbyname(). The default value is normally ++"smtp", but if protocol is set to "lmtp", the default is "lmtp". If the ++expansion fails, or if a port number cannot be found, delivery is deferred. ++ +++---------------------------------------------+ ++|protocol|Use: smtp|Type: string|Default: smtp| +++---------------------------------------------+ ++ ++If this option is set to "lmtp" instead of "smtp", the default value for the ++port option changes to "lmtp", and the transport operates the LMTP protocol ++(RFC 2033) instead of SMTP. This protocol is sometimes used for local ++deliveries into closed message stores. Exim also has support for running LMTP ++over a pipe to a local process - see chapter 28. ++ ++If this option is set to "smtps", the default vaule for the port option changes ++to "smtps", and the transport initiates TLS immediately after connecting, as an ++outbound SSL-on-connect, instead of using STARTTLS to upgrade. The Internet ++standards bodies strongly discourage use of this mode. ++ +++--------------------------------------------------------------+ ++|retry_include_ip_address|Use: smtp|Type: boolean|Default: true| +++--------------------------------------------------------------+ ++ ++Exim normally includes both the host name and the IP address in the key it ++constructs for indexing retry data after a temporary delivery failure. This ++means that when one of several IP addresses for a host is failing, it gets ++tried periodically (controlled by the retry rules), but use of the other IP ++addresses is not affected. ++ ++However, in some dialup environments hosts are assigned a different IP address ++each time they connect. In this situation the use of the IP address as part of ++the retry key leads to undesirable behaviour. Setting this option false causes ++Exim to use only the host name. This should normally be done on a separate ++instance of the smtp transport, set up specially to handle the dialup hosts. ++ +++---------------------------------------------------------+ ++|serialize_hosts|Use: smtp|Type: host list*|Default: unset| +++---------------------------------------------------------+ ++ ++Because Exim operates in a distributed manner, if several messages for the same ++host arrive at around the same time, more than one simultaneous connection to ++the remote host can occur. This is not usually a problem except when there is a ++slow link between the hosts. In that situation it may be helpful to restrict ++Exim to one connection at a time. This can be done by setting serialize_hosts ++to match the relevant hosts. ++ ++Exim implements serialization by means of a hints database in which a record is ++written whenever a process connects to one of the restricted hosts. The record ++is deleted when the connection is completed. Obviously there is scope for ++records to get left lying around if there is a system or program crash. To ++guard against this, Exim ignores any records that are more than six hours old. ++ ++If you set up this kind of serialization, you should also arrange to delete the ++relevant hints database whenever your system reboots. The names of the files ++start with misc and they are kept in the spool/db directory. There may be one ++or two files, depending on the type of DBM in use. The same files are used for ++ETRN serialization. ++ +++---------------------------------------------------+ ++|size_addition|Use: smtp|Type: integer|Default: 1024| +++---------------------------------------------------+ ++ ++If a remote SMTP server indicates that it supports the SIZE option of the MAIL ++command, Exim uses this to pass over the message size at the start of an SMTP ++transaction. It adds the value of size_addition to the value it sends, to allow ++for headers and other text that may be added during delivery by configuration ++options or in a transport filter. It may be necessary to increase this if a lot ++of text is added to messages. ++ ++Alternatively, if the value of size_addition is set negative, it disables the ++use of the SIZE option altogether. ++ +++------------------------------------------------------+ ++|tls_certificate|Use: smtp|Type: string*|Default: unset| +++------------------------------------------------------+ ++ ++The value of this option must be the absolute path to a file which contains the ++client's certificate, for possible use when sending a message over an encrypted ++connection. The values of $host and $host_address are set to the name and ++address of the server during the expansion. See chapter 41 for details of TLS. ++ ++Note: This option must be set if you want Exim to be able to use a TLS ++certificate when sending messages as a client. The global option of the same ++name specifies the certificate for Exim as a server; it is not automatically ++assumed that the same certificate should be used when Exim is operating as a ++client. ++ +++----------------------------------------------+ ++|tls_crl|Use: smtp|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++This option specifies a certificate revocation list. The expanded value must be ++the name of a file that contains a CRL in PEM format. ++ +++-----------------------------------------------------+ ++|tls_dh_min_bits|Use: smtp|Type: integer|Default: 1024| +++-----------------------------------------------------+ ++ ++When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman key ++agreement is negotiated, the server will provide a large prime number for use. ++This option establishes the minimum acceptable size of that number. If the ++parameter offered by the server is too small, then the TLS handshake will fail. ++ ++Only supported when using GnuTLS. ++ +++-----------------------------------------------------+ ++|tls_privatekey|Use: smtp|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++The value of this option must be the absolute path to a file which contains the ++client's private key. This is used when sending a message over an encrypted ++connection using a client certificate. The values of $host and $host_address ++are set to the name and address of the server during the expansion. If this ++option is unset, or the expansion is forced to fail, or the result is an empty ++string, the private key is assumed to be in the same file as the certificate. ++See chapter 41 for details of TLS. ++ +++----------------------------------------------------------+ ++|tls_require_ciphers|Use: smtp|Type: string*|Default: unset| +++----------------------------------------------------------+ ++ ++The value of this option must be a list of permitted cipher suites, for use ++when setting up an outgoing encrypted connection. (There is a global option of ++the same name for controlling incoming connections.) The values of $host and ++$host_address are set to the name and address of the server during the ++expansion. See chapter 41 for details of TLS; note that this option is used in ++different ways by OpenSSL and GnuTLS (see sections 41.4 and 41.5). For GnuTLS, ++the order of the ciphers is a preference order. ++ +++----------------------------------------------+ ++|tls_sni|Use: smtp|Type: string*|Default: unset| +++----------------------------------------------+ ++ ++If this option is set then it sets the $tls_out_sni variable and causes any TLS ++session to pass this value as the Server Name Indication extension to the ++remote side, which can be used by the remote side to select an appropriate ++certificate and private key for the session. ++ ++See 41.10 for more information. ++ ++Note that for OpenSSL, this feature requires a build of OpenSSL that supports ++TLS extensions. ++ +++-----------------------------------------------------------+ ++|tls_tempfail_tryclear|Use: smtp|Type: boolean|Default: true| +++-----------------------------------------------------------+ ++ ++When the server host is not in hosts_require_tls, and there is a problem in ++setting up a TLS session, this option determines whether or not Exim should try ++to deliver the message unencrypted. If it is set false, delivery to the current ++host is deferred; if there are other hosts, they are tried. If this option is ++set true, Exim attempts to deliver unencrypted after a 4xx response to ++STARTTLS. Also, if STARTTLS is accepted, but the subsequent TLS negotiation ++fails, Exim closes the current connection (because it is in an unknown state), ++opens a new one to the same host, and then tries the delivery in clear. ++ +++--------------------------------------------------------------+ ++|tls_verify_certificates|Use: smtp|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++The value of this option must be the absolute path to a file containing ++permitted server certificates, for use when setting up an encrypted connection. ++Alternatively, if you are using OpenSSL, you can set tls_verify_certificates to ++the name of a directory containing certificate files. This does not work with ++GnuTLS; the option must be set to the name of a single file if you are using ++GnuTLS. The values of $host and $host_address are set to the name and address ++of the server during the expansion of this option. See chapter 41 for details ++of TLS. ++ ++ ++30.5 How the limits for the number of hosts to try are used ++----------------------------------------------------------- ++ ++There are two options that are concerned with the number of hosts that are ++tried when an SMTP delivery takes place. They are hosts_max_try and ++hosts_max_try_hardlimit. ++ ++The hosts_max_try option limits the number of hosts that are tried for a single ++delivery. However, despite the term "host" in its name, the option actually ++applies to each IP address independently. In other words, a multihomed host is ++treated as several independent hosts, just as it is for retrying. ++ ++Many of the larger ISPs have multiple MX records which often point to ++multihomed hosts. As a result, a list of a dozen or more IP addresses may be ++created as a result of routing one of these domains. ++ ++Trying every single IP address on such a long list does not seem sensible; if ++several at the top of the list fail, it is reasonable to assume there is some ++problem that is likely to affect all of them. Roughly speaking, the value of ++hosts_max_try is the maximum number that are tried before deferring the ++delivery. However, the logic cannot be quite that simple. ++ ++Firstly, IP addresses that are skipped because their retry times have not ++arrived do not count, and in addition, addresses that are past their retry ++limits are also not counted, even when they are tried. This means that when ++some IP addresses are past their retry limits, more than the value of ++hosts_max_retry may be tried. The reason for this behaviour is to ensure that ++all IP addresses are considered before timing out an email address (but see ++below for an exception). ++ ++Secondly, when the hosts_max_try limit is reached, Exim looks down the host ++list to see if there is a subsequent host with a different (higher valued) MX. ++If there is, that host is considered next, and the current IP address is used ++but not counted. This behaviour helps in the case of a domain with a retry rule ++that hardly ever delays any hosts, as is now explained: ++ ++Consider the case of a long list of hosts with one MX value, and a few with a ++higher MX value. If hosts_max_try is small (the default is 5) only a few hosts ++at the top of the list are tried at first. With the default retry rule, which ++specifies increasing retry times, the higher MX hosts are eventually tried when ++those at the top of the list are skipped because they have not reached their ++retry times. ++ ++However, it is common practice to put a fixed short retry time on domains for ++large ISPs, on the grounds that their servers are rarely down for very long. ++Unfortunately, these are exactly the domains that tend to resolve to long lists ++of hosts. The short retry time means that the lowest MX hosts are tried every ++time. The attempts may be in a different order because of random sorting, but ++without the special MX check, the higher MX hosts would never be tried until ++all the lower MX hosts had timed out (which might be several days), because ++there are always some lower MX hosts that have reached their retry times. With ++the special check, Exim considers at least one IP address from each MX value at ++every delivery attempt, even if the hosts_max_try limit has already been ++reached. ++ ++The above logic means that hosts_max_try is not a hard limit, and in ++particular, Exim normally eventually tries all the IP addresses before timing ++out an email address. When hosts_max_try was implemented, this seemed a ++reasonable thing to do. Recently, however, some lunatic DNS configurations have ++been set up with hundreds of IP addresses for some domains. It can take a very ++long time indeed for an address to time out in these cases. ++ ++The hosts_max_try_hardlimit option was added to help with this problem. Exim ++never tries more than this number of IP addresses; if it hits this limit and ++they are all timed out, the email address is bounced, even though not all ++possible IP addresses have been tried. ++ ++ ++ ++=============================================================================== ++31. ADDRESS REWRITING ++ ++There are some circumstances in which Exim automatically rewrites domains in ++addresses. The two most common are when an address is given without a domain ++(referred to as an "unqualified address") or when an address contains an ++abbreviated domain that is expanded by DNS lookup. ++ ++Unqualified envelope addresses are accepted only for locally submitted ++messages, or for messages that are received from hosts matching ++sender_unqualified_hosts or recipient_unqualified_hosts, as appropriate. ++Unqualified addresses in header lines are qualified if they are in locally ++submitted messages, or messages from hosts that are permitted to send ++unqualified envelope addresses. Otherwise, unqualified addresses in header ++lines are neither qualified nor rewritten. ++ ++One situation in which Exim does not automatically rewrite a domain is when it ++is the name of a CNAME record in the DNS. The older RFCs suggest that such a ++domain should be rewritten using the "canonical" name, and some MTAs do this. ++The new RFCs do not contain this suggestion. ++ ++ ++31.1 Explicitly configured address rewriting ++-------------------------------------------- ++ ++This chapter describes the rewriting rules that can be used in the main rewrite ++section of the configuration file, and also in the generic headers_rewrite ++option that can be set on any transport. ++ ++Some people believe that configured address rewriting is a Mortal Sin. Others ++believe that life is not possible without it. Exim provides the facility; you ++do not have to use it. ++ ++The main rewriting rules that appear in the "rewrite" section of the ++configuration file are applied to addresses in incoming messages, both envelope ++addresses and addresses in header lines. Each rule specifies the types of ++address to which it applies. ++ ++Whether or not addresses in header lines are rewritten depends on the origin of ++the headers and the type of rewriting. Global rewriting, that is, rewriting ++rules from the rewrite section of the configuration file, is applied only to ++those headers that were received with the message. Header lines that are added ++by ACLs or by a system filter or by individual routers or transports (which are ++specific to individual recipient addresses) are not rewritten by the global ++rules. ++ ++Rewriting at transport time, by means of the headers_rewrite option, applies ++all headers except those added by routers and transports. That is, as well as ++the headers that were received with the message, it also applies to headers ++that were added by an ACL or a system filter. ++ ++In general, rewriting addresses from your own system or domain has some ++legitimacy. Rewriting other addresses should be done only with great care and ++in special circumstances. The author of Exim believes that rewriting should be ++used sparingly, and mainly for "regularizing" addresses in your own domains. ++Although it can sometimes be used as a routing tool, this is very strongly ++discouraged. ++ ++There are two commonly encountered circumstances where rewriting is used, as ++illustrated by these examples: ++ ++ * The company whose domain is hitch.fict.example has a number of hosts that ++ exchange mail with each other behind a firewall, but there is only a single ++ gateway to the outer world. The gateway rewrites *.hitch.fict.example as ++ hitch.fict.example when sending mail off-site. ++ ++ * A host rewrites the local parts of its own users so that, for example, ++ fp42@hitch.fict.example becomes Ford.Prefect@hitch.fict.example. ++ ++ ++31.2 When does rewriting happen? ++-------------------------------- ++ ++Configured address rewriting can take place at several different stages of a ++message's processing. ++ ++At the start of an ACL for MAIL, the sender address may have been rewritten by ++a special SMTP-time rewrite rule (see section 31.9), but no ordinary rewrite ++rules have yet been applied. If, however, the sender address is verified in the ++ACL, it is rewritten before verification, and remains rewritten thereafter. The ++subsequent value of $sender_address is the rewritten address. This also applies ++if sender verification happens in a RCPT ACL. Otherwise, when the sender ++address is not verified, it is rewritten as soon as a message's header lines ++have been received. ++ ++Similarly, at the start of an ACL for RCPT, the current recipient's address may ++have been rewritten by a special SMTP-time rewrite rule, but no ordinary ++rewrite rules have yet been applied to it. However, the behaviour is different ++from the sender address when a recipient is verified. The address is rewritten ++for the verification, but the rewriting is not remembered at this stage. The ++value of $local_part and $domain after verification are always the same as they ++were before (that is, they contain the unrewritten - except for SMTP-time ++rewriting - address). ++ ++As soon as a message's header lines have been received, all the envelope ++recipient addresses are permanently rewritten, and rewriting is also applied to ++the addresses in the header lines (if configured). This happens before adding ++any header lines that were specified in MAIL or RCPT ACLs, and before the DATA ++ACL and local_scan() functions are run. ++ ++When an address is being routed, either for delivery or for verification, ++rewriting is applied immediately to child addresses that are generated by ++redirection, unless no_rewrite is set on the router. ++ ++At transport time, additional rewriting of addresses in header lines can be ++specified by setting the generic headers_rewrite option on a transport. This ++option contains rules that are identical in form to those in the rewrite ++section of the configuration file. They are applied to the original message ++header lines and any that were added by ACLs or a system filter. They are not ++applied to header lines that are added by routers or the transport. ++ ++The outgoing envelope sender can be rewritten by means of the return_path ++transport option. However, it is not possible to rewrite envelope recipients at ++transport time. ++ ++ ++31.3 Testing the rewriting rules that apply on input ++---------------------------------------------------- ++ ++Exim's input rewriting configuration appears in a part of the run time ++configuration file headed by "begin rewrite". It can be tested by the -brw ++command line option. This takes an address (which can be a full RFC 2822 ++address) as its argument. The output is a list of how the address would be ++transformed by the rewriting rules for each of the different places it might ++appear in an incoming message, that is, for each different header and for the ++envelope sender and recipient fields. For example, ++ ++exim -brw ph10@exim.workshop.example ++ ++might produce the output ++ ++sender: Philip.Hazel@exim.workshop.example ++from: Philip.Hazel@exim.workshop.example ++to: ph10@exim.workshop.example ++cc: ph10@exim.workshop.example ++bcc: ph10@exim.workshop.example ++reply-to: Philip.Hazel@exim.workshop.example ++env-from: Philip.Hazel@exim.workshop.example ++env-to: ph10@exim.workshop.example ++ ++which shows that rewriting has been set up for that address when used in any of ++the source fields, but not when it appears as a recipient address. At the ++present time, there is no equivalent way of testing rewriting rules that are ++set for a particular transport. ++ ++ ++31.4 Rewriting rules ++-------------------- ++ ++The rewrite section of the configuration file consists of lines of rewriting ++rules in the form ++ ++<source pattern> <replacement> <flags> ++ ++Rewriting rules that are specified for the headers_rewrite generic transport ++option are given as a colon-separated list. Each item in the list takes the ++same form as a line in the main rewriting configuration (except that any colons ++must be doubled, of course). ++ ++The formats of source patterns and replacement strings are described below. ++Each is terminated by white space, unless enclosed in double quotes, in which ++case normal quoting conventions apply inside the quotes. The flags are single ++characters which may appear in any order. Spaces and tabs between them are ++ignored. ++ ++For each address that could potentially be rewritten, the rules are scanned in ++order, and replacements for the address from earlier rules can themselves be ++replaced by later rules (but see the "q" and "R" flags). ++ ++The order in which addresses are rewritten is undefined, may change between ++releases, and must not be relied on, with one exception: when a message is ++received, the envelope sender is always rewritten first, before any header ++lines are rewritten. For example, the replacement string for a rewrite of an ++address in To: must not assume that the message's address in From: has (or has ++not) already been rewritten. However, a rewrite of From: may assume that the ++envelope sender has already been rewritten. ++ ++The variables $local_part and $domain can be used in the replacement string to ++refer to the address that is being rewritten. Note that lookup-driven rewriting ++can be done by a rule of the form ++ ++*@* ${lookup ... ++ ++where the lookup key uses $1 and $2 or $local_part and $domain to refer to the ++address that is being rewritten. ++ ++ ++31.5 Rewriting patterns ++----------------------- ++ ++The source pattern in a rewriting rule is any item which may appear in an ++address list (see section 10.19). It is in fact processed as a single-item ++address list, which means that it is expanded before being tested against the ++address. As always, if you use a regular expression as a pattern, you must take ++care to escape dollar and backslash characters, or use the "\N" facility to ++suppress string expansion within the regular expression. ++ ++Domains in patterns should be given in lower case. Local parts in patterns are ++case-sensitive. If you want to do case-insensitive matching of local parts, you ++can use a regular expression that starts with "^(?i)". ++ ++After matching, the numerical variables $1, $2, etc. may be set, depending on ++the type of match which occurred. These can be used in the replacement string ++to insert portions of the incoming address. $0 always refers to the complete ++incoming address. When a regular expression is used, the numerical variables ++are set from its capturing subexpressions. For other types of pattern they are ++set as follows: ++ ++ * If a local part or domain starts with an asterisk, the numerical variables ++ refer to the character strings matched by asterisks, with $1 associated ++ with the first asterisk, and $2 with the second, if present. For example, ++ if the pattern ++ ++ *queen@*.fict.example ++ ++ is matched against the address hearts-queen@wonderland.fict.example then ++ ++ $0 = hearts-queen@wonderland.fict.example ++ $1 = hearts- ++ $2 = wonderland ++ ++ Note that if the local part does not start with an asterisk, but the domain ++ does, it is $1 that contains the wild part of the domain. ++ ++ * If the domain part of the pattern is a partial lookup, the wild and fixed ++ parts of the domain are placed in the next available numerical variables. ++ Suppose, for example, that the address foo@bar.baz.example is processed by ++ a rewriting rule of the form ++ ++ *@partial-dbm;/some/dbm/file <replacement string> ++ ++ and the key in the file that matches the domain is "*.baz.example". Then ++ ++ $1 = foo ++ $2 = bar ++ $3 = baz.example ++ ++ If the address foo@baz.example is looked up, this matches the same wildcard ++ file entry, and in this case $2 is set to the empty string, but $3 is still ++ set to baz.example. If a non-wild key is matched in a partial lookup, $2 is ++ again set to the empty string and $3 is set to the whole domain. For ++ non-partial domain lookups, no numerical variables are set. ++ ++ ++31.6 Rewriting replacements ++--------------------------- ++ ++If the replacement string for a rule is a single asterisk, addresses that match ++the pattern and the flags are not rewritten, and no subsequent rewriting rules ++are scanned. For example, ++ ++hatta@lookingglass.fict.example * f ++ ++specifies that hatta@lookingglass.fict.example is never to be rewritten in ++From: headers. ++ ++If the replacement string is not a single asterisk, it is expanded, and must ++yield a fully qualified address. Within the expansion, the variables ++$local_part and $domain refer to the address that is being rewritten. Any ++letters they contain retain their original case - they are not lower cased. The ++numerical variables are set up according to the type of pattern that matched ++the address, as described above. If the expansion is forced to fail by the ++presence of "fail" in a conditional or lookup item, rewriting by the current ++rule is abandoned, but subsequent rules may take effect. Any other expansion ++failure causes the entire rewriting operation to be abandoned, and an entry ++written to the panic log. ++ ++ ++31.7 Rewriting flags ++-------------------- ++ ++There are three different kinds of flag that may appear on rewriting rules: ++ ++ * Flags that specify which headers and envelope addresses to rewrite: E, F, ++ T, b, c, f, h, r, s, t. ++ ++ * A flag that specifies rewriting at SMTP time: S. ++ ++ * Flags that control the rewriting process: Q, q, R, w. ++ ++For rules that are part of the headers_rewrite generic transport option, E, F, ++T, and S are not permitted. ++ ++ ++31.8 Flags specifying which headers and envelope addresses to rewrite ++--------------------------------------------------------------------- ++ ++If none of the following flag letters, nor the "S" flag (see section 31.9) are ++present, a main rewriting rule applies to all headers and to both the sender ++and recipient fields of the envelope, whereas a transport-time rewriting rule ++just applies to all headers. Otherwise, the rewriting rule is skipped unless ++the relevant addresses are being processed. ++ ++E rewrite all envelope fields ++F rewrite the envelope From field ++T rewrite the envelope To field ++b rewrite the Bcc: header ++c rewrite the Cc: header ++f rewrite the From: header ++h rewrite all headers ++r rewrite the Reply-To: header ++s rewrite the Sender: header ++t rewrite the To: header ++ ++"All headers" means all of the headers listed above that can be selected ++individually, plus their Resent- versions. It does not include other headers ++such as Subject: etc. ++ ++You should be particularly careful about rewriting Sender: headers, and ++restrict this to special known cases in your own domains. ++ ++ ++31.9 The SMTP-time rewriting flag ++--------------------------------- ++ ++The rewrite flag "S" specifies a rewrite of incoming envelope addresses at SMTP ++time, as soon as an address is received in a MAIL or RCPT command, and before ++any other processing; even before syntax checking. The pattern is required to ++be a regular expression, and it is matched against the whole of the data for ++the command, including any surrounding angle brackets. ++ ++This form of rewrite rule allows for the handling of addresses that are not ++compliant with RFCs 2821 and 2822 (for example, "bang paths" in batched SMTP ++input). Because the input is not required to be a syntactically valid address, ++the variables $local_part and $domain are not available during the expansion of ++the replacement string. The result of rewriting replaces the original address ++in the MAIL or RCPT command. ++ ++ ++31.10 Flags controlling the rewriting process ++--------------------------------------------- ++ ++There are four flags which control the way the rewriting process works. These ++take effect only when a rule is invoked, that is, when the address is of the ++correct type (matches the flags) and matches the pattern: ++ ++ * If the "Q" flag is set on a rule, the rewritten address is permitted to be ++ an unqualified local part. It is qualified with qualify_recipient. In the ++ absence of "Q" the rewritten address must always include a domain. ++ ++ * If the "q" flag is set on a rule, no further rewriting rules are ++ considered, even if no rewriting actually takes place because of a "fail" ++ in the expansion. The "q" flag is not effective if the address is of the ++ wrong type (does not match the flags) or does not match the pattern. ++ ++ * The "R" flag causes a successful rewriting rule to be re-applied to the new ++ address, up to ten times. It can be combined with the "q" flag, to stop ++ rewriting once it fails to match (after at least one successful rewrite). ++ ++ * When an address in a header is rewritten, the rewriting normally applies ++ only to the working part of the address, with any comments and RFC 2822 ++ "phrase" left unchanged. For example, rewriting might change ++ ++ From: Ford Prefect <fp42@restaurant.hitch.fict.example> ++ ++ into ++ ++ From: Ford Prefect <prefectf@hitch.fict.example> ++ ++ Sometimes there is a need to replace the whole address item, and this can ++ be done by adding the flag letter "w" to a rule. If this is set on a rule ++ that causes an address in a header line to be rewritten, the entire address ++ is replaced, not just the working part. The replacement must be a complete ++ RFC 2822 address, including the angle brackets if necessary. If text ++ outside angle brackets contains a character whose value is greater than 126 ++ or less than 32 (except for tab), the text is encoded according to RFC ++ 2047. The character set is taken from headers_charset, which defaults to ++ ISO-8859-1. ++ ++ When the "w" flag is set on a rule that causes an envelope address to be ++ rewritten, all but the working part of the replacement address is ++ discarded. ++ ++ ++31.11 Rewriting examples ++------------------------ ++ ++Here is an example of the two common rewriting paradigms: ++ ++*@*.hitch.fict.example $1@hitch.fict.example ++*@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\ ++ {$value}fail}@hitch.fict.example bctfrF ++ ++Note the use of "fail" in the lookup expansion in the second rule, forcing the ++string expansion to fail if the lookup does not succeed. In this context it has ++the effect of leaving the original address unchanged, but Exim goes on to ++consider subsequent rewriting rules, if any, because the "q" flag is not ++present in that rule. An alternative to "fail" would be to supply $1 ++explicitly, which would cause the rewritten address to be the same as before, ++at the cost of a small bit of processing. Not supplying either of these is an ++error, since the rewritten address would then contain no local part. ++ ++The first example above replaces the domain with a superior, more general ++domain. This may not be desirable for certain local parts. If the rule ++ ++root@*.hitch.fict.example * ++ ++were inserted before the first rule, rewriting would be suppressed for the ++local part root at any domain ending in hitch.fict.example. ++ ++Rewriting can be made conditional on a number of tests, by making use of ${if ++in the expansion item. For example, to apply a rewriting rule only to messages ++that originate outside the local host: ++ ++*@*.hitch.fict.example "${if !eq {$sender_host_address}{}\ ++ {$1@hitch.fict.example}fail}" ++ ++The replacement string is quoted in this example because it contains white ++space. ++ ++Exim does not handle addresses in the form of "bang paths". If it sees such an ++address it treats it as an unqualified local part which it qualifies with the ++local qualification domain (if the source of the message is local or if the ++remote host is permitted to send unqualified addresses). Rewriting can ++sometimes be used to handle simple bang paths with a fixed number of ++components. For example, the rule ++ ++\N^([^!]+)!(.*)@your.domain.example$\N $2@$1 ++ ++rewrites a two-component bang path host.name!user as the domain address ++user@host.name. However, there is a security implication in using this as a ++global rewriting rule for envelope addresses. It can provide a backdoor method ++for using your system as a relay, because the incoming addresses appear to be ++local. If the bang path addresses are received via SMTP, it is safer to use the ++"S" flag to rewrite them as they are received, so that relay checking can be ++done on the rewritten addresses. ++ ++ ++ ++=============================================================================== ++32. RETRY CONFIGURATION ++ ++The "retry" section of the runtime configuration file contains a list of retry ++rules that control how often Exim tries to deliver messages that cannot be ++delivered at the first attempt. If there are no retry rules (the section is ++empty or not present), there are no retries. In this situation, temporary ++errors are treated as permanent. The default configuration contains a single, ++general-purpose retry rule (see section 7.5). The -brt command line option can ++be used to test which retry rule will be used for a given address, domain and ++error. ++ ++The most common cause of retries is temporary failure to deliver to a remote ++host because the host is down, or inaccessible because of a network problem. ++Exim's retry processing in this case is applied on a per-host (strictly, per IP ++address) basis, not on a per-message basis. Thus, if one message has recently ++been delayed, delivery of a new message to the same host is not immediately ++tried, but waits for the host's retry time to arrive. If the retry_defer log ++selector is set, the message "retry time not reached" is written to the main ++log whenever a delivery is skipped for this reason. Section 47.2 contains more ++details of the handling of errors during remote deliveries. ++ ++Retry processing applies to routing as well as to delivering, except as covered ++in the next paragraph. The retry rules do not distinguish between these ++actions. It is not possible, for example, to specify different behaviour for ++failures to route the domain snark.fict.example and failures to deliver to the ++host snark.fict.example. I didn't think anyone would ever need this added ++complication, so did not implement it. However, although they share the same ++retry rule, the actual retry times for routing and transporting a given domain ++are maintained independently. ++ ++When a delivery is not part of a queue run (typically an immediate delivery on ++receipt of a message), the routers are always run, and local deliveries are ++always attempted, even if retry times are set for them. This makes for better ++behaviour if one particular message is causing problems (for example, causing ++quota overflow, or provoking an error in a filter file). If such a delivery ++suffers a temporary failure, the retry data is updated as normal, and ++subsequent delivery attempts from queue runs occur only when the retry time for ++the local address is reached. ++ ++ ++32.1 Changing retry rules ++------------------------- ++ ++If you change the retry rules in your configuration, you should consider ++whether or not to delete the retry data that is stored in Exim's spool area in ++files with names like db/retry. Deleting any of Exim's hints files is always ++safe; that is why they are called "hints". ++ ++The hints retry data contains suggested retry times based on the previous ++rules. In the case of a long-running problem with a remote host, it might ++record the fact that the host has timed out. If your new rules increase the ++timeout time for such a host, you should definitely remove the old retry data ++and let Exim recreate it, based on the new rules. Otherwise Exim might bounce ++messages that it should now be retaining. ++ ++ ++32.2 Format of retry rules ++-------------------------- ++ ++Each retry rule occupies one line and consists of three or four parts, ++separated by white space: a pattern, an error name, an optional list of sender ++addresses, and a list of retry parameters. The pattern and sender lists must be ++enclosed in double quotes if they contain white space. The rules are searched ++in order until one is found where the pattern, error name, and sender list (if ++present) match the failing host or address, the error that occurred, and the ++message's sender, respectively. ++ ++The pattern is any single item that may appear in an address list (see section ++10.19). It is in fact processed as a one-item address list, which means that it ++is expanded before being tested against the address that has been delayed. A ++negated address list item is permitted. Address list processing treats a plain ++domain name as if it were preceded by "*@", which makes it possible for many ++retry rules to start with just a domain. For example, ++ ++lookingglass.fict.example * F,24h,30m; ++ ++provides a rule for any address in the lookingglass.fict.example domain, ++whereas ++ ++alice@lookingglass.fict.example * F,24h,30m; ++ ++applies only to temporary failures involving the local part alice. In practice, ++almost all rules start with a domain name pattern without a local part. ++ ++Warning: If you use a regular expression in a routing rule pattern, it must ++match a complete address, not just a domain, because that is how regular ++expressions work in address lists. ++ ++^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2 Wrong ++^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2 Right ++ ++ ++32.3 Choosing which retry rule to use for address errors ++-------------------------------------------------------- ++ ++When Exim is looking for a retry rule after a routing attempt has failed (for ++example, after a DNS timeout), each line in the retry configuration is tested ++against the complete address only if retry_use_local_part is set for the ++router. Otherwise, only the domain is used, except when matching against a ++regular expression, when the local part of the address is replaced with "*". A ++domain on its own can match a domain pattern, or a pattern that starts with ++"*@". By default, retry_use_local_part is true for routers where ++check_local_user is true, and false for other routers. ++ ++Similarly, when Exim is looking for a retry rule after a local delivery has ++failed (for example, after a mailbox full error), each line in the retry ++configuration is tested against the complete address only if ++retry_use_local_part is set for the transport (it defaults true for all local ++transports). ++ ++However, when Exim is looking for a retry rule after a remote delivery attempt ++suffers an address error (a 4xx SMTP response for a recipient address), the ++whole address is always used as the key when searching the retry rules. The ++rule that is found is used to create a retry time for the combination of the ++failing address and the message's sender. It is the combination of sender and ++recipient that is delayed in subsequent queue runs until its retry time is ++reached. You can delay the recipient without regard to the sender by setting ++address_retry_include_sender false in the smtp transport but this can lead to ++problems with servers that regularly issue 4xx responses to RCPT commands. ++ ++ ++32.4 Choosing which retry rule to use for host and message errors ++----------------------------------------------------------------- ++ ++For a temporary error that is not related to an individual address (for ++example, a connection timeout), each line in the retry configuration is checked ++twice. First, the name of the remote host is used as a domain name (preceded by ++"*@" when matching a regular expression). If this does not match the line, the ++domain from the email address is tried in a similar fashion. For example, ++suppose the MX records for a.b.c.example are ++ ++a.b.c.example MX 5 x.y.z.example ++ MX 6 p.q.r.example ++ MX 7 m.n.o.example ++ ++and the retry rules are ++ ++p.q.r.example * F,24h,30m; ++a.b.c.example * F,4d,45m; ++ ++and a delivery to the host x.y.z.example suffers a connection failure. The ++first rule matches neither the host nor the domain, so Exim looks at the second ++rule. This does not match the host, but it does match the domain, so it is used ++to calculate the retry time for the host x.y.z.example. Meanwhile, Exim tries ++to deliver to p.q.r.example. If this also suffers a host error, the first retry ++rule is used, because it matches the host. ++ ++In other words, temporary failures to deliver to host p.q.r.example use the ++first rule to determine retry times, but for all the other hosts for the domain ++a.b.c.example, the second rule is used. The second rule is also used if routing ++to a.b.c.example suffers a temporary failure. ++ ++Note: The host name is used when matching the patterns, not its IP address. ++However, if a message is routed directly to an IP address without the use of a ++host name, for example, if a manualroute router contains a setting such as: ++ ++route_list = *.a.example 192.168.34.23 ++ ++then the "host name" that is used when searching for a retry rule is the ++textual form of the IP address. ++ ++ ++32.5 Retry rules for specific errors ++------------------------------------ ++ ++The second field in a retry rule is the name of a particular error, or an ++asterisk, which matches any error. The errors that can be tested for are: ++ ++auth_failed ++ ++ Authentication failed when trying to send to a host in the ++ hosts_require_auth list in an smtp transport. ++ ++data_4xx ++ ++ A 4xx error was received for an outgoing DATA command, either immediately ++ after the command, or after sending the message's data. ++ ++mail_4xx ++ ++ A 4xx error was received for an outgoing MAIL command. ++ ++rcpt_4xx ++ ++ A 4xx error was received for an outgoing RCPT command. ++ ++For the three 4xx errors, either the first or both of the x's can be given as ++specific digits, for example: "mail_45x" or "rcpt_436". For example, to ++recognize 452 errors given to RCPT commands for addresses in a certain domain, ++and have retries every ten minutes with a one-hour timeout, you could set up a ++retry rule of this form: ++ ++the.domain.name rcpt_452 F,1h,10m ++ ++These errors apply to both outgoing SMTP (the smtp transport) and outgoing LMTP ++(either the lmtp transport, or the smtp transport in LMTP mode). ++ ++lost_connection ++ ++ A server unexpectedly closed the SMTP connection. There may, of course, ++ legitimate reasons for this (host died, network died), but if it repeats a ++ lot for the same host, it indicates something odd. ++ ++refused_MX ++ ++ A connection to a host obtained from an MX record was refused. ++ ++refused_A ++ ++ A connection to a host not obtained from an MX record was refused. ++ ++refused ++ ++ A connection was refused. ++ ++timeout_connect_MX ++ ++ A connection attempt to a host obtained from an MX record timed out. ++ ++timeout_connect_A ++ ++ A connection attempt to a host not obtained from an MX record timed out. ++ ++timeout_connect ++ ++ A connection attempt timed out. ++ ++timeout_MX ++ ++ There was a timeout while connecting or during an SMTP session with a host ++ obtained from an MX record. ++ ++timeout_A ++ ++ There was a timeout while connecting or during an SMTP session with a host ++ not obtained from an MX record. ++ ++timeout ++ ++ There was a timeout while connecting or during an SMTP session. ++ ++tls_required ++ ++ The server was required to use TLS (it matched hosts_require_tls in the ++ smtp transport), but either did not offer TLS, or it responded with 4xx to ++ STARTTLS, or there was a problem setting up the TLS connection. ++ ++quota ++ ++ A mailbox quota was exceeded in a local delivery by the appendfile ++ transport. ++ ++quota_<time> ++ ++ A mailbox quota was exceeded in a local delivery by the appendfile ++ transport, and the mailbox has not been accessed for <time>. For example, ++ quota_4d applies to a quota error when the mailbox has not been accessed ++ for four days. ++ ++The idea of quota_<time> is to make it possible to have shorter timeouts when ++the mailbox is full and is not being read by its owner. Ideally, it should be ++based on the last time that the user accessed the mailbox. However, it is not ++always possible to determine this. Exim uses the following heuristic rules: ++ ++ * If the mailbox is a single file, the time of last access (the "atime") is ++ used. As no new messages are being delivered (because the mailbox is over ++ quota), Exim does not access the file, so this is the time of last user ++ access. ++ ++ * For a maildir delivery, the time of last modification of the new ++ subdirectory is used. As the mailbox is over quota, no new files are ++ created in the new subdirectory, because no new messages are being ++ delivered. Any change to the new subdirectory is therefore assumed to be ++ the result of an MUA moving a new message to the cur directory when it is ++ first read. The time that is used is therefore the last time that the user ++ read a new message. ++ ++ * For other kinds of multi-file mailbox, the time of last access cannot be ++ obtained, so a retry rule that uses this type of error field is never ++ matched. ++ ++The quota errors apply both to system-enforced quotas and to Exim's own quota ++mechanism in the appendfile transport. The quota error also applies when a ++local delivery is deferred because a partition is full (the ENOSPC error). ++ ++ ++32.6 Retry rules for specified senders ++-------------------------------------- ++ ++You can specify retry rules that apply only when the failing message has a ++specific sender. In particular, this can be used to define retry rules that ++apply only to bounce messages. The third item in a retry rule can be of this ++form: ++ ++senders=<address list> ++ ++The retry timings themselves are then the fourth item. For example: ++ ++* rcpt_4xx senders=: F,1h,30m ++ ++matches recipient 4xx errors for bounce messages sent to any address at any ++host. If the address list contains white space, it must be enclosed in quotes. ++For example: ++ ++a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5 ++ ++Warning: This facility can be unhelpful if it is used for host errors (which do ++not depend on the recipient). The reason is that the sender is used only to ++match the retry rule. Once the rule has been found for a host error, its ++contents are used to set a retry time for the host, and this will apply to all ++messages, not just those with specific senders. ++ ++When testing retry rules using -brt, you can supply a sender using the -f ++command line option, like this: ++ ++exim -f "" -brt user@dom.ain ++ ++If you do not set -f with -brt, a retry rule that contains a senders list is ++never matched. ++ ++ ++32.7 Retry parameters ++--------------------- ++ ++The third (or fourth, if a senders list is present) field in a retry rule is a ++sequence of retry parameter sets, separated by semicolons. Each set consists of ++ ++<letter>,<cutoff time>,<arguments> ++ ++The letter identifies the algorithm for computing a new retry time; the cutoff ++time is the time beyond which this algorithm no longer applies, and the ++arguments vary the algorithm's action. The cutoff time is measured from the ++time that the first failure for the domain (combined with the local part if ++relevant) was detected, not from the time the message was received. ++ ++The available algorithms are: ++ ++ * F: retry at fixed intervals. There is a single time parameter specifying ++ the interval. ++ ++ * G: retry at geometrically increasing intervals. The first argument ++ specifies a starting value for the interval, and the second a multiplier, ++ which is used to increase the size of the interval at each retry. ++ ++ * H: retry at randomized intervals. The arguments are as for G. For each ++ retry, the previous interval is multiplied by the factor in order to get a ++ maximum for the next interval. The minimum interval is the first argument ++ of the parameter, and an actual interval is chosen randomly between them. ++ Such a rule has been found to be helpful in cluster configurations when all ++ the members of the cluster restart at once, and may therefore synchronize ++ their queue processing times. ++ ++When computing the next retry time, the algorithm definitions are scanned in ++order until one whose cutoff time has not yet passed is reached. This is then ++used to compute a new retry time that is later than the current time. In the ++case of fixed interval retries, this simply means adding the interval to the ++current time. For geometrically increasing intervals, retry intervals are ++computed from the rule's parameters until one that is greater than the previous ++interval is found. The main configuration variable retry_interval_max limits ++the maximum interval between retries. It cannot be set greater than "24h", ++which is its default value. ++ ++A single remote domain may have a number of hosts associated with it, and each ++host may have more than one IP address. Retry algorithms are selected on the ++basis of the domain name, but are applied to each IP address independently. If, ++for example, a host has two IP addresses and one is unusable, Exim will ++generate retry times for it and will not try to use it until its next retry ++time comes. Thus the good IP address is likely to be tried first most of the ++time. ++ ++Retry times are hints rather than promises. Exim does not make any attempt to ++run deliveries exactly at the computed times. Instead, a queue runner process ++starts delivery processes for delayed messages periodically, and these attempt ++new deliveries only for those addresses that have passed their next retry time. ++If a new message arrives for a deferred address, an immediate delivery attempt ++occurs only if the address has passed its retry time. In the absence of new ++messages, the minimum time between retries is the interval between queue runner ++processes. There is not much point in setting retry times of five minutes if ++your queue runners happen only once an hour, unless there are a significant ++number of incoming messages (which might be the case on a system that is ++sending everything to a smart host, for example). ++ ++The data in the retry hints database can be inspected by using the exim_dumpdb ++or exim_fixdb utility programs (see chapter 52). The latter utility can also be ++used to change the data. The exinext utility script can be used to find out ++what the next retry times are for the hosts associated with a particular mail ++domain, and also for local deliveries that have been deferred. ++ ++ ++32.8 Retry rule examples ++------------------------ ++ ++Here are some example retry rules: ++ ++alice@wonderland.fict.example quota_5d F,7d,3h ++wonderland.fict.example quota_5d ++wonderland.fict.example * F,1h,15m; G,2d,1h,2; ++lookingglass.fict.example * F,24h,30m; ++* refused_A F,2h,20m; ++* * F,2h,15m; G,16h,1h,1.5; F,5d,8h ++ ++The first rule sets up special handling for mail to ++alice@wonderland.fict.example when there is an over-quota error and the mailbox ++has not been read for at least 5 days. Retries continue every three hours for 7 ++days. The second rule handles over-quota errors for all other local parts at ++wonderland.fict.example; the absence of a local part has the same effect as ++supplying "*@". As no retry algorithms are supplied, messages that fail are ++bounced immediately if the mailbox has not been read for at least 5 days. ++ ++The third rule handles all other errors at wonderland.fict.example; retries ++happen every 15 minutes for an hour, then with geometrically increasing ++intervals until two days have passed since a delivery first failed. After the ++first hour there is a delay of one hour, then two hours, then four hours, and ++so on (this is a rather extreme example). ++ ++The fourth rule controls retries for the domain lookingglass.fict.example. They ++happen every 30 minutes for 24 hours only. The remaining two rules handle all ++other domains, with special action for connection refusal from hosts that were ++not obtained from an MX record. ++ ++The final rule in a retry configuration should always have asterisks in the ++first two fields so as to provide a general catch-all for any addresses that do ++not have their own special handling. This example tries every 15 minutes for 2 ++hours, then with intervals starting at one hour and increasing by a factor of ++1.5 up to 16 hours, then every 8 hours up to 5 days. ++ ++ ++32.9 Timeout of retry data ++-------------------------- ++ ++Exim timestamps the data that it writes to its retry hints database. When it ++consults the data during a delivery it ignores any that is older than the value ++set in retry_data_expire (default 7 days). If, for example, a host hasn't been ++tried for 7 days, Exim will try to deliver to it immediately a message arrives, ++and if that fails, it will calculate a retry time as if it were failing for the ++first time. ++ ++This improves the behaviour for messages routed to rarely-used hosts such as MX ++backups. If such a host was down at one time, and happens to be down again when ++Exim tries a month later, using the old retry data would imply that it had been ++down all the time, which is not a justified assumption. ++ ++If a host really is permanently dead, this behaviour causes a burst of retries ++every now and again, but only if messages routed to it are rare. If there is a ++message at least once every 7 days the retry data never expires. ++ ++ ++32.10 Long-term failures ++------------------------ ++ ++Special processing happens when an email address has been failing for so long ++that the cutoff time for the last algorithm is reached. For example, using the ++default retry rule: ++ ++* * F,2h,15m; G,16h,1h,1.5; F,4d,6h ++ ++the cutoff time is four days. Reaching the retry cutoff is independent of how ++long any specific message has been failing; it is the length of continuous ++failure for the recipient address that counts. ++ ++When the cutoff time is reached for a local delivery, or for all the IP ++addresses associated with a remote delivery, a subsequent delivery failure ++causes Exim to give up on the address, and a bounce message is generated. In ++order to cater for new messages that use the failing address, a next retry time ++is still computed from the final algorithm, and is used as follows: ++ ++For local deliveries, one delivery attempt is always made for any subsequent ++messages. If this delivery fails, the address fails immediately. The ++post-cutoff retry time is not used. ++ ++If the delivery is remote, there are two possibilities, controlled by the ++delay_after_cutoff option of the smtp transport. The option is true by default. ++Until the post-cutoff retry time for one of the IP addresses is reached, the ++failing email address is bounced immediately, without a delivery attempt taking ++place. After that time, one new delivery attempt is made to those IP addresses ++that are past their retry times, and if that still fails, the address is ++bounced and new retry times are computed. ++ ++In other words, when all the hosts for a given email address have been failing ++for a long time, Exim bounces rather then defers until one of the hosts' retry ++times is reached. Then it tries once, and bounces if that attempt fails. This ++behaviour ensures that few resources are wasted in repeatedly trying to deliver ++to a broken destination, but if the host does recover, Exim will eventually ++notice. ++ ++If delay_after_cutoff is set false, Exim behaves differently. If all IP ++addresses are past their final cutoff time, Exim tries to deliver to those IP ++addresses that have not been tried since the message arrived. If there are no ++suitable IP addresses, or if they all fail, the address is bounced. In other ++words, it does not delay when a new message arrives, but tries the expired ++addresses immediately, unless they have been tried since the message arrived. ++If there is a continuous stream of messages for the failing domains, setting ++delay_after_cutoff false means that there will be many more attempts to deliver ++to permanently failing IP addresses than when delay_after_cutoff is true. ++ ++ ++32.11 Deliveries that work intermittently ++----------------------------------------- ++ ++Some additional logic is needed to cope with cases where a host is ++intermittently available, or when a message has some attribute that prevents ++its delivery when others to the same address get through. In this situation, ++because some messages are successfully delivered, the "retry clock" for the ++host or address keeps getting reset by the successful deliveries, and so ++failing messages remain on the queue for ever because the cutoff time is never ++reached. ++ ++Two exceptional actions are applied to prevent this happening. The first ++applies to errors that are related to a message rather than a remote host. ++Section 47.2 has a discussion of the different kinds of error; examples of ++message-related errors are 4xx responses to MAIL or DATA commands, and quota ++failures. For this type of error, if a message's arrival time is earlier than ++the "first failed" time for the error, the earlier time is used when scanning ++the retry rules to decide when to try next and when to time out the address. ++ ++The exceptional second action applies in all cases. If a message has been on ++the queue for longer than the cutoff time of any applicable retry rule for a ++given address, a delivery is attempted for that address, even if it is not yet ++time, and if this delivery fails, the address is timed out. A new retry time is ++not computed in this case, so that other messages for the same address are ++considered immediately. ++ ++ ++ ++=============================================================================== ++33. SMTP AUTHENTICATION ++ ++The "authenticators" section of Exim's run time configuration is concerned with ++SMTP authentication. This facility is an extension to the SMTP protocol, ++described in RFC 2554, which allows a client SMTP host to authenticate itself ++to a server. This is a common way for a server to recognize clients that are ++permitted to use it as a relay. SMTP authentication is not of relevance to the ++transfer of mail between servers that have no managerial connection with each ++other. ++ ++Very briefly, the way SMTP authentication works is as follows: ++ ++ * The server advertises a number of authentication mechanisms in response to ++ the client's EHLO command. ++ ++ * The client issues an AUTH command, naming a specific mechanism. The command ++ may, optionally, contain some authentication data. ++ ++ * The server may issue one or more challenges, to which the client must send ++ appropriate responses. In simple authentication mechanisms, the challenges ++ are just prompts for user names and passwords. The server does not have to ++ issue any challenges - in some mechanisms the relevant data may all be ++ transmitted with the AUTH command. ++ ++ * The server either accepts or denies authentication. ++ ++ * If authentication succeeds, the client may optionally make use of the AUTH ++ option on the MAIL command to pass an authenticated sender in subsequent ++ mail transactions. Authentication lasts for the remainder of the SMTP ++ connection. ++ ++ * If authentication fails, the client may give up, or it may try a different ++ authentication mechanism, or it may try transferring mail over the ++ unauthenticated connection. ++ ++If you are setting up a client, and want to know which authentication ++mechanisms the server supports, you can use Telnet to connect to port 25 (the ++SMTP port) on the server, and issue an EHLO command. The response to this ++includes the list of supported mechanisms. For example: ++ ++$ telnet server.example 25 ++Trying 192.168.34.25... ++Connected to server.example. ++Escape character is '^]'. ++220 server.example ESMTP Exim 4.20 ... ++ehlo client.example ++250-server.example Hello client.example [10.8.4.5] ++250-SIZE 52428800 ++250-PIPELINING ++250-AUTH PLAIN ++250 HELP ++ ++The second-last line of this example output shows that the server supports ++authentication using the PLAIN mechanism. In Exim, the different authentication ++mechanisms are configured by specifying authenticator drivers. Like the routers ++and transports, which authenticators are included in the binary is controlled ++by build-time definitions. The following are currently available, included by ++setting ++ ++AUTH_CRAM_MD5=yes ++AUTH_CYRUS_SASL=yes ++AUTH_DOVECOT=yes ++AUTH_GSASL=yes ++AUTH_HEIMDAL_GSSAPI=yes ++AUTH_PLAINTEXT=yes ++AUTH_SPA=yes ++ ++in Local/Makefile, respectively. The first of these supports the CRAM-MD5 ++authentication mechanism (RFC 2195), and the second provides an interface to ++the Cyrus SASL authentication library. The third is an interface to Dovecot's ++authentication system, delegating the work via a socket interface. The fourth ++provides an interface to the GNU SASL authentication library, which provides ++mechanisms but typically not data sources. The fifth provides direct access to ++Heimdal GSSAPI, geared for Kerberos, but supporting setting a server keytab. ++The sixth can be configured to support the PLAIN authentication mechanism (RFC ++2595) or the LOGIN mechanism, which is not formally documented, but used by ++several MUAs. The seventh authenticator supports Microsoft's Secure Password ++Authentication mechanism. ++ ++The authenticators are configured using the same syntax as other drivers (see ++section 6.22). If no authenticators are required, no authentication section ++need be present in the configuration file. Each authenticator can in principle ++have both server and client functions. When Exim is receiving SMTP mail, it is ++acting as a server; when it is sending out messages over SMTP, it is acting as ++a client. Authenticator configuration options are provided for use in both ++these circumstances. ++ ++To make it clear which options apply to which situation, the prefixes server_ ++and client_ are used on option names that are specific to either the server or ++the client function, respectively. Server and client functions are disabled if ++none of their options are set. If an authenticator is to be used for both ++server and client functions, a single definition, using both sets of options, ++is required. For example: ++ ++cram: ++ driver = cram_md5 ++ public_name = CRAM-MD5 ++ server_secret = ${if eq{$auth1}{ph10}{secret1}fail} ++ client_name = ph10 ++ client_secret = secret2 ++ ++The server_ option is used when Exim is acting as a server, and the client_ ++options when it is acting as a client. ++ ++Descriptions of the individual authenticators are given in subsequent chapters. ++The remainder of this chapter covers the generic options for the ++authenticators, followed by general discussion of the way authentication works ++in Exim. ++ ++Beware: the meaning of $auth1, $auth2, ... varies on a per-driver and ++per-mechanism basis. Please read carefully to determine which variables hold ++account labels such as usercodes and which hold passwords or other ++authenticating data. ++ ++Note that some mechanisms support two different identifiers for accounts: the ++authentication id and the authorization id. The contractions authn and authz ++are commonly encountered. The American spelling is standard here. Conceptually, ++authentication data such as passwords are tied to the identifier used to ++authenticate; servers may have rules to permit one user to act as a second ++user, so that after login the session is treated as though that second user had ++logged in. That second user is the authorization id. A robust configuration ++might confirm that the authz field is empty or matches the authn field. Often ++this is just ignored. The authn can be considered as verified data, the authz ++as an unverified request which the server might choose to honour. ++ ++A realm is a text string, typically a domain name, presented by a server to a ++client to help it select an account and credentials to use. In some mechanisms, ++the client and server provably agree on the realm, but clients typically can ++not treat the realm as secure data to be blindly trusted. ++ ++ ++33.1 Generic options for authenticators ++--------------------------------------- ++ +++-----------------------------------------------------------------+ ++|client_condition|Use: authenticators|Type: string*|Default: unset| +++-----------------------------------------------------------------+ ++ ++When Exim is authenticating as a client, it skips any authenticator whose ++client_condition expansion yields "0", "no", or "false". This can be used, for ++example, to skip plain text authenticators when the connection is not encrypted ++by a setting such as: ++ ++client_condition = ${if !eq{$tls_out_cipher}{}} ++ +++--------------------------------------------------------------+ ++|client_set_id|Use: authenticators|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++When client authentication succeeds, this condition is expanded; the result is ++used in the log lines for outbound messasges. Typically it will be the user ++name used for authentication. ++ +++------------------------------------------------------+ ++|driver|Use: authenticators|Type: string|Default: unset| +++------------------------------------------------------+ ++ ++This option must always be set. It specifies which of the available ++authenticators is to be used. ++ +++-----------------------------------------------------------+ ++|public_name|Use: authenticators|Type: string|Default: unset| +++-----------------------------------------------------------+ ++ ++This option specifies the name of the authentication mechanism that the driver ++implements, and by which it is known to the outside world. These names should ++contain only upper case letters, digits, underscores, and hyphens (RFC 2222), ++but Exim in fact matches them caselessly. If public_name is not set, it ++defaults to the driver's instance name. ++ +++---------------------------------------------------------------------------+ ++|server_advertise_condition|Use: authenticators|Type: string*|Default: unset| +++---------------------------------------------------------------------------+ ++ ++When a server is about to advertise an authentication mechanism, the condition ++is expanded. If it yields the empty string, "0", "no", or "false", the ++mechanism is not advertised. If the expansion fails, the mechanism is not ++advertised. If the failure was not forced, and was not caused by a lookup ++defer, the incident is logged. See section 33.3 below for further discussion. ++ +++-----------------------------------------------------------------+ ++|server_condition|Use: authenticators|Type: string*|Default: unset| +++-----------------------------------------------------------------+ ++ ++This option must be set for a plaintext server authenticator, where it is used ++directly to control authentication. See section 34.2 for details. ++ ++For the gsasl authenticator, this option is required for various mechanisms; ++see chapter 38 for details. ++ ++For the other authenticators, server_condition can be used as an additional ++authentication or authorization mechanism that is applied after the other ++authenticator conditions succeed. If it is set, it is expanded when the ++authenticator would otherwise return a success code. If the expansion is forced ++to fail, authentication fails. Any other expansion failure causes a temporary ++error code to be returned. If the result of a successful expansion is an empty ++string, "0", "no", or "false", authentication fails. If the result of the ++expansion is "1", "yes", or "true", authentication succeeds. For any other ++result, a temporary error code is returned, with the expanded string as the ++error text. ++ +++-------------------------------------------------------------------+ ++|server_debug_print|Use: authenticators|Type: string*|Default: unset| +++-------------------------------------------------------------------+ ++ ++If this option is set and authentication debugging is enabled (see the -d ++command line option), the string is expanded and included in the debugging ++output when the authenticator is run as a server. This can help with checking ++out the values of variables. If expansion of the string fails, the error ++message is written to the debugging output, and Exim carries on processing. ++ +++--------------------------------------------------------------+ ++|server_set_id|Use: authenticators|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++When an Exim server successfully authenticates a client, this string is ++expanded using data from the authentication, and preserved for any incoming ++messages in the variable $authenticated_id. It is also included in the log ++lines for incoming messages. For example, a user/password authenticator ++configuration might preserve the user name that was used to authenticate, and ++refer to it subsequently during delivery of the message. If expansion fails, ++the option is ignored. ++ +++---------------------------------------------------------------------------+ ++|server_mail_auth_condition|Use: authenticators|Type: string*|Default: unset| +++---------------------------------------------------------------------------+ ++ ++This option allows a server to discard authenticated sender addresses supplied ++as part of MAIL commands in SMTP connections that are authenticated by the ++driver on which server_mail_auth_condition is set. The option is not used as ++part of the authentication process; instead its (unexpanded) value is ++remembered for later use. How it is used is described in the following section. ++ ++ ++33.2 The AUTH parameter on MAIL commands ++---------------------------------------- ++ ++When a client supplied an AUTH= item on a MAIL command, Exim applies the ++following checks before accepting it as the authenticated sender of the ++message: ++ ++ * If the connection is not using extended SMTP (that is, HELO was used rather ++ than EHLO), the use of AUTH= is a syntax error. ++ ++ * If the value of the AUTH= parameter is "<>", it is ignored. ++ ++ * If acl_smtp_mailauth is defined, the ACL it specifies is run. While it is ++ running, the value of $authenticated_sender is set to the value obtained ++ from the AUTH= parameter. If the ACL does not yield "accept", the value of ++ $authenticated_sender is deleted. The acl_smtp_mailauth ACL may not return ++ "drop" or "discard". If it defers, a temporary error code (451) is given ++ for the MAIL command. ++ ++ * If acl_smtp_mailauth is not defined, the value of the AUTH= parameter is ++ accepted and placed in $authenticated_sender only if the client has ++ authenticated. ++ ++ * If the AUTH= value was accepted by either of the two previous rules, and ++ the client has authenticated, and the authenticator has a setting for the ++ server_mail_auth_condition, the condition is checked at this point. The ++ valued that was saved from the authenticator is expanded. If the expansion ++ fails, or yields an empty string, "0", "no", or "false", the value of ++ $authenticated_sender is deleted. If the expansion yields any other value, ++ the value of $authenticated_sender is retained and passed on with the ++ message. ++ ++When $authenticated_sender is set for a message, it is passed on to other hosts ++to which Exim authenticates as a client. Do not confuse this value with ++$authenticated_id, which is a string obtained from the authentication process, ++and which is not usually a complete email address. ++ ++Whenever an AUTH= value is ignored, the incident is logged. The ACL for MAIL, ++if defined, is run after AUTH= is accepted or ignored. It can therefore make ++use of $authenticated_sender. The converse is not true: the value of ++$sender_address is not yet set up when the acl_smtp_mailauth ACL is run. ++ ++ ++33.3 Authentication on an Exim server ++------------------------------------- ++ ++When Exim receives an EHLO command, it advertises the public names of those ++authenticators that are configured as servers, subject to the following ++conditions: ++ ++ * The client host must match auth_advertise_hosts (default *). ++ ++ * It the server_advertise_condition option is set, its expansion must not ++ yield the empty string, "0", "no", or "false". ++ ++The order in which the authenticators are defined controls the order in which ++the mechanisms are advertised. ++ ++Some mail clients (for example, some versions of Netscape) require the user to ++provide a name and password for authentication whenever AUTH is advertised, ++even though authentication may not in fact be needed (for example, Exim may be ++set up to allow unconditional relaying from the client by an IP address check). ++You can make such clients more friendly by not advertising AUTH to them. For ++example, if clients on the 10.9.8.0/24 network are permitted (by the ACL that ++runs for RCPT) to relay without authentication, you should set ++ ++auth_advertise_hosts = ! 10.9.8.0/24 ++ ++so that no authentication mechanisms are advertised to them. ++ ++The server_advertise_condition controls the advertisement of individual ++authentication mechanisms. For example, it can be used to restrict the ++advertisement of a particular mechanism to encrypted connections, by a setting ++such as: ++ ++server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}} ++ ++If the session is encrypted, $tls_in_cipher is not empty, and so the expansion ++yields "yes", which allows the advertisement to happen. ++ ++When an Exim server receives an AUTH command from a client, it rejects it ++immediately if AUTH was not advertised in response to an earlier EHLO command. ++This is the case if ++ ++ * The client host does not match auth_advertise_hosts; or ++ ++ * No authenticators are configured with server options; or ++ ++ * Expansion of server_advertise_condition blocked the advertising of all the ++ server authenticators. ++ ++Otherwise, Exim runs the ACL specified by acl_smtp_auth in order to decide ++whether to accept the command. If acl_smtp_auth is not set, AUTH is accepted ++from any client host. ++ ++If AUTH is not rejected by the ACL, Exim searches its configuration for a ++server authentication mechanism that was advertised in response to EHLO and ++that matches the one named in the AUTH command. If it finds one, it runs the ++appropriate authentication protocol, and authentication either succeeds or ++fails. If there is no matching advertised mechanism, the AUTH command is ++rejected with a 504 error. ++ ++When a message is received from an authenticated host, the value of ++$received_protocol is set to "esmtpa" or "esmtpsa" instead of "esmtp" or ++"esmtps", and $sender_host_authenticated contains the name (not the public ++name) of the authenticator driver that successfully authenticated the client ++from which the message was received. This variable is empty if there was no ++successful authentication. ++ ++ ++33.4 Testing server authentication ++---------------------------------- ++ ++Exim's -bh option can be useful for testing server authentication ++configurations. The data for the AUTH command has to be sent using base64 ++encoding. A quick way to produce such data for testing is the following Perl ++script: ++ ++use MIME::Base64; ++printf ("%s", encode_base64(eval "\"$ARGV[0]\"")); ++ ++This interprets its argument as a Perl string, and then encodes it. The ++interpretation as a Perl string allows binary zeros, which are required for ++some kinds of authentication, to be included in the data. For example, a ++command line to run this script on such data might be ++ ++encode '\0user\0password' ++ ++Note the use of single quotes to prevent the shell interpreting the ++backslashes, so that they can be interpreted by Perl to specify characters ++whose code value is zero. ++ ++Warning 1: If either of the user or password strings starts with an octal ++digit, you must use three zeros instead of one after the leading backslash. If ++you do not, the octal digit that starts your string will be incorrectly ++interpreted as part of the code for the first character. ++ ++Warning 2: If there are characters in the strings that Perl interprets ++specially, you must use a Perl escape to prevent them being misinterpreted. For ++example, a command such as ++ ++encode '\0user@domain.com\0pas$$word' ++ ++gives an incorrect answer because of the unescaped "@" and "$" characters. ++ ++If you have the mimencode command installed, another way to do produce ++base64-encoded strings is to run the command ++ ++echo -e -n `\0user\0password' | mimencode ++ ++The -e option of echo enables the interpretation of backslash escapes in the ++argument, and the -n option specifies no newline at the end of its output. ++However, not all versions of echo recognize these options, so you should check ++your version before relying on this suggestion. ++ ++ ++33.5 Authentication by an Exim client ++------------------------------------- ++ ++The smtp transport has two options called hosts_require_auth and hosts_try_auth ++. When the smtp transport connects to a server that announces support for ++authentication, and the host matches an entry in either of these options, Exim ++(as a client) tries to authenticate as follows: ++ ++ * For each authenticator that is configured as a client, in the order in ++ which they are defined in the configuration, it searches the authentication ++ mechanisms announced by the server for one whose name matches the public ++ name of the authenticator. ++ ++ * When it finds one that matches, it runs the authenticator's client code. ++ The variables $host and $host_address are available for any string ++ expansions that the client might do. They are set to the server's name and ++ IP address. If any expansion is forced to fail, the authentication attempt ++ is abandoned, and Exim moves on to the next authenticator. Otherwise an ++ expansion failure causes delivery to be deferred. ++ ++ * If the result of the authentication attempt is a temporary error or a ++ timeout, Exim abandons trying to send the message to the host for the ++ moment. It will try again later. If there are any backup hosts available, ++ they are tried in the usual way. ++ ++ * If the response to authentication is a permanent error (5xx code), Exim ++ carries on searching the list of authenticators and tries another one if ++ possible. If all authentication attempts give permanent errors, or if there ++ are no attempts because no mechanisms match (or option expansions force ++ failure), what happens depends on whether the host matches ++ hosts_require_auth or hosts_try_auth. In the first case, a temporary error ++ is generated, and delivery is deferred. The error can be detected in the ++ retry rules, and thereby turned into a permanent error if you wish. In the ++ second case, Exim tries to deliver the message unauthenticated. ++ ++When Exim has authenticated itself to a remote server, it adds the AUTH ++parameter to the MAIL commands it sends, if it has an authenticated sender for ++the message. If the message came from a remote host, the authenticated sender ++is the one that was receiving on an incoming MAIL command, provided that the ++incoming connection was authenticated and the server_mail_auth condition ++allowed the authenticated sender to be retained. If a local process calls Exim ++to send a message, the sender address that is built from the login name and ++qualify_domain is treated as authenticated. However, if the ++authenticated_sender option is set on the smtp transport, it overrides the ++authenticated sender that was received with the message. ++ ++ ++ ++=============================================================================== ++34. THE PLAINTEXT AUTHENTICATOR ++ ++The plaintext authenticator can be configured to support the PLAIN and LOGIN ++authentication mechanisms, both of which transfer authentication data as plain ++(unencrypted) text (though base64 encoded). The use of plain text is a security ++risk; you are strongly advised to insist on the use of SMTP encryption (see ++chapter 41) if you use the PLAIN or LOGIN mechanisms. If you do use unencrypted ++plain text, you should not use the same passwords for SMTP connections as you ++do for login accounts. ++ ++ ++34.1 Plaintext options ++---------------------- ++ ++When configured as a server, plaintext uses the following options: ++ +++-----------------------------------------------------------------+ ++|server_condition|Use: authenticators|Type: string*|Default: unset| +++-----------------------------------------------------------------+ ++ ++This is actually a global authentication option, but it must be set in order to ++configure the plaintext driver as a server. Its use is described below. ++ +++----------------------------------------------------------+ ++|server_prompts|Use: plaintext|Type: string*|Default: unset| +++----------------------------------------------------------+ ++ ++The contents of this option, after expansion, must be a colon-separated list of ++prompt strings. If expansion fails, a temporary authentication rejection is ++given. ++ ++ ++34.2 Using plaintext in a server ++-------------------------------- ++ ++When running as a server, plaintext performs the authentication test by ++expanding a string. The data sent by the client with the AUTH command, or in ++response to subsequent prompts, is base64 encoded, and so may contain any byte ++values when decoded. If any data is supplied with the command, it is treated as ++a list of strings, separated by NULs (binary zeros), the first three of which ++are placed in the expansion variables $auth1, $auth2, and $auth3 (neither LOGIN ++nor PLAIN uses more than three strings). ++ ++For compatibility with previous releases of Exim, the values are also placed in ++the expansion variables $1, $2, and $3. However, the use of these variables for ++this purpose is now deprecated, as it can lead to confusion in string ++expansions that also use them for other things. ++ ++If there are more strings in server_prompts than the number of strings supplied ++with the AUTH command, the remaining prompts are used to obtain more data. Each ++response from the client may be a list of NUL-separated strings. ++ ++Once a sufficient number of data strings have been received, server_condition ++is expanded. If the expansion is forced to fail, authentication fails. Any ++other expansion failure causes a temporary error code to be returned. If the ++result of a successful expansion is an empty string, "0", "no", or "false", ++authentication fails. If the result of the expansion is "1", "yes", or "true", ++authentication succeeds and the generic server_set_id option is expanded and ++saved in $authenticated_id. For any other result, a temporary error code is ++returned, with the expanded string as the error text, and the failed id saved ++in $authenticated_fail_id. ++ ++Warning: If you use a lookup in the expansion to find the user's password, be ++sure to make the authentication fail if the user is unknown. There are good and ++bad examples at the end of the next section. ++ ++ ++34.3 The PLAIN authentication mechanism ++--------------------------------------- ++ ++The PLAIN authentication mechanism (RFC 2595) specifies that three strings be ++sent as one item of data (that is, one combined string containing two NUL ++separators). The data is sent either as part of the AUTH command, or ++subsequently in response to an empty prompt from the server. ++ ++The second and third strings are a user name and a corresponding password. ++Using a single fixed user name and password as an example, this could be ++configured as follows: ++ ++fixed_plain: ++ driver = plaintext ++ public_name = PLAIN ++ server_prompts = : ++ server_condition = \ ++ ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}} ++ server_set_id = $auth2 ++ ++Note that the default result strings from if ("true" or an empty string) are ++exactly what we want here, so they need not be specified. Obviously, if the ++password contains expansion-significant characters such as dollar, backslash, ++or closing brace, they have to be escaped. ++ ++The server_prompts setting specifies a single, empty prompt (empty items at the ++end of a string list are ignored). If all the data comes as part of the AUTH ++command, as is commonly the case, the prompt is not used. This authenticator is ++advertised in the response to EHLO as ++ ++250-AUTH PLAIN ++ ++and a client host can authenticate itself by sending the command ++ ++AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0 ++ ++As this contains three strings (more than the number of prompts), no further ++data is required from the client. Alternatively, the client may just send ++ ++AUTH PLAIN ++ ++to initiate authentication, in which case the server replies with an empty ++prompt. The client must respond with the combined data string. ++ ++The data string is base64 encoded, as required by the RFC. This example, when ++decoded, is <NUL>"username"<NUL>"mysecret", where <NUL> represents a zero byte. ++This is split up into three strings, the first of which is empty. The ++server_condition option in the authenticator checks that the second two are ++"username" and "mysecret" respectively. ++ ++Having just one fixed user name and password, as in this example, is not very ++realistic, though for a small organization with only a handful of ++authenticating clients it could make sense. ++ ++A more sophisticated instance of this authenticator could use the user name in ++$auth2 to look up a password in a file or database, and maybe do an encrypted ++comparison (see crypteq in chapter 11). Here is a example of this approach, ++where the passwords are looked up in a DBM file. Warning: This is an incorrect ++example: ++ ++server_condition = \ ++ ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}} ++ ++The expansion uses the user name ($auth2) as the key to look up a password, ++which it then compares to the supplied password ($auth3). Why is this example ++incorrect? It works fine for existing users, but consider what happens if a ++non-existent user name is given. The lookup fails, but as no success/failure ++strings are given for the lookup, it yields an empty string. Thus, to defeat ++the authentication, all a client has to do is to supply a non-existent user ++name and an empty password. The correct way of writing this test is: ++ ++server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\ ++ {${if eq{$value}{$auth3}}} {false}} ++ ++In this case, if the lookup succeeds, the result is checked; if the lookup ++fails, "false" is returned and authentication fails. If crypteq is being used ++instead of eq, the first example is in fact safe, because crypteq always fails ++if its second argument is empty. However, the second way of writing the test ++makes the logic clearer. ++ ++ ++34.4 The LOGIN authentication mechanism ++--------------------------------------- ++ ++The LOGIN authentication mechanism is not documented in any RFC, but is in use ++in a number of programs. No data is sent with the AUTH command. Instead, a user ++name and password are supplied separately, in response to prompts. The ++plaintext authenticator can be configured to support this as in this example: ++ ++fixed_login: ++ driver = plaintext ++ public_name = LOGIN ++ server_prompts = User Name : Password ++ server_condition = \ ++ ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}} ++ server_set_id = $auth1 ++ ++Because of the way plaintext operates, this authenticator accepts data supplied ++with the AUTH command (in contravention of the specification of LOGIN), but if ++the client does not supply it (as is the case for LOGIN clients), the prompt ++strings are used to obtain two data items. ++ ++Some clients are very particular about the precise text of the prompts. For ++example, Outlook Express is reported to recognize only "Username:" and ++"Password:". Here is an example of a LOGIN authenticator that uses those ++strings. It uses the ldapauth expansion condition to check the user name and ++password by binding to an LDAP server: ++ ++login: ++ driver = plaintext ++ public_name = LOGIN ++ server_prompts = Username:: : Password:: ++ server_condition = ${if and{{ \ ++ !eq{}{$auth1} }{ \ ++ ldapauth{\ ++ user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \ ++ pass=${quote:$auth2} \ ++ ldap://ldap.example.org/} }} } ++ server_set_id = uid=$auth1,ou=people,o=example.org ++ ++We have to check that the username is not empty before using it, because LDAP ++does not permit empty DN components. We must also use the quote_ldap_dn ++operator to correctly quote the DN for authentication. However, the basic quote ++operator, rather than any of the LDAP quoting operators, is the correct one to ++use for the password, because quoting is needed only to make the password ++conform to the Exim syntax. At the LDAP level, the password is an uninterpreted ++string. ++ ++ ++34.5 Support for different kinds of authentication ++-------------------------------------------------- ++ ++A number of string expansion features are provided for the purpose of ++interfacing to different ways of user authentication. These include checking ++traditionally encrypted passwords from /etc/passwd (or equivalent), PAM, ++Radius, ldapauth, pwcheck, and saslauthd. For details see section 11.7. ++ ++ ++34.6 Using plaintext in a client ++-------------------------------- ++ ++The plaintext authenticator has two client options: ++ +++------------------------------------------------------------------------+ ++|client_ignore_invalid_base64|Use: plaintext|Type: boolean|Default: false| +++------------------------------------------------------------------------+ ++ ++If the client receives a server prompt that is not a valid base64 string, ++authentication is abandoned by default. However, if this option is set true, ++the error in the challenge is ignored and the client sends the response as ++usual. ++ +++-------------------------------------------------------+ ++|client_send|Use: plaintext|Type: string*|Default: unset| +++-------------------------------------------------------+ ++ ++The string is a colon-separated list of authentication data strings. Each ++string is independently expanded before being sent to the server. The first ++string is sent with the AUTH command; any more strings are sent in response to ++prompts from the server. Before each string is expanded, the value of the most ++recent prompt is placed in the next $auth<n> variable, starting with $auth1 for ++the first prompt. Up to three prompts are stored in this way. Thus, the prompt ++that is received in response to sending the first string (with the AUTH ++command) can be used in the expansion of the second string, and so on. If an ++invalid base64 string is received when client_ignore_invalid_base64 is set, an ++empty string is put in the $auth<n> variable. ++ ++Note: You cannot use expansion to create multiple strings, because splitting ++takes priority and happens first. ++ ++Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in ++the data, further processing is applied to each string before it is sent. If ++there are any single circumflex characters in the string, they are converted to ++NULs. Should an actual circumflex be required as data, it must be doubled in ++the string. ++ ++This is an example of a client configuration that implements the PLAIN ++authentication mechanism with a fixed user name and password: ++ ++fixed_plain: ++ driver = plaintext ++ public_name = PLAIN ++ client_send = ^username^mysecret ++ ++The lack of colons means that the entire text is sent with the AUTH command, ++with the circumflex characters converted to NULs. A similar example that uses ++the LOGIN mechanism is: ++ ++fixed_login: ++ driver = plaintext ++ public_name = LOGIN ++ client_send = : username : mysecret ++ ++The initial colon means that the first string is empty, so no data is sent with ++the AUTH command itself. The remaining strings are sent in response to prompts. ++ ++ ++ ++=============================================================================== ++35. THE CRAM_MD5 AUTHENTICATOR ++ ++The CRAM-MD5 authentication mechanism is described in RFC 2195. The server ++sends a challenge string to the client, and the response consists of a user ++name and the CRAM-MD5 digest of the challenge string combined with a secret ++string (password) which is known to both server and client. Thus, the secret is ++not sent over the network as plain text, which makes this authenticator more ++secure than plaintext. However, the downside is that the secret has to be ++available in plain text at either end. ++ ++ ++35.1 Using cram_md5 as a server ++------------------------------- ++ ++This authenticator has one server option, which must be set to configure the ++authenticator as a server: ++ +++--------------------------------------------------------+ ++|server_secret|Use: cram_md5|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++When the server receives the client's response, the user name is placed in the ++expansion variable $auth1, and server_secret is expanded to obtain the password ++for that user. The server then computes the CRAM-MD5 digest that the client ++should have sent, and checks that it received the correct string. If the ++expansion of server_secret is forced to fail, authentication fails. If the ++expansion fails for some other reason, a temporary error code is returned to ++the client. ++ ++For compatibility with previous releases of Exim, the user name is also placed ++in $1. However, the use of this variables for this purpose is now deprecated, ++as it can lead to confusion in string expansions that also use numeric ++variables for other things. ++ ++For example, the following authenticator checks that the user name given by the ++client is "ph10", and if so, uses "secret" as the password. For any other user ++name, authentication fails. ++ ++fixed_cram: ++ driver = cram_md5 ++ public_name = CRAM-MD5 ++ server_secret = ${if eq{$auth1}{ph10}{secret}fail} ++ server_set_id = $auth1 ++ ++If authentication succeeds, the setting of server_set_id preserves the user ++name in $authenticated_id. A more typical configuration might look up the ++secret string in a file, using the user name as the key. For example: ++ ++lookup_cram: ++ driver = cram_md5 ++ public_name = CRAM-MD5 ++ server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\ ++ {$value}fail} ++ server_set_id = $auth1 ++ ++Note that this expansion explicitly forces failure if the lookup fails because ++$auth1 contains an unknown user name. ++ ++As another example, if you wish to re-use a Cyrus SASL sasldb2 file without ++using the relevant libraries, you need to know the realm to specify in the ++lookup and then ask for the "userPassword" attribute for that user in that ++realm, with: ++ ++cyrusless_crammd5: ++ driver = cram_md5 ++ public_name = CRAM-MD5 ++ server_secret = ${lookup{$auth1:mail.example.org:userPassword}\ ++ dbmjz{/etc/sasldb2}} ++ server_set_id = $auth1 ++ ++ ++35.2 Using cram_md5 as a client ++------------------------------- ++ ++When used as a client, the cram_md5 authenticator has two options: ++ +++----------------------------------------------------------------------+ ++|client_name|Use: cram_md5|Type: string*|Default: the primary host name| +++----------------------------------------------------------------------+ ++ ++This string is expanded, and the result used as the user name data when ++computing the response to the server's challenge. ++ +++--------------------------------------------------------+ ++|client_secret|Use: cram_md5|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++This option must be set for the authenticator to work as a client. Its value is ++expanded and the result used as the secret string when computing the response. ++ ++Different user names and secrets can be used for different servers by referring ++to $host or $host_address in the options. Forced failure of either expansion ++string is treated as an indication that this authenticator is not prepared to ++handle this case. Exim moves on to the next configured client authenticator. ++Any other expansion failure causes Exim to give up trying to send the message ++to the current server. ++ ++A simple example configuration of a cram_md5 authenticator, using fixed ++strings, is: ++ ++fixed_cram: ++ driver = cram_md5 ++ public_name = CRAM-MD5 ++ client_name = ph10 ++ client_secret = secret ++ ++ ++ ++=============================================================================== ++36. THE CYRUS_SASL AUTHENTICATOR ++ ++The code for this authenticator was provided by Matthew Byng-Maddick of A L ++Digital Ltd (http://www.aldigital.co.uk). ++ ++The cyrus_sasl authenticator provides server support for the Cyrus SASL library ++implementation of the RFC 2222 ("Simple Authentication and Security Layer"). ++This library supports a number of authentication mechanisms, including PLAIN ++and LOGIN, but also several others that Exim does not support directly. In ++particular, there is support for Kerberos authentication. ++ ++The cyrus_sasl authenticator provides a gatewaying mechanism directly to the ++Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5, then ++so can the cyrus_sasl authenticator. By default it uses the public name of the ++driver to determine which mechanism to support. ++ ++Where access to some kind of secret file is required, for example in GSSAPI or ++CRAM-MD5, it is worth noting that the authenticator runs as the Exim user, and ++that the Cyrus SASL library has no way of escalating privileges by default. You ++may also find you need to set environment variables, depending on the driver ++you are using. ++ ++The application name provided by Exim is "exim", so various SASL options may be ++set in exim.conf in your SASL directory. If you are using GSSAPI for Kerberos, ++note that because of limitations in the GSSAPI interface, changing the server ++keytab might need to be communicated down to the Kerberos layer independently. ++The mechanism for doing so is dependent upon the Kerberos implementation. ++ ++For example, for older releases of Heimdal, the environment variable ++KRB5_KTNAME may be set to point to an alternative keytab file. Exim will pass ++this variable through from its own inherited environment when started as root ++or the Exim user. The keytab file needs to be readable by the Exim user. With ++newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the ++environment variable. In practice, for those releases, the Cyrus authenticator ++is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider ++the heimdal_gssapi authenticator, described in chapter 39 ++ ++ ++36.1 Using cyrus_sasl as a server ++--------------------------------- ++ ++The cyrus_sasl authenticator has four private options. It puts the username (on ++a successful authentication) into $auth1. For compatibility with previous ++releases of Exim, the username is also placed in $1. However, the use of this ++variable for this purpose is now deprecated, as it can lead to confusion in ++string expansions that also use numeric variables for other things. ++ +++----------------------------------------------------------------+ ++|server_hostname|Use: cyrus_sasl|Type: string*|Default: see below| +++----------------------------------------------------------------+ ++ ++This option selects the hostname that is used when communicating with the ++library. The default value is "$primary_hostname". It is up to the underlying ++SASL plug-in what it does with this data. ++ +++-----------------------------------------------------------+ ++|server_mech|Use: cyrus_sasl|Type: string|Default: see below| +++-----------------------------------------------------------+ ++ ++This option selects the authentication mechanism this driver should use. The ++default is the value of the generic public_name option. This option allows you ++to use a different underlying mechanism from the advertised name. For example: ++ ++sasl: ++ driver = cyrus_sasl ++ public_name = X-ANYTHING ++ server_mech = CRAM-MD5 ++ server_set_id = $auth1 ++ +++---------------------------------------------------------+ ++|server_realm|Use: cyrus_sasl|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++This specifies the SASL realm that the server claims to be in. ++ +++-----------------------------------------------------------+ ++|server_service|Use: cyrus_sasl|Type: string|Default: "smtp"| +++-----------------------------------------------------------+ ++ ++This is the SASL service that the server claims to implement. ++ ++For straightforward cases, you do not need to set any of the authenticator's ++private options. All you need to do is to specify an appropriate mechanism as ++the public name. Thus, if you have a SASL library that supports CRAM-MD5 and ++PLAIN, you could have two authenticators as follows: ++ ++sasl_cram_md5: ++ driver = cyrus_sasl ++ public_name = CRAM-MD5 ++ server_set_id = $auth1 ++ ++sasl_plain: ++ driver = cyrus_sasl ++ public_name = PLAIN ++ server_set_id = $auth2 ++ ++Cyrus SASL does implement the LOGIN authentication method, even though it is ++not a standard method. It is disabled by default in the source distribution, ++but it is present in many binary distributions. ++ ++ ++ ++=============================================================================== ++37. THE DOVECOT AUTHENTICATOR ++ ++This authenticator is an interface to the authentication facility of the ++Dovecot POP/IMAP server, which can support a number of authentication methods. ++If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful ++to use the same mechanisms for SMTP authentication. This is a server ++authenticator only. There is only one option: ++ +++------------------------------------------------------+ ++|server_socket|Use: dovecot|Type: string|Default: unset| +++------------------------------------------------------+ ++ ++This option must specify the socket that is the interface to Dovecot ++authentication. The public_name option must specify an authentication mechanism ++that Dovecot is configured to support. You can have several authenticators for ++different mechanisms. For example: ++ ++dovecot_plain: ++ driver = dovecot ++ public_name = PLAIN ++ server_socket = /var/run/dovecot/auth-client ++ server_set_id = $auth2 ++ ++dovecot_ntlm: ++ driver = dovecot ++ public_name = NTLM ++ server_socket = /var/run/dovecot/auth-client ++ server_set_id = $auth1 ++ ++If the SMTP connection is encrypted, or if $sender_host_address is equal to ++$received_ip_address (that is, the connection is local), the "secured" option ++is passed in the Dovecot authentication command. If, for a TLS connection, a ++client certificate has been verified, the "valid-client-cert" option is passed. ++When authentication succeeds, the identity of the user who authenticated is ++placed in $auth1. ++ ++ ++ ++=============================================================================== ++38. THE GSASL AUTHENTICATOR ++ ++The gsasl authenticator provides server integration for the GNU SASL library ++and the mechanisms it provides. This is new as of the 4.80 release and there ++are a few areas where the library does not let Exim smoothly scale to handle ++future authentication mechanisms, so no guarantee can be made that any ++particular new authentication mechanism will be supported without code changes ++in Exim. ++ +++-------------------------------------------------------------+ ++|server_channelbinding|Use: gsasl|Type: boolean|Default: false| +++-------------------------------------------------------------+ ++ ++Some authentication mechanisms are able to use external context at both ends of ++the session to bind the authentication to that context, and fail the ++authentication process if that context differs. Specifically, some TLS ++ciphersuites can provide identifying information about the cryptographic ++context. ++ ++This means that certificate identity and verification becomes a non-issue, as a ++man-in-the-middle attack will cause the correct client and server to see ++different identifiers and authentication will fail. ++ ++This is currently only supported when using the GnuTLS library. This is only ++usable by mechanisms which support "channel binding"; at time of writing, ++that's the SCRAM family. ++ ++This defaults off to ensure smooth upgrade across Exim releases, in case this ++option causes some clients to start failing. Some future release of Exim may ++switch the default to be true. ++ +++-----------------------------------------------------------+ ++|server_hostname|Use: gsasl|Type: string*|Default: see below| +++-----------------------------------------------------------+ ++ ++This option selects the hostname that is used when communicating with the ++library. The default value is "$primary_hostname". Some mechanisms will use ++this data. ++ +++------------------------------------------------------+ ++|server_mech|Use: gsasl|Type: string|Default: see below| +++------------------------------------------------------+ ++ ++This option selects the authentication mechanism this driver should use. The ++default is the value of the generic public_name option. This option allows you ++to use a different underlying mechanism from the advertised name. For example: ++ ++sasl: ++ driver = gsasl ++ public_name = X-ANYTHING ++ server_mech = CRAM-MD5 ++ server_set_id = $auth1 ++ +++-------------------------------------------------------+ ++|server_password|Use: gsasl|Type: string*|Default: unset| +++-------------------------------------------------------+ ++ ++Various mechanisms need access to the cleartext password on the server, so that ++proof-of-possession can be demonstrated on the wire, without sending the ++password itself. ++ ++The data available for lookup varies per mechanism. In all cases, $auth1 is set ++to the authentication id. The $auth2 variable will always be the authorization ++id (authz) if available, else the empty string. The $auth3 variable will always ++be the realm if available, else the empty string. ++ ++A forced failure will cause authentication to defer. ++ ++If using this option, it may make sense to set the server_condition option to ++be simply "true". ++ +++----------------------------------------------------+ ++|server_realm|Use: gsasl|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++This specifies the SASL realm that the server claims to be in. Some mechanisms ++will use this data. ++ +++---------------------------------------------------------+ ++|server_scram_iter|Use: gsasl|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++This option provides data for the SCRAM family of mechanisms. $auth1 is not ++available at evaluation time. (This may change, as we receive feedback on use) ++ +++---------------------------------------------------------+ ++|server_scram_salt|Use: gsasl|Type: string*|Default: unset| +++---------------------------------------------------------+ ++ ++This option provides data for the SCRAM family of mechanisms. $auth1 is not ++available at evaluation time. (This may change, as we receive feedback on use) ++ +++------------------------------------------------------+ ++|server_service|Use: gsasl|Type: string|Default: "smtp"| +++------------------------------------------------------+ ++ ++This is the SASL service that the server claims to implement. Some mechanisms ++will use this data. ++ ++ ++38.1 gsasl auth variables ++------------------------- ++ ++These may be set when evaluating specific options, as detailed above. They will ++also be set when evaluating server_condition. ++ ++Unless otherwise stated below, the gsasl integration will use the following ++meanings for these variables: ++ ++ * $auth1: the authentication id ++ ++ * $auth2: the authorization id ++ ++ * $auth3: the realm ++ ++On a per-mechanism basis: ++ ++ * EXTERNAL: only $auth1 is set, to the possibly empty authorization id; the ++ server_condition option must be present. ++ ++ * ANONYMOUS: only $auth1 is set, to the possibly empty anonymous token; the ++ server_condition option must be present. ++ ++ * GSSAPI: $auth1 will be set to the GSSAPI Display Name; $auth2 will be set ++ to the authorization id, the server_condition option must be present. ++ ++An anonymous token is something passed along as an unauthenticated identifier; ++this is analogous to FTP anonymous authentication passing an email address, or ++software-identifier@, as the "password". ++ ++An example showing the password having the realm specified in the callback and ++demonstrating a Cyrus SASL to GSASL migration approach is: ++ ++gsasl_cyrusless_crammd5: ++ driver = gsasl ++ public_name = CRAM-MD5 ++ server_realm = imap.example.org ++ server_password = ${lookup{$auth1:$auth3:userPassword}\ ++ dbmjz{/etc/sasldb2}{$value}fail} ++ server_set_id = ${quote:$auth1} ++ server_condition = yes ++ ++ ++ ++=============================================================================== ++39. THE HEIMDAL_GSSAPI AUTHENTICATOR ++ ++The heimdal_gssapi authenticator provides server integration for the Heimdal ++GSSAPI/Kerberos library, permitting Exim to set a keytab pathname reliably. ++ +++--------------------------------------------------------------------+ ++|server_hostname|Use: heimdal_gssapi|Type: string*|Default: see below| +++--------------------------------------------------------------------+ ++ ++This option selects the hostname that is used, with server_service, for ++constructing the GSS server name, as a GSS_C_NT_HOSTBASED_SERVICE identifier. ++The default value is "$primary_hostname". ++ +++--------------------------------------------------------------+ ++|server_keytab|Use: heimdal_gssapi|Type: string*|Default: unset| +++--------------------------------------------------------------+ ++ ++If set, then Heimdal will not use the system default keytab (typically /etc/ ++krb5.keytab) but instead the pathname given in this option. The value should be ++a pathname, with no "file:" prefix. ++ +++--------------------------------------------------------------+ ++|server_service|Use: heimdal_gssapi|Type: string*|Default: smtp| +++--------------------------------------------------------------+ ++ ++This option specifies the service identifier used, in conjunction with ++server_hostname, for building the identifer for finding credentials from the ++keytab. ++ ++ ++39.1 heimdal_gssapi auth variables ++---------------------------------- ++ ++Beware that these variables will typically include a realm, thus will appear to ++be roughly like an email address already. The authzid in $auth2 is not ++verified, so a malicious client can set it to anything. ++ ++The $auth1 field should be safely trustable as a value from the Key ++Distribution Center. Note that these are not quite email addresses. Each ++identifier is for a role, and so the left-hand-side may include a role suffix. ++For instance, "joe/admin@EXAMPLE.ORG". ++ ++ * $auth1: the authentication id, set to the GSS Display Name. ++ ++ * $auth2: the authorization id, sent within SASL encapsulation after ++ authentication. If that was empty, this will also be set to the GSS Display ++ Name. ++ ++ ++ ++=============================================================================== ++40. THE SPA AUTHENTICATOR ++ ++The spa authenticator provides client support for Microsoft's Secure Password ++Authentication mechanism, which is also sometimes known as NTLM (NT LanMan). ++The code for client side of this authenticator was contributed by Marc ++Prud'hommeaux, and much of it is taken from the Samba project (http:// ++www.samba.org). The code for the server side was subsequently contributed by ++Tom Kistner. The mechanism works as follows: ++ ++ * After the AUTH command has been accepted, the client sends an SPA ++ authentication request based on the user name and optional domain. ++ ++ * The server sends back a challenge. ++ ++ * The client builds a challenge response which makes use of the user's ++ password and sends it to the server, which then accepts or rejects it. ++ ++Encryption is used to protect the password in transit. ++ ++ ++40.1 Using spa as a server ++-------------------------- ++ ++The spa authenticator has just one server option: ++ +++-----------------------------------------------------+ ++|server_password|Use: spa|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++This option is expanded, and the result must be the cleartext password for the ++authenticating user, whose name is at this point in $auth1. For compatibility ++with previous releases of Exim, the user name is also placed in $1. However, ++the use of this variable for this purpose is now deprecated, as it can lead to ++confusion in string expansions that also use numeric variables for other ++things. For example: ++ ++spa: ++ driver = spa ++ public_name = NTLM ++ server_password = \ ++ ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail} ++ ++If the expansion is forced to fail, authentication fails. Any other expansion ++failure causes a temporary error code to be returned. ++ ++ ++40.2 Using spa as a client ++-------------------------- ++ ++The spa authenticator has the following client options: ++ +++---------------------------------------------------+ ++|client_domain|Use: spa|Type: string*|Default: unset| +++---------------------------------------------------+ ++ ++This option specifies an optional domain for the authentication. ++ +++-----------------------------------------------------+ ++|client_password|Use: spa|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++This option specifies the user's password, and must be set. ++ +++-----------------------------------------------------+ ++|client_username|Use: spa|Type: string*|Default: unset| +++-----------------------------------------------------+ ++ ++This option specifies the user name, and must be set. Here is an example of a ++configuration of this authenticator for use with the mail servers at msn.com: ++ ++msn: ++ driver = spa ++ public_name = MSN ++ client_username = msn/msn_username ++ client_password = msn_plaintext_password ++ client_domain = DOMAIN_OR_UNSET ++ ++ ++ ++=============================================================================== ++41. ENCRYPTED SMTP CONNECTIONS USING TLS/SSL ++ ++Support for TLS (Transport Layer Security), formerly known as SSL (Secure ++Sockets Layer), is implemented by making use of the OpenSSL library or the ++GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no ++cryptographic code in the Exim distribution itself for implementing TLS. In ++order to use this feature you must install OpenSSL or GnuTLS, and then build a ++version of Exim that includes TLS support (see section 4.7). You also need to ++understand the basic concepts of encryption at a managerial level, and in ++particular, the way that public keys, private keys, and certificates are used. ++ ++RFC 3207 defines how SMTP connections can make use of encryption. Once a ++connection is established, the client issues a STARTTLS command. If the server ++accepts this, the client and the server negotiate an encryption mechanism. If ++the negotiation succeeds, the data that subsequently passes between them is ++encrypted. ++ ++Exim's ACLs can detect whether the current SMTP session is encrypted or not, ++and if so, what cipher suite is in use, whether the client supplied a ++certificate, and whether or not that certificate was verified. This makes it ++possible for an Exim server to deny or accept certain commands based on the ++encryption state. ++ ++Warning: Certain types of firewall and certain anti-virus products can disrupt ++TLS connections. You need to turn off SMTP scanning for these products in order ++to get TLS to work. ++ ++ ++41.1 Support for the legacy "ssmtp" (aka "smtps") protocol ++---------------------------------------------------------- ++ ++Early implementations of encrypted SMTP used a different TCP port from normal ++SMTP, and expected an encryption negotiation to start immediately, instead of ++waiting for a STARTTLS command from the client using the standard SMTP port. ++The protocol was called "ssmtp" or "smtps", and port 465 was allocated for this ++purpose. ++ ++This approach was abandoned when encrypted SMTP was standardized, but there are ++still some legacy clients that use it. Exim supports these clients by means of ++the tls_on_connect_ports global option. Its value must be a list of port ++numbers; the most common use is expected to be: ++ ++tls_on_connect_ports = 465 ++ ++The port numbers specified by this option apply to all SMTP connections, both ++via the daemon and via inetd. You still need to specify all the ports that the ++daemon uses (by setting daemon_smtp_ports or local_interfaces or the -oX ++command line option) because tls_on_connect_ports does not add an extra port - ++rather, it specifies different behaviour on a port that is defined elsewhere. ++ ++There is also a -tls-on-connect command line option. This overrides ++tls_on_connect_ports; it forces the legacy behaviour for all ports. ++ ++ ++41.2 OpenSSL vs GnuTLS ++---------------------- ++ ++The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS ++followed later, when the first versions of GnuTLS were released. To build Exim ++to use GnuTLS, you need to set ++ ++USE_GNUTLS=yes ++ ++in Local/Makefile, in addition to ++ ++SUPPORT_TLS=yes ++ ++You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the include ++files and libraries for GnuTLS can be found. ++ ++There are some differences in usage when using GnuTLS instead of OpenSSL: ++ ++ * The tls_verify_certificates option must contain the name of a file, not the ++ name of a directory (for OpenSSL it can be either). ++ ++ * The default value for tls_dhparam differs for historical reasons. ++ ++ * Distinguished Name (DN) strings reported by the OpenSSL library use a slash ++ for separating fields; GnuTLS uses commas, in accordance with RFC 2253. ++ This affects the value of the $tls_in_peerdn and $tls_out_peerdn variables. ++ ++ * OpenSSL identifies cipher suites using hyphens as separators, for example: ++ DES-CBC3-SHA. GnuTLS historically used underscores, for example: ++ RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present ++ in a cipher list. To make life simpler, Exim changes underscores to hyphens ++ for OpenSSL and passes the string unchanged to GnuTLS (expecting the ++ library to handle its own older variants) when processing lists of cipher ++ suites in the tls_require_ciphers options (the global option and the smtp ++ transport option). ++ ++ * The tls_require_ciphers options operate differently, as described in the ++ sections 41.4 and 41.5. ++ ++ * The tls_dh_min_bits SMTP transport option is only honoured by GnuTLS. When ++ using OpenSSL, this option is ignored. (If an API is found to let OpenSSL ++ be configured in this way, let the Exim Maintainers know and we'll likely ++ use it). ++ ++ * Some other recently added features may only be available in one or the ++ other. This should be documented with the feature. If the documentation ++ does not explicitly state that the feature is infeasible in the other TLS ++ implementation, then patches are welcome. ++ ++ ++41.3 GnuTLS parameter computation ++--------------------------------- ++ ++This section only applies if tls_dhparam is set to "historic" or to an explicit ++path; if the latter, then the text about generation still applies, but not the ++chosen filename. By default, as of Exim 4.80 a hard-coded D-H prime is used. ++See the documentation of tls_dhparam for more information. ++ ++GnuTLS uses D-H parameters that may take a substantial amount of time to ++compute. It is unreasonable to re-compute them for every TLS session. ++Therefore, Exim keeps this data in a file in its spool directory, called ++gnutls-params-NNNN for some value of NNNN, corresponding to the number of bits ++requested. The file is owned by the Exim user and is readable only by its ++owner. Every Exim process that start up GnuTLS reads the D-H parameters from ++this file. If the file does not exist, the first Exim process that needs it ++computes the data and writes it to a temporary file which is renamed once it is ++complete. It does not matter if several Exim processes do this simultaneously ++(apart from wasting a few resources). Once a file is in place, new Exim ++processes immediately start using it. ++ ++For maximum security, the parameters that are stored in this file should be ++recalculated periodically, the frequency depending on your paranoia level. If ++you are avoiding using the fixed D-H primes published in RFCs, then you are ++concerned about some advanced attacks and will wish to do this; if you do not ++regenerate then you might as well stick to the standard primes. ++ ++Arranging this is easy in principle; just delete the file when you want new ++values to be computed. However, there may be a problem. The calculation of new ++parameters needs random numbers, and these are obtained from /dev/random. If ++the system is not very active, /dev/random may delay returning data until ++enough randomness (entropy) is available. This may cause Exim to hang for a ++substantial amount of time, causing timeouts on incoming connections. ++ ++The solution is to generate the parameters externally to Exim. They are stored ++in gnutls-params-N in PEM format, which means that they can be generated ++externally using the certtool command that is part of GnuTLS. ++ ++To replace the parameters with new ones, instead of deleting the file and ++letting Exim re-create it, you can generate new parameters using certtool and, ++when this has been done, replace Exim's cache file by renaming. The relevant ++commands are something like this: ++ ++# ls ++[ look for file; assume gnutls-params-2236 is the most recent ] ++# rm -f new-params ++# touch new-params ++# chown exim:exim new-params ++# chmod 0600 new-params ++# certtool --generate-dh-params --bits 2236 >>new-params ++# openssl dhparam -noout -text -in new-params | head ++[ check the first line, make sure it's not more than 2236; ++ if it is, then go back to the start ("rm") and repeat ++ until the size generated is at most the size requested ] ++# chmod 0400 new-params ++# mv new-params gnutls-params-2236 ++ ++If Exim never has to generate the parameters itself, the possibility of ++stalling is removed. ++ ++The filename changed in Exim 4.80, to gain the -bits suffix. The value which ++Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS, ++the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is a ++way for Exim to ask for the "normal" number of bits for D-H public-key usage, ++and Exim does so. This attempt to remove Exim from TLS policy decisions failed, ++as GnuTLS 2.12 returns a value higher than the current hard-coded limit of the ++NSS library. Thus Exim gains the tls_dh_max_bits global option, which applies ++to all D-H usage, client or server. If the value returned by GnuTLS is greater ++than tls_dh_max_bits then the value will be clamped down to tls_dh_max_bits. ++The default value has been set at the current NSS limit, which is still much ++higher than Exim historically used. ++ ++The filename and bits used will change as the GnuTLS maintainers change the ++value for their parameter "GNUTLS_SEC_PARAM_NORMAL", as clamped by ++tls_dh_max_bits. At the time of writing (mid 2012), GnuTLS 2.12 recommends 2432 ++bits, while NSS is limited to 2236 bits. ++ ++In fact, the requested value will be *lower* than tls_dh_max_bits, to increase ++the chance of the generated prime actually being within acceptable bounds, as ++GnuTLS has been observed to overshoot. Note the check step in the procedure ++above. There is no sane procedure available to Exim to double-check the size of ++the generated prime, so it might still be too large. ++ ++ ++41.4 Requiring specific ciphers in OpenSSL ++------------------------------------------ ++ ++There is a function in the OpenSSL library that can be passed a list of cipher ++suites before the cipher negotiation takes place. This specifies which ciphers ++are acceptable. The list is colon separated and may contain names like ++DES-CBC3-SHA. Exim passes the expanded value of tls_require_ciphers directly to ++this function call. Many systems will install the OpenSSL manual-pages, so you ++may have ciphers(1) available to you. The following quotation from the OpenSSL ++documentation specifies what forms of item are allowed in the cipher string: ++ ++ * It can consist of a single cipher suite such as RC4-SHA. ++ ++ * It can represent a list of cipher suites containing a certain algorithm, or ++ cipher suites of a certain type. For example SHA1 represents all ciphers ++ suites using the digest algorithm SHA1 and SSLv3 represents all SSL v3 ++ algorithms. ++ ++ * Lists of cipher suites can be combined in a single cipher string using the ++ + character. This is used as a logical and operation. For example SHA1+DES ++ represents all cipher suites containing the SHA1 and the DES algorithms. ++ ++Each cipher string can be optionally preceded by one of the characters "!", "-" ++or "+". ++ ++ * If "!" is used, the ciphers are permanently deleted from the list. The ++ ciphers deleted can never reappear in the list even if they are explicitly ++ stated. ++ ++ * If "-" is used, the ciphers are deleted from the list, but some or all of ++ the ciphers can be added again by later options. ++ ++ * If "+" is used, the ciphers are moved to the end of the list. This option ++ does not add any new ciphers; it just moves matching existing ones. ++ ++If none of these characters is present, the string is interpreted as a list of ++ciphers to be appended to the current preference list. If the list includes any ++ciphers already present they will be ignored: that is, they will not be moved ++to the end of the list. ++ ++The OpenSSL ciphers(1) command may be used to test the results of a given ++string: ++ ++# note single-quotes to get ! past any shell history expansion ++$ openssl ciphers 'HIGH:!MD5:!SHA1' ++ ++This example will let the library defaults be permitted on the MX port, where ++there's probably no identity verification anyway, but ups the ante on the ++submission ports where the administrator might have some influence on the ++choice of clients used: ++ ++# OpenSSL variant; see man ciphers(1) ++tls_require_ciphers = ${if =={$received_port}{25}\ ++ {DEFAULT}\ ++ {HIGH:!MD5:!SHA1}} ++ ++ ++41.5 Requiring specific ciphers or other parameters in GnuTLS ++------------------------------------------------------------- ++ ++The GnuTLS library allows the caller to provide a "priority string", documented ++as part of the gnutls_priority_init function. This is very similar to the ++ciphersuite specification in OpenSSL. ++ ++The tls_require_ciphers option is treated as the GnuTLS priority string. ++ ++The tls_require_ciphers option is available both as an global option, ++controlling how Exim behaves as a server, and also as an option of the smtp ++transport, controlling how Exim behaves as a client. In both cases the value is ++string expanded. The resulting string is not an Exim list and the string is ++given to the GnuTLS library, so that Exim does not need to be aware of future ++feature enhancements of GnuTLS. ++ ++Documentation of the strings accepted may be found in the GnuTLS manual, under ++"Priority strings". This is online as http://www.gnutls.org/manual/html_node/ ++Priority-Strings.html, but beware that this relates to GnuTLS 3, which may be ++newer than the version installed on your system. If you are using GnuTLS 3, ++then the example code on that site can be used to test a given string. ++ ++Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three ++additional options, "gnutls_require_kx", "gnutls_require_mac" and " ++gnutls_require_protocols". tls_require_ciphers was an Exim list. ++ ++This example will let the library defaults be permitted on the MX port, where ++there's probably no identity verification anyway, and lowers security further ++by increasing compatibility; but this ups the ante on the submission ports ++where the administrator might have some influence on the choice of clients ++used: ++ ++# GnuTLS variant ++tls_require_ciphers = ${if =={$received_port}{25}\ ++ {NORMAL:%COMPAT}\ ++ {SECURE128}} ++ ++ ++41.6 Configuring an Exim server to use TLS ++------------------------------------------ ++ ++When Exim has been built with TLS support, it advertises the availability of ++the STARTTLS command to client hosts that match tls_advertise_hosts, but not to ++any others. The default value of this option is unset, which means that ++STARTTLS is not advertised at all. This default is chosen because you need to ++set some other options in order to make TLS available, and also it is sensible ++for systems that want to use TLS only as a client. ++ ++If a client issues a STARTTLS command and there is some configuration problem ++in the server, the command is rejected with a 454 error. If the client persists ++in trying to issue SMTP commands, all except QUIT are rejected with the error ++ ++554 Security failure ++ ++If a STARTTLS command is issued within an existing TLS session, it is rejected ++with a 554 error code. ++ ++To enable TLS operations on a server, you must set tls_advertise_hosts to match ++some hosts. You can, of course, set it to * to match all hosts. However, this ++is not all you need to do. TLS sessions to a server won't work without some ++further configuration at the server end. ++ ++It is rumoured that all existing clients that support TLS/SSL use RSA ++encryption. To make this work you need to set, in the server, ++ ++tls_certificate = /some/file/name ++tls_privatekey = /some/file/name ++ ++These options are, in fact, expanded strings, so you can make them depend on ++the identity of the client that is connected if you wish. The first file ++contains the server's X509 certificate, and the second contains the private key ++that goes with it. These files need to be readable by the Exim user, and must ++always be given as full path names. They can be the same file if both the ++certificate and the key are contained within it. If tls_privatekey is not set, ++or if its expansion is forced to fail or results in an empty string, this is ++assumed to be the case. The certificate file may also contain intermediate ++certificates that need to be sent to the client to enable it to authenticate ++the server's certificate. ++ ++If you do not understand about certificates and keys, please try to find a ++source of this background information, which is not Exim-specific. (There are a ++few comments below in section 41.12.) ++ ++Note: These options do not apply when Exim is operating as a client - they ++apply only in the case of a server. If you need to use a certificate in an Exim ++client, you must set the options of the same names in an smtp transport. ++ ++With just these options, an Exim server will be able to use TLS. It does not ++require the client to have a certificate (but see below for how to insist on ++this). There is one other option that may be needed in other situations. If ++ ++tls_dhparam = /some/file/name ++ ++is set, the SSL library is initialized for the use of Diffie-Hellman ciphers ++with the parameters contained in the file. Set this to "none" to disable use of ++DH entirely, by making no prime available: ++ ++tls_dhparam = none ++ ++This may also be set to a string identifying a standard prime to be used for ++DH; if it is set to "default" or, for OpenSSL, is unset, then the prime used is ++"ike23". There are a few standard primes available, see the documentation for ++tls_dhparam for the complete list. ++ ++See the command ++ ++openssl dhparam ++ ++for a way of generating file data. ++ ++The strings supplied for these three options are expanded every time a client ++host connects. It is therefore possible to use different certificates and keys ++for different hosts, if you so wish, by making use of the client's IP address ++in $sender_host_address to control the expansion. If a string expansion is ++forced to fail, Exim behaves as if the option is not set. ++ ++The variable $tls_in_cipher is set to the cipher suite that was negotiated for ++an incoming TLS connection. It is included in the Received: header of an ++incoming message (by default - you can, of course, change this), and it is also ++included in the log line that records a message's arrival, keyed by "X=", ++unless the tls_cipher log selector is turned off. The encrypted condition can ++be used to test for specific cipher suites in ACLs. ++ ++Once TLS has been established, the ACLs that run for subsequent SMTP commands ++can check the name of the cipher suite and vary their actions accordingly. The ++cipher suite names vary, depending on which TLS library is being used. For ++example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other ++contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS ++documentation for more details. ++ ++For outgoing SMTP deliveries, $tls_out_cipher is used and logged (again ++depending on the tls_cipher log selector). ++ ++ ++41.7 Requesting and verifying client certificates ++------------------------------------------------- ++ ++If you want an Exim server to request a certificate when negotiating a TLS ++session with a client, you must set either tls_verify_hosts or ++tls_try_verify_hosts. You can, of course, set either of them to * to apply to ++all TLS connections. For any host that matches one of these options, Exim ++requests a certificate as part of the setup of the TLS session. The contents of ++the certificate are verified by comparing it with a list of expected ++certificates. These must be available in a file or, for OpenSSL only (not ++GnuTLS), a directory, identified by tls_verify_certificates. ++ ++A file can contain multiple certificates, concatenated end to end. If a ++directory is used (OpenSSL only), each certificate must be in a separate file, ++with a name (or a symbolic link) of the form <hash>.0, where <hash> is a hash ++value constructed from the certificate. You can compute the relevant hash by ++running the command ++ ++openssl x509 -hash -noout -in /cert/file ++ ++where /cert/file contains a single certificate. ++ ++The difference between tls_verify_hosts and tls_try_verify_hosts is what ++happens if the client does not supply a certificate, or if the certificate does ++not match any of the certificates in the collection named by ++tls_verify_certificates. If the client matches tls_verify_hosts, the attempt to ++set up a TLS session is aborted, and the incoming connection is dropped. If the ++client matches tls_try_verify_hosts, the (encrypted) SMTP session continues. ++ACLs that run for subsequent SMTP commands can detect the fact that no ++certificate was verified, and vary their actions accordingly. For example, you ++can insist on a certificate before accepting a message for relaying, but not ++when the message is destined for local delivery. ++ ++When a client supplies a certificate (whether it verifies or not), the value of ++the Distinguished Name of the certificate is made available in the variable ++$tls_in_peerdn during subsequent processing of the message. ++ ++Because it is often a long text string, it is not included in the log line or ++Received: header by default. You can arrange for it to be logged, keyed by "DN= ++", by setting the tls_peerdn log selector, and you can use received_header_text ++to change the Received: header. When no certificate is supplied, $tls_in_peerdn ++is empty. ++ ++ ++41.8 Revoked certificates ++------------------------- ++ ++Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when ++certificates are revoked. If you have such a list, you can pass it to an Exim ++server using the global option called tls_crl and to an Exim client using an ++identically named option for the smtp transport. In each case, the value of the ++option is expanded and must then be the name of a file that contains a CRL in ++PEM format. ++ ++ ++41.9 Configuring an Exim client to use TLS ++------------------------------------------ ++ ++The tls_cipher and tls_peerdn log selectors apply to outgoing SMTP deliveries ++as well as to incoming, the latter one causing logging of the server ++certificate's DN. The remaining client configuration for TLS is all within the ++smtp transport. ++ ++It is not necessary to set any options to have TLS work in the smtp transport. ++If Exim is built with TLS support, and TLS is advertised by a server, the smtp ++transport always tries to start a TLS session. However, this can be prevented ++by setting hosts_avoid_tls (an option of the transport) to a list of server ++hosts for which TLS should not be used. ++ ++If you do not want Exim to attempt to send messages unencrypted when an attempt ++to set up an encrypted connection fails in any way, you can set ++hosts_require_tls to a list of hosts for which encryption is mandatory. For ++those hosts, delivery is always deferred if an encrypted connection cannot be ++set up. If there are any other hosts for the address, they are tried in the ++usual way. ++ ++When the server host is not in hosts_require_tls, Exim may try to deliver the ++message unencrypted. It always does this if the response to STARTTLS is a 5xx ++code. For a temporary error code, or for a failure to negotiate a TLS session ++after a success response code, what happens is controlled by the ++tls_tempfail_tryclear option of the smtp transport. If it is false, delivery to ++this host is deferred, and other hosts (if available) are tried. If it is true, ++Exim attempts to deliver unencrypted after a 4xx response to STARTTLS, and if ++STARTTLS is accepted, but the subsequent TLS negotiation fails, Exim closes the ++current connection (because it is in an unknown state), opens a new one to the ++same host, and then tries the delivery unencrypted. ++ ++The tls_certificate and tls_privatekey options of the smtp transport provide ++the client with a certificate, which is passed to the server if it requests it. ++If the server is Exim, it will request a certificate only if tls_verify_hosts ++or tls_try_verify_hosts matches the client. ++ ++If the tls_verify_certificates option is set on the smtp transport, it must ++name a file or, for OpenSSL only (not GnuTLS), a directory, that contains a ++collection of expected server certificates. The client verifies the server's ++certificate against this collection, taking into account any revoked ++certificates that are in the list defined by tls_crl. ++ ++If tls_require_ciphers is set on the smtp transport, it must contain a list of ++permitted cipher suites. If either of these checks fails, delivery to the ++current host is abandoned, and the smtp transport tries to deliver to ++alternative hosts, if any. ++ ++Note: These options must be set in the smtp transport for Exim to use TLS when ++it is operating as a client. Exim does not assume that a server certificate ++(set by the global options of the same name) should also be used when operating ++as a client. ++ ++All the TLS options in the smtp transport are expanded before use, with $host ++and $host_address containing the name and address of the server to which the ++client is connected. Forced failure of an expansion causes Exim to behave as if ++the relevant option were unset. ++ ++Before an SMTP connection is established, the $tls_out_bits, $tls_out_cipher, ++$tls_out_peerdn and $tls_out_sni variables are emptied. (Until the first ++connection, they contain the values that were set when the message was ++received.) If STARTTLS is subsequently successfully obeyed, these variables are ++set to the relevant values for the outgoing connection. ++ ++ ++41.10 Use of TLS Server Name Indication ++--------------------------------------- ++ ++With TLS1.0 or above, there is an extension mechanism by which extra ++information can be included at various points in the protocol. One of these ++extensions, documented in RFC 6066 (and before that RFC 4366) is "Server Name ++Indication", commonly "SNI". This extension is sent by the client in the ++initial handshake, so that the server can examine the servername within and ++possibly choose to use different certificates and keys (and more) for this ++session. ++ ++This is analagous to HTTP's "Host:" header, and is the main mechanism by which ++HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP address. ++ ++With SMTP to MX, there are the same problems here as in choosing the identity ++against which to validate a certificate: you can't rely on insecure DNS to ++provide the identity which you then cryptographically verify. So this will be ++of limited use in that environment. ++ ++With SMTP to Submission, there is a well-defined hostname which clients are ++connecting to and can validate certificates against. Thus clients can choose to ++include this information in the TLS negotiation. If this becomes wide-spread, ++then hosters can choose to present different certificates to different clients. ++Or even negotiate different cipher suites. ++ ++The tls_sni option on an SMTP transport is an expanded string; the result, if ++not empty, will be sent on a TLS session as part of the handshake. There's ++nothing more to it. Choosing a sensible value not derived insecurely is the ++only point of caution. The $tls_out_sni variable will be set to this string for ++the lifetime of the client connection (including during authentication). ++ ++Except during SMTP client sessions, if $tls_in_sni is set then it is a string ++received from a client. It can be logged with the log_selector item "+tls_sni". ++ ++If the string "tls_in_sni" appears in the main section's tls_certificate option ++(prior to expansion) then the following options will be re-expanded during TLS ++session handshake, to permit alternative values to be chosen: ++ ++ * tls_certificate ++ ++ * tls_crl ++ ++ * tls_privatekey ++ ++ * tls_verify_certificates ++ ++Great care should be taken to deal with matters of case, various injection ++attacks in the string ("../" or SQL), and ensuring that a valid filename can ++always be referenced; it is important to remember that $tls_sni is arbitrary ++unverified data provided prior to authentication. ++ ++The Exim developers are proceeding cautiously and so far no other TLS options ++are re-expanded. ++ ++When Exim is built againt OpenSSL, OpenSSL must have been built with support ++for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with ++enable-tlsext in EXTRACONFIGURE. If you invoke openssl s_client -h and see ++"-servername" in the output, then OpenSSL has support. ++ ++When Exim is built against GnuTLS, SNI support is available as of GnuTLS ++0.5.10. (Its presence predates the current API which Exim uses, so if Exim ++built, then you have SNI support). ++ ++ ++41.11 Multiple messages on the same encrypted TCP/IP connection ++--------------------------------------------------------------- ++ ++Exim sends multiple messages down the same TCP/IP connection by starting up an ++entirely new delivery process for each message, passing the socket from one ++process to the next. This implementation does not fit well with the use of TLS, ++because there is quite a lot of state information associated with a TLS ++connection, not just a socket identification. Passing all the state information ++to a new process is not feasible. Consequently, Exim shuts down an existing TLS ++session before passing the socket to a new process. The new process may then ++try to start a new TLS session, and if successful, may try to re-authenticate ++if AUTH is in use, before sending the next message. ++ ++The RFC is not clear as to whether or not an SMTP session continues in clear ++after TLS has been shut down, or whether TLS may be restarted again later, as ++just described. However, if the server is Exim, this shutdown and ++reinitialization works. It is not known which (if any) other servers operate ++successfully if the client closes a TLS session and continues with unencrypted ++SMTP, but there are certainly some that do not work. For such servers, Exim ++should not pass the socket to another process, because the failure of the ++subsequent attempt to use it would cause Exim to record a temporary host error, ++and delay other deliveries to that host. ++ ++To test for this case, Exim sends an EHLO command to the server after closing ++down the TLS session. If this fails in any way, the connection is closed ++instead of being passed to a new delivery process, but no retry information is ++recorded. ++ ++There is also a manual override; you can set hosts_nopass_tls on the smtp ++transport to match those hosts for which Exim should not pass connections to ++new processes if TLS has been used. ++ ++ ++41.12 Certificates and all that ++------------------------------- ++ ++In order to understand fully how TLS works, you need to know about ++certificates, certificate signing, and certificate authorities. This is not the ++place to give a tutorial, especially as I do not know very much about it ++myself. Some helpful introduction can be found in the FAQ for the SSL addition ++to Apache, currently at ++ ++http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24 ++ ++Other parts of the modssl documentation are also helpful, and have links to ++further files. Eric Rescorla's book, SSL and TLS, published by Addison-Wesley ++(ISBN 0-201-61598-3), contains both introductory and more in-depth ++descriptions. Some sample programs taken from the book are available from ++ ++http://www.rtfm.com/openssl-examples/ ++ ++ ++41.13 Certificate chains ++------------------------ ++ ++The file named by tls_certificate may contain more than one certificate. This ++is useful in the case where the certificate that is being sent is validated by ++an intermediate certificate which the other end does not have. Multiple ++certificates must be in the correct order in the file. First the host's ++certificate itself, then the first intermediate certificate to validate the ++issuer of the host certificate, then the next intermediate certificate to ++validate the issuer of the first intermediate certificate, and so on, until ++finally (optionally) the root certificate. The root certificate must already be ++trusted by the recipient for validation to succeed, of course, but if it's not ++preinstalled, sending the root certificate along with the rest makes it ++available for the user to install if the receiving end is a client MUA that can ++interact with a user. ++ ++ ++41.14 Self-signed certificates ++------------------------------ ++ ++You can create a self-signed certificate using the req command provided with ++OpenSSL, like this: ++ ++openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \ ++ -days 9999 -nodes ++ ++file1 and file2 can be the same file; the key and the certificate are delimited ++and so can be identified independently. The -days option specifies a period for ++which the certificate is valid. The -nodes option is important: if you do not ++set it, the key is encrypted with a passphrase that you are prompted for, and ++any use that is made of the key causes more prompting for the passphrase. This ++is not helpful if you are going to use this certificate and key in an MTA, ++where prompting is not possible. ++ ++NB: we are now past the point where 9999 days takes us past the 32-bit Unix ++epoch. If your system uses unsigned time_t (most do) and is 32-bit, then the ++above command might produce a date in the past. Think carefully about the ++lifetime of the systems you're deploying, and either reduce the duration of the ++certificate or reconsider your platform deployment. (At time of writing, ++reducing the duration is the most likely choice, but the inexorable progression ++of time takes us steadily towards an era where this will not be a sensible ++resolution). ++ ++A self-signed certificate made in this way is sufficient for testing, and may ++be adequate for all your requirements if you are mainly interested in ++encrypting transfers, and not in secure identification. ++ ++However, many clients require that the certificate presented by the server be a ++user (also called "leaf" or "site") certificate, and not a self-signed ++certificate. In this situation, the self-signed certificate described above ++must be installed on the client host as a trusted root certification authority ++(CA), and the certificate used by Exim must be a user certificate signed with ++that self-signed certificate. ++ ++For information on creating self-signed CA certificates and using them to sign ++user certificates, see the General implementation overview chapter of the ++Open-source PKI book, available online at http://ospkibook.sourceforge.net/. ++ ++ ++ ++=============================================================================== ++42. ACCESS CONTROL LISTS ++ ++Access Control Lists (ACLs) are defined in a separate section of the run time ++configuration file, headed by "begin acl". Each ACL definition starts with a ++name, terminated by a colon. Here is a complete ACL section that contains just ++one very small ACL: ++ ++begin acl ++small_acl: ++ accept hosts = one.host.only ++ ++You can have as many lists as you like in the ACL section, and the order in ++which they appear does not matter. The lists are self-terminating. ++ ++The majority of ACLs are used to control Exim's behaviour when it receives ++certain SMTP commands. This applies both to incoming TCP/IP connections, and ++when a local process submits a message using SMTP by specifying the -bs option. ++The most common use is for controlling which recipients are accepted in ++incoming messages. In addition, you can define an ACL that is used to check ++local non-SMTP messages. The default configuration file contains an example of ++a realistic ACL for checking RCPT commands. This is discussed in chapter 7. ++ ++ ++42.1 Testing ACLs ++----------------- ++ ++The -bh command line option provides a way of testing your ACL configuration ++locally by running a fake SMTP session with which you interact. The host ++relay-test.mail-abuse.org provides a service for checking your relaying ++configuration (see section 42.52 for more details). ++ ++ ++42.2 Specifying when ACLs are used ++---------------------------------- ++ ++In order to cause an ACL to be used, you have to name it in one of the relevant ++options in the main part of the configuration. These options are: ++ ++ acl_not_smtp ACL for non-SMTP messages ++ acl_not_smtp_mime ACL for non-SMTP MIME parts ++ acl_not_smtp_start ACL at start of non-SMTP message ++ acl_smtp_auth ACL for AUTH ++ acl_smtp_connect ACL for start of SMTP connection ++ acl_smtp_data ACL after DATA is complete ++ acl_smtp_etrn ACL for ETRN ++ acl_smtp_expn ACL for EXPN ++ acl_smtp_helo ACL for HELO or EHLO ++ acl_smtp_mail ACL for MAIL ++ acl_smtp_mailauth ACL for the AUTH parameter of MAIL ++ acl_smtp_mime ACL for content-scanning MIME parts ++ acl_smtp_notquit ACL for non-QUIT terminations ++ acl_smtp_predata ACL at start of DATA command ++ acl_smtp_quit ACL for QUIT ++ acl_smtp_rcpt ACL for RCPT ++ acl_smtp_starttls ACL for STARTTLS ++ acl_smtp_vrfy ACL for VRFY ++ ++For example, if you set ++ ++acl_smtp_rcpt = small_acl ++ ++the little ACL defined above is used whenever Exim receives a RCPT command in ++an SMTP dialogue. The majority of policy tests on incoming messages can be done ++when RCPT commands arrive. A rejection of RCPT should cause the sending MTA to ++give up on the recipient address contained in the RCPT command, whereas ++rejection at other times may cause the client MTA to keep on trying to deliver ++the message. It is therefore recommended that you do as much testing as ++possible at RCPT time. ++ ++ ++42.3 The non-SMTP ACLs ++---------------------- ++ ++The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they ++apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not ++really SMTP.) Many of the ACL conditions (for example, host tests, and tests on ++the state of the SMTP connection such as encryption and authentication) are not ++relevant and are forbidden in these ACLs. However, the sender and recipients ++are known, so the senders and sender_domains conditions and the $sender_address ++and $recipients variables can be used. Variables such as $authenticated_sender ++are also available. You can specify added header lines in any of these ACLs. ++ ++The acl_not_smtp_start ACL is run right at the start of receiving a non-SMTP ++message, before any of the message has been read. (This is the analogue of the ++acl_smtp_predata ACL for SMTP input.) In the case of batched SMTP input, it ++runs after the DATA command has been reached. The result of this ACL is ++ignored; it cannot be used to reject a message. If you really need to, you ++could set a value in an ACL variable here and reject based on that in the ++acl_not_smtp ACL. However, this ACL can be used to set controls, and in ++particular, it can be used to set ++ ++control = suppress_local_fixups ++ ++This cannot be used in the other non-SMTP ACLs because by the time they are ++run, it is too late. ++ ++The acl_not_smtp_mime ACL is available only when Exim is compiled with the ++content-scanning extension. For details, see chapter 43. ++ ++The acl_not_smtp ACL is run just before the local_scan() function. Any kind of ++rejection is treated as permanent, because there is no way of sending a ++temporary error for these kinds of message. ++ ++ ++42.4 The SMTP connect ACL ++------------------------- ++ ++The ACL test specified by acl_smtp_connect happens at the start of an SMTP ++session, after the test specified by host_reject_connection (which is now an ++anomaly) and any TCP Wrappers testing (if configured). If the connection is ++accepted by an accept verb that has a message modifier, the contents of the ++message override the banner message that is otherwise specified by the ++smtp_banner option. ++ ++ ++42.5 The EHLO/HELO ACL ++---------------------- ++ ++The ACL test specified by acl_smtp_helo happens when the client issues an EHLO ++or HELO command, after the tests specified by helo_accept_junk_hosts, ++helo_allow_chars, helo_verify_hosts, and helo_try_verify_hosts. Note that a ++client may issue more than one EHLO or HELO command in an SMTP session, and ++indeed is required to issue a new EHLO or HELO after successfully setting up ++encryption following a STARTTLS command. ++ ++If the command is accepted by an accept verb that has a message modifier, the ++message may not contain more than one line (it will be truncated at the first ++newline and a panic logged if it does). Such a message cannot affect the EHLO ++options that are listed on the second and subsequent lines of an EHLO response. ++ ++ ++42.6 The DATA ACLs ++------------------ ++ ++Two ACLs are associated with the DATA command, because it is two-stage command, ++with two responses being sent to the client. When the DATA command is received, ++the ACL defined by acl_smtp_predata is obeyed. This gives you control after all ++the RCPT commands, but before the message itself is received. It offers the ++opportunity to give a negative response to the DATA command before the data is ++transmitted. Header lines added by MAIL or RCPT ACLs are not visible at this ++time, but any that are defined here are visible when the acl_smtp_data ACL is ++run. ++ ++You cannot test the contents of the message, for example, to verify addresses ++in the headers, at RCPT time or when the DATA command is received. Such tests ++have to appear in the ACL that is run after the message itself has been ++received, before the final response to the DATA command is sent. This is the ++ACL specified by acl_smtp_data, which is the second ACL that is associated with ++the DATA command. ++ ++For both of these ACLs, it is not possible to reject individual recipients. An ++error response rejects the entire message. Unfortunately, it is known that some ++MTAs do not treat hard (5xx) responses to the DATA command (either before or ++after the data) correctly - they keep the message on their queues and try again ++later, but that is their problem, though it does waste some of your resources. ++ ++The acl_smtp_data ACL is run after both the acl_smtp_dkim and the acl_smtp_mime ++ACLs. ++ ++ ++42.7 The SMTP DKIM ACL ++---------------------- ++ ++The acl_smtp_dkim ACL is available only when Exim is compiled with DKIM support ++enabled (which is the default). ++ ++The ACL test specified by acl_smtp_dkim happens after a message has been ++received, and is executed for each DKIM signature found in a message. If not ++otherwise specified, the default action is to accept. ++ ++This ACL is evaluated before acl_smtp_mime and acl_smtp_data. ++ ++For details on the operation of DKIM, see chapter 56. ++ ++ ++42.8 The SMTP MIME ACL ++---------------------- ++ ++The acl_smtp_mime option is available only when Exim is compiled with the ++content-scanning extension. For details, see chapter 43. ++ ++This ACL is evaluated after acl_smtp_dkim but before acl_smtp_data. ++ ++ ++42.9 The QUIT ACL ++----------------- ++ ++The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL ++does not affect the response code to QUIT, which is always 221. Thus, the ACL ++does not in fact control any access. For this reason, the only verbs that are ++permitted are accept and warn. ++ ++This ACL can be used for tasks such as custom logging at the end of an SMTP ++session. For example, you can use ACL variables in other ACLs to count ++messages, recipients, etc., and log the totals at QUIT time using one or more ++logwrite modifiers on a warn verb. ++ ++Warning: Only the $acl_cx variables can be used for this, because the $acl_mx ++variables are reset at the end of each incoming message. ++ ++You do not need to have a final accept, but if you do, you can use a message ++modifier to specify custom text that is sent as part of the 221 response to ++QUIT. ++ ++This ACL is run only for a "normal" QUIT. For certain kinds of disastrous ++failure (for example, failure to open a log file, or when Exim is bombing out ++because it has detected an unrecoverable error), all SMTP commands from the ++client are given temporary error responses until QUIT is received or the ++connection is closed. In these special cases, the QUIT ACL does not run. ++ ++ ++42.10 The not-QUIT ACL ++---------------------- ++ ++The not-QUIT ACL, specified by acl_smtp_notquit, is run in most cases when an ++SMTP session ends without sending QUIT. However, when Exim itself is in bad ++trouble, such as being unable to write to its log files, this ACL is not run, ++because it might try to do things (such as write to log files) that make the ++situation even worse. ++ ++Like the QUIT ACL, this ACL is provided to make it possible to do customized ++logging or to gather statistics, and its outcome is ignored. The delay modifier ++is forbidden in this ACL, and the only permitted verbs are accept and warn. ++ ++When the not-QUIT ACL is running, the variable $smtp_notquit_reason is set to a ++string that indicates the reason for the termination of the SMTP connection. ++The possible values are: ++ ++ "acl-drop" Another ACL issued a drop command ++ "bad-commands" Too many unknown or non-mail commands ++ "command-timeout" Timeout while reading SMTP commands ++ "connection-lost" The SMTP connection has been lost ++ "data-timeout" Timeout while reading message data ++ "local-scan-error" The local_scan() function crashed ++ "local-scan-timeout" The local_scan() function timed out ++ "signal-exit" SIGTERM or SIGINT ++ "synchronization-error" SMTP synchronization error ++ "tls-failed" TLS failed to start ++ ++In most cases when an SMTP connection is closed without having received QUIT, ++Exim sends an SMTP response message before actually closing the connection. ++With the exception of the "acl-drop" case, the default message can be ++overridden by the message modifier in the not-QUIT ACL. In the case of a drop ++verb in another ACL, it is the message from the other ACL that is used. ++ ++ ++42.11 Finding an ACL to use ++--------------------------- ++ ++The value of an acl_smtp_xxx option is expanded before use, so you can use ++different ACLs in different circumstances. For example, ++ ++acl_smtp_rcpt = ${if ={25}{$interface_port} \ ++ {acl_check_rcpt} {acl_check_rcpt_submit} } ++ ++In the default configuration file there are some example settings for providing ++an RFC 4409 message submission service on port 587 and a non-standard "smtps" ++service on port 465. You can use a string expansion like this to choose an ACL ++for MUAs on these ports which is more appropriate for this purpose than the ++default ACL on port 25. ++ ++The expanded string does not have to be the name of an ACL in the configuration ++file; there are other possibilities. Having expanded the string, Exim searches ++for an ACL as follows: ++ ++ * If the string begins with a slash, Exim uses it as a file name, and reads ++ its contents as an ACL. The lines are processed in the same way as lines in ++ the Exim configuration file. In particular, continuation lines are ++ supported, blank lines are ignored, as are lines whose first non-whitespace ++ character is "#". If the file does not exist or cannot be read, an error ++ occurs (typically causing a temporary failure of whatever caused the ACL to ++ be run). For example: ++ ++ acl_smtp_data = /etc/acls/\ ++ ${lookup{$sender_host_address}lsearch\ ++ {/etc/acllist}{$value}{default}} ++ ++ This looks up an ACL file to use on the basis of the host's IP address, ++ falling back to a default if the lookup fails. If an ACL is successfully ++ read from a file, it is retained in memory for the duration of the Exim ++ process, so that it can be re-used without having to re-read the file. ++ ++ * If the string does not start with a slash, and does not contain any spaces, ++ Exim searches the ACL section of the configuration for an ACL whose name ++ matches the string. ++ ++ * If no named ACL is found, or if the string contains spaces, Exim parses the ++ string as an inline ACL. This can save typing in cases where you just want ++ to have something like ++ ++ acl_smtp_vrfy = accept ++ ++ in order to allow free use of the VRFY command. Such a string may contain ++ newlines; it is processed in the same way as an ACL that is read from a ++ file. ++ ++ ++42.12 ACL return codes ++---------------------- ++ ++Except for the QUIT ACL, which does not affect the SMTP return code (see ++section 42.9 above), the result of running an ACL is either "accept" or "deny", ++or, if some test cannot be completed (for example, if a database is down), ++"defer". These results cause 2xx, 5xx, and 4xx return codes, respectively, to ++be used in the SMTP dialogue. A fourth return, "error", occurs when there is an ++error such as invalid syntax in the ACL. This also causes a 4xx return code. ++ ++For the non-SMTP ACL, "defer" and "error" are treated in the same way as ++"deny", because there is no mechanism for passing temporary errors to the ++submitters of non-SMTP messages. ++ ++ACLs that are relevant to message reception may also return "discard". This has ++the effect of "accept", but causes either the entire message or an individual ++recipient address to be discarded. In other words, it is a blackholing ++facility. Use it with care. ++ ++If the ACL for MAIL returns "discard", all recipients are discarded, and no ACL ++is run for subsequent RCPT commands. The effect of "discard" in a RCPT ACL is ++to discard just the one recipient address. If there are no recipients left when ++the message's data is received, the DATA ACL is not run. A "discard" return ++from the DATA or the non-SMTP ACL discards all the remaining recipients. The ++"discard" return is not permitted for the acl_smtp_predata ACL. ++ ++The local_scan() function is always run, even if there are no remaining ++recipients; it may create new recipients. ++ ++ ++42.13 Unset ACL options ++----------------------- ++ ++The default actions when any of the acl_xxx options are unset are not all the ++same. Note: These defaults apply only when the relevant ACL is not defined at ++all. For any defined ACL, the default action when control reaches the end of ++the ACL statements is "deny". ++ ++For acl_smtp_quit and acl_not_smtp_start there is no default because these two ++are ACLs that are used only for their side effects. They cannot be used to ++accept or reject anything. ++ ++For acl_not_smtp, acl_smtp_auth, acl_smtp_connect, acl_smtp_data, acl_smtp_helo ++, acl_smtp_mail, acl_smtp_mailauth, acl_smtp_mime, acl_smtp_predata, and ++acl_smtp_starttls, the action when the ACL is not defined is "accept". ++ ++For the others (acl_smtp_etrn, acl_smtp_expn, acl_smtp_rcpt, and acl_smtp_vrfy ++), the action when the ACL is not defined is "deny". This means that ++acl_smtp_rcpt must be defined in order to receive any messages over an SMTP ++connection. For an example, see the ACL in the default configuration file. ++ ++ ++42.14 Data for message ACLs ++--------------------------- ++ ++When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables ++that contain information about the host and the message's sender (for example, ++$sender_host_address and $sender_address) are set, and can be used in ACL ++statements. In the case of RCPT (but not MAIL or DATA), $domain and $local_part ++are set from the argument address. The entire SMTP command is available in ++$smtp_command. ++ ++When an ACL for the AUTH parameter of MAIL is running, the variables that ++contain information about the host are set, but $sender_address is not yet set. ++Section 33.2 contains a discussion of this parameter and how it is used. ++ ++The $message_size variable is set to the value of the SIZE parameter on the ++MAIL command at MAIL, RCPT and pre-data time, or to -1 if that parameter is not ++given. The value is updated to the true message size by the time the final DATA ++ACL is run (after the message data has been received). ++ ++The $rcpt_count variable increases by one for each RCPT command received. The ++$recipients_count variable increases by one each time a RCPT command is ++accepted, so while an ACL for RCPT is being processed, it contains the number ++of previously accepted recipients. At DATA time (for both the DATA ACLs), ++$rcpt_count contains the total number of RCPT commands, and $recipients_count ++contains the total number of accepted recipients. ++ ++ ++42.15 Data for non-message ACLs ++------------------------------- ++ ++When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY, ++the remainder of the SMTP command line is placed in $smtp_command_argument, and ++the entire SMTP command is available in $smtp_command. These variables can be ++tested using a condition condition. For example, here is an ACL for use with ++AUTH, which insists that either the session is encrypted, or the CRAM-MD5 ++authentication method is used. In other words, it does not permit ++authentication methods that use cleartext passwords on unencrypted connections. ++ ++acl_check_auth: ++ accept encrypted = * ++ accept condition = ${if eq{${uc:$smtp_command_argument}}\ ++ {CRAM-MD5}} ++ deny message = TLS encryption or CRAM-MD5 required ++ ++(Another way of applying this restriction is to arrange for the authenticators ++that use cleartext passwords not to be advertised when the connection is not ++encrypted. You can use the generic server_advertise_condition authenticator ++option to do this.) ++ ++ ++42.16 Format of an ACL ++---------------------- ++ ++An individual ACL consists of a number of statements. Each statement starts ++with a verb, optionally followed by a number of conditions and "modifiers". ++Modifiers can change the way the verb operates, define error and log messages, ++set variables, insert delays, and vary the processing of accepted messages. ++ ++If all the conditions are met, the verb is obeyed. The same condition may be ++used (with different arguments) more than once in the same statement. This ++provides a means of specifying an "and" conjunction between conditions. For ++example: ++ ++deny dnslists = list1.example ++dnslists = list2.example ++ ++If there are no conditions, the verb is always obeyed. Exim stops evaluating ++the conditions and modifiers when it reaches a condition that fails. What ++happens then depends on the verb (and in one case, on a special modifier). Not ++all the conditions make sense at every testing point. For example, you cannot ++test a sender address in the ACL that is run for a VRFY command. ++ ++ ++42.17 ACL verbs ++--------------- ++ ++The ACL verbs are as follows: ++ ++ * accept: If all the conditions are met, the ACL returns "accept". If any of ++ the conditions are not met, what happens depends on whether endpass appears ++ among the conditions (for syntax see below). If the failing condition is ++ before endpass, control is passed to the next ACL statement; if it is after ++ endpass, the ACL returns "deny". Consider this statement, used to check a ++ RCPT command: ++ ++ accept domains = +local_domains ++ endpass ++ verify = recipient ++ ++ If the recipient domain does not match the domains condition, control ++ passes to the next statement. If it does match, the recipient is verified, ++ and the command is accepted if verification succeeds. However, if ++ verification fails, the ACL yields "deny", because the failing condition is ++ after endpass. ++ ++ The endpass feature has turned out to be confusing to many people, so its ++ use is not recommended nowadays. It is always possible to rewrite an ACL so ++ that endpass is not needed, and it is no longer used in the default ++ configuration. ++ ++ If a message modifier appears on an accept statement, its action depends on ++ whether or not endpass is present. In the absence of endpass (when an ++ accept verb either accepts or passes control to the next statement), ++ message can be used to vary the message that is sent when an SMTP command ++ is accepted. For example, in a RCPT ACL you could have: ++ ++ accept <some conditions> ++ message = OK, I will allow you through today ++ ++ You can specify an SMTP response code, optionally followed by an "extended ++ response code" at the start of the message, but the first digit must be the ++ same as would be sent by default, which is 2 for an accept verb. ++ ++ If endpass is present in an accept statement, message specifies an error ++ message that is used when access is denied. This behaviour is retained for ++ backward compatibility, but current "best practice" is to avoid the use of ++ endpass. ++ ++ * defer: If all the conditions are true, the ACL returns "defer" which, in an ++ SMTP session, causes a 4xx response to be given. For a non-SMTP ACL, defer ++ is the same as deny, because there is no way of sending a temporary error. ++ For a RCPT command, defer is much the same as using a redirect router and ++ ":defer:" while verifying, but the defer verb can be used in any ACL, and ++ even for a recipient it might be a simpler approach. ++ ++ * deny: If all the conditions are met, the ACL returns "deny". If any of the ++ conditions are not met, control is passed to the next ACL statement. For ++ example, ++ ++ deny dnslists = blackholes.mail-abuse.org ++ ++ rejects commands from hosts that are on a DNS black list. ++ ++ * discard: This verb behaves like accept, except that it returns "discard" ++ from the ACL instead of "accept". It is permitted only on ACLs that are ++ concerned with receiving messages. When all the conditions are true, the ++ sending entity receives a "success" response. However, discard causes ++ recipients to be discarded. If it is used in an ACL for RCPT, just the one ++ recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all ++ the message's recipients are discarded. Recipients that are discarded ++ before DATA do not appear in the log line when the received_recipients log ++ selector is set. ++ ++ If the log_message modifier is set when discard operates, its contents are ++ added to the line that is automatically written to the log. The message ++ modifier operates exactly as it does for accept. ++ ++ * drop: This verb behaves like deny, except that an SMTP connection is ++ forcibly closed after the 5xx error message has been sent. For example: ++ ++ drop message = I don't take more than 20 RCPTs ++ condition = ${if > {$rcpt_count}{20}} ++ ++ There is no difference between deny and drop for the connect-time ACL. The ++ connection is always dropped after sending a 550 response. ++ ++ * require: If all the conditions are met, control is passed to the next ACL ++ statement. If any of the conditions are not met, the ACL returns "deny". ++ For example, when checking a RCPT command, ++ ++ require message = Sender did not verify ++ verify = sender ++ ++ passes control to subsequent statements only if the message's sender can be ++ verified. Otherwise, it rejects the command. Note the positioning of the ++ message modifier, before the verify condition. The reason for this is ++ discussed in section 42.19. ++ ++ * warn: If all the conditions are true, a line specified by the log_message ++ modifier is written to Exim's main log. Control always passes to the next ++ ACL statement. If any condition is false, the log line is not written. If ++ an identical log line is requested several times in the same message, only ++ one copy is actually written to the log. If you want to force duplicates to ++ be written, use the logwrite modifier instead. ++ ++ If log_message is not present, a warn verb just checks its conditions and ++ obeys any "immediate" modifiers (such as control, set, logwrite, add_header ++ , and remove_header) that appear before the first failing condition. There ++ is more about adding header lines in section 42.23. ++ ++ If any condition on a warn statement cannot be completed (that is, there is ++ some sort of defer), the log line specified by log_message is not written. ++ This does not include the case of a forced failure from a lookup, which is ++ considered to be a successful completion. After a defer, no further ++ conditions or modifiers in the warn statement are processed. The incident ++ is logged, and the ACL continues to be processed, from the next statement ++ onwards. ++ ++ When one of the warn conditions is an address verification that fails, the ++ text of the verification failure message is in $acl_verify_message. If you ++ want this logged, you must set it up explicitly. For example: ++ ++ warn !verify = sender ++ log_message = sender verify failed: $acl_verify_message ++ ++At the end of each ACL there is an implicit unconditional deny. ++ ++As you can see from the examples above, the conditions and modifiers are ++written one to a line, with the first one on the same line as the verb, and ++subsequent ones on following lines. If you have a very long condition, you can ++continue it onto several physical lines by the usual backslash continuation ++mechanism. It is conventional to align the conditions vertically. ++ ++ ++42.18 ACL variables ++------------------- ++ ++There are some special variables that can be set during ACL processing. They ++can be used to pass information between different ACLs, different invocations ++of the same ACL in the same SMTP connection, and between ACLs and the routers, ++transports, and filters that are used to deliver a message. The names of these ++variables must begin with $acl_c or $acl_m, followed either by a digit or an ++underscore, but the remainder of the name can be any sequence of alphanumeric ++characters and underscores that you choose. There is no limit on the number of ++ACL variables. The two sets act as follows: ++ ++ * The values of those variables whose names begin with $acl_c persist ++ throughout an SMTP connection. They are never reset. Thus, a value that is ++ set while receiving one message is still available when receiving the next ++ message on the same SMTP connection. ++ ++ * The values of those variables whose names begin with $acl_m persist only ++ while a message is being received. They are reset afterwards. They are also ++ reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session. ++ ++When a message is accepted, the current values of all the ACL variables are ++preserved with the message and are subsequently made available at delivery ++time. The ACL variables are set by a modifier called set. For example: ++ ++accept hosts = whatever ++ set acl_m4 = some value ++accept authenticated = * ++ set acl_c_auth = yes ++ ++Note: A leading dollar sign is not used when naming a variable that is to be ++set. If you want to set a variable without taking any action, you can use a ++warn verb without any other modifiers or conditions. ++ ++What happens if a syntactically valid but undefined ACL variable is referenced ++depends on the setting of the strict_acl_vars option. If it is false (the ++default), an empty string is substituted; if it is true, an error is generated. ++ ++Versions of Exim before 4.64 have a limited set of numbered variables, but ++their names are compatible, so there is no problem with upgrading. ++ ++ ++42.19 Condition and modifier processing ++--------------------------------------- ++ ++An exclamation mark preceding a condition negates its result. For example: ++ ++deny domains = *.dom.example ++ !verify = recipient ++ ++causes the ACL to return "deny" if the recipient domain ends in dom.example and ++the recipient address cannot be verified. Sometimes negation can be used on the ++right-hand side of a condition. For example, these two statements are ++equivalent: ++ ++deny hosts = !192.168.3.4 ++deny !hosts = 192.168.3.4 ++ ++However, for many conditions (verify being a good example), only left-hand side ++negation of the whole condition is possible. ++ ++The arguments of conditions and modifiers are expanded. A forced failure of an ++expansion causes a condition to be ignored, that is, it behaves as if the ++condition is true. Consider these two statements: ++ ++accept senders = ${lookup{$host_name}lsearch\ ++ {/some/file}{$value}fail} ++accept senders = ${lookup{$host_name}lsearch\ ++ {/some/file}{$value}{}} ++ ++Each attempts to look up a list of acceptable senders. If the lookup succeeds, ++the returned list is searched, but if the lookup fails the behaviour is ++different in the two cases. The fail in the first statement causes the ++condition to be ignored, leaving no further conditions. The accept verb ++therefore succeeds. The second statement, however, generates an empty list when ++the lookup fails. No sender can match an empty list, so the condition fails, ++and therefore the accept also fails. ++ ++ACL modifiers appear mixed in with conditions in ACL statements. Some of them ++specify actions that are taken as the conditions for a statement are checked; ++others specify text for messages that are used when access is denied or a ++warning is generated. The control modifier affects the way an incoming message ++is handled. ++ ++The positioning of the modifiers in an ACL statement is important, because the ++processing of a verb ceases as soon as its outcome is known. Only those ++modifiers that have already been encountered will take effect. For example, ++consider this use of the message modifier: ++ ++require message = Can't verify sender ++ verify = sender ++ message = Can't verify recipient ++ verify = recipient ++ message = This message cannot be used ++ ++If sender verification fails, Exim knows that the result of the statement is ++"deny", so it goes no further. The first message modifier has been seen, so its ++text is used as the error message. If sender verification succeeds, but ++recipient verification fails, the second message is used. If recipient ++verification succeeds, the third message becomes "current", but is never used ++because there are no more conditions to cause failure. ++ ++For the deny verb, on the other hand, it is always the last message modifier ++that is used, because all the conditions must be true for rejection to happen. ++Specifying more than one message modifier does not make sense, and the message ++can even be specified after all the conditions. For example: ++ ++deny hosts = ... ++ !senders = *@my.domain.example ++ message = Invalid sender from client host ++ ++The "deny" result does not happen until the end of the statement is reached, by ++which time Exim has set up the message. ++ ++ ++42.20 ACL modifiers ++------------------- ++ ++The ACL modifiers are as follows: ++ ++add_header = <text> ++ ++ This modifier specifies one or more header lines that are to be added to an ++ incoming message, assuming, of course, that the message is ultimately ++ accepted. For details, see section 42.23. ++ ++continue = <text> ++ ++ This modifier does nothing of itself, and processing of the ACL always ++ continues with the next condition or modifier. The value of continue is in ++ the side effects of expanding its argument. Typically this could be used to ++ update a database. It is really just a syntactic tidiness, to avoid having ++ to write rather ugly lines like this: ++ ++ condition = ${if eq{0}{<some expansion>}{true}{true}} ++ ++ Instead, all you need is ++ ++ continue = <some expansion> ++ ++control = <text> ++ ++ This modifier affects the subsequent processing of the SMTP connection or ++ of an incoming message that is accepted. The effect of the first type of ++ control lasts for the duration of the connection, whereas the effect of the ++ second type lasts only until the current message has been received. The ++ message-specific controls always apply to the whole message, not to ++ individual recipients, even if the control modifier appears in a RCPT ACL. ++ ++ As there are now quite a few controls that can be applied, they are ++ described separately in section 42.21. The control modifier can be used in ++ several different ways. For example: ++ ++ + It can be at the end of an accept statement: ++ ++ accept ...some conditions ++ control = queue_only ++ ++ In this case, the control is applied when this statement yields ++ "accept", in other words, when the conditions are all true. ++ ++ + It can be in the middle of an accept statement: ++ ++ accept ...some conditions... ++ control = queue_only ++ ...some more conditions... ++ ++ If the first set of conditions are true, the control is applied, even ++ if the statement does not accept because one of the second set of ++ conditions is false. In this case, some subsequent statement must yield ++ "accept" for the control to be relevant. ++ ++ + It can be used with warn to apply the control, leaving the decision ++ about accepting or denying to a subsequent verb. For example: ++ ++ warn ...some conditions... ++ control = freeze ++ accept ... ++ ++ This example of warn does not contain message, log_message, or logwrite ++ , so it does not add anything to the message and does not write a log ++ entry. ++ ++ + If you want to apply a control unconditionally, you can use it with a ++ require verb. For example: ++ ++ require control = no_multiline_responses ++ ++delay = <time> ++ ++ This modifier may appear in any ACL except notquit. It causes Exim to wait ++ for the time interval before proceeding. However, when testing Exim using ++ the -bh option, the delay is not actually imposed (an appropriate message ++ is output instead). The time is given in the usual Exim notation, and the ++ delay happens as soon as the modifier is processed. In an SMTP session, ++ pending output is flushed before the delay is imposed. ++ ++ Like control, delay can be used with accept or deny, for example: ++ ++ deny ...some conditions... ++ delay = 30s ++ ++ The delay happens if all the conditions are true, before the statement ++ returns "deny". Compare this with: ++ ++ deny delay = 30s ++ ...some conditions... ++ ++ which waits for 30s before processing the conditions. The delay modifier ++ can also be used with warn and together with control: ++ ++ warn ...some conditions... ++ delay = 2m ++ control = freeze ++ accept ... ++ ++ If delay is encountered when the SMTP PIPELINING extension is in use, ++ responses to several commands are no longer buffered and sent in one packet ++ (as they would normally be) because all output is flushed before imposing ++ the delay. This optimization is disabled so that a number of small delays ++ do not appear to the client as one large aggregated delay that might ++ provoke an unwanted timeout. You can, however, disable output flushing for ++ delay by using a control modifier to set no_delay_flush. ++ ++endpass ++ ++ This modifier, which has no argument, is recognized only in accept and ++ discard statements. It marks the boundary between the conditions whose ++ failure causes control to pass to the next statement, and the conditions ++ whose failure causes the ACL to return "deny". This concept has proved to ++ be confusing to some people, so the use of endpass is no longer recommended ++ as "best practice". See the description of accept above for more details. ++ ++log_message = <text> ++ ++ This modifier sets up a message that is used as part of the log message if ++ the ACL denies access or a warn statement's conditions are true. For ++ example: ++ ++ require log_message = wrong cipher suite $tls_in_cipher ++ encrypted = DES-CBC3-SHA ++ ++ log_message is also used when recipients are discarded by discard. For ++ example: ++ ++ discard <some conditions> ++ log_message = Discarded $local_part@$domain because... ++ ++ When access is denied, log_message adds to any underlying error message ++ that may exist because of a condition failure. For example, while verifying ++ a recipient address, a :fail: redirection might have already set up a ++ message. ++ ++ The message may be defined before the conditions to which it applies, ++ because the string expansion does not happen until Exim decides that access ++ is to be denied. This means that any variables that are set by the ++ condition are available for inclusion in the message. For example, the ++ $dnslist_<xxx> variables are set after a DNS black list lookup succeeds. If ++ the expansion of log_message fails, or if the result is an empty string, ++ the modifier is ignored. ++ ++ If you want to use a warn statement to log the result of an address ++ verification, you can use $acl_verify_message to include the verification ++ error message. ++ ++ If log_message is used with a warn statement, "Warning:" is added to the ++ start of the logged message. If the same warning log message is requested ++ more than once while receiving a single email message, only one copy is ++ actually logged. If you want to log multiple copies, use logwrite instead ++ of log_message. In the absence of log_message and logwrite, nothing is ++ logged for a successful warn statement. ++ ++ If log_message is not present and there is no underlying error message (for ++ example, from the failure of address verification), but message is present, ++ the message text is used for logging rejections. However, if any text for ++ logging contains newlines, only the first line is logged. In the absence of ++ both log_message and message, a default built-in message is used for ++ logging rejections. ++ ++log_reject_target = <log name list> ++ ++ This modifier makes it possible to specify which logs are used for messages ++ about ACL rejections. Its argument is a colon-separated list of words that ++ can be "main", "reject", or "panic". The default is "main:reject". The list ++ may be empty, in which case a rejection is not logged at all. For example, ++ this ACL fragment writes no logging information when access is denied: ++ ++ deny <some conditions> ++ log_reject_target = ++ ++ This modifier can be used in SMTP and non-SMTP ACLs. It applies to both ++ permanent and temporary rejections. Its effect lasts for the rest of the ++ current ACL. ++ ++logwrite = <text> ++ ++ This modifier writes a message to a log file as soon as it is encountered ++ when processing an ACL. (Compare log_message, which, except in the case of ++ warn and discard, is used only if the ACL statement denies access.) The ++ logwrite modifier can be used to log special incidents in ACLs. For ++ example: ++ ++ accept <some special conditions> ++ control = freeze ++ logwrite = froze message because ... ++ ++ By default, the message is written to the main log. However, it may begin ++ with a colon, followed by a comma-separated list of log names, and then ++ another colon, to specify exactly which logs are to be written. For ++ example: ++ ++ logwrite = :main,reject: text for main and reject logs ++ logwrite = :panic: text for panic log only ++ ++message = <text> ++ ++ This modifier sets up a text string that is expanded and used as a response ++ message when an ACL statement terminates the ACL with an "accept", "deny", ++ or "defer" response. (In the case of the accept and discard verbs, there is ++ some complication if endpass is involved; see the description of accept for ++ details.) ++ ++ The expansion of the message happens at the time Exim decides that the ACL ++ is to end, not at the time it processes message. If the expansion fails, or ++ generates an empty string, the modifier is ignored. Here is an example ++ where message must be specified first, because the ACL ends with a ++ rejection if the hosts condition fails: ++ ++ require message = Host not recognized ++ hosts = 10.0.0.0/8 ++ ++ (Once a condition has failed, no further conditions or modifiers are ++ processed.) ++ ++ For ACLs that are triggered by SMTP commands, the message is returned as ++ part of the SMTP response. The use of message with accept (or discard) is ++ meaningful only for SMTP, as no message is returned when a non-SMTP message ++ is accepted. In the case of the connect ACL, accepting with a message ++ modifier overrides the value of smtp_banner. For the EHLO/HELO ACL, a ++ customized accept message may not contain more than one line (otherwise it ++ will be truncated at the first newline and a panic logged), and it cannot ++ affect the EHLO options. ++ ++ When SMTP is involved, the message may begin with an overriding response ++ code, consisting of three digits optionally followed by an "extended ++ response code" of the form n.n.n, each code being followed by a space. For ++ example: ++ ++ deny message = 599 1.2.3 Host not welcome ++ hosts = 192.168.34.0/24 ++ ++ The first digit of the supplied response code must be the same as would be ++ sent by default. A panic occurs if it is not. Exim uses a 550 code when it ++ denies access, but for the predata ACL, note that the default success code ++ is 354, not 2xx. ++ ++ Notwithstanding the previous paragraph, for the QUIT ACL, unlike the ++ others, the message modifier cannot override the 221 response code. ++ ++ The text in a message modifier is literal; any quotes are taken as ++ literals, but because the string is expanded, backslash escapes are ++ processed anyway. If the message contains newlines, this gives rise to a ++ multi-line SMTP response. ++ ++ If message is used on a statement that verifies an address, the message ++ specified overrides any message that is generated by the verification ++ process. However, the original message is available in the variable ++ $acl_verify_message, so you can incorporate it into your message if you ++ wish. In particular, if you want the text from :fail: items in redirect ++ routers to be passed back as part of the SMTP response, you should either ++ not use a message modifier, or make use of $acl_verify_message. ++ ++ For compatibility with previous releases of Exim, a message modifier that ++ is used with a warn verb behaves in a similar way to the add_header ++ modifier, but this usage is now deprecated. However, message acts only when ++ all the conditions are true, wherever it appears in an ACL command, whereas ++ add_header acts as soon as it is encountered. If message is used with warn ++ in an ACL that is not concerned with receiving a message, it has no effect. ++ ++remove_header = <text> ++ ++ This modifier specifies one or more header names in a colon-separated list ++ that are to be removed from an incoming message, assuming, of course, that ++ the message is ultimately accepted. For details, see section 42.24. ++ ++set <acl_name> = <value> ++ ++ This modifier puts a value into one of the ACL variables (see section 42.18 ++ ). ++ ++udpsend = <parameters> ++ ++ This modifier sends a UDP packet, for purposes such as statistics ++ collection or behaviour monitoring. The parameters are expanded, and the ++ result of the expansion must be a colon-separated list consisting of a ++ destination server, port number, and the packet contents. The server can be ++ specified as a host name or IPv4 or IPv6 address. The separator can be ++ changed with the usual angle bracket syntax. For example, you might want to ++ collect information on which hosts connect when: ++ ++ udpsend = <; 2001:dB8::dead:beef ; 1234 ;\ ++ $tod_zulu $sender_host_address ++ ++ ++42.21 Use of the control modifier ++--------------------------------- ++ ++The control modifier supports the following settings: ++ ++control = allow_auth_unadvertised ++ ++ This modifier allows a client host to use the SMTP AUTH command even when ++ it has not been advertised in response to EHLO. Furthermore, because there ++ are apparently some really broken clients that do this, Exim will accept ++ AUTH after HELO (rather than EHLO) when this control is set. It should be ++ used only if you really need it, and you should limit its use to those ++ broken clients that do not work without it. For example: ++ ++ warn hosts = 192.168.34.25 ++ control = allow_auth_unadvertised ++ ++ Normally, when an Exim server receives an AUTH command, it checks the name ++ of the authentication mechanism that is given in the command to ensure that ++ it matches an advertised mechanism. When this control is set, the check ++ that a mechanism has been advertised is bypassed. Any configured mechanism ++ can be used by the client. This control is permitted only in the connection ++ and HELO ACLs. ++ ++control = caseful_local_part, control = caselower_local_part ++ ++ These two controls are permitted only in the ACL specified by acl_smtp_rcpt ++ (that is, during RCPT processing). By default, the contents of $local_part ++ are lower cased before ACL processing. If "caseful_local_part" is ++ specified, any uppercase letters in the original local part are restored in ++ $local_part for the rest of the ACL, or until a control that sets ++ "caselower_local_part" is encountered. ++ ++ These controls affect only the current recipient. Moreover, they apply only ++ to local part handling that takes place directly in the ACL (for example, ++ as a key in lookups). If a test to verify the recipient is obeyed, the ++ case-related handling of the local part during the verification is ++ controlled by the router configuration (see the caseful_local_part generic ++ router option). ++ ++ This facility could be used, for example, to add a spam score to local ++ parts containing upper case letters. For example, using $acl_m4 to ++ accumulate the spam score: ++ ++ warn control = caseful_local_part ++ set acl_m4 = ${eval:\ ++ $acl_m4 + \ ++ ${if match{$local_part}{[A-Z]}{1}{0}}\ ++ } ++ control = caselower_local_part ++ ++ Notice that we put back the lower cased version afterwards, assuming that ++ is what is wanted for subsequent tests. ++ ++control = cutthrough_delivery ++ ++ This option requests delivery be attempted while the item is being ++ received. It is usable in the RCPT ACL and valid only for single-recipient ++ mails forwarded from one SMTP connection to another. If a recipient-verify ++ callout connection is requested in the same ACL it is held open and used ++ for the data, otherwise one is made after the ACL completes. Note that ++ routers are used in verify mode. ++ ++ Should the ultimate destination system positively accept or reject the ++ mail, a corresponding indication is given to the source system and nothing ++ is queued. If there is a temporary error the item is queued for later ++ delivery in the usual fashion. If the item is successfully delivered in ++ cutthrough mode the log line is tagged with ">>" rather than "=>" and ++ appears before the acceptance "<=" line. ++ ++ Delivery in this mode avoids the generation of a bounce mail to a (possibly ++ faked) sender when the destination system is doing content-scan based ++ rejection. ++ ++control = debug/<options> ++ ++ This control turns on debug logging, almost as though Exim had been invoked ++ with "-d", with the output going to a new logfile, by default called ++ debuglog. The filename can be adjusted with the tag option, which may ++ access any variables already defined. The logging may be adjusted with the ++ opts option, which takes the same values as the "-d" command-line option. ++ Some examples (which depend on variables that don't exist in all contexts): ++ ++ control = debug ++ control = debug/tag=.$sender_host_address ++ control = debug/opts=+expand+acl ++ control = debug/tag=.$message_exim_id/opts=+expand ++ ++control = dkim_disable_verify ++ ++ This control turns off DKIM verification processing entirely. For details ++ on the operation and configuration of DKIM, see chapter 56. ++ ++control = dscp/<value> ++ ++ This option causes the DSCP value associated with the socket for the ++ inbound connection to be adjusted to a given value, given as one of a ++ number of fixed strings or to numeric value. The -bI:dscp option may be ++ used to ask Exim which names it knows of. Common values include ++ "throughput", "mincost", and on newer systems "ef", "af41", etc. Numeric ++ values may be in the range 0 to 0x3F. ++ ++ The outbound packets from Exim will be marked with this value in the header ++ (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no ++ guarantee that these values will have any effect, not be stripped by ++ networking equipment, or do much of anything without cooperation with your ++ Network Engineer and those of all network operators between the source and ++ destination. ++ ++control = enforce_sync, control = no_enforce_sync ++ ++ These controls make it possible to be selective about when SMTP ++ synchronization is enforced. The global option smtp_enforce_sync specifies ++ the initial state of the switch (it is true by default). See the ++ description of this option in chapter 14 for details of SMTP ++ synchronization checking. ++ ++ The effect of these two controls lasts for the remainder of the SMTP ++ connection. They can appear in any ACL except the one for the non-SMTP ++ messages. The most straightforward place to put them is in the ACL defined ++ by acl_smtp_connect, which is run at the start of an incoming SMTP ++ connection, before the first synchronization check. The expected use is to ++ turn off the synchronization checks for badly-behaved hosts that you ++ nevertheless need to work with. ++ ++control = fakedefer/<message> ++ ++ This control works in exactly the same way as fakereject (described below) ++ except that it causes an SMTP 450 response after the message data instead ++ of a 550 response. You must take care when using fakedefer because it ++ causes the messages to be duplicated when the sender retries. Therefore, ++ you should not use fakedefer if the message is to be delivered normally. ++ ++control = fakereject/<message> ++ ++ This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other ++ words, only when an SMTP message is being received. If Exim accepts the ++ message, instead the final 250 response, a 550 rejection message is sent. ++ However, Exim proceeds to deliver the message as normal. The control ++ applies only to the current message, not to any subsequent ones that may be ++ received in the same SMTP connection. ++ ++ The text for the 550 response is taken from the control modifier. If no ++ message is supplied, the following is used: ++ ++ 550-Your message has been rejected but is being ++ 550-kept for evaluation. ++ 550-If it was a legitimate message, it may still be ++ 550 delivered to the target recipient(s). ++ ++ This facility should be used with extreme caution. ++ ++control = freeze ++ ++ This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, ++ in other words, only when a message is being received. If the message is ++ accepted, it is placed on Exim's queue and frozen. The control applies only ++ to the current message, not to any subsequent ones that may be received in ++ the same SMTP connection. ++ ++ This modifier can optionally be followed by "/no_tell". If the global ++ option freeze_tell is set, it is ignored for the current message (that is, ++ nobody is told about the freezing), provided all the control=freeze ++ modifiers that are obeyed for the current message have the "/no_tell" ++ option. ++ ++control = no_delay_flush ++ ++ Exim normally flushes SMTP output before implementing a delay in an ACL, to ++ avoid unexpected timeouts in clients when the SMTP PIPELINING extension is ++ in use. This control, as long as it is encountered before the delay ++ modifier, disables such output flushing. ++ ++control = no_callout_flush ++ ++ Exim normally flushes SMTP output before performing a callout in an ACL, to ++ avoid unexpected timeouts in clients when the SMTP PIPELINING extension is ++ in use. This control, as long as it is encountered before the verify ++ condition that causes the callout, disables such output flushing. ++ ++control = no_mbox_unspool ++ ++ This control is available when Exim is compiled with the content scanning ++ extension. Content scanning may require a copy of the current message, or ++ parts of it, to be written in "mbox format" to a spool file, for passing to ++ a virus or spam scanner. Normally, such copies are deleted when they are no ++ longer needed. If this control is set, the copies are not deleted. The ++ control applies only to the current message, not to any subsequent ones ++ that may be received in the same SMTP connection. It is provided for ++ debugging purposes and is unlikely to be useful in production. ++ ++control = no_multiline_responses ++ ++ This control is permitted for any ACL except the one for non-SMTP messages. ++ It seems that there are broken clients in use that cannot handle multiline ++ SMTP responses, despite the fact that RFC 821 defined them over 20 years ++ ago. ++ ++ If this control is set, multiline SMTP responses from ACL rejections are ++ suppressed. One way of doing this would have been to put out these ++ responses as one long line. However, RFC 2821 specifies a maximum of 512 ++ bytes per response ("use multiline responses for more" it says - ha!), and ++ some of the responses might get close to that. So this facility, which is ++ after all only a sop to broken clients, is implemented by doing two very ++ easy things: ++ ++ + Extra information that is normally output as part of a rejection caused ++ by sender verification failure is omitted. Only the final line ++ (typically "sender verification failed") is sent. ++ ++ + If a message modifier supplies a multiline response, only the first ++ line is output. ++ ++ The setting of the switch can, of course, be made conditional on the ++ calling host. Its effect lasts until the end of the SMTP connection. ++ ++control = no_pipelining ++ ++ This control turns off the advertising of the PIPELINING extension to SMTP ++ in the current session. To be useful, it must be obeyed before Exim sends ++ its response to an EHLO command. Therefore, it should normally appear in an ++ ACL controlled by acl_smtp_connect or acl_smtp_helo. See also ++ pipelining_advertise_hosts. ++ ++control = queue_only ++ ++ This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, ++ in other words, only when a message is being received. If the message is ++ accepted, it is placed on Exim's queue and left there for delivery by a ++ subsequent queue runner. No immediate delivery process is started. In other ++ words, it has the effect as the queue_only global option. However, the ++ control applies only to the current message, not to any subsequent ones ++ that may be received in the same SMTP connection. ++ ++control = submission/<options> ++ ++ This control is permitted only for the MAIL, RCPT, and start of data ACLs ++ (the latter is the one defined by acl_smtp_predata). Setting it tells Exim ++ that the current message is a submission from a local MUA. In this case, ++ Exim operates in "submission mode", and applies certain fixups to the ++ message if necessary. For example, it adds a Date: header line if one is ++ not present. This control is not permitted in the acl_smtp_data ACL, ++ because that is too late (the message has already been created). ++ ++ Chapter 46 describes the processing that Exim applies to messages. Section ++ 46.1 covers the processing that happens in submission mode; the available ++ options for this control are described there. The control applies only to ++ the current message, not to any subsequent ones that may be received in the ++ same SMTP connection. ++ ++control = suppress_local_fixups ++ ++ This control applies to locally submitted (non TCP/IP) messages, and is the ++ complement of "control = submission". It disables the fixups that are ++ normally applied to locally-submitted messages. Specifically: ++ ++ + Any Sender: header line is left alone (in this respect, it is a dynamic ++ version of local_sender_retain). ++ ++ + No Message-ID:, From:, or Date: header lines are added. ++ ++ + There is no check that From: corresponds to the actual sender. ++ ++ This control may be useful when a remotely-originated message is accepted, ++ passed to some scanning program, and then re-submitted for delivery. It can ++ be used only in the acl_smtp_mail, acl_smtp_rcpt, acl_smtp_predata, and ++ acl_not_smtp_start ACLs, because it has to be set before the message's data ++ is read. ++ ++ Note: This control applies only to the current message, not to any others ++ that are being submitted at the same time using -bs or -bS. ++ ++ ++42.22 Summary of message fixup control ++-------------------------------------- ++ ++All four possibilities for message fixups can be specified: ++ ++ * Locally submitted, fixups applied: the default. ++ ++ * Locally submitted, no fixups applied: use "control = ++ suppress_local_fixups". ++ ++ * Remotely submitted, no fixups applied: the default. ++ ++ * Remotely submitted, fixups applied: use "control = submission". ++ ++ ++42.23 Adding header lines in ACLs ++--------------------------------- ++ ++The add_header modifier can be used to add one or more extra header lines to an ++incoming message, as in this example: ++ ++warn dnslists = sbl.spamhaus.org : \ ++ dialup.mail-abuse.org ++ add_header = X-blacklisted-at: $dnslist_domain ++ ++The add_header modifier is permitted in the MAIL, RCPT, PREDATA, DATA, MIME, ++and non-SMTP ACLs (in other words, those that are concerned with receiving a ++message). The message must ultimately be accepted for add_header to have any ++significant effect. You can use add_header with any ACL verb, including deny ++(though this is potentially useful only in a RCPT ACL). ++ ++Leading and trailing newlines are removed from the data for the add_header ++modifier; if it then contains one or more newlines that are not followed by a ++space or a tab, it is assumed to contain multiple header lines. Each one is ++checked for valid syntax; "X-ACL-Warn:" is added to the front of any line that ++is not a valid header line. ++ ++Added header lines are accumulated during the MAIL, RCPT, and predata ACLs. ++They are added to the message before processing the DATA and MIME ACLs. ++However, if an identical header line is requested more than once, only one copy ++is actually added to the message. Further header lines may be accumulated ++during the DATA and MIME ACLs, after which they are added to the message, again ++with duplicates suppressed. Thus, it is possible to add two identical header ++lines to an SMTP message, but only if one is added before DATA and one after. ++In the case of non-SMTP messages, new headers are accumulated during the ++non-SMTP ACLs, and are added to the message after all the ACLs have run. If a ++message is rejected after DATA or by the non-SMTP ACL, all added header lines ++are included in the entry that is written to the reject log. ++ ++Header lines are not visible in string expansions of message headers until they ++are added to the message. It follows that header lines defined in the MAIL, ++RCPT, and predata ACLs are not visible until the DATA ACL and MIME ACLs are ++run. Similarly, header lines that are added by the DATA or MIME ACLs are not ++visible in those ACLs. Because of this restriction, you cannot use header lines ++as a way of passing data between (for example) the MAIL and RCPT ACLs. If you ++want to do this, you can use ACL variables, as described in section 42.18. ++ ++The list of headers yet to be added is given by the $headers_added variable. ++ ++The add_header modifier acts immediately as it is encountered during the ++processing of an ACL. Notice the difference between these two cases: ++ ++accept add_header = ADDED: some text ++ <some condition> ++ ++accept <some condition> ++ add_header = ADDED: some text ++ ++In the first case, the header line is always added, whether or not the ++condition is true. In the second case, the header line is added only if the ++condition is true. Multiple occurrences of add_header may occur in the same ACL ++statement. All those that are encountered before a condition fails are ++honoured. ++ ++For compatibility with previous versions of Exim, a message modifier for a warn ++verb acts in the same way as add_header, except that it takes effect only if ++all the conditions are true, even if it appears before some of them. ++Furthermore, only the last occurrence of message is honoured. This usage of ++message is now deprecated. If both add_header and message are present on a warn ++verb, both are processed according to their specifications. ++ ++By default, new header lines are added to a message at the end of the existing ++header lines. However, you can specify that any particular header line should ++be added right at the start (before all the Received: lines), immediately after ++the first block of Received: lines, or immediately before any line that is not ++a Received: or Resent-something: header. ++ ++This is done by specifying ":at_start:", ":after_received:", or ++":at_start_rfc:" (or, for completeness, ":at_end:") before the text of the ++header line, respectively. (Header text cannot start with a colon, as there has ++to be a header name first.) For example: ++ ++warn add_header = \ ++ :after_received:X-My-Header: something or other... ++ ++If more than one header line is supplied in a single add_header modifier, each ++one is treated independently and can therefore be placed differently. If you ++add more than one line at the start, or after the Received: block, they end up ++in reverse order. ++ ++Warning: This facility currently applies only to header lines that are added in ++an ACL. It does NOT work for header lines that are added in a system filter or ++in a router or transport. ++ ++ ++42.24 Removing header lines in ACLs ++----------------------------------- ++ ++The remove_header modifier can be used to remove one or more header lines from ++an incoming message, as in this example: ++ ++warn message = Remove internal headers ++ remove_header = x-route-mail1 : x-route-mail2 ++ ++The remove_header modifier is permitted in the MAIL, RCPT, PREDATA, DATA, MIME, ++and non-SMTP ACLs (in other words, those that are concerned with receiving a ++message). The message must ultimately be accepted for remove_header to have any ++significant effect. You can use remove_header with any ACL verb, including deny ++, though this is really not useful for any verb that doesn't result in a ++delivered message. ++ ++More than one header can be removed at the same time by using a colon separated ++list of header names. The header matching is case insensitive. Wildcards are ++not permitted, nor is list expansion performed, so you cannot use hostlists to ++create a list of headers, however both connection and message variable ++expansion are performed ($acl_c_* and $acl_m_*), illustrated in this example: ++ ++warn hosts = +internal_hosts ++ set acl_c_ihdrs = x-route-mail1 : x-route-mail2 ++warn message = Remove internal headers ++ remove_header = $acl_c_ihdrs ++ ++Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs. ++They are removed from the message before processing the DATA and MIME ACLs. ++There is no harm in attempting to remove the same header twice nor is removing ++a non-existent header. Further header lines to be removed may be accumulated ++during the DATA and MIME ACLs, after which they are removed from the message, ++if present. In the case of non-SMTP messages, headers to be removed are ++accumulated during the non-SMTP ACLs, and are removed from the message after ++all the ACLs have run. If a message is rejected after DATA or by the non-SMTP ++ACL, there really is no effect because there is no logging of what headers ++would have been removed. ++ ++Header lines are not visible in string expansions until the DATA phase when it ++is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are ++not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are ++removed by the DATA or MIME ACLs are still visible in those ACLs. Because of ++this restriction, you cannot use header lines as a way of controlling data ++passed between (for example) the MAIL and RCPT ACLs. If you want to do this, ++you should instead use ACL variables, as described in section 42.18. ++ ++The remove_header modifier acts immediately as it is encountered during the ++processing of an ACL. Notice the difference between these two cases: ++ ++accept remove_header = X-Internal ++ <some condition> ++ ++accept <some condition> ++ remove_header = X-Internal ++ ++In the first case, the header line is always removed, whether or not the ++condition is true. In the second case, the header line is removed only if the ++condition is true. Multiple occurrences of remove_header may occur in the same ++ACL statement. All those that are encountered before a condition fails are ++honoured. ++ ++Warning: This facility currently applies only to header lines that are present ++during ACL processing. It does NOT remove header lines that are added in a ++system filter or in a router or transport. ++ ++ ++42.25 ACL conditions ++-------------------- ++ ++Some of the conditions listed in this section are available only when Exim is ++compiled with the content-scanning extension. They are included here briefly ++for completeness. More detailed descriptions can be found in the discussion on ++content scanning in chapter 43. ++ ++Not all conditions are relevant in all circumstances. For example, testing ++senders and recipients does not make sense in an ACL that is being run as the ++result of the arrival of an ETRN command, and checks on message headers can be ++done only in the ACLs specified by acl_smtp_data and acl_not_smtp. You can use ++the same condition (with different parameters) more than once in the same ACL ++statement. This provides a way of specifying an "and" conjunction. The ++conditions are as follows: ++ ++acl = <name of acl or ACL string or file name > ++ ++ The possible values of the argument are the same as for the acl_smtp_xxx ++ options. The named or inline ACL is run. If it returns "accept" the ++ condition is true; if it returns "deny" the condition is false. If it ++ returns "defer", the current ACL returns "defer" unless the condition is on ++ a warn verb. In that case, a "defer" return makes the condition false. This ++ means that further processing of the warn verb ceases, but processing of ++ the ACL continues. ++ ++ If the argument is a named ACL, up to nine space-separated optional values ++ can be appended; they appear within the called ACL in $acl_arg1 to ++ $acl_arg9, and $acl_narg is set to the count of values. Previous values of ++ these variables are restored after the call returns. The name and values ++ are expanded separately. ++ ++ If the nested acl returns "drop" and the outer condition denies access, the ++ connection is dropped. If it returns "discard", the verb must be accept or ++ discard, and the action is taken immediately - no further conditions are ++ tested. ++ ++ ACLs may be nested up to 20 deep; the limit exists purely to catch runaway ++ loops. This condition allows you to use different ACLs in different ++ circumstances. For example, different ACLs can be used to handle RCPT ++ commands for different local users or different local domains. ++ ++authenticated = <string list> ++ ++ If the SMTP connection is not authenticated, the condition is false. ++ Otherwise, the name of the authenticator is tested against the list. To ++ test for authentication by any authenticator, you can set ++ ++ authenticated = * ++ ++condition = <string> ++ ++ This feature allows you to make up custom conditions. If the result of ++ expanding the string is an empty string, the number zero, or one of the ++ strings "no" or "false", the condition is false. If the result is any ++ non-zero number, or one of the strings "yes" or "true", the condition is ++ true. For any other value, some error is assumed to have occurred, and the ++ ACL returns "defer". However, if the expansion is forced to fail, the ++ condition is ignored. The effect is to treat it as true, whether it is ++ positive or negative. ++ ++decode = <location> ++ ++ This condition is available only when Exim is compiled with the ++ content-scanning extension, and it is allowed only in the ACL defined by ++ acl_smtp_mime. It causes the current MIME part to be decoded into a file. ++ If all goes well, the condition is true. It is false only if there are ++ problems such as a syntax error or a memory shortage. For more details, see ++ chapter 43. ++ ++demime = <extension list> ++ ++ This condition is available only when Exim is compiled with the ++ content-scanning extension. Its use is described in section 43.6. ++ ++dnslists = <list of domain names and other data> ++ ++ This condition checks for entries in DNS black lists. These are also known ++ as "RBL lists", after the original Realtime Blackhole List, but note that ++ the use of the lists at mail-abuse.org now carries a charge. There are too ++ many different variants of this condition to describe briefly here. See ++ sections 42.26-42.36 for details. ++ ++domains = <domain list> ++ ++ This condition is relevant only after a RCPT command. It checks that the ++ domain of the recipient address is in the domain list. If percent-hack ++ processing is enabled, it is done before this test is done. If the check ++ succeeds with a lookup, the result of the lookup is placed in $domain_data ++ until the next domains test. ++ ++ Note carefully (because many people seem to fall foul of this): you cannot ++ use domains in a DATA ACL. ++ ++encrypted = <string list> ++ ++ If the SMTP connection is not encrypted, the condition is false. Otherwise, ++ the name of the cipher suite in use is tested against the list. To test for ++ encryption without testing for any specific cipher suite(s), set ++ ++ encrypted = * ++ ++hosts = <host list> ++ ++ This condition tests that the calling host matches the host list. If you ++ have name lookups or wildcarded host names and IP addresses in the same ++ host list, you should normally put the IP addresses first. For example, you ++ could have: ++ ++ accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts ++ ++ The lookup in this example uses the host name for its key. This is implied ++ by the lookup type "dbm". (For a host address lookup you would use ++ "net-dbm" and it wouldn't matter which way round you had these two items.) ++ ++ The reason for the problem with host names lies in the left-to-right way ++ that Exim processes lists. It can test IP addresses without doing any DNS ++ lookups, but when it reaches an item that requires a host name, it fails if ++ it cannot find a host name to compare with the pattern. If the above list ++ is given in the opposite order, the accept statement fails for a host whose ++ name cannot be found, even if its IP address is 10.9.8.7. ++ ++ If you really do want to do the name check first, and still recognize the ++ IP address even if the name lookup fails, you can rewrite the ACL like ++ this: ++ ++ accept hosts = dbm;/etc/friendly/hosts ++ accept hosts = 10.9.8.7 ++ ++ The default action on failing to find the host name is to assume that the ++ host is not in the list, so the first accept statement fails. The second ++ statement can then check the IP address. ++ ++ If a hosts condition is satisfied by means of a lookup, the result of the ++ lookup is made available in the $host_data variable. This allows you, for ++ example, to set up a statement like this: ++ ++ deny hosts = net-lsearch;/some/file ++ message = $host_data ++ ++ which gives a custom error message for each denied host. ++ ++local_parts = <local part list> ++ ++ This condition is relevant only after a RCPT command. It checks that the ++ local part of the recipient address is in the list. If percent-hack ++ processing is enabled, it is done before this test. If the check succeeds ++ with a lookup, the result of the lookup is placed in $local_part_data, ++ which remains set until the next local_parts test. ++ ++malware = <option> ++ ++ This condition is available only when Exim is compiled with the ++ content-scanning extension. It causes the incoming message to be scanned ++ for viruses. For details, see chapter 43. ++ ++mime_regex = <list of regular expressions> ++ ++ This condition is available only when Exim is compiled with the ++ content-scanning extension, and it is allowed only in the ACL defined by ++ acl_smtp_mime. It causes the current MIME part to be scanned for a match ++ with any of the regular expressions. For details, see chapter 43. ++ ++ratelimit = <parameters> ++ ++ This condition can be used to limit the rate at which a user or host ++ submits messages. Details are given in section 42.37. ++ ++recipients = <address list> ++ ++ This condition is relevant only after a RCPT command. It checks the entire ++ recipient address against a list of recipients. ++ ++regex = <list of regular expressions> ++ ++ This condition is available only when Exim is compiled with the ++ content-scanning extension, and is available only in the DATA, MIME, and ++ non-SMTP ACLs. It causes the incoming message to be scanned for a match ++ with any of the regular expressions. For details, see chapter 43. ++ ++sender_domains = <domain list> ++ ++ This condition tests the domain of the sender of the message against the ++ given domain list. Note: The domain of the sender address is in ++ $sender_address_domain. It is not put in $domain during the testing of this ++ condition. This is an exception to the general rule for testing domain ++ lists. It is done this way so that, if this condition is used in an ACL for ++ a RCPT command, the recipient's domain (which is in $domain) can be used to ++ influence the sender checking. ++ ++ Warning: It is a bad idea to use this condition on its own as a control on ++ relaying, because sender addresses are easily, and commonly, forged. ++ ++senders = <address list> ++ ++ This condition tests the sender of the message against the given list. To ++ test for a bounce message, which has an empty sender, set ++ ++ senders = : ++ ++ Warning: It is a bad idea to use this condition on its own as a control on ++ relaying, because sender addresses are easily, and commonly, forged. ++ ++spam = <username> ++ ++ This condition is available only when Exim is compiled with the ++ content-scanning extension. It causes the incoming message to be scanned by ++ SpamAssassin. For details, see chapter 43. ++ ++verify = certificate ++ ++ This condition is true in an SMTP session if the session is encrypted, and ++ a certificate was received from the client, and the certificate was ++ verified. The server requests a certificate only if the client matches ++ tls_verify_hosts or tls_try_verify_hosts (see chapter 41). ++ ++verify = csa ++ ++ This condition checks whether the sending host (the client) is authorized ++ to send email. Details of how this works are given in section 42.49. ++ ++verify = header_sender/<options> ++ ++ This condition is relevant only in an ACL that is run after a message has ++ been received, that is, in an ACL specified by acl_smtp_data or ++ acl_not_smtp. It checks that there is a verifiable address in at least one ++ of the Sender:, Reply-To:, or From: header lines. Such an address is ++ loosely thought of as a "sender" address (hence the name of the test). ++ However, an address that appears in one of these headers need not be an ++ address that accepts bounce messages; only sender addresses in envelopes ++ are required to accept bounces. Therefore, if you use the callout option on ++ this check, you might want to arrange for a non-empty address in the MAIL ++ command. ++ ++ Details of address verification and the options are given later, starting ++ at section 42.43 (callouts are described in section 42.44). You can combine ++ this condition with the senders condition to restrict it to bounce messages ++ only: ++ ++ deny senders = : ++ message = A valid sender header is required for bounces ++ !verify = header_sender ++ ++verify = header_syntax ++ ++ This condition is relevant only in an ACL that is run after a message has ++ been received, that is, in an ACL specified by acl_smtp_data or ++ acl_not_smtp. It checks the syntax of all header lines that can contain ++ lists of addresses (Sender:, From:, Reply-To:, To:, Cc:, and Bcc:). ++ Unqualified addresses (local parts without domains) are permitted only in ++ locally generated messages and from hosts that match ++ sender_unqualified_hosts or recipient_unqualified_hosts, as appropriate. ++ ++ Note that this condition is a syntax check only. However, a common spamming ++ ploy used to be to send syntactically invalid headers such as ++ ++ To: @ ++ ++ and this condition can be used to reject such messages, though they are not ++ as common as they used to be. ++ ++verify = helo ++ ++ This condition is true if a HELO or EHLO command has been received from the ++ client host, and its contents have been verified. If there has been no ++ previous attempt to verify the HELO/EHLO contents, it is carried out when ++ this condition is encountered. See the description of the helo_verify_hosts ++ and helo_try_verify_hosts options for details of how to request ++ verification independently of this condition. ++ ++ For SMTP input that does not come over TCP/IP (the -bs command line ++ option), this condition is always true. ++ ++verify = not_blind ++ ++ This condition checks that there are no blind (bcc) recipients in the ++ message. Every envelope recipient must appear either in a To: header line ++ or in a Cc: header line for this condition to be true. Local parts are ++ checked case-sensitively; domains are checked case-insensitively. If ++ Resent-To: or Resent-Cc: header lines exist, they are also checked. This ++ condition can be used only in a DATA or non-SMTP ACL. ++ ++ There are, of course, many legitimate messages that make use of blind (bcc) ++ recipients. This check should not be used on its own for blocking messages. ++ ++verify = recipient/<options> ++ ++ This condition is relevant only after a RCPT command. It verifies the ++ current recipient. Details of address verification are given later, ++ starting at section 42.43. After a recipient has been verified, the value ++ of $address_data is the last value that was set while routing the address. ++ This applies even if the verification fails. When an address that is being ++ verified is redirected to a single address, verification continues with the ++ new address, and in that case, the subsequent value of $address_data is the ++ value for the child address. ++ ++verify = reverse_host_lookup ++ ++ This condition ensures that a verified host name has been looked up from ++ the IP address of the client host. (This may have happened already if the ++ host name was needed for checking a host list, or if the host matched ++ host_lookup.) Verification ensures that the host name obtained from a ++ reverse DNS lookup, or one of its aliases, does, when it is itself looked ++ up in the DNS, yield the original IP address. ++ ++ If this condition is used for a locally generated message (that is, when ++ there is no client host involved), it always succeeds. ++ ++verify = sender/<options> ++ ++ This condition is relevant only after a MAIL or RCPT command, or after a ++ message has been received (the acl_smtp_data or acl_not_smtp ACLs). If the ++ message's sender is empty (that is, this is a bounce message), the ++ condition is true. Otherwise, the sender address is verified. ++ ++ If there is data in the $address_data variable at the end of routing, its ++ value is placed in $sender_address_data at the end of verification. This ++ value can be used in subsequent conditions and modifiers in the same ACL ++ statement. It does not persist after the end of the current statement. If ++ you want to preserve the value for longer, you can save it in an ACL ++ variable. ++ ++ Details of verification are given later, starting at section 42.43. Exim ++ caches the result of sender verification, to avoid doing it more than once ++ per message. ++ ++verify = sender=<address>/<options> ++ ++ This is a variation of the previous option, in which a modified address is ++ verified as a sender. ++ ++ ++42.26 Using DNS lists ++--------------------- ++ ++In its simplest form, the dnslists condition tests whether the calling host is ++on at least one of a number of DNS lists by looking up the inverted IP address ++in one or more DNS domains. (Note that DNS list domains are not mail domains, ++so the "+" syntax for named lists doesn't work - it is used for special options ++instead.) For example, if the calling host's IP address is 192.168.62.43, and ++the ACL statement is ++ ++deny dnslists = blackholes.mail-abuse.org : \ ++ dialups.mail-abuse.org ++ ++the following records are looked up: ++ ++43.62.168.192.blackholes.mail-abuse.org ++43.62.168.192.dialups.mail-abuse.org ++ ++As soon as Exim finds an existing DNS record, processing of the list stops. ++Thus, multiple entries on the list provide an "or" conjunction. If you want to ++test that a host is on more than one list (an "and" conjunction), you can use ++two separate conditions: ++ ++deny dnslists = blackholes.mail-abuse.org ++ dnslists = dialups.mail-abuse.org ++ ++If a DNS lookup times out or otherwise fails to give a decisive answer, Exim ++behaves as if the host does not match the list item, that is, as if the DNS ++record does not exist. If there are further items in the DNS list, they are ++processed. ++ ++This is usually the required action when dnslists is used with deny (which is ++the most common usage), because it prevents a DNS failure from blocking mail. ++However, you can change this behaviour by putting one of the following special ++items in the list: ++ +++include_unknown behave as if the item is on the list +++exclude_unknown behave as if the item is not on the list (default) +++defer_unknown give a temporary error ++ ++Each of these applies to any subsequent items on the list. For example: ++ ++deny dnslists = +defer_unknown : foo.bar.example ++ ++Testing the list of domains stops as soon as a match is found. If you want to ++warn for one list and block for another, you can use two different statements: ++ ++deny dnslists = blackholes.mail-abuse.org ++warn message = X-Warn: sending host is on dialups list ++ dnslists = dialups.mail-abuse.org ++ ++DNS list lookups are cached by Exim for the duration of the SMTP session, so a ++lookup based on the IP address is done at most once for any incoming ++connection. Exim does not share information between multiple incoming ++connections (but your local name server cache should be active). ++ ++ ++42.27 Specifying the IP address for a DNS list lookup ++----------------------------------------------------- ++ ++By default, the IP address that is used in a DNS list lookup is the IP address ++of the calling host. However, you can specify another IP address by listing it ++after the domain name, introduced by a slash. For example: ++ ++deny dnslists = black.list.tld/192.168.1.2 ++ ++This feature is not very helpful with explicit IP addresses; it is intended for ++use with IP addresses that are looked up, for example, the IP addresses of the ++MX hosts or nameservers of an email sender address. For an example, see section ++42.29 below. ++ ++ ++42.28 DNS lists keyed on domain names ++------------------------------------- ++ ++There are some lists that are keyed on domain names rather than inverted IP ++addresses (see for example the domain based zones link at http:// ++www.rfc-ignorant.org/). No reversing of components is used with these lists. ++You can change the name that is looked up in a DNS list by listing it after the ++domain name, introduced by a slash. For example, ++ ++deny message = Sender's domain is listed at $dnslist_domain ++ dnslists = dsn.rfc-ignorant.org/$sender_address_domain ++ ++This particular example is useful only in ACLs that are obeyed after the RCPT ++or DATA commands, when a sender address is available. If (for example) the ++message's sender is user@tld.example the name that is looked up by this example ++is ++ ++tld.example.dsn.rfc-ignorant.org ++ ++A single dnslists condition can contain entries for both names and IP ++addresses. For example: ++ ++deny dnslists = sbl.spamhaus.org : \ ++ dsn.rfc-ignorant.org/$sender_address_domain ++ ++The first item checks the sending host's IP address; the second checks a domain ++name. The whole condition is true if either of the DNS lookups succeeds. ++ ++ ++42.29 Multiple explicit keys for a DNS list ++------------------------------------------- ++ ++The syntax described above for looking up explicitly-defined values (either ++names or IP addresses) in a DNS blacklist is a simplification. After the domain ++name for the DNS list, what follows the slash can in fact be a list of items. ++As with all lists in Exim, the default separator is a colon. However, because ++this is a sublist within the list of DNS blacklist domains, it is necessary ++either to double the separators like this: ++ ++dnslists = black.list.tld/name.1::name.2 ++ ++or to change the separator character, like this: ++ ++dnslists = black.list.tld/<;name.1;name.2 ++ ++If an item in the list is an IP address, it is inverted before the DNS ++blacklist domain is appended. If it is not an IP address, no inversion occurs. ++Consider this condition: ++ ++dnslists = black.list.tld/<;192.168.1.2;a.domain ++ ++The DNS lookups that occur are: ++ ++2.1.168.192.black.list.tld ++a.domain.black.list.tld ++ ++Once a DNS record has been found (that matches a specific IP return address, if ++specified - see section 42.32), no further lookups are done. If there is a ++temporary DNS error, the rest of the sublist of domains or IP addresses is ++tried. A temporary error for the whole dnslists item occurs only if no other ++DNS lookup in this sublist succeeds. In other words, a successful lookup for ++any of the items in the sublist overrides a temporary error for a previous ++item. ++ ++The ability to supply a list of items after the slash is in some sense just a ++syntactic convenience. These two examples have the same effect: ++ ++dnslists = black.list.tld/a.domain : black.list.tld/b.domain ++dnslists = black.list.tld/a.domain::b.domain ++ ++However, when the data for the list is obtained from a lookup, the second form ++is usually much more convenient. Consider this example: ++ ++deny message = The mail servers for the domain \ ++ $sender_address_domain \ ++ are listed at $dnslist_domain ($dnslist_value); \ ++ see $dnslist_text. ++ dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\ ++ ${lookup dnsdb {>|mxh=\ ++ $sender_address_domain} }} } ++ ++Note the use of ">|" in the dnsdb lookup to specify the separator for multiple ++DNS records. The inner dnsdb lookup produces a list of MX hosts and the outer ++dnsdb lookup finds the IP addresses for these hosts. The result of expanding ++the condition might be something like this: ++ ++dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|... ++ ++Thus, this example checks whether or not the IP addresses of the sender ++domain's mail servers are on the Spamhaus black list. ++ ++The key that was used for a successful DNS list lookup is put into the variable ++$dnslist_matched (see section 42.31). ++ ++ ++42.30 Data returned by DNS lists ++-------------------------------- ++ ++DNS lists are constructed using address records in the DNS. The original RBL ++just used the address 127.0.0.1 on the right hand side of each record, but the ++RBL+ list and some other lists use a number of values with different meanings. ++The values used on the RBL+ list are: ++ ++127.1.0.1 RBL ++127.1.0.2 DUL ++127.1.0.3 DUL and RBL ++127.1.0.4 RSS ++127.1.0.5 RSS and RBL ++127.1.0.6 RSS and DUL ++127.1.0.7 RSS and DUL and RBL ++ ++Section 42.32 below describes how you can distinguish between different values. ++Some DNS lists may return more than one address record; see section 42.34 for ++details of how they are checked. ++ ++ ++42.31 Variables set from DNS lists ++---------------------------------- ++ ++When an entry is found in a DNS list, the variable $dnslist_domain contains the ++name of the overall domain that matched (for example, "spamhaus.example"), ++$dnslist_matched contains the key within that domain (for example, ++"192.168.5.3"), and $dnslist_value contains the data from the DNS record. When ++the key is an IP address, it is not reversed in $dnslist_matched (though it is, ++of course, in the actual lookup). In simple cases, for example: ++ ++deny dnslists = spamhaus.example ++ ++the key is also available in another variable (in this case, ++$sender_host_address). In more complicated cases, however, this is not true. ++For example, using a data lookup (as described in section 42.29) might generate ++a dnslists lookup like this: ++ ++deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|... ++ ++If this condition succeeds, the value in $dnslist_matched might be ++"192.168.6.7" (for example). ++ ++If more than one address record is returned by the DNS lookup, all the IP ++addresses are included in $dnslist_value, separated by commas and spaces. The ++variable $dnslist_text contains the contents of any associated TXT record. For ++lists such as RBL+ the TXT record for a merged entry is often not very ++meaningful. See section 42.35 for a way of obtaining more information. ++ ++You can use the DNS list variables in message or log_message modifiers - ++although these appear before the condition in the ACL, they are not expanded ++until after it has failed. For example: ++ ++deny hosts = !+local_networks ++ message = $sender_host_address is listed \ ++ at $dnslist_domain ++ dnslists = rbl-plus.mail-abuse.example ++ ++ ++42.32 Additional matching conditions for DNS lists ++-------------------------------------------------- ++ ++You can add an equals sign and an IP address after a dnslists domain name in ++order to restrict its action to DNS records with a matching right hand side. ++For example, ++ ++deny dnslists = rblplus.mail-abuse.org=127.0.0.2 ++ ++rejects only those hosts that yield 127.0.0.2. Without this additional data, ++any address record is considered to be a match. For the moment, we assume that ++the DNS lookup returns just one record. Section 42.34 describes how multiple ++records are handled. ++ ++More than one IP address may be given for checking, using a comma as a ++separator. These are alternatives - if any one of them matches, the dnslists ++condition is true. For example: ++ ++deny dnslists = a.b.c=127.0.0.2,127.0.0.3 ++ ++If you want to specify a constraining address list and also specify names or IP ++addresses to be looked up, the constraining address list must be specified ++first. For example: ++ ++deny dnslists = dsn.rfc-ignorant.org\ ++ =127.0.0.2/$sender_address_domain ++ ++If the character "&" is used instead of "=", the comparison for each listed IP ++address is done by a bitwise "and" instead of by an equality test. In other ++words, the listed addresses are used as bit masks. The comparison is true if ++all the bits in the mask are present in the address that is being tested. For ++example: ++ ++dnslists = a.b.c&0.0.0.3 ++ ++matches if the address is x.x.x.3, x.x.x.7, x.x.x.11, etc. If you want to test ++whether one bit or another bit is present (as opposed to both being present), ++you must use multiple values. For example: ++ ++dnslists = a.b.c&0.0.0.1,0.0.0.2 ++ ++matches if the final component of the address is an odd number or two times an ++odd number. ++ ++ ++42.33 Negated DNS matching conditions ++------------------------------------- ++ ++You can supply a negative list of IP addresses as part of a dnslists condition. ++Whereas ++ ++deny dnslists = a.b.c=127.0.0.2,127.0.0.3 ++ ++means "deny if the host is in the black list at the domain a.b.c and the IP ++address yielded by the list is either 127.0.0.2 or 127.0.0.3", ++ ++deny dnslists = a.b.c!=127.0.0.2,127.0.0.3 ++ ++means "deny if the host is in the black list at the domain a.b.c and the IP ++address yielded by the list is not 127.0.0.2 and not 127.0.0.3". In other ++words, the result of the test is inverted if an exclamation mark appears before ++the "=" (or the "&") sign. ++ ++Note: This kind of negation is not the same as negation in a domain, host, or ++address list (which is why the syntax is different). ++ ++If you are using just one list, the negation syntax does not gain you much. The ++previous example is precisely equivalent to ++ ++deny dnslists = a.b.c ++ !dnslists = a.b.c=127.0.0.2,127.0.0.3 ++ ++However, if you are using multiple lists, the negation syntax is clearer. ++Consider this example: ++ ++deny dnslists = sbl.spamhaus.org : \ ++ list.dsbl.org : \ ++ dnsbl.njabl.org!=127.0.0.3 : \ ++ relays.ordb.org ++ ++Using only positive lists, this would have to be: ++ ++deny dnslists = sbl.spamhaus.org : \ ++ list.dsbl.org ++deny dnslists = dnsbl.njabl.org ++ !dnslists = dnsbl.njabl.org=127.0.0.3 ++deny dnslists = relays.ordb.org ++ ++which is less clear, and harder to maintain. ++ ++ ++42.34 Handling multiple DNS records from a DNS list ++--------------------------------------------------- ++ ++A DNS lookup for a dnslists condition may return more than one DNS record, ++thereby providing more than one IP address. When an item in a dnslists list is ++followed by "=" or "&" and a list of IP addresses, in order to restrict the ++match to specific results from the DNS lookup, there are two ways in which the ++checking can be handled. For example, consider the condition: ++ ++dnslists = a.b.c=127.0.0.1 ++ ++What happens if the DNS lookup for the incoming IP address yields both ++127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the condition ++true because at least one given value was found, or is it false because at ++least one of the found values was not listed? And how does this affect negated ++conditions? Both possibilities are provided for with the help of additional ++separators "==" and "=&". ++ ++ * If "=" or "&" is used, the condition is true if any one of the looked up IP ++ addresses matches one of the listed addresses. For the example above, the ++ condition is true because 127.0.0.1 matches. ++ ++ * If "==" or "=&" is used, the condition is true only if every one of the ++ looked up IP addresses matches one of the listed addresses. If the ++ condition is changed to: ++ ++ dnslists = a.b.c==127.0.0.1 ++ ++ and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is ++ false because 127.0.0.2 is not listed. You would need to have: ++ ++ dnslists = a.b.c==127.0.0.1,127.0.0.2 ++ ++ for the condition to be true. ++ ++When "!" is used to negate IP address matching, it inverts the result, giving ++the precise opposite of the behaviour above. Thus: ++ ++ * If "!=" or "!&" is used, the condition is true if none of the looked up IP ++ addresses matches one of the listed addresses. Consider: ++ ++ dnslists = a.b.c!&0.0.0.1 ++ ++ If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is ++ false because 127.0.0.1 matches. ++ ++ * If "!==" or "!=&" is used, the condition is true if there is at least one ++ looked up IP address that does not match. Consider: ++ ++ dnslists = a.b.c!=&0.0.0.1 ++ ++ If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is ++ true, because 127.0.0.2 does not match. You would need to have: ++ ++ dnslists = a.b.c!=&0.0.0.1,0.0.0.2 ++ ++ for the condition to be false. ++ ++When the DNS lookup yields only a single IP address, there is no difference ++between "=" and "==" and between "&" and "=&". ++ ++ ++42.35 Detailed information from merged DNS lists ++------------------------------------------------ ++ ++When the facility for restricting the matching IP values in a DNS list is used, ++the text from the TXT record that is set in $dnslist_text may not reflect the ++true reason for rejection. This happens when lists are merged and the IP ++address in the A record is used to distinguish them; unfortunately there is ++only one TXT record. One way round this is not to use merged lists, but that ++can be inefficient because it requires multiple DNS lookups where one would do ++in the vast majority of cases when the host of interest is not on any of the ++lists. ++ ++A less inefficient way of solving this problem is available. If two domain ++names, comma-separated, are given, the second is used first to do an initial ++check, making use of any IP value restrictions that are set. If there is a ++match, the first domain is used, without any IP value restrictions, to get the ++TXT record. As a byproduct of this, there is also a check that the IP being ++tested is indeed on the first list. The first domain is the one that is put in ++$dnslist_domain. For example: ++ ++reject message = \ ++ rejected because $sender_host_address is blacklisted \ ++ at $dnslist_domain\n$dnslist_text ++ dnslists = \ ++ sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \ ++ dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10 ++ ++For the first blacklist item, this starts by doing a lookup in ++sbl-xbl.spamhaus.org and testing for a 127.0.0.2 return. If there is a match, ++it then looks in sbl.spamhaus.org, without checking the return value, and as ++long as something is found, it looks for the corresponding TXT record. If there ++is no match in sbl-xbl.spamhaus.org, nothing more is done. The second blacklist ++item is processed similarly. ++ ++If you are interested in more than one merged list, the same list must be given ++several times, but because the results of the DNS lookups are cached, the DNS ++calls themselves are not repeated. For example: ++ ++reject dnslists = \ ++ http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \ ++ socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \ ++ misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \ ++ dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10 ++ ++In this case there is one lookup in dnsbl.sorbs.net, and if none of the IP ++values matches (or if no record is found), this is the only lookup that is ++done. Only if there is a match is one of the more specific lists consulted. ++ ++ ++42.36 DNS lists and IPv6 ++------------------------ ++ ++If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it ++nibble by nibble. For example, if the calling host's IP address is ++3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up ++ ++1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8. ++ f.f.f.f.e.f.f.3.blackholes.mail-abuse.org ++ ++(split over two lines here to fit on the page). Unfortunately, some of the DNS ++lists contain wildcard records, intended for IPv4, that interact badly with ++IPv6. For example, the DNS entry ++ ++*.3.some.list.example. A 127.0.0.1 ++ ++is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list. ++Unfortunately, it also matches the entire 3::/4 IPv6 network. ++ ++You can exclude IPv6 addresses from DNS lookups by making use of a suitable ++condition condition, as in this example: ++ ++deny condition = ${if isip4{$sender_host_address}} ++ dnslists = some.list.example ++ ++ ++42.37 Rate limiting incoming messages ++------------------------------------- ++ ++The ratelimit ACL condition can be used to measure and control the rate at ++which clients can send email. This is more powerful than the smtp_ratelimit_* ++options, because those options control the rate of commands in a single SMTP ++session only, whereas the ratelimit condition works across all connections ++(concurrent and sequential) from the same client host. The syntax of the ++ratelimit condition is: ++ ++ratelimit = <m> / <p> / <options> / <key> ++ ++If the average client sending rate is less than m messages per time period p ++then the condition is false; otherwise it is true. ++ ++As a side-effect, the ratelimit condition sets the expansion variable ++$sender_rate to the client's computed rate, $sender_rate_limit to the ++configured value of m, and $sender_rate_period to the configured value of p. ++ ++The parameter p is the smoothing time constant, in the form of an Exim time ++interval, for example, "8h" for eight hours. A larger time constant means that ++it takes Exim longer to forget a client's past behaviour. The parameter m is ++the maximum number of messages that a client is permitted to send in each time ++interval. It also specifies the number of messages permitted in a fast burst. ++By increasing both m and p but keeping m/p constant, you can allow a client to ++send more messages in a burst without changing its long-term sending rate ++limit. Conversely, if m and p are both small, messages must be sent at an even ++rate. ++ ++There is a script in util/ratelimit.pl which extracts sending rates from log ++files, to assist with choosing appropriate settings for m and p when deploying ++the ratelimit ACL condition. The script prints usage instructions when it is ++run with no arguments. ++ ++The key is used to look up the data for calculating the client's average ++sending rate. This data is stored in Exim's spool directory, alongside the ++retry and other hints databases. The default key is $sender_host_address, which ++means Exim computes the sending rate of each client host IP address. By ++changing the key you can change how Exim identifies clients for the purpose of ++ratelimiting. For example, to limit the sending rate of each authenticated ++user, independent of the computer they are sending from, set the key to ++$authenticated_id. You must ensure that the lookup key is meaningful; for ++example, $authenticated_id is only meaningful if the client has authenticated ++(which you can check with the authenticated ACL condition). ++ ++The lookup key does not have to identify clients: If you want to limit the rate ++at which a recipient receives messages, you can use the key ++"$local_part@$domain" with the per_rcpt option (see below) in a RCPT ACL. ++ ++Each ratelimit condition can have up to four options. A per_* option specifies ++what Exim measures the rate of, for example messages or recipients or bytes. ++You can adjust the measurement using the unique= and/or count= options. You can ++also control when Exim updates the recorded rate using a strict, leaky, or ++readonly option. The options are separated by a slash, like the other ++parameters. They may appear in any order. ++ ++Internally, Exim appends the smoothing constant p onto the lookup key with any ++options that alter the meaning of the stored data. The limit m is not stored, ++so you can alter the configured maximum rate and Exim will still remember ++clients' past behaviour. If you change the per_* mode or add or remove the ++unique= option, the lookup key changes so Exim will forget past behaviour. The ++lookup key is not affected by changes to the update mode and the count= option. ++ ++ ++42.38 Ratelimit options for what is being measured ++-------------------------------------------------- ++ ++The per_conn option limits the client's connection rate. It is not normally ++used in the acl_not_smtp, acl_not_smtp_mime, or acl_not_smtp_start ACLs. ++ ++The per_mail option limits the client's rate of sending messages. This is the ++default if none of the per_* options is specified. It can be used in ++acl_smtp_mail, acl_smtp_rcpt, acl_smtp_predata, acl_smtp_mime, acl_smtp_data, ++or acl_not_smtp. ++ ++The per_byte option limits the sender's email bandwidth. It can be used in the ++same ACLs as the per_mail option, though it is best to use this option in the ++acl_smtp_mime, acl_smtp_data or acl_not_smtp ACLs; if it is used in an earlier ++ACL, Exim relies on the SIZE parameter given by the client in its MAIL command, ++which may be inaccurate or completely missing. You can follow the limit m in ++the configuration with K, M, or G to specify limits in kilobytes, megabytes, or ++gigabytes, respectively. ++ ++The per_rcpt option causes Exim to limit the rate at which recipients are ++accepted. It can be used in the acl_smtp_rcpt, acl_smtp_predata, acl_smtp_mime, ++acl_smtp_data, or acl_smtp_rcpt ACLs. In acl_smtp_rcpt the rate is updated one ++recipient at a time; in the other ACLs the rate is updated with the total ++recipient count in one go. Note that in either case the rate limiting engine ++will see a message with many recipients as a large high-speed burst. ++ ++The per_addr option is like the per_rcpt option, except it counts the number of ++different recipients that the client has sent messages to in the last time ++period. That is, if the client repeatedly sends messages to the same recipient, ++its measured rate is not increased. This option can only be used in ++acl_smtp_rcpt. ++ ++The per_cmd option causes Exim to recompute the rate every time the condition ++is processed. This can be used to limit the rate of any SMTP command. If it is ++used in multiple ACLs it can limit the aggregate rate of multiple different ++commands. ++ ++The count= option can be used to alter how much Exim adds to the client's ++measured rate. For example, the per_byte option is equivalent to "per_mail/ ++count=$message_size". If there is no count= option, Exim increases the measured ++rate by one (except for the per_rcpt option in ACLs other than acl_smtp_rcpt). ++The count does not have to be an integer. ++ ++The unique= option is described in section 42.41 below. ++ ++ ++42.39 Ratelimit update modes ++---------------------------- ++ ++You can specify one of three options with the ratelimit condition to control ++when its database is updated. This section describes the readonly mode, and the ++next section describes the strict and leaky modes. ++ ++If the ratelimit condition is used in readonly mode, Exim looks up a ++previously-computed rate to check against the limit. ++ ++For example, you can test the client's sending rate and deny it access (when it ++is too fast) in the connect ACL. If the client passes this check then it can go ++on to send a message, in which case its recorded rate will be updated in the ++MAIL ACL. Subsequent connections from the same client will check this new rate. ++ ++acl_check_connect: ++ deny ratelimit = 100 / 5m / readonly ++ log_message = RATE CHECK: $sender_rate/$sender_rate_period \ ++ (max $sender_rate_limit) ++# ... ++acl_check_mail: ++ warn ratelimit = 100 / 5m / strict ++ log_message = RATE UPDATE: $sender_rate/$sender_rate_period \ ++ (max $sender_rate_limit) ++ ++If Exim encounters multiple ratelimit conditions with the same key when ++processing a message then it may increase the client's measured rate more than ++it should. For example, this will happen if you check the per_rcpt option in ++both acl_smtp_rcpt and acl_smtp_data. However it's OK to check the same ++ratelimit condition multiple times in the same ACL. You can avoid any multiple ++update problems by using the readonly option on later ratelimit checks. ++ ++The per_* options described above do not make sense in some ACLs. If you use a ++per_* option in an ACL where it is not normally permitted then the update mode ++defaults to readonly and you cannot specify the strict or leaky modes. In other ++ACLs the default update mode is leaky (see the next section) so you must ++specify the readonly option explicitly. ++ ++ ++42.40 Ratelimit options for handling fast clients ++------------------------------------------------- ++ ++If a client's average rate is greater than the maximum, the rate limiting ++engine can react in two possible ways, depending on the presence of the strict ++or leaky update modes. This is independent of the other counter-measures (such ++as rejecting the message) that may be specified by the rest of the ACL. ++ ++The leaky (default) option means that the client's recorded rate is not updated ++if it is above the limit. The effect of this is that Exim measures the client's ++average rate of successfully sent email, which cannot be greater than the ++maximum allowed. If the client is over the limit it may suffer some ++counter-measures (as specified in the ACL), but it will still be able to send ++email at the configured maximum rate, whatever the rate of its attempts. This ++is generally the better choice if you have clients that retry automatically. ++For example, it does not prevent a sender with an over-aggressive retry rate ++from getting any email through. ++ ++The strict option means that the client's recorded rate is always updated. The ++effect of this is that Exim measures the client's average rate of attempts to ++send email, which can be much higher than the maximum it is actually allowed. ++If the client is over the limit it may be subjected to counter-measures by the ++ACL. It must slow down and allow sufficient time to pass that its computed rate ++falls below the maximum before it can send email again. The time (the number of ++smoothing periods) it must wait and not attempt to send mail can be calculated ++with this formula: ++ ++ ln(peakrate/maxrate) ++ ++ ++42.41 Limiting the rate of different events ++------------------------------------------- ++ ++The ratelimit unique= option controls a mechanism for counting the rate of ++different events. For example, the per_addr option uses this mechanism to count ++the number of different recipients that the client has sent messages to in the ++last time period; it is equivalent to "per_rcpt/unique=$local_part@$domain". ++You could use this feature to measure the rate that a client uses different ++sender addresses with the options "per_mail/unique=$sender_address". ++ ++For each ratelimit key Exim stores the set of unique= values that it has seen ++for that key. The whole set is thrown away when it is older than the rate ++smoothing period p, so each different event is counted at most once per period. ++In the leaky update mode, an event that causes the client to go over the limit ++is not added to the set, in the same way that the client's recorded rate is not ++updated in the same situation. ++ ++When you combine the unique= and readonly options, the specific unique= value ++is ignored, and Exim just retrieves the client's stored rate. ++ ++The unique= mechanism needs more space in the ratelimit database than the other ++ratelimit options in order to store the event set. The number of unique values ++is potentially as large as the rate limit, so the extra space required ++increases with larger limits. ++ ++The uniqueification is not perfect: there is a small probability that Exim will ++think a new event has happened before. If the sender's rate is less than the ++limit, Exim should be more than 99.9% correct. However in strict mode the ++measured rate can go above the limit, in which case Exim may under-count events ++by a significant margin. Fortunately, if the rate is high enough (2.7 times the ++limit) that the false positive rate goes above 9%, then Exim will throw away ++the over-full event set before the measured rate falls below the limit. ++Therefore the only harm should be that exceptionally high sending rates are ++logged incorrectly; any countermeasures you configure will be as effective as ++intended. ++ ++ ++42.42 Using rate limiting ++------------------------- ++ ++Exim's other ACL facilities are used to define what counter-measures are taken ++when the rate limit is exceeded. This might be anything from logging a warning ++(for example, while measuring existing sending rates in order to define ++policy), through time delays to slow down fast senders, up to rejecting the ++message. For example: ++ ++# Log all senders' rates ++warn ratelimit = 0 / 1h / strict ++ log_message = Sender rate $sender_rate / $sender_rate_period ++ ++# Slow down fast senders; note the need to truncate $sender_rate ++# at the decimal point. ++warn ratelimit = 100 / 1h / per_rcpt / strict ++ delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \ ++ $sender_rate_limit }s ++ ++# Keep authenticated users under control ++deny authenticated = * ++ ratelimit = 100 / 1d / strict / $authenticated_id ++ ++# System-wide rate limit ++defer message = Sorry, too busy. Try again later. ++ ratelimit = 10 / 1s / $primary_hostname ++ ++# Restrict incoming rate from each host, with a default ++# set using a macro and special cases looked up in a table. ++defer message = Sender rate exceeds $sender_rate_limit \ ++ messages per $sender_rate_period ++ ratelimit = ${lookup {$sender_host_address} \ ++ cdb {DB/ratelimits.cdb} \ ++ {$value} {RATELIMIT} } ++ ++Warning: If you have a busy server with a lot of ratelimit tests, especially ++with the per_rcpt option, you may suffer from a performance bottleneck caused ++by locking on the ratelimit hints database. Apart from making your ACLs less ++complicated, you can reduce the problem by using a RAM disk for Exim's hints ++directory (usually /var/spool/exim/db/). However this means that Exim will lose ++its hints data after a reboot (including retry hints, the callout cache, and ++ratelimit data). ++ ++ ++42.43 Address verification ++-------------------------- ++ ++Several of the verify conditions described in section 42.25 cause addresses to ++be verified. Section 42.47 discusses the reporting of sender verification ++failures. The verification conditions can be followed by options that modify ++the verification process. The options are separated from the keyword and from ++each other by slashes, and some of them contain parameters. For example: ++ ++verify = sender/callout ++verify = recipient/defer_ok/callout=10s,defer_ok ++ ++The first stage of address verification, which always happens, is to run the ++address through the routers, in "verify mode". Routers can detect the ++difference between verification and routing for delivery, and their actions can ++be varied by a number of generic options such as verify and verify_only (see ++chapter 15). If routing fails, verification fails. The available options are as ++follows: ++ ++ * If the callout option is specified, successful routing to one or more ++ remote hosts is followed by a "callout" to those hosts as an additional ++ check. Callouts and their sub-options are discussed in the next section. ++ ++ * If there is a defer error while doing verification routing, the ACL ++ normally returns "defer". However, if you include defer_ok in the options, ++ the condition is forced to be true instead. Note that this is a main ++ verification option as well as a suboption for callouts. ++ ++ * The no_details option is covered in section 42.47, which discusses the ++ reporting of sender address verification failures. ++ ++ * The success_on_redirect option causes verification always to succeed ++ immediately after a successful redirection. By default, if a redirection ++ generates just one address, that address is also verified. See further ++ discussion in section 42.48. ++ ++After an address verification failure, $acl_verify_message contains the error ++message that is associated with the failure. It can be preserved by coding like ++this: ++ ++warn !verify = sender ++ set acl_m0 = $acl_verify_message ++ ++If you are writing your own custom rejection message or log message when ++denying access, you can use this variable to include information about the ++verification failure. ++ ++In addition, $sender_verify_failure or $recipient_verify_failure (as ++appropriate) contains one of the following words: ++ ++ * qualify: The address was unqualified (no domain), and the message was ++ neither local nor came from an exempted host. ++ ++ * route: Routing failed. ++ ++ * mail: Routing succeeded, and a callout was attempted; rejection occurred at ++ or before the MAIL command (that is, on initial connection, HELO, or MAIL). ++ ++ * recipient: The RCPT command in a callout was rejected. ++ ++ * postmaster: The postmaster check in a callout was rejected. ++ ++The main use of these variables is expected to be to distinguish between ++rejections of MAIL and rejections of RCPT in callouts. ++ ++ ++42.44 Callout verification ++-------------------------- ++ ++For non-local addresses, routing verifies the domain, but is unable to do any ++checking of the local part. There are situations where some means of verifying ++the local part is desirable. One way this can be done is to make an SMTP ++callback to a delivery host for the sender address or a callforward to a ++subsequent host for a recipient address, to see if the host accepts the ++address. We use the term callout to cover both cases. Note that for a sender ++address, the callback is not to the client host that is trying to deliver the ++message, but to one of the hosts that accepts incoming mail for the sender's ++domain. ++ ++Exim does not do callouts by default. If you want them to happen, you must ++request them by setting appropriate options on the verify condition, as ++described below. This facility should be used with care, because it can add a ++lot of resource usage to the cost of verifying an address. However, Exim does ++cache the results of callouts, which helps to reduce the cost. Details of ++caching are in section 42.46. ++ ++Recipient callouts are usually used only between hosts that are controlled by ++the same administration. For example, a corporate gateway host could use ++callouts to check for valid recipients on an internal mailserver. A successful ++callout does not guarantee that a real delivery to the address would succeed; ++on the other hand, a failing callout does guarantee that a delivery would fail. ++ ++If the callout option is present on a condition that verifies an address, a ++second stage of verification occurs if the address is successfully routed to ++one or more remote hosts. The usual case is routing by a dnslookup or a ++manualroute router, where the router specifies the hosts. However, if a router ++that does not set up hosts routes to an smtp transport with a hosts setting, ++the transport's hosts are used. If an smtp transport has hosts_override set, ++its hosts are always used, whether or not the router supplies a host list. ++ ++The port that is used is taken from the transport, if it is specified and is a ++remote transport. (For routers that do verification only, no transport need be ++specified.) Otherwise, the default SMTP port is used. If a remote transport ++specifies an outgoing interface, this is used; otherwise the interface is not ++specified. Likewise, the text that is used for the HELO command is taken from ++the transport's helo_data option; if there is no transport, the value of ++$smtp_active_hostname is used. ++ ++For a sender callout check, Exim makes SMTP connections to the remote hosts, to ++test whether a bounce message could be delivered to the sender address. The ++following SMTP commands are sent: ++ ++HELO <local host name> ++MAIL FROM:<> ++RCPT TO:<the address to be tested> ++QUIT ++ ++LHLO is used instead of HELO if the transport's protocol option is set to ++"lmtp". ++ ++The callout may use EHLO, AUTH and/or STARTTLS given appropriate option ++settings. ++ ++A recipient callout check is similar. By default, it also uses an empty address ++for the sender. This default is chosen because most hosts do not make use of ++the sender address when verifying a recipient. Using the same address means ++that a single cache entry can be used for each recipient. Some sites, however, ++do make use of the sender address when verifying. These are catered for by the ++use_sender and use_postmaster options, described in the next section. ++ ++If the response to the RCPT command is a 2xx code, the verification succeeds. ++If it is 5xx, the verification fails. For any other condition, Exim tries the ++next host, if any. If there is a problem with all the remote hosts, the ACL ++yields "defer", unless the defer_ok parameter of the callout option is given, ++in which case the condition is forced to succeed. ++ ++A callout may take a little time. For this reason, Exim normally flushes SMTP ++output before performing a callout in an ACL, to avoid unexpected timeouts in ++clients when the SMTP PIPELINING extension is in use. The flushing can be ++disabled by using a control modifier to set no_callout_flush. ++ ++ ++42.45 Additional parameters for callouts ++---------------------------------------- ++ ++The callout option can be followed by an equals sign and a number of optional ++parameters, separated by commas. For example: ++ ++verify = recipient/callout=10s,defer_ok ++ ++The old syntax, which had callout_defer_ok and check_postmaster as separate ++verify options, is retained for backwards compatibility, but is now deprecated. ++The additional parameters for callout are as follows: ++ ++<a time interval> ++ ++ This specifies the timeout that applies for the callout attempt to each ++ host. For example: ++ ++ verify = sender/callout=5s ++ ++ The default is 30 seconds. The timeout is used for each response from the ++ remote host. It is also used for the initial connection, unless overridden ++ by the connect parameter. ++ ++connect = <time interval> ++ ++ This parameter makes it possible to set a different (usually smaller) ++ timeout for making the SMTP connection. For example: ++ ++ verify = sender/callout=5s,connect=1s ++ ++ If not specified, this timeout defaults to the general timeout value. ++ ++defer_ok ++ ++ When this parameter is present, failure to contact any host, or any other ++ kind of temporary error, is treated as success by the ACL. However, the ++ cache is not updated in this circumstance. ++ ++fullpostmaster ++ ++ This operates like the postmaster option (see below), but if the check for ++ postmaster@domain fails, it tries just postmaster, without a domain, in ++ accordance with the specification in RFC 2821. The RFC states that the ++ unqualified address postmaster should be accepted. ++ ++mailfrom = <email address> ++ ++ When verifying addresses in header lines using the header_sender ++ verification option, Exim behaves by default as if the addresses are ++ envelope sender addresses from a message. Callout verification therefore ++ tests to see whether a bounce message could be delivered, by using an empty ++ address in the MAIL command. However, it is arguable that these addresses ++ might never be used as envelope senders, and could therefore justifiably ++ reject bounce messages (empty senders). The mailfrom callout parameter ++ allows you to specify what address to use in the MAIL command. For example: ++ ++ require verify = header_sender/callout=mailfrom=abcd@x.y.z ++ ++ This parameter is available only for the header_sender verification option. ++ ++maxwait = <time interval> ++ ++ This parameter sets an overall timeout for performing a callout ++ verification. For example: ++ ++ verify = sender/callout=5s,maxwait=30s ++ ++ This timeout defaults to four times the callout timeout for individual SMTP ++ commands. The overall timeout applies when there is more than one host that ++ can be tried. The timeout is checked before trying the next host. This ++ prevents very long delays if there are a large number of hosts and all are ++ timing out (for example, when network connections are timing out). ++ ++no_cache ++ ++ When this parameter is given, the callout cache is neither read nor ++ updated. ++ ++postmaster ++ ++ When this parameter is set, a successful callout check is followed by a ++ similar check for the local part postmaster at the same domain. If this ++ address is rejected, the callout fails (but see fullpostmaster above). The ++ result of the postmaster check is recorded in a cache record; if it is a ++ failure, this is used to fail subsequent callouts for the domain without a ++ connection being made, until the cache record expires. ++ ++postmaster_mailfrom = <email address> ++ ++ The postmaster check uses an empty sender in the MAIL command by default. ++ You can use this parameter to do a postmaster check using a different ++ address. For example: ++ ++ require verify = sender/callout=postmaster_mailfrom=abc@x.y.z ++ ++ If both postmaster and postmaster_mailfrom are present, the rightmost one ++ overrides. The postmaster parameter is equivalent to this example: ++ ++ require verify = sender/callout=postmaster_mailfrom= ++ ++ Warning: The caching arrangements for postmaster checking do not take ++ account of the sender address. It is assumed that either the empty address ++ or a fixed non-empty address will be used. All that Exim remembers is that ++ the postmaster check for the domain succeeded or failed. ++ ++random ++ ++ When this parameter is set, before doing the normal callout check, Exim ++ does a check for a "random" local part at the same domain. The local part ++ is not really random - it is defined by the expansion of the option ++ callout_random_local_part, which defaults to ++ ++ $primary_hostname-$tod_epoch-testing ++ ++ The idea here is to try to determine whether the remote host accepts all ++ local parts without checking. If it does, there is no point in doing ++ callouts for specific local parts. If the "random" check succeeds, the ++ result is saved in a cache record, and used to force the current and ++ subsequent callout checks to succeed without a connection being made, until ++ the cache record expires. ++ ++use_postmaster ++ ++ This parameter applies to recipient callouts only. For example: ++ ++ deny !verify = recipient/callout=use_postmaster ++ ++ It causes a non-empty postmaster address to be used in the MAIL command ++ when performing the callout for the recipient, and also for a "random" ++ check if that is configured. The local part of the address is "postmaster" ++ and the domain is the contents of $qualify_domain. ++ ++use_sender ++ ++ This option applies to recipient callouts only. For example: ++ ++ require verify = recipient/callout=use_sender ++ ++ It causes the message's actual sender address to be used in the MAIL ++ command when performing the callout, instead of an empty address. There is ++ no need to use this option unless you know that the called hosts make use ++ of the sender when checking recipients. If used indiscriminately, it ++ reduces the usefulness of callout caching. ++ ++If you use any of the parameters that set a non-empty sender for the MAIL ++command (mailfrom, postmaster_mailfrom, use_postmaster, or use_sender), you ++should think about possible loops. Recipient checking is usually done between ++two hosts that are under the same management, and the host that receives the ++callouts is not normally configured to do callouts itself. Therefore, it is ++normally safe to use use_postmaster or use_sender in these circumstances. ++ ++However, if you use a non-empty sender address for a callout to an arbitrary ++host, there is the likelihood that the remote host will itself initiate a ++callout check back to your host. As it is checking what appears to be a message ++sender, it is likely to use an empty address in MAIL, thus avoiding a callout ++loop. However, to be on the safe side it would be best to set up your own ACLs ++so that they do not do sender verification checks when the recipient is the ++address you use for header sender or postmaster callout checking. ++ ++Another issue to think about when using non-empty senders for callouts is ++caching. When you set mailfrom or use_sender, the cache record is keyed by the ++sender/recipient combination; thus, for any given recipient, many more actual ++callouts are performed than when an empty sender or postmaster is used. ++ ++ ++42.46 Callout caching ++--------------------- ++ ++Exim caches the results of callouts in order to reduce the amount of resources ++used, unless you specify the no_cache parameter with the callout option. A ++hints database called "callout" is used for the cache. Two different record ++types are used: one records the result of a callout check for a specific ++address, and the other records information that applies to the entire domain ++(for example, that it accepts the local part postmaster). ++ ++When an original callout fails, a detailed SMTP error message is given about ++the failure. However, for subsequent failures use the cache data, this message ++is not available. ++ ++The expiry times for negative and positive address cache records are ++independent, and can be set by the global options callout_negative_expire ++(default 2h) and callout_positive_expire (default 24h), respectively. ++ ++If a host gives a negative response to an SMTP connection, or rejects any ++commands up to and including ++ ++MAIL FROM:<> ++ ++(but not including the MAIL command with a non-empty address), any callout ++attempt is bound to fail. Exim remembers such failures in a domain cache ++record, which it uses to fail callouts for the domain without making new ++connections, until the domain record times out. There are two separate expiry ++times for domain cache records: callout_domain_negative_expire (default 3h) and ++callout_domain_positive_expire (default 7d). ++ ++Domain records expire when the negative expiry time is reached if callouts ++cannot be made for the domain, or if the postmaster check failed. Otherwise, ++they expire when the positive expiry time is reached. This ensures that, for ++example, a host that stops accepting "random" local parts will eventually be ++noticed. ++ ++The callout caching mechanism is based on the domain of the address that is ++being tested. If the domain routes to several hosts, it is assumed that their ++behaviour will be the same. ++ ++ ++42.47 Sender address verification reporting ++------------------------------------------- ++ ++See section 42.43 for a general discussion of verification. When sender ++verification fails in an ACL, the details of the failure are given as ++additional output lines before the 550 response to the relevant SMTP command ++(RCPT or DATA). For example, if sender callout is in use, you might see: ++ ++MAIL FROM:<xyz@abc.example> ++250 OK ++RCPT TO:<pqr@def.example> ++550-Verification failed for <xyz@abc.example> ++550-Called: 192.168.34.43 ++550-Sent: RCPT TO:<xyz@abc.example> ++550-Response: 550 Unknown local part xyz in <xyz@abc.example> ++550 Sender verification failed ++ ++If more than one RCPT command fails in the same way, the details are given only ++for the first of them. However, some administrators do not want to send out ++this much information. You can suppress the details by adding "/no_details" to ++the ACL statement that requests sender verification. For example: ++ ++verify = sender/no_details ++ ++ ++42.48 Redirection while verifying ++--------------------------------- ++ ++A dilemma arises when a local address is redirected by aliasing or forwarding ++during verification: should the generated addresses themselves be verified, or ++should the successful expansion of the original address be enough to verify it? ++By default, Exim takes the following pragmatic approach: ++ ++ * When an incoming address is redirected to just one child address, ++ verification continues with the child address, and if that fails to verify, ++ the original verification also fails. ++ ++ * When an incoming address is redirected to more than one child address, ++ verification does not continue. A success result is returned. ++ ++This seems the most reasonable behaviour for the common use of aliasing as a ++way of redirecting different local parts to the same mailbox. It means, for ++example, that a pair of alias entries of the form ++ ++A.Wol: aw123 ++aw123: :fail: Gone away, no forwarding address ++ ++work as expected, with both local parts causing verification failure. When a ++redirection generates more than one address, the behaviour is more like a ++mailing list, where the existence of the alias itself is sufficient for ++verification to succeed. ++ ++It is possible, however, to change the default behaviour so that all successful ++redirections count as successful verifications, however many new addresses are ++generated. This is specified by the success_on_redirect verification option. ++For example: ++ ++require verify = recipient/success_on_redirect/callout=10s ++ ++In this example, verification succeeds if a router generates a new address, and ++the callout does not occur, because no address was routed to a remote host. ++ ++When verification is being tested via the -bv option, the treatment of ++redirections is as just described, unless the -v or any debugging option is ++also specified. In that case, full verification is done for every generated ++address and a report is output for each of them. ++ ++ ++42.49 Client SMTP authorization (CSA) ++------------------------------------- ++ ++Client SMTP Authorization is a system that allows a site to advertise which ++machines are and are not permitted to send email. This is done by placing ++special SRV records in the DNS; these are looked up using the client's HELO ++domain. At the time of writing, CSA is still an Internet Draft. Client SMTP ++Authorization checks in Exim are performed by the ACL condition: ++ ++verify = csa ++ ++This fails if the client is not authorized. If there is a DNS problem, or if no ++valid CSA SRV record is found, or if the client is authorized, the condition ++succeeds. These three cases can be distinguished using the expansion variable ++$csa_status, which can take one of the values "fail", "defer", "unknown", or ++"ok". The condition does not itself defer because that would be likely to cause ++problems for legitimate email. ++ ++The error messages produced by the CSA code include slightly more detail. If ++$csa_status is "defer", this may be because of problems looking up the CSA SRV ++record, or problems looking up the CSA target address record. There are four ++reasons for $csa_status being "fail": ++ ++ * The client's host name is explicitly not authorized. ++ ++ * The client's IP address does not match any of the CSA target IP addresses. ++ ++ * The client's host name is authorized but it has no valid target IP ++ addresses (for example, the target's addresses are IPv6 and the client is ++ using IPv4). ++ ++ * The client's host name has no CSA SRV record but a parent domain has ++ asserted that all subdomains must be explicitly authorized. ++ ++The csa verification condition can take an argument which is the domain to use ++for the DNS query. The default is: ++ ++verify = csa/$sender_helo_name ++ ++This implementation includes an extension to CSA. If the query domain is an ++address literal such as [192.0.2.95], or if it is a bare IP address, Exim ++searches for CSA SRV records in the reverse DNS as if the HELO domain was (for ++example) 95.2.0.192.in-addr.arpa. Therefore it is meaningful to say: ++ ++verify = csa/$sender_host_address ++ ++In fact, this is the check that Exim performs if the client does not say HELO. ++This extension can be turned off by setting the main configuration option ++dns_csa_use_reverse to be false. ++ ++If a CSA SRV record is not found for the domain itself, a search is performed ++through its parent domains for a record which might be making assertions about ++subdomains. The maximum depth of this search is limited using the main ++configuration option dns_csa_search_limit, which is 5 by default. Exim does not ++look for CSA SRV records in a top level domain, so the default settings handle ++HELO domains as long as seven (hostname.five.four.three.two.one.com). This ++encompasses the vast majority of legitimate HELO domains. ++ ++The dnsdb lookup also has support for CSA. Although dnsdb also supports direct ++SRV lookups, this is not sufficient because of the extra parent domain search ++behaviour of CSA, and (as with PTR lookups) dnsdb also turns IP addresses into ++lookups in the reverse DNS space. The result of a successful lookup such as: ++ ++${lookup dnsdb {csa=$sender_helo_name}} ++ ++has two space-separated fields: an authorization code and a target host name. ++The authorization code can be "Y" for yes, "N" for no, "X" for explicit ++authorization required but absent, or "?" for unknown. ++ ++ ++42.50 Bounce address tag validation ++----------------------------------- ++ ++Bounce address tag validation (BATV) is a scheme whereby the envelope senders ++of outgoing messages have a cryptographic, timestamped "tag" added to them. ++Genuine incoming bounce messages should therefore always be addressed to ++recipients that have a valid tag. This scheme is a way of detecting unwanted ++bounce messages caused by sender address forgeries (often called "collateral ++spam"), because the recipients of such messages do not include valid tags. ++ ++There are two expansion items to help with the implementation of the BATV ++"prvs" (private signature) scheme in an Exim configuration. This scheme signs ++the original envelope sender address by using a simple key to add a hash of the ++address and some time-based randomizing information. The prvs expansion item ++creates a signed address, and the prvscheck expansion item checks one. The ++syntax of these expansion items is described in section 11.5. ++ ++As an example, suppose the secret per-address keys are stored in an MySQL ++database. A query to look up the key for an address could be defined as a macro ++like this: ++ ++PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \ ++ WHERE sender='${quote_mysql:$prvscheck_address}'\ ++ }{$value}} ++ ++Suppose also that the senders who make use of BATV are defined by an address ++list called batv_senders. Then, in the ACL for RCPT commands, you could use ++this: ++ ++# Bounces: drop unsigned addresses for BATV senders ++deny message = This address does not send an unsigned reverse path ++ senders = : ++ recipients = +batv_senders ++ ++# Bounces: In case of prvs-signed address, check signature. ++deny message = Invalid reverse path signature. ++ senders = : ++ condition = ${prvscheck {$local_part@$domain}\ ++ {PRVSCHECK_SQL}{1}} ++ !condition = $prvscheck_result ++ ++The first statement rejects recipients for bounce messages that are addressed ++to plain BATV sender addresses, because it is known that BATV senders do not ++send out messages with plain sender addresses. The second statement rejects ++recipients that are prvs-signed, but with invalid signatures (either because ++the key is wrong, or the signature has timed out). ++ ++A non-prvs-signed address is not rejected by the second statement, because the ++prvscheck expansion yields an empty string if its first argument is not a ++prvs-signed address, thus causing the condition condition to be false. If the ++first argument is a syntactically valid prvs-signed address, the yield is the ++third string (in this case "1"), whether or not the cryptographic and timeout ++checks succeed. The $prvscheck_result variable contains the result of the ++checks (empty for failure, "1" for success). ++ ++There is one more issue you must consider when implementing prvs-signing: you ++have to ensure that the routers accept prvs-signed addresses and deliver them ++correctly. The easiest way to handle this is to use a redirect router to remove ++the signature with a configuration along these lines: ++ ++batv_redirect: ++ driver = redirect ++ data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}} ++ ++This works because, if the third argument of prvscheck is empty, the result of ++the expansion of a prvs-signed address is the decoded value of the original ++address. This router should probably be the first of your routers that handles ++local addresses. ++ ++To create BATV-signed addresses in the first place, a transport of this form ++can be used: ++ ++external_smtp_batv: ++ driver = smtp ++ return_path = ${prvs {$return_path} \ ++ {${lookup mysql{SELECT \ ++ secret FROM batv_prvs WHERE \ ++ sender='${quote_mysql:$sender_address}'} \ ++ {$value}fail}}} ++ ++If no key can be found for the existing return path, no signing takes place. ++ ++ ++42.51 Using an ACL to control relaying ++-------------------------------------- ++ ++An MTA is said to relay a message if it receives it from some host and delivers ++it directly to another host as a result of a remote address contained within ++it. Redirecting a local address via an alias or forward file and then passing ++the message on to another host is not relaying, but a redirection as a result ++of the "percent hack" is. ++ ++Two kinds of relaying exist, which are termed "incoming" and "outgoing". A host ++which is acting as a gateway or an MX backup is concerned with incoming ++relaying from arbitrary hosts to a specific set of domains. On the other hand, ++a host which is acting as a smart host for a number of clients is concerned ++with outgoing relaying from those clients to the Internet at large. Often the ++same host is fulfilling both functions, but in principle these two kinds of ++relaying are entirely independent. What is not wanted is the transmission of ++mail from arbitrary remote hosts through your system to arbitrary domains. ++ ++You can implement relay control by means of suitable statements in the ACL that ++runs for each RCPT command. For convenience, it is often easiest to use Exim's ++named list facility to define the domains and hosts involved. For example, ++suppose you want to do the following: ++ ++ * Deliver a number of domains to mailboxes on the local host (or process them ++ locally in some other way). Let's say these are my.dom1.example and ++ my.dom2.example. ++ ++ * Relay mail for a number of other domains for which you are the secondary ++ MX. These might be friend1.example and friend2.example. ++ ++ * Relay mail from the hosts on your local LAN, to whatever domains are ++ involved. Suppose your LAN is 192.168.45.0/24. ++ ++In the main part of the configuration, you put the following definitions: ++ ++domainlist local_domains = my.dom1.example : my.dom2.example ++domainlist relay_to_domains = friend1.example : friend2.example ++hostlist relay_from_hosts = 192.168.45.0/24 ++ ++Now you can use these definitions in the ACL that is run for every RCPT ++command: ++ ++acl_check_rcpt: ++ accept domains = +local_domains : +relay_to_domains ++ accept hosts = +relay_from_hosts ++ ++The first statement accepts any RCPT command that contains an address in the ++local or relay domains. For any other domain, control passes to the second ++statement, which accepts the command only if it comes from one of the relay ++hosts. In practice, you will probably want to make your ACL more sophisticated ++than this, for example, by including sender and recipient verification. The ++default configuration includes a more comprehensive example, which is described ++in chapter 7. ++ ++ ++42.52 Checking a relay configuration ++------------------------------------ ++ ++You can check the relay characteristics of your configuration in the same way ++that you can test any ACL behaviour for an incoming SMTP connection, by using ++the -bh option to run a fake SMTP session with which you interact. ++ ++For specifically testing for unwanted relaying, the host ++relay-test.mail-abuse.org provides a useful service. If you telnet to this host ++from the host on which Exim is running, using the normal telnet port, you will ++see a normal telnet connection message and then quite a long delay. Be patient. ++The remote host is making an SMTP connection back to your host, and trying a ++number of common probes to test for open relay vulnerability. The results of ++the tests will eventually appear on your terminal. ++ ++ ++ ++=============================================================================== ++43. CONTENT SCANNING AT ACL TIME ++ ++The extension of Exim to include content scanning at ACL time, formerly known ++as "exiscan", was originally implemented as a patch by Tom Kistner. The code ++was integrated into the main source for Exim release 4.50, and Tom continues to ++maintain it. Most of the wording of this chapter is taken from Tom's ++specification. ++ ++It is also possible to scan the content of messages at other times. The ++local_scan() function (see chapter 44) allows for content scanning after all ++the ACLs have run. A transport filter can be used to scan messages at delivery ++time (see the transport_filter option, described in chapter 24). ++ ++If you want to include the ACL-time content-scanning features when you compile ++Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your Local/ ++Makefile. When you do that, the Exim binary is built with: ++ ++ * Two additional ACLs (acl_smtp_mime and acl_not_smtp_mime) that are run for ++ all MIME parts for SMTP and non-SMTP messages, respectively. ++ ++ * Additional ACL conditions and modifiers: decode, malware, mime_regex, regex ++ , and spam. These can be used in the ACL that is run at the end of message ++ reception (the acl_smtp_data ACL). ++ ++ * An additional control feature ("no_mbox_unspool") that saves spooled copies ++ of messages, or parts of messages, for debugging purposes. ++ ++ * Additional expansion variables that are set in the new ACL and by the new ++ conditions. ++ ++ * Two new main configuration options: av_scanner and spamd_address. ++ ++There is another content-scanning configuration option for Local/Makefile, ++called WITH_OLD_DEMIME. If this is set, the old, deprecated demime ACL ++condition is compiled, in addition to all the other content-scanning features. ++ ++Content-scanning is continually evolving, and new features are still being ++added. While such features are still unstable and liable to incompatible ++changes, they are made available in Exim by setting options whose names begin ++EXPERIMENTAL_ in Local/Makefile. Such features are not documented in this ++manual. You can find out about them by reading the file called doc/ ++experimental.txt. ++ ++All the content-scanning facilities work on a MBOX copy of the message that is ++temporarily created in a file called: ++ ++<spool_directory>/scan/<message_id>/<message_id>.eml ++ ++The .eml extension is a friendly hint to virus scanners that they can expect an ++MBOX-like structure inside that file. The file is created when the first ++content scanning facility is called. Subsequent calls to content scanning ++conditions open the same file again. The directory is recursively removed when ++the acl_smtp_data ACL has finished running, unless ++ ++control = no_mbox_unspool ++ ++has been encountered. When the MIME ACL decodes files, they are put into the ++same directory by default. ++ ++ ++43.1 Scanning for viruses ++------------------------- ++ ++The malware ACL condition lets you connect virus scanner software to Exim. It ++supports a "generic" interface to scanners called via the shell, and ++specialized interfaces for "daemon" type virus scanners, which are resident in ++memory and thus are much faster. ++ ++You can set the av_scanner option in first part of the Exim configuration file ++to specify which scanner to use, together with any additional options that are ++needed. The basic syntax is as follows: ++ ++av_scanner = <scanner-type>:<option1>:<option2>:[...] ++ ++If you do not set av_scanner, it defaults to ++ ++av_scanner = sophie:/var/run/sophie ++ ++If the value of av_scanner starts with a dollar character, it is expanded ++before use. The following scanner types are supported in this release: ++ ++aveserver ++ ++ This is the scanner daemon of Kaspersky Version 5. You can get a trial ++ version at http://www.kaspersky.com. This scanner type takes one option, ++ which is the path to the daemon's UNIX socket. The default is shown in this ++ example: ++ ++ av_scanner = aveserver:/var/run/aveserver ++ ++clamd ++ ++ This daemon-type scanner is GPL and free. You can get it at http:// ++ www.clamav.net/. Some older versions of clamd do not seem to unpack MIME ++ containers, so it used to be recommended to unpack MIME attachments in the ++ MIME ACL. This no longer believed to be necessary. One option is required: ++ either the path and name of a UNIX socket file, or a hostname or IP number, ++ and a port, separated by space, as in the second of these examples: ++ ++ av_scanner = clamd:/opt/clamd/socket ++ av_scanner = clamd:192.0.2.3 1234 ++ av_scanner = clamd:192.0.2.3 1234:local ++ ++ If the value of av_scanner points to a UNIX socket file or contains the ++ local keyword, then the ClamAV interface will pass a filename containing ++ the data to be scanned, which will should normally result in less I/O ++ happening and be more efficient. Normally in the TCP case, the data is ++ streamed to ClamAV as Exim does not assume that there is a common ++ filesystem with the remote host. There is an option WITH_OLD_CLAMAV_STREAM ++ in src/EDITME available, should you be running a version of ClamAV prior to ++ 0.95. If the option is unset, the default is /tmp/clamd. Thanks to David ++ Saez for contributing the code for this scanner. ++ ++cmdline ++ ++ This is the keyword for the generic command line scanner interface. It can ++ be used to attach virus scanners that are invoked from the shell. This ++ scanner type takes 3 mandatory options: ++ ++ 1. The full path and name of the scanner binary, with all command line ++ options, and a placeholder ("%s") for the directory to scan. ++ ++ 2. A regular expression to match against the STDOUT and STDERR output of ++ the virus scanner. If the expression matches, a virus was found. You ++ must make absolutely sure that this expression matches on "virus ++ found". This is called the "trigger" expression. ++ ++ 3. Another regular expression, containing exactly one pair of parentheses, ++ to match the name of the virus found in the scanners output. This is ++ called the "name" expression. ++ ++ For example, Sophos Sweep reports a virus on a line like this: ++ ++ Virus 'W32/Magistr-B' found in file ./those.bat ++ ++ For the trigger expression, we can match the phrase "found in file". For ++ the name expression, we want to extract the W32/Magistr-B string, so we can ++ match for the single quotes left and right of it. Altogether, this makes ++ the configuration setting: ++ ++ av_scanner = cmdline:\ ++ /path/to/sweep -ss -all -rec -archive %s:\ ++ found in file:'(.+)' ++ ++drweb ++ ++ The DrWeb daemon scanner (http://www.sald.com/) interface takes one ++ argument, either a full path to a UNIX socket, or an IP address and port ++ separated by white space, as in these examples: ++ ++ av_scanner = drweb:/var/run/drwebd.sock ++ av_scanner = drweb:192.168.2.20 31337 ++ ++ If you omit the argument, the default path /usr/local/drweb/run/drwebd.sock ++ is used. Thanks to Alex Miller for contributing the code for this scanner. ++ ++fsecure ++ ++ The F-Secure daemon scanner (http://www.f-secure.com) takes one argument ++ which is the path to a UNIX socket. For example: ++ ++ av_scanner = fsecure:/path/to/.fsav ++ ++ If no argument is given, the default is /var/run/.fsav. Thanks to Johan ++ Thelmen for contributing the code for this scanner. ++ ++kavdaemon ++ ++ This is the scanner daemon of Kaspersky Version 4. This version of the ++ Kaspersky scanner is outdated. Please upgrade (see aveserver above). This ++ scanner type takes one option, which is the path to the daemon's UNIX ++ socket. For example: ++ ++ av_scanner = kavdaemon:/opt/AVP/AvpCtl ++ ++ The default path is /var/run/AvpCtl. ++ ++mksd ++ ++ This is a daemon type scanner that is aimed mainly at Polish users, though ++ some parts of documentation are now available in English. You can get it at ++ http://linux.mks.com.pl/. The only option for this scanner type is the ++ maximum number of processes used simultaneously to scan the attachments, ++ provided that the demime facility is employed and also provided that mksd ++ has been run with at least the same number of child processes. For example: ++ ++ av_scanner = mksd:2 ++ ++ You can safely omit this option (the default value is 1). ++ ++sophie ++ ++ Sophie is a daemon that uses Sophos' libsavi library to scan for viruses. ++ You can get Sophie at http://www.clanfield.info/sophie/. The only option ++ for this scanner type is the path to the UNIX socket that Sophie uses for ++ client communication. For example: ++ ++ av_scanner = sophie:/tmp/sophie ++ ++ The default path is /var/run/sophie, so if you are using this, you can omit ++ the option. ++ ++When av_scanner is correctly set, you can use the malware condition in the DATA ++ACL. Note: You cannot use the malware condition in the MIME ACL. ++ ++The av_scanner option is expanded each time malware is called. This makes it ++possible to use different scanners. See further below for an example. The ++malware condition caches its results, so when you use it multiple times for the ++same message, the actual scanning process is only carried out once. However, ++using expandable items in av_scanner disables this caching, in which case each ++use of the malware condition causes a new scan of the message. ++ ++The malware condition takes a right-hand argument that is expanded before use. ++It can then be one of ++ ++ * "true", "*", or "1", in which case the message is scanned for viruses. The ++ condition succeeds if a virus was found, and fail otherwise. This is the ++ recommended usage. ++ ++ * "false" or "0" or an empty string, in which case no scanning is done and ++ the condition fails immediately. ++ ++ * A regular expression, in which case the message is scanned for viruses. The ++ condition succeeds if a virus is found and its name matches the regular ++ expression. This allows you to take special actions on certain types of ++ virus. ++ ++You can append "/defer_ok" to the malware condition to accept messages even if ++there is a problem with the virus scanner. Otherwise, such a problem causes the ++ACL to defer. ++ ++When a virus is found, the condition sets up an expansion variable called ++$malware_name that contains the name of the virus. You can use it in a message ++modifier that specifies the error returned to the sender, and/or in logging ++data. ++ ++If your virus scanner cannot unpack MIME and TNEF containers itself, you should ++use the demime condition (see section 43.6) before the malware condition. ++ ++Beware the interaction of Exim's message_size_limit with any size limits ++imposed by your anti-virus scanner. ++ ++Here is a very simple scanning example: ++ ++deny message = This message contains malware ($malware_name) ++ demime = * ++ malware = * ++ ++The next example accepts messages when there is a problem with the scanner: ++ ++deny message = This message contains malware ($malware_name) ++ demime = * ++ malware = */defer_ok ++ ++The next example shows how to use an ACL variable to scan with both sophie and ++aveserver. It assumes you have set: ++ ++av_scanner = $acl_m0 ++ ++in the main Exim configuration. ++ ++deny message = This message contains malware ($malware_name) ++ set acl_m0 = sophie ++ malware = * ++ ++deny message = This message contains malware ($malware_name) ++ set acl_m0 = aveserver ++ malware = * ++ ++ ++43.2 Scanning with SpamAssassin ++------------------------------- ++ ++The spam ACL condition calls SpamAssassin's spamd daemon to get a spam score ++and a report for the message. You can get SpamAssassin at http:// ++www.spamassassin.org, or, if you have a working Perl installation, you can use ++CPAN by running: ++ ++perl -MCPAN -e 'install Mail::SpamAssassin' ++ ++SpamAssassin has its own set of configuration files. Please review its ++documentation to see how you can tweak it. The default installation should work ++nicely, however. ++ ++After having installed and configured SpamAssassin, start the spamd daemon. By ++default, it listens on 127.0.0.1, TCP port 783. If you use another host or port ++for spamd, you must set the spamd_address option in the global part of the Exim ++configuration as follows (example): ++ ++spamd_address = 192.168.99.45 387 ++ ++You do not need to set this option if you use the default. As of version 2.60, ++spamd also supports communication over UNIX sockets. If you want to use these, ++supply spamd_address with an absolute file name instead of a address/port pair: ++ ++spamd_address = /var/run/spamd_socket ++ ++You can have multiple spamd servers to improve scalability. These can reside on ++other hardware reachable over the network. To specify multiple spamd servers, ++put multiple address/port pairs in the spamd_address option, separated with ++colons: ++ ++spamd_address = 192.168.2.10 783 : \ ++ 192.168.2.11 783 : \ ++ 192.168.2.12 783 ++ ++Up to 32 spamd servers are supported. The servers are queried in a random ++fashion. When a server fails to respond to the connection attempt, all other ++servers are tried until one succeeds. If no server responds, the spam condition ++defers. ++ ++Warning: It is not possible to use the UNIX socket connection method with ++multiple spamd servers. ++ ++The spamd_address variable is expanded before use if it starts with a dollar ++sign. In this case, the expansion may return a string that is used as the list ++so that multiple spamd servers can be the result of an expansion. ++ ++ ++43.3 Calling SpamAssassin from an Exim ACL ++------------------------------------------ ++ ++Here is a simple example of the use of the spam condition in a DATA ACL: ++ ++deny message = This message was classified as SPAM ++ spam = joe ++ ++The right-hand side of the spam condition specifies a name. This is relevant if ++you have set up multiple SpamAssassin profiles. If you do not want to scan ++using a specific profile, but rather use the SpamAssassin system-wide default ++profile, you can scan for an unknown name, or simply use "nobody". However, you ++must put something on the right-hand side. ++ ++The name allows you to use per-domain or per-user antispam profiles in ++principle, but this is not straightforward in practice, because a message may ++have multiple recipients, not necessarily all in the same domain. Because the ++spam condition has to be called from a DATA ACL in order to be able to read the ++contents of the message, the variables $local_part and $domain are not set. ++ ++The right-hand side of the spam condition is expanded before being used, so you ++can put lookups or conditions there. When the right-hand side evaluates to "0" ++or "false", no scanning is done and the condition fails immediately. ++ ++Scanning with SpamAssassin uses a lot of resources. If you scan every message, ++large ones may cause significant performance degradation. As most spam messages ++are quite small, it is recommended that you do not scan the big ones. For ++example: ++ ++deny message = This message was classified as SPAM ++ condition = ${if < {$message_size}{10K}} ++ spam = nobody ++ ++The spam condition returns true if the threshold specified in the user's ++SpamAssassin profile has been matched or exceeded. If you want to use the spam ++condition for its side effects (see the variables below), you can make it ++always return "true" by appending ":true" to the username. ++ ++When the spam condition is run, it sets up a number of expansion variables. ++These variables are saved with the received message, thus they are available ++for use at delivery time. ++ ++$spam_score ++ ++ The spam score of the message, for example "3.4" or "30.5". This is useful ++ for inclusion in log or reject messages. ++ ++$spam_score_int ++ ++ The spam score of the message, multiplied by ten, as an integer value. For ++ example "34" or "305". It may appear to disagree with $spam_score because ++ $spam_score is rounded and $spam_score_int is truncated. The integer value ++ is useful for numeric comparisons in conditions. ++ ++$spam_bar ++ ++ A string consisting of a number of "+" or "-" characters, representing the ++ integer part of the spam score value. A spam score of 4.4 would have a ++ $spam_bar value of "++++". This is useful for inclusion in warning headers, ++ since MUAs can match on such strings. ++ ++$spam_report ++ ++ A multiline text table, containing the full SpamAssassin report for the ++ message. Useful for inclusion in headers or reject messages. ++ ++The spam condition caches its results unless expansion in spamd_address was ++used. If you call it again with the same user name, it does not scan again, but ++rather returns the same values as before. ++ ++The spam condition returns DEFER if there is any error while running the ++message through SpamAssassin or if the expansion of spamd_address failed. If ++you want to treat DEFER as FAIL (to pass on to the next ACL statement block), ++append "/defer_ok" to the right-hand side of the spam condition, like this: ++ ++deny message = This message was classified as SPAM ++ spam = joe/defer_ok ++ ++This causes messages to be accepted even if there is a problem with spamd. ++ ++Here is a longer, commented example of the use of the spam condition: ++ ++# put headers in all messages (no matter if spam or not) ++warn spam = nobody:true ++ add_header = X-Spam-Score: $spam_score ($spam_bar) ++ add_header = X-Spam-Report: $spam_report ++ ++# add second subject line with *SPAM* marker when message ++# is over threshold ++warn spam = nobody ++ add_header = Subject: *SPAM* $h_Subject: ++ ++# reject spam at high scores (> 12) ++deny message = This message scored $spam_score spam points. ++ spam = nobody:true ++ condition = ${if >{$spam_score_int}{120}{1}{0}} ++ ++ ++43.4 Scanning MIME parts ++------------------------ ++ ++The acl_smtp_mime global option specifies an ACL that is called once for each ++MIME part of an SMTP message, including multipart types, in the sequence of ++their position in the message. Similarly, the acl_not_smtp_mime option ++specifies an ACL that is used for the MIME parts of non-SMTP messages. These ++options may both refer to the same ACL if you want the same processing in both ++cases. ++ ++These ACLs are called (possibly many times) just before the acl_smtp_data ACL ++in the case of an SMTP message, or just before the acl_not_smtp ACL in the case ++of a non-SMTP message. However, a MIME ACL is called only if the message ++contains a Content-Type: header line. When a call to a MIME ACL does not yield ++"accept", ACL processing is aborted and the appropriate result code is sent to ++the client. In the case of an SMTP message, the acl_smtp_data ACL is not called ++when this happens. ++ ++You cannot use the malware or spam conditions in a MIME ACL; these can only be ++used in the DATA or non-SMTP ACLs. However, you can use the regex condition to ++match against the raw MIME part. You can also use the mime_regex condition to ++match against the decoded MIME part (see section 43.5). ++ ++At the start of a MIME ACL, a number of variables are set from the header ++information for the relevant MIME part. These are described below. The contents ++of the MIME part are not by default decoded into a disk file except for MIME ++parts whose content-type is "message/rfc822". If you want to decode a MIME part ++into a disk file, you can use the decode condition. The general syntax is: ++ ++decode = [/<path>/]<filename> ++ ++The right hand side is expanded before use. After expansion, the value can be: ++ ++ 1. "0" or "false", in which case no decoding is done. ++ ++ 2. The string "default". In that case, the file is put in the temporary ++ "default" directory <spool_directory>/scan/<message_id>/ with a sequential ++ file name consisting of the message id and a sequence number. The full path ++ and name is available in $mime_decoded_filename after decoding. ++ ++ 3. A full path name starting with a slash. If the full name is an existing ++ directory, it is used as a replacement for the default directory. The ++ filename is then sequentially assigned. If the path does not exist, it is ++ used as the full path and file name. ++ ++ 4. If the string does not start with a slash, it is used as the filename, and ++ the default path is then used. ++ ++The decode condition normally succeeds. It is only false for syntax errors or ++unusual circumstances such as memory shortages. You can easily decode a file ++with its original, proposed filename using ++ ++decode = $mime_filename ++ ++However, you should keep in mind that $mime_filename might contain anything. If ++you place files outside of the default path, they are not automatically ++unlinked. ++ ++For RFC822 attachments (these are messages attached to messages, with a ++content-type of "message/rfc822"), the ACL is called again in the same manner ++as for the primary message, only that the $mime_is_rfc822 expansion variable is ++set (see below). Attached messages are always decoded to disk before being ++checked, and the files are unlinked once the check is done. ++ ++The MIME ACL supports the regex and mime_regex conditions. These can be used to ++match regular expressions against raw and decoded MIME parts, respectively. ++They are described in section 43.5. ++ ++The following list describes all expansion variables that are available in the ++MIME ACL: ++ ++$mime_boundary ++ ++ If the current part is a multipart (see $mime_is_multipart) below, it ++ should have a boundary string, which is stored in this variable. If the ++ current part has no boundary parameter in the Content-Type: header, this ++ variable contains the empty string. ++ ++$mime_charset ++ ++ This variable contains the character set identifier, if one was found in ++ the Content-Type: header. Examples for charset identifiers are: ++ ++ us-ascii ++ gb2312 (Chinese) ++ iso-8859-1 ++ ++ Please note that this value is not normalized, so you should do matches ++ case-insensitively. ++ ++$mime_content_description ++ ++ This variable contains the normalized content of the Content-Description: ++ header. It can contain a human-readable description of the parts content. ++ Some implementations repeat the filename for attachments here, but they are ++ usually only used for display purposes. ++ ++$mime_content_disposition ++ ++ This variable contains the normalized content of the Content-Disposition: ++ header. You can expect strings like "attachment" or "inline" here. ++ ++$mime_content_id ++ ++ This variable contains the normalized content of the Content-ID: header. ++ This is a unique ID that can be used to reference a part from another part. ++ ++$mime_content_size ++ ++ This variable is set only after the decode modifier (see above) has been ++ successfully run. It contains the size of the decoded part in kilobytes. ++ The size is always rounded up to full kilobytes, so only a completely empty ++ part has a $mime_content_size of zero. ++ ++$mime_content_transfer_encoding ++ ++ This variable contains the normalized content of the ++ Content-transfer-encoding: header. This is a symbolic name for an encoding ++ type. Typical values are "base64" and "quoted-printable". ++ ++$mime_content_type ++ ++ If the MIME part has a Content-Type: header, this variable contains its ++ value, lowercased, and without any options (like "name" or "charset"). Here ++ are some examples of popular MIME types, as they may appear in this ++ variable: ++ ++ text/plain ++ text/html ++ application/octet-stream ++ image/jpeg ++ audio/midi ++ ++ If the MIME part has no Content-Type: header, this variable contains the ++ empty string. ++ ++$mime_decoded_filename ++ ++ This variable is set only after the decode modifier (see above) has been ++ successfully run. It contains the full path and file name of the file ++ containing the decoded data. ++ ++$mime_filename ++ ++ This is perhaps the most important of the MIME variables. It contains a ++ proposed filename for an attachment, if one was found in either the ++ Content-Type: or Content-Disposition: headers. The filename will be RFC2047 ++ decoded, but no additional sanity checks are done. If no filename was ++ found, this variable contains the empty string. ++ ++$mime_is_coverletter ++ ++ This variable attempts to differentiate the "cover letter" of an e-mail ++ from attached data. It can be used to clamp down on flashy or unnecessarily ++ encoded content in the cover letter, while not restricting attachments at ++ all. ++ ++ The variable contains 1 (true) for a MIME part believed to be part of the ++ cover letter, and 0 (false) for an attachment. At present, the algorithm is ++ as follows: ++ ++ 1. The outermost MIME part of a message is always a cover letter. ++ ++ 2. If a multipart/alternative or multipart/related MIME part is a cover ++ letter, so are all MIME subparts within that multipart. ++ ++ 3. If any other multipart is a cover letter, the first subpart is a cover ++ letter, and the rest are attachments. ++ ++ 4. All parts contained within an attachment multipart are attachments. ++ ++ As an example, the following will ban "HTML mail" (including that sent with ++ alternative plain text), while allowing HTML files to be attached. HTML ++ coverletter mail attached to non-HMTL coverletter mail will also be ++ allowed: ++ ++ deny message = HTML mail is not accepted here ++ !condition = $mime_is_rfc822 ++ condition = $mime_is_coverletter ++ condition = ${if eq{$mime_content_type}{text/html}{1}{0}} ++ ++$mime_is_multipart ++ ++ This variable has the value 1 (true) when the current part has the main ++ type "multipart", for example "multipart/alternative" or "multipart/mixed". ++ Since multipart entities only serve as containers for other parts, you may ++ not want to carry out specific actions on them. ++ ++$mime_is_rfc822 ++ ++ This variable has the value 1 (true) if the current part is not a part of ++ the checked message itself, but part of an attached message. Attached ++ message decoding is fully recursive. ++ ++$mime_part_count ++ ++ This variable is a counter that is raised for each processed MIME part. It ++ starts at zero for the very first part (which is usually a multipart). The ++ counter is per-message, so it is reset when processing RFC822 attachments ++ (see $mime_is_rfc822). The counter stays set after acl_smtp_mime is ++ complete, so you can use it in the DATA ACL to determine the number of MIME ++ parts of a message. For non-MIME messages, this variable contains the value ++ -1. ++ ++ ++43.5 Scanning with regular expressions ++-------------------------------------- ++ ++You can specify your own custom regular expression matches on the full body of ++the message, or on individual MIME parts. ++ ++The regex condition takes one or more regular expressions as arguments and ++matches them against the full message (when called in the DATA ACL) or a raw ++MIME part (when called in the MIME ACL). The regex condition matches linewise, ++with a maximum line length of 32K characters. That means you cannot have ++multiline matches with the regex condition. ++ ++The mime_regex condition can be called only in the MIME ACL. It matches up to ++32K of decoded content (the whole content at once, not linewise). If the part ++has not been decoded with the decode modifier earlier in the ACL, it is decoded ++automatically when mime_regex is executed (using default path and filename ++values). If the decoded data is larger than 32K, only the first 32K characters ++are checked. ++ ++The regular expressions are passed as a colon-separated list. To include a ++literal colon, you must double it. Since the whole right-hand side string is ++expanded before being used, you must also escape dollar signs and backslashes ++with more backslashes, or use the "\N" facility to disable expansion. Here is a ++simple example that contains two regular expressions: ++ ++deny message = contains blacklisted regex ($regex_match_string) ++ regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL ++ ++The conditions returns true if any one of the regular expressions matches. The ++$regex_match_string expansion variable is then set up and contains the matching ++regular expression. ++ ++Warning: With large messages, these conditions can be fairly CPU-intensive. ++ ++ ++43.6 The demime condition ++------------------------- ++ ++The demime ACL condition provides MIME unpacking, sanity checking and file ++extension blocking. It is usable only in the DATA and non-SMTP ACLs. The demime ++condition uses a simpler interface to MIME decoding than the MIME ACL ++functionality, but provides no additional facilities. Please note that this ++condition is deprecated and kept only for backward compatibility. You must set ++the WITH_OLD_DEMIME option in Local/Makefile at build time to be able to use ++the demime condition. ++ ++The demime condition unpacks MIME containers in the message. It detects errors ++in MIME containers and can match file extensions found in the message against a ++list. Using this facility produces files containing the unpacked MIME parts of ++the message in the temporary scan directory. If you do antivirus scanning, it ++is recommended that you use the demime condition before the antivirus (malware) ++condition. ++ ++On the right-hand side of the demime condition you can pass a colon-separated ++list of file extensions that it should match against. For example: ++ ++deny message = Found blacklisted file attachment ++ demime = vbs:com:bat:pif:prf:lnk ++ ++If one of the file extensions is found, the condition is true, otherwise it is ++false. If there is a temporary error while demimeing (for example, "disk ++full"), the condition defers, and the message is temporarily rejected (unless ++the condition is on a warn verb). ++ ++The right-hand side is expanded before being treated as a list, so you can have ++conditions and lookups there. If it expands to an empty string, "false", or ++zero ("0"), no demimeing is done and the condition is false. ++ ++The demime condition set the following variables: ++ ++$demime_errorlevel ++ ++ When an error is detected in a MIME container, this variable contains the ++ severity of the error, as an integer number. The higher the value, the more ++ severe the error (the current maximum value is 3). If this variable is ++ unset or zero, no error occurred. ++ ++$demime_reason ++ ++ When $demime_errorlevel is greater than zero, this variable contains a ++ human-readable text string describing the MIME error that occurred. ++ ++$found_extension ++ ++ When the demime condition is true, this variable contains the file ++ extension it found. ++ ++Both $demime_errorlevel and $demime_reason are set by the first call of the ++demime condition, and are not changed on subsequent calls. ++ ++If you do not want to check for file extensions, but rather use the demime ++condition for unpacking or error checking purposes, pass "*" as the right-hand ++side value. Here is a more elaborate example of how to use this facility: ++ ++# Reject messages with serious MIME container errors ++deny message = Found MIME error ($demime_reason). ++ demime = * ++ condition = ${if >{$demime_errorlevel}{2}{1}{0}} ++ ++# Reject known virus spreading file extensions. ++# Accepting these is pretty much braindead. ++deny message = contains $found_extension file (blacklisted). ++ demime = com:vbs:bat:pif:scr ++ ++# Freeze .exe and .doc files. Postmaster can ++# examine them and eventually thaw them. ++deny log_message = Another $found_extension file. ++ demime = exe:doc ++ control = freeze ++ ++ ++ ++=============================================================================== ++44. ADDING A LOCAL SCAN FUNCTION TO EXIM ++ ++In these days of email worms, viruses, and ever-increasing spam, some sites ++want to apply a lot of checking to messages before accepting them. ++ ++The content scanning extension (chapter 43) has facilities for passing messages ++to external virus and spam scanning software. You can also do a certain amount ++in Exim itself through string expansions and the condition condition in the ACL ++that runs after the SMTP DATA command or the ACL for non-SMTP messages (see ++chapter 42), but this has its limitations. ++ ++To allow for further customization to a site's own requirements, there is the ++possibility of linking Exim with a private message scanning function, written ++in C. If you want to run code that is written in something other than C, you ++can of course use a little C stub to call it. ++ ++The local scan function is run once for every incoming message, at the point ++when Exim is just about to accept the message. It can therefore be used to ++control non-SMTP messages from local processes as well as messages arriving via ++SMTP. ++ ++Exim applies a timeout to calls of the local scan function, and there is an ++option called local_scan_timeout for setting it. The default is 5 minutes. Zero ++means "no timeout". Exim also sets up signal handlers for SIGSEGV, SIGILL, ++SIGFPE, and SIGBUS before calling the local scan function, so that the most ++common types of crash are caught. If the timeout is exceeded or one of those ++signals is caught, the incoming message is rejected with a temporary error if ++it is an SMTP message. For a non-SMTP message, the message is dropped and Exim ++ends with a non-zero code. The incident is logged on the main and reject logs. ++ ++ ++44.1 Building Exim to use a local scan function ++----------------------------------------------- ++ ++To make use of the local scan function feature, you must tell Exim where your ++function is before building Exim, by setting LOCAL_SCAN_SOURCE in your Local/ ++Makefile. A recommended place to put it is in the Local directory, so you might ++set ++ ++LOCAL_SCAN_SOURCE=Local/local_scan.c ++ ++for example. The function must be called local_scan(). It is called by Exim ++after it has received a message, when the success return code is about to be ++sent. This is after all the ACLs have been run. The return code from your ++function controls whether the message is actually accepted or not. There is a ++commented template function (that just accepts the message) in the file _src/ ++local_scan.c_. ++ ++If you want to make use of Exim's run time configuration file to set options ++for your local_scan() function, you must also set ++ ++LOCAL_SCAN_HAS_OPTIONS=yes ++ ++in Local/Makefile (see section 44.3 below). ++ ++ ++44.2 API for local_scan() ++------------------------- ++ ++You must include this line near the start of your code: ++ ++#include "local_scan.h" ++ ++This header file defines a number of variables and other values, and the ++prototype for the function itself. Exim is coded to use unsigned char values ++almost exclusively, and one of the things this header defines is a shorthand ++for "unsigned char" called "uschar". It also contains the following macro ++definitions, to simplify casting character strings and pointers to character ++strings: ++ ++#define CS (char *) ++#define CCS (const char *) ++#define CSS (char **) ++#define US (unsigned char *) ++#define CUS (const unsigned char *) ++#define USS (unsigned char **) ++ ++The function prototype for local_scan() is: ++ ++extern int local_scan(int fd, uschar **return_text); ++ ++The arguments are as follows: ++ ++ * fd is a file descriptor for the file that contains the body of the message ++ (the -D file). The file is open for reading and writing, but updating it is ++ not recommended. Warning: You must not close this file descriptor. ++ ++ The descriptor is positioned at character 19 of the file, which is the ++ first character of the body itself, because the first 19 characters are the ++ message id followed by "-D" and a newline. If you rewind the file, you ++ should use the macro SPOOL_DATA_START_OFFSET to reset to the start of the ++ data, just in case this changes in some future version. ++ ++ * return_text is an address which you can use to return a pointer to a text ++ string at the end of the function. The value it points to on entry is NULL. ++ ++The function must return an int value which is one of the following macros: ++ ++"LOCAL_SCAN_ACCEPT" ++ ++ The message is accepted. If you pass back a string of text, it is saved ++ with the message, and made available in the variable $local_scan_data. No ++ newlines are permitted (if there are any, they are turned into spaces) and ++ the maximum length of text is 1000 characters. ++ ++"LOCAL_SCAN_ACCEPT_FREEZE" ++ ++ This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is ++ queued without immediate delivery, and is frozen. ++ ++"LOCAL_SCAN_ACCEPT_QUEUE" ++ ++ This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is ++ queued without immediate delivery. ++ ++"LOCAL_SCAN_REJECT" ++ ++ The message is rejected; the returned text is used as an error message ++ which is passed back to the sender and which is also logged. Newlines are ++ permitted - they cause a multiline response for SMTP rejections, but are ++ converted to "\n" in log lines. If no message is given, "Administrative ++ prohibition" is used. ++ ++"LOCAL_SCAN_TEMPREJECT" ++ ++ The message is temporarily rejected; the returned text is used as an error ++ message as for LOCAL_SCAN_REJECT. If no message is given, "Temporary local ++ problem" is used. ++ ++"LOCAL_SCAN_REJECT_NOLOGHDR" ++ ++ This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected ++ message is not written to the reject log. It has the effect of unsetting ++ the rejected_header log selector for just this rejection. If ++ rejected_header is already unset (see the discussion of the log_selection ++ option in section 51.15), this code is the same as LOCAL_SCAN_REJECT. ++ ++"LOCAL_SCAN_TEMPREJECT_NOLOGHDR" ++ ++ This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that ++ LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT. ++ ++If the message is not being received by interactive SMTP, rejections are ++reported by writing to stderr or by sending an email, as configured by the -oe ++command line options. ++ ++ ++44.3 Configuration options for local_scan() ++------------------------------------------- ++ ++It is possible to have option settings in the main configuration file that set ++values in static variables in the local_scan() module. If you want to do this, ++you must have the line ++ ++LOCAL_SCAN_HAS_OPTIONS=yes ++ ++in your Local/Makefile when you build Exim. (This line is in OS/ ++Makefile-Default, commented out). Then, in the local_scan() source file, you ++must define static variables to hold the option values, and a table to define ++them. ++ ++The table must be a vector called local_scan_options, of type "optionlist". ++Each entry is a triplet, consisting of a name, an option type, and a pointer to ++the variable that holds the value. The entries must appear in alphabetical ++order. Following local_scan_options you must also define a variable called ++local_scan_options_count that contains the number of entries in the table. Here ++is a short example, showing two kinds of option: ++ ++static int my_integer_option = 42; ++static uschar *my_string_option = US"a default string"; ++ ++optionlist local_scan_options[] = { ++ { "my_integer", opt_int, &my_integer_option }, ++ { "my_string", opt_stringptr, &my_string_option } ++}; ++ ++int local_scan_options_count = ++ sizeof(local_scan_options)/sizeof(optionlist); ++ ++The values of the variables can now be changed from Exim's runtime ++configuration file by including a local scan section as in this example: ++ ++begin local_scan ++my_integer = 99 ++my_string = some string of text... ++ ++The available types of option data are as follows: ++ ++opt_bool ++ ++ This specifies a boolean (true/false) option. The address should point to a ++ variable of type "BOOL", which will be set to TRUE or FALSE, which are ++ macros that are defined as "1" and "0", respectively. If you want to detect ++ whether such a variable has been set at all, you can initialize it to ++ TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than ++ two values.) ++ ++opt_fixed ++ ++ This specifies a fixed point number, such as is used for load averages. The ++ address should point to a variable of type "int". The value is stored ++ multiplied by 1000, so, for example, 1.4142 is truncated and stored as ++ 1414. ++ ++opt_int ++ ++ This specifies an integer; the address should point to a variable of type ++ "int". The value may be specified in any of the integer formats accepted by ++ Exim. ++ ++opt_mkint ++ ++ This is the same as opt_int, except that when such a value is output in a ++ -bP listing, if it is an exact number of kilobytes or megabytes, it is ++ printed with the suffix K or M. ++ ++opt_octint ++ ++ This also specifies an integer, but the value is always interpreted as an ++ octal integer, whether or not it starts with the digit zero, and it is ++ always output in octal. ++ ++opt_stringptr ++ ++ This specifies a string value; the address must be a pointer to a variable ++ that points to a string (for example, of type "uschar *"). ++ ++opt_time ++ ++ This specifies a time interval value. The address must point to a variable ++ of type "int". The value that is placed there is a number of seconds. ++ ++If the -bP command line option is followed by "local_scan", Exim prints out the ++values of all the local_scan() options. ++ ++ ++44.4 Available Exim variables ++----------------------------- ++ ++The header local_scan.h gives you access to a number of C variables. These are ++the only ones that are guaranteed to be maintained from release to release. ++Note, however, that you can obtain the value of any Exim expansion variable, ++including $recipients, by calling expand_string(). The exported C variables are ++as follows: ++ ++int body_linecount ++ ++ This variable contains the number of lines in the message's body. ++ ++int body_zerocount ++ ++ This variable contains the number of binary zero bytes in the message's ++ body. ++ ++unsigned int debug_selector ++ ++ This variable is set to zero when no debugging is taking place. Otherwise, ++ it is a bitmap of debugging selectors. Two bits are identified for use in ++ local_scan(); they are defined as macros: ++ ++ + The "D_v" bit is set when -v was present on the command line. This is a ++ testing option that is not privileged - any caller may set it. All the ++ other selector bits can be set only by admin users. ++ ++ + The "D_local_scan" bit is provided for use by local_scan(); it is set ++ by the "+local_scan" debug selector. It is not included in the default ++ set of debugging bits. ++ ++ Thus, to write to the debugging output only when "+local_scan" has been ++ selected, you should use code like this: ++ ++ if ((debug_selector & D_local_scan) != 0) ++ debug_printf("xxx", ...); ++ ++uschar *expand_string_message ++ ++ After a failing call to expand_string() (returned value NULL), the variable ++ expand_string_message contains the error message, zero-terminated. ++ ++header_line *header_list ++ ++ A pointer to a chain of header lines. The header_line structure is ++ discussed below. ++ ++header_line *header_last ++ ++ A pointer to the last of the header lines. ++ ++uschar *headers_charset ++ ++ The value of the headers_charset configuration option. ++ ++BOOL host_checking ++ ++ This variable is TRUE during a host checking session that is initiated by ++ the -bh command line option. ++ ++uschar *interface_address ++ ++ The IP address of the interface that received the message, as a string. ++ This is NULL for locally submitted messages. ++ ++int interface_port ++ ++ The port on which this message was received. When testing with the -bh ++ command line option, the value of this variable is -1 unless a port has ++ been specified via the -oMi option. ++ ++uschar *message_id ++ ++ This variable contains Exim's message id for the incoming message (the ++ value of $message_exim_id) as a zero-terminated string. ++ ++uschar *received_protocol ++ ++ The name of the protocol by which the message was received. ++ ++int recipients_count ++ ++ The number of accepted recipients. ++ ++recipient_item *recipients_list ++ ++ The list of accepted recipients, held in a vector of length ++ recipients_count. The recipient_item structure is discussed below. You can ++ add additional recipients by calling receive_add_recipient() (see below). ++ You can delete recipients by removing them from the vector and adjusting ++ the value in recipients_count. In particular, by setting recipients_count ++ to zero you remove all recipients. If you then return the value ++ "LOCAL_SCAN_ACCEPT", the message is accepted, but immediately blackholed. ++ To replace the recipients, you can set recipients_count to zero and then ++ call receive_add_recipient() as often as needed. ++ ++uschar *sender_address ++ ++ The envelope sender address. For bounce messages this is the empty string. ++ ++uschar *sender_host_address ++ ++ The IP address of the sending host, as a string. This is NULL for ++ locally-submitted messages. ++ ++uschar *sender_host_authenticated ++ ++ The name of the authentication mechanism that was used, or NULL if the ++ message was not received over an authenticated SMTP connection. ++ ++uschar *sender_host_name ++ ++ The name of the sending host, if known. ++ ++int sender_host_port ++ ++ The port on the sending host. ++ ++BOOL smtp_input ++ ++ This variable is TRUE for all SMTP input, including BSMTP. ++ ++BOOL smtp_batched_input ++ ++ This variable is TRUE for BSMTP input. ++ ++int store_pool ++ ++ The contents of this variable control which pool of memory is used for new ++ requests. See section 44.8 for details. ++ ++ ++44.5 Structure of header lines ++------------------------------ ++ ++The header_line structure contains the members listed below. You can add ++additional header lines by calling the header_add() function (see below). You ++can cause header lines to be ignored (deleted) by setting their type to *. ++ ++struct header_line *next ++ ++ A pointer to the next header line, or NULL for the last line. ++ ++int type ++ ++ A code identifying certain headers that Exim recognizes. The codes are ++ printing characters, and are documented in chapter 55 of this manual. ++ Notice in particular that any header line whose type is * is not ++ transmitted with the message. This flagging is used for header lines that ++ have been rewritten, or are to be removed (for example, Envelope-sender: ++ header lines.) Effectively, * means "deleted". ++ ++int slen ++ ++ The number of characters in the header line, including the terminating and ++ any internal newlines. ++ ++uschar *text ++ ++ A pointer to the text of the header. It always ends with a newline, ++ followed by a zero byte. Internal newlines are preserved. ++ ++ ++44.6 Structure of recipient items ++--------------------------------- ++ ++The recipient_item structure contains these members: ++ ++uschar *address ++ ++ This is a pointer to the recipient address as it was received. ++ ++int pno ++ ++ This is used in later Exim processing when top level addresses are created ++ by the one_time option. It is not relevant at the time local_scan() is run ++ and must always contain -1 at this stage. ++ ++uschar *errors_to ++ ++ If this value is not NULL, bounce messages caused by failing to deliver to ++ the recipient are sent to the address it contains. In other words, it ++ overrides the envelope sender for this one recipient. (Compare the ++ errors_to generic router option.) If a local_scan() function sets an ++ errors_to field to an unqualified address, Exim qualifies it using the ++ domain from qualify_recipient. When local_scan() is called, the errors_to ++ field is NULL for all recipients. ++ ++ ++44.7 Available Exim functions ++----------------------------- ++ ++The header local_scan.h gives you access to a number of Exim functions. These ++are the only ones that are guaranteed to be maintained from release to release: ++ ++pid_t child_open ++ (uschar **argv, uschar **envp, int newumask, int *infdptr, int *outfdptr, ++ BOOL make_leader) ++ ++ This function creates a child process that runs the command specified by ++ argv. The environment for the process is specified by envp, which can be ++ NULL if no environment variables are to be passed. A new umask is supplied ++ for the process in newumask. ++ ++ Pipes to the standard input and output of the new process are set up and ++ returned to the caller via the infdptr and outfdptr arguments. The standard ++ error is cloned to the standard output. If there are any file descriptors ++ "in the way" in the new process, they are closed. If the final argument is ++ TRUE, the new process is made into a process group leader. ++ ++ The function returns the pid of the new process, or -1 if things go wrong. ++ ++int child_close(pid_t pid, int timeout) ++ ++ This function waits for a child process to terminate, or for a timeout (in ++ seconds) to expire. A timeout value of zero means wait as long as it takes. ++ The return value is as follows: ++ ++ + >= 0 ++ ++ The process terminated by a normal exit and the value is the process ++ ending status. ++ ++ + < 0 and > -256 ++ ++ The process was terminated by a signal and the value is the negation of ++ the signal number. ++ ++ + -256 ++ ++ The process timed out. ++ ++ + -257 ++ ++ The was some other error in wait(); errno is still set. ++ ++pid_t child_open_exim(int *fd) ++ ++ This function provide you with a means of submitting a new message to Exim. ++ (Of course, you can also call /usr/sbin/sendmail yourself if you want, but ++ this packages it all up for you.) The function creates a pipe, forks a ++ subprocess that is running ++ ++ exim -t -oem -oi -f <> ++ ++ and returns to you (via the "int *" argument) a file descriptor for the ++ pipe that is connected to the standard input. The yield of the function is ++ the PID of the subprocess. You can then write a message to the file ++ descriptor, with recipients in To:, Cc:, and/or Bcc: header lines. ++ ++ When you have finished, call child_close() to wait for the process to ++ finish and to collect its ending status. A timeout value of zero is usually ++ fine in this circumstance. Unless you have made a mistake with the ++ recipient addresses, you should get a return code of zero. ++ ++pid_t child_open_exim2(int *fd, uschar *sender, uschar *sender_authentication) ++ ++ This function is a more sophisticated version of child_open(). The command ++ that it runs is: ++ ++ exim -t -oem -oi -f sender -oMas sender_authentication ++ ++ The third argument may be NULL, in which case the -oMas option is omitted. ++ ++void debug_printf(char *, ...) ++ ++ This is Exim's debugging function, with arguments as for (printf(). The ++ output is written to the standard error stream. If no debugging is ++ selected, calls to debug_printf() have no effect. Normally, you should make ++ calls conditional on the "local_scan" debug selector by coding like this: ++ ++ if ((debug_selector & D_local_scan) != 0) ++ debug_printf("xxx", ...); ++ ++uschar *expand_string(uschar *string) ++ ++ This is an interface to Exim's string expansion code. The return value is ++ the expanded string, or NULL if there was an expansion failure. The C ++ variable expand_string_message contains an error message after an expansion ++ failure. If expansion does not change the string, the return value is the ++ pointer to the input string. Otherwise, the return value points to a new ++ block of memory that was obtained by a call to store_get(). See section ++ 44.8 below for a discussion of memory handling. ++ ++void header_add(int type, char *format, ...) ++ ++ This function allows you to an add additional header line at the end of the ++ existing ones. The first argument is the type, and should normally be a ++ space character. The second argument is a format string and any number of ++ substitution arguments as for sprintf(). You may include internal newlines ++ if you want, and you must ensure that the string ends with a newline. ++ ++void header_add_at_position ++ (BOOL after, uschar *name, BOOL topnot, int type, char *format, ...) ++ ++ This function adds a new header line at a specified point in the header ++ chain. The header itself is specified as for header_add(). ++ ++ If name is NULL, the new header is added at the end of the chain if after ++ is true, or at the start if after is false. If name is not NULL, the header ++ lines are searched for the first non-deleted header that matches the name. ++ If one is found, the new header is added before it if after is false. If ++ after is true, the new header is added after the found header and any ++ adjacent subsequent ones with the same name (even if marked "deleted"). If ++ no matching non-deleted header is found, the topnot option controls where ++ the header is added. If it is true, addition is at the top; otherwise at ++ the bottom. Thus, to add a header after all the Received: headers, or at ++ the top if there are no Received: headers, you could use ++ ++ header_add_at_position(TRUE, US"Received", TRUE, ++ ' ', "X-xxx: ..."); ++ ++ Normally, there is always at least one non-deleted Received: header, but ++ there may not be if received_header_text expands to an empty string. ++ ++void header_remove(int occurrence, uschar *name) ++ ++ This function removes header lines. If occurrence is zero or negative, all ++ occurrences of the header are removed. If occurrence is greater than zero, ++ that particular instance of the header is removed. If no header(s) can be ++ found that match the specification, the function does nothing. ++ ++BOOL header_testname(header_line *hdr, uschar *name, int length, BOOL notdel) ++ ++ This function tests whether the given header has the given name. It is not ++ just a string comparison, because white space is permitted between the name ++ and the colon. If the notdel argument is true, a false return is forced for ++ all "deleted" headers; otherwise they are not treated specially. For ++ example: ++ ++ if (header_testname(h, US"X-Spam", 6, TRUE)) ... ++ ++uschar *lss_b64encode(uschar *cleartext, int length) ++ ++ This function base64-encodes a string, which is passed by address and ++ length. The text may contain bytes of any value, including zero. The result ++ is passed back in dynamic memory that is obtained by calling store_get(). ++ It is zero-terminated. ++ ++int lss_b64decode(uschar *codetext, uschar **cleartext) ++ ++ This function decodes a base64-encoded string. Its arguments are a ++ zero-terminated base64-encoded string and the address of a variable that is ++ set to point to the result, which is in dynamic memory. The length of the ++ decoded string is the yield of the function. If the input is invalid base64 ++ data, the yield is -1. A zero byte is added to the end of the output string ++ to make it easy to interpret as a C string (assuming it contains no zeros ++ of its own). The added zero byte is not included in the returned count. ++ ++int lss_match_domain(uschar *domain, uschar *list) ++ ++ This function checks for a match in a domain list. Domains are always ++ matched caselessly. The return value is one of the following: ++ ++ OK match succeeded ++ FAIL match failed ++ DEFER match deferred ++ ++ DEFER is usually caused by some kind of lookup defer, such as the inability ++ to contact a database. ++ ++int lss_match_local_part(uschar *localpart, uschar *list, BOOL caseless) ++ ++ This function checks for a match in a local part list. The third argument ++ controls case-sensitivity. The return values are as for lss_match_domain(). ++ ++int lss_match_address(uschar *address, uschar *list, BOOL caseless) ++ ++ This function checks for a match in an address list. The third argument ++ controls the case-sensitivity of the local part match. The domain is always ++ matched caselessly. The return values are as for lss_match_domain(). ++ ++int lss_match_host(uschar *host_name, uschar *host_address, uschar *list) ++ ++ This function checks for a match in a host list. The most common usage is ++ expected to be ++ ++ lss_match_host(sender_host_name, sender_host_address, ...) ++ ++ An empty address field matches an empty item in the host list. If the host ++ name is NULL, the name corresponding to $sender_host_address is ++ automatically looked up if a host name is required to match an item in the ++ list. The return values are as for lss_match_domain(), but in addition, ++ lss_match_host() returns ERROR in the case when it had to look up a host ++ name, but the lookup failed. ++ ++void log_write(unsigned int selector, int which, char *format, ...) ++ ++ This function writes to Exim's log files. The first argument should be zero ++ (it is concerned with log_selector). The second argument can be "LOG_MAIN" ++ or "LOG_REJECT" or "LOG_PANIC" or the inclusive "or" of any combination of ++ them. It specifies to which log or logs the message is written. The ++ remaining arguments are a format and relevant insertion arguments. The ++ string should not contain any newlines, not even at the end. ++ ++void receive_add_recipient(uschar *address, int pno) ++ ++ This function adds an additional recipient to the message. The first ++ argument is the recipient address. If it is unqualified (has no domain), it ++ is qualified with the qualify_recipient domain. The second argument must ++ always be -1. ++ ++ This function does not allow you to specify a private errors_to address (as ++ described with the structure of recipient_item above), because it pre-dates ++ the addition of that field to the structure. However, it is easy to add ++ such a value afterwards. For example: ++ ++ receive_add_recipient(US"monitor@mydom.example", -1); ++ recipients_list[recipients_count-1].errors_to = ++ US"postmaster@mydom.example"; ++ ++BOOL receive_remove_recipient(uschar *recipient) ++ ++ This is a convenience function to remove a named recipient from the list of ++ recipients. It returns true if a recipient was removed, and false if no ++ matching recipient could be found. The argument must be a complete email ++ address. ++ ++uschar rfc2047_decode ++ (uschar *string, BOOL lencheck, uschar *target, int zeroval, int *lenptr, ++ uschar **error) ++ ++ This function decodes strings that are encoded according to RFC 2047. ++ Typically these are the contents of header lines. First, each "encoded ++ word" is decoded from the Q or B encoding into a byte-string. Then, if ++ provided with the name of a charset encoding, and if the iconv() function ++ is available, an attempt is made to translate the result to the named ++ character set. If this fails, the binary string is returned with an error ++ message. ++ ++ The first argument is the string to be decoded. If lencheck is TRUE, the ++ maximum MIME word length is enforced. The third argument is the target ++ encoding, or NULL if no translation is wanted. ++ ++ If a binary zero is encountered in the decoded string, it is replaced by ++ the contents of the zeroval argument. For use with Exim headers, the value ++ must not be 0 because header lines are handled as zero-terminated strings. ++ ++ The function returns the result of processing the string, zero-terminated; ++ if lenptr is not NULL, the length of the result is set in the variable to ++ which it points. When zeroval is 0, lenptr should not be NULL. ++ ++ If an error is encountered, the function returns NULL and uses the error ++ argument to return an error message. The variable pointed to by error is ++ set to NULL if there is no error; it may be set non-NULL even when the ++ function returns a non-NULL value if decoding was successful, but there was ++ a problem with translation. ++ ++int smtp_fflush(void) ++ ++ This function is used in conjunction with smtp_printf(), as described ++ below. ++ ++void smtp_printf(char *, ...) ++ ++ The arguments of this function are like printf(); it writes to the SMTP ++ output stream. You should use this function only when there is an SMTP ++ output stream, that is, when the incoming message is being received via ++ interactive SMTP. This is the case when smtp_input is TRUE and ++ smtp_batched_input is FALSE. If you want to test for an incoming message ++ from another host (as opposed to a local process that used the -bs command ++ line option), you can test the value of sender_host_address, which is ++ non-NULL when a remote host is involved. ++ ++ If an SMTP TLS connection is established, smtp_printf() uses the TLS output ++ function, so it can be used for all forms of SMTP connection. ++ ++ Strings that are written by smtp_printf() from within local_scan() must ++ start with an appropriate response code: 550 if you are going to return ++ LOCAL_SCAN_REJECT, 451 if you are going to return LOCAL_SCAN_TEMPREJECT, ++ and 250 otherwise. Because you are writing the initial lines of a ++ multi-line response, the code must be followed by a hyphen to indicate that ++ the line is not the final response line. You must also ensure that the ++ lines you write terminate with CRLF. For example: ++ ++ smtp_printf("550-this is some extra info\r\n"); ++ return LOCAL_SCAN_REJECT; ++ ++ Note that you can also create multi-line responses by including newlines in ++ the data returned via the return_text argument. The added value of using ++ smtp_printf() is that, for instance, you could introduce delays between ++ multiple output lines. ++ ++ The smtp_printf() function does not return any error indication, because it ++ does not automatically flush pending output, and therefore does not test ++ the state of the stream. (In the main code of Exim, flushing and error ++ detection is done when Exim is ready for the next SMTP input command.) If ++ you want to flush the output and check for an error (for example, the ++ dropping of a TCP/IP connection), you can call smtp_fflush(), which has no ++ arguments. It flushes the output stream, and returns a non-zero value if ++ there is an error. ++ ++void *store_get(int) ++ ++ This function accesses Exim's internal store (memory) manager. It gets a ++ new chunk of memory whose size is given by the argument. Exim bombs out if ++ it ever runs out of memory. See the next section for a discussion of memory ++ handling. ++ ++void *store_get_perm(int) ++ ++ This function is like store_get(), but it always gets memory from the ++ permanent pool. See the next section for a discussion of memory handling. ++ ++uschar *string_copy(uschar *string) ++ ++ See below. ++ ++uschar *string_copyn(uschar *string, int length) ++ ++ See below. ++ ++uschar *string_sprintf(char *format, ...) ++ ++ These three functions create strings using Exim's dynamic memory ++ facilities. The first makes a copy of an entire string. The second copies ++ up to a maximum number of characters, indicated by the second argument. The ++ third uses a format and insertion arguments to create a new string. In each ++ case, the result is a pointer to a new string in the current memory pool. ++ See the next section for more discussion. ++ ++ ++44.8 More about Exim's memory handling ++-------------------------------------- ++ ++No function is provided for freeing memory, because that is never needed. The ++dynamic memory that Exim uses when receiving a message is automatically ++recycled if another message is received by the same process (this applies only ++to incoming SMTP connections - other input methods can supply only one message ++at a time). After receiving the last message, a reception process terminates. ++ ++Because it is recycled, the normal dynamic memory cannot be used for holding ++data that must be preserved over a number of incoming messages on the same SMTP ++connection. However, Exim in fact uses two pools of dynamic memory; the second ++one is not recycled, and can be used for this purpose. ++ ++If you want to allocate memory that remains available for subsequent messages ++in the same SMTP connection, you should set ++ ++store_pool = POOL_PERM ++ ++before calling the function that does the allocation. There is no need to ++restore the value if you do not need to; however, if you do want to revert to ++the normal pool, you can either restore the previous value of store_pool or set ++it explicitly to POOL_MAIN. ++ ++The pool setting applies to all functions that get dynamic memory, including ++expand_string(), store_get(), and the string_xxx() functions. There is also a ++convenience function called store_get_perm() that gets a block of memory from ++the permanent pool while preserving the value of store_pool. ++ ++ ++ ++=============================================================================== ++45. SYSTEM-WIDE MESSAGE FILTERING ++ ++The previous chapters (on ACLs and the local scan function) describe checks ++that can be applied to messages before they are accepted by a host. There is ++also a mechanism for checking messages once they have been received, but before ++they are delivered. This is called the system filter. ++ ++The system filter operates in a similar manner to users' filter files, but it ++is run just once per message (however many recipients the message has). It ++should not normally be used as a substitute for routing, because deliver ++commands in a system router provide new envelope recipient addresses. The ++system filter must be an Exim filter. It cannot be a Sieve filter. ++ ++The system filter is run at the start of a delivery attempt, before any routing ++is done. If a message fails to be completely delivered at the first attempt, ++the system filter is run again at the start of every retry. If you want your ++filter to do something only once per message, you can make use of the ++first_delivery condition in an if command in the filter to prevent it happening ++on retries. ++ ++Warning: Because the system filter runs just once, variables that are specific ++to individual recipient addresses, such as $local_part and $domain, are not ++set, and the "personal" condition is not meaningful. If you want to run a ++centrally-specified filter for each recipient address independently, you can do ++so by setting up a suitable redirect router, as described in section 45.8 ++below. ++ ++ ++45.1 Specifying a system filter ++------------------------------- ++ ++The name of the file that contains the system filter must be specified by ++setting system_filter. If you want the filter to run under a uid and gid other ++than root, you must also set system_filter_user and system_filter_group as ++appropriate. For example: ++ ++system_filter = /etc/mail/exim.filter ++system_filter_user = exim ++ ++If a system filter generates any deliveries directly to files or pipes (via the ++save or pipe commands), transports to handle these deliveries must be specified ++by setting system_filter_file_transport and system_filter_pipe_transport, ++respectively. Similarly, system_filter_reply_transport must be set to handle ++any messages generated by the reply command. ++ ++ ++45.2 Testing a system filter ++---------------------------- ++ ++You can run simple tests of a system filter in the same way as for a user ++filter, but you should use -bF rather than -bf, so that features that are ++permitted only in system filters are recognized. ++ ++If you want to test the combined effect of a system filter and a user filter, ++you can use both -bF and -bf on the same command line. ++ ++ ++45.3 Contents of a system filter ++-------------------------------- ++ ++The language used to specify system filters is the same as for users' filter ++files. It is described in the separate end-user document Exim's interface to ++mail filtering. However, there are some additional features that are available ++only in system filters; these are described in subsequent sections. If they are ++encountered in a user's filter file or when testing with -bf, they cause ++errors. ++ ++There are two special conditions which, though available in users' filter ++files, are designed for use in system filters. The condition first_delivery is ++true only for the first attempt at delivering a message, and manually_thawed is ++true only if the message has been frozen, and subsequently thawed by an admin ++user. An explicit forced delivery counts as a manual thaw, but thawing as a ++result of the auto_thaw setting does not. ++ ++Warning: If a system filter uses the first_delivery condition to specify an ++"unseen" (non-significant) delivery, and that delivery does not succeed, it ++will not be tried again. If you want Exim to retry an unseen delivery until it ++succeeds, you should arrange to set it up every time the filter runs. ++ ++When a system filter finishes running, the values of the variables $n0 - $n9 ++are copied into $sn0 - $sn9 and are thereby made available to users' filter ++files. Thus a system filter can, for example, set up "scores" to which users' ++filter files can refer. ++ ++ ++45.4 Additional variable for system filters ++------------------------------------------- ++ ++The expansion variable $recipients, containing a list of all the recipients of ++the message (separated by commas and white space), is available in system ++filters. It is not available in users' filters for privacy reasons. ++ ++ ++45.5 Defer, freeze, and fail commands for system filters ++-------------------------------------------------------- ++ ++There are three extra commands (defer, freeze and fail) which are always ++available in system filters, but are not normally enabled in users' filters. ++(See the allow_defer, allow_freeze and allow_fail options for the redirect ++router.) These commands can optionally be followed by the word text and a ++string containing an error message, for example: ++ ++fail text "this message looks like spam to me" ++ ++The keyword text is optional if the next character is a double quote. ++ ++The defer command defers delivery of the original recipients of the message. ++The fail command causes all the original recipients to be failed, and a bounce ++message to be created. The freeze command suspends all delivery attempts for ++the original recipients. In all cases, any new deliveries that are specified by ++the filter are attempted as normal after the filter has run. ++ ++The freeze command is ignored if the message has been manually unfrozen and not ++manually frozen since. This means that automatic freezing by a system filter ++can be used as a way of checking out suspicious messages. If a message is found ++to be all right, manually unfreezing it allows it to be delivered. ++ ++The text given with a fail command is used as part of the bounce message as ++well as being written to the log. If the message is quite long, this can fill ++up a lot of log space when such failures are common. To reduce the size of the ++log message, Exim interprets the text in a special way if it starts with the ++two characters "<<" and contains ">>" later. The text between these two strings ++is written to the log, and the rest of the text is used in the bounce message. ++For example: ++ ++fail "<<filter test 1>>Your message is rejected \ ++ because it contains attachments that we are \ ++ not prepared to receive." ++ ++Take great care with the fail command when basing the decision to fail on the ++contents of the message, because the bounce message will of course include the ++contents of the original message and will therefore trigger the fail command ++again (causing a mail loop) unless steps are taken to prevent this. Testing the ++error_message condition is one way to prevent this. You could use, for example ++ ++if $message_body contains "this is spam" and not error_message ++then fail text "spam is not wanted here" endif ++ ++though of course that might let through unwanted bounce messages. The ++alternative is clever checking of the body and/or headers to detect bounces ++generated by the filter. ++ ++The interpretation of a system filter file ceases after a defer, freeze, or ++fail command is obeyed. However, any deliveries that were set up earlier in the ++filter file are honoured, so you can use a sequence such as ++ ++mail ... ++freeze ++ ++to send a specified message when the system filter is freezing (or deferring or ++failing) a message. The normal deliveries for the message do not, of course, ++take place. ++ ++ ++45.6 Adding and removing headers in a system filter ++--------------------------------------------------- ++ ++Two filter commands that are available only in system filters are: ++ ++headers add <string> ++headers remove <string> ++ ++The argument for the headers add is a string that is expanded and then added to ++the end of the message's headers. It is the responsibility of the filter ++maintainer to make sure it conforms to RFC 2822 syntax. Leading white space is ++ignored, and if the string is otherwise empty, or if the expansion is forced to ++fail, the command has no effect. ++ ++You can use "\n" within the string, followed by white space, to specify ++continued header lines. More than one header may be added in one command by ++including "\n" within the string without any following white space. For ++example: ++ ++headers add "X-header-1: ....\n \ ++ continuation of X-header-1 ...\n\ ++ X-header-2: ...." ++ ++Note that the header line continuation white space after the first newline must ++be placed before the backslash that continues the input string, because white ++space after input continuations is ignored. ++ ++The argument for headers remove is a colon-separated list of header names. This ++command applies only to those headers that are stored with the message; those ++that are added at delivery time (such as Envelope-To: and Return-Path:) cannot ++be removed by this means. If there is more than one header with the same name, ++they are all removed. ++ ++The headers command in a system filter makes an immediate change to the set of ++header lines that was received with the message (with possible additions from ++ACL processing). Subsequent commands in the system filter operate on the ++modified set, which also forms the basis for subsequent message delivery. ++Unless further modified during routing or transporting, this set of headers is ++used for all recipients of the message. ++ ++During routing and transporting, the variables that refer to the contents of ++header lines refer only to those lines that are in this set. Thus, header lines ++that are added by a system filter are visible to users' filter files and to all ++routers and transports. This contrasts with the manipulation of header lines by ++routers and transports, which is not immediate, but which instead is saved up ++until the message is actually being written (see section 46.17). ++ ++If the message is not delivered at the first attempt, header lines that were ++added by the system filter are stored with the message, and so are still ++present at the next delivery attempt. Header lines that were removed are still ++present, but marked "deleted" so that they are not transported with the ++message. For this reason, it is usual to make the headers command conditional ++on first_delivery so that the set of header lines is not modified more than ++once. ++ ++Because header modification in a system filter acts immediately, you have to ++use an indirect approach if you want to modify the contents of a header line. ++For example: ++ ++headers add "Old-Subject: $h_subject:" ++headers remove "Subject" ++headers add "Subject: new subject (was: $h_old-subject:)" ++headers remove "Old-Subject" ++ ++ ++45.7 Setting an errors address in a system filter ++------------------------------------------------- ++ ++In a system filter, if a deliver command is followed by ++ ++errors_to <some address> ++ ++in order to change the envelope sender (and hence the error reporting) for that ++delivery, any address may be specified. (In a user filter, only the current ++user's address can be set.) For example, if some mail is being monitored, you ++might use ++ ++unseen deliver monitor@spying.example errors_to root@local.example ++ ++to take a copy which would not be sent back to the normal error reporting ++address if its delivery failed. ++ ++ ++45.8 Per-address filtering ++-------------------------- ++ ++In contrast to the system filter, which is run just once per message for each ++delivery attempt, it is also possible to set up a system-wide filtering ++operation that runs once for each recipient address. In this case, variables ++such as $local_part and $domain can be used, and indeed, the choice of filter ++file could be made dependent on them. This is an example of a router which ++implements such a filter: ++ ++central_filter: ++ check_local_user ++ driver = redirect ++ domains = +local_domains ++ file = /central/filters/$local_part ++ no_verify ++ allow_filter ++ allow_freeze ++ ++The filter is run in a separate process under its own uid. Therefore, either ++check_local_user must be set (as above), in which case the filter is run as the ++local user, or the user option must be used to specify which user to use. If ++both are set, user overrides. ++ ++Care should be taken to ensure that none of the commands in the filter file ++specify a significant delivery if the message is to go on to be delivered to ++its intended recipient. The router will not then claim to have dealt with the ++address, so it will be passed on to subsequent routers to be delivered in the ++normal way. ++ ++ ++ ++=============================================================================== ++46. MESSAGE PROCESSING ++ ++Exim performs various transformations on the sender and recipient addresses of ++all messages that it handles, and also on the messages' header lines. Some of ++these are optional and configurable, while others always take place. All of ++this processing, except rewriting as a result of routing, and the addition or ++removal of header lines while delivering, happens when a message is received, ++before it is placed on Exim's queue. ++ ++Some of the automatic processing takes place by default only for ++"locally-originated" messages. This adjective is used to describe messages that ++are not received over TCP/IP, but instead are passed to an Exim process on its ++standard input. This includes the interactive "local SMTP" case that is set up ++by the -bs command line option. ++ ++Note: Messages received over TCP/IP on the loopback interface (127.0.0.1 or ++::1) are not considered to be locally-originated. Exim does not treat the ++loopback interface specially in any way. ++ ++If you want the loopback interface to be treated specially, you must ensure ++that there are appropriate entries in your ACLs. ++ ++ ++46.1 Submission mode for non-local messages ++------------------------------------------- ++ ++Processing that happens automatically for locally-originated messages (unless ++suppress_local_fixups is set) can also be requested for messages that are ++received over TCP/IP. The term "submission mode" is used to describe this ++state. Submission mode is set by the modifier ++ ++control = submission ++ ++in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections 42.20 ++and 42.21). This makes Exim treat the message as a local submission, and is ++normally used when the source of the message is known to be an MUA running on a ++client host (as opposed to an MTA). For example, to set submission mode for ++messages originating on the IPv4 loopback interface, you could include the ++following in the MAIL ACL: ++ ++warn hosts = 127.0.0.1 ++ control = submission ++ ++There are some options that can be used when setting submission mode. A slash ++is used to separate options. For example: ++ ++control = submission/sender_retain ++ ++Specifying sender_retain has the effect of setting local_sender_retain true and ++local_from_check false for the current incoming message. The first of these ++allows an existing Sender: header in the message to remain, and the second ++suppresses the check to ensure that From: matches the authenticated sender. ++With this setting, Exim still fixes up messages by adding Date: and Message-ID: ++header lines if they are missing, but makes no attempt to check sender ++authenticity in header lines. ++ ++When sender_retain is not set, a submission mode setting may specify a domain ++to be used when generating a From: or Sender: header line. For example: ++ ++control = submission/domain=some.domain ++ ++The domain may be empty. How this value is used is described in sections 46.11 ++and 46.16. There is also a name option that allows you to specify the user's ++full name for inclusion in a created Sender: or From: header line. For example: ++ ++accept authenticated = * ++ control = submission/domain=wonderland.example/\ ++ name=${lookup {$authenticated_id} \ ++ lsearch {/etc/exim/namelist}} ++ ++Because the name may contain any characters, including slashes, the name option ++must be given last. The remainder of the string is used as the name. For the ++example above, if /etc/exim/namelist contains: ++ ++bigegg: Humpty Dumpty ++ ++then when the sender has authenticated as bigegg, the generated Sender: line ++would be: ++ ++Sender: Humpty Dumpty <bigegg@wonderland.example> ++ ++By default, submission mode forces the return path to the same address as is ++used to create the Sender: header. However, if sender_retain is specified, the ++return path is also left unchanged. ++ ++Note: The changes caused by submission mode take effect after the predata ACL. ++This means that any sender checks performed before the fix-ups use the ++untrusted sender address specified by the user, not the trusted sender address ++specified by submission mode. Although this might be slightly unexpected, it ++does mean that you can configure ACL checks to spot that a user is trying to ++spoof another's address. ++ ++ ++46.2 Line endings ++----------------- ++ ++RFC 2821 specifies that CRLF (two characters: carriage-return, followed by ++linefeed) is the line ending for messages transmitted over the Internet using ++SMTP over TCP/IP. However, within individual operating systems, different ++conventions are used. For example, Unix-like systems use just LF, but others ++use CRLF or just CR. ++ ++Exim was designed for Unix-like systems, and internally, it stores messages ++using the system's convention of a single LF as a line terminator. When ++receiving a message, all line endings are translated to this standard format. ++Originally, it was thought that programs that passed messages directly to an ++MTA within an operating system would use that system's convention. Experience ++has shown that this is not the case; for example, there are Unix applications ++that use CRLF in this circumstance. For this reason, and for compatibility with ++other MTAs, the way Exim handles line endings for all messages is now as ++follows: ++ ++ * LF not preceded by CR is treated as a line ending. ++ ++ * CR is treated as a line ending; if it is immediately followed by LF, the LF ++ is ignored. ++ ++ * The sequence "CR, dot, CR" does not terminate an incoming SMTP message, nor ++ a local message in the state where a line containing only a dot is a ++ terminator. ++ ++ * If a bare CR is encountered within a header line, an extra space is added ++ after the line terminator so as not to end the header line. The reasoning ++ behind this is that bare CRs in header lines are most likely either to be ++ mistakes, or people trying to play silly games. ++ ++ * If the first header line received in a message ends with CRLF, a subsequent ++ bare LF in a header line is treated in the same way as a bare CR in a ++ header line. ++ ++ ++46.3 Unqualified addresses ++-------------------------- ++ ++By default, Exim expects every envelope address it receives from an external ++host to be fully qualified. Unqualified addresses cause negative responses to ++SMTP commands. However, because SMTP is used as a means of transporting ++messages from MUAs running on personal workstations, there is sometimes a ++requirement to accept unqualified addresses from specific hosts or IP networks. ++ ++Exim has two options that separately control which hosts may send unqualified ++sender or recipient addresses in SMTP commands, namely sender_unqualified_hosts ++and recipient_unqualified_hosts. In both cases, if an unqualified address is ++accepted, it is qualified by adding the value of qualify_domain or ++qualify_recipient, as appropriate. ++ ++Unqualified addresses in header lines are automatically qualified for messages ++that are locally originated, unless the -bnq option is given on the command ++line. For messages received over SMTP, unqualified addresses in header lines ++are qualified only if unqualified addresses are permitted in SMTP commands. In ++other words, such qualification is also controlled by sender_unqualified_hosts ++and recipient_unqualified_hosts, ++ ++ ++46.4 The UUCP From line ++----------------------- ++ ++Messages that have come from UUCP (and some other applications) often begin ++with a line containing the envelope sender and a timestamp, following the word ++"From". Examples of two common formats are: ++ ++From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996 ++From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT ++ ++This line precedes the RFC 2822 header lines. For compatibility with Sendmail, ++Exim recognizes such lines at the start of messages that are submitted to it ++via the command line (that is, on the standard input). It does not recognize ++such lines in incoming SMTP messages, unless the sending host matches ++ignore_fromline_hosts or the -bs option was used for a local message and ++ignore_fromline_local is set. The recognition is controlled by a regular ++expression that is defined by the uucp_from_pattern option, whose default value ++matches the two common cases shown above and puts the address that follows ++"From" into $1. ++ ++When the caller of Exim for a non-SMTP message that contains a "From" line is a ++trusted user, the message's sender address is constructed by expanding the ++contents of uucp_sender_address, whose default value is "$1". This is then ++parsed as an RFC 2822 address. If there is no domain, the local part is ++qualified with qualify_domain unless it is the empty string. However, if the ++command line -f option is used, it overrides the "From" line. ++ ++If the caller of Exim is not trusted, the "From" line is recognized, but the ++sender address is not changed. This is also the case for incoming SMTP messages ++that are permitted to contain "From" lines. ++ ++Only one "From" line is recognized. If there is more than one, the second is ++treated as a data line that starts the body of the message, as it is not valid ++as a header line. This also happens if a "From" line is present in an incoming ++SMTP message from a source that is not permitted to send them. ++ ++ ++46.5 Resent- header lines ++------------------------- ++ ++RFC 2822 makes provision for sets of header lines starting with the string ++"Resent-" to be added to a message when it is resent by the original recipient ++to somebody else. These headers are Resent-Date:, Resent-From:, Resent-Sender:, ++Resent-To:, Resent-Cc:, Resent-Bcc: and Resent-Message-ID:. The RFC says: ++ ++ Resent fields are strictly informational. They MUST NOT be used in the ++ normal processing of replies or other such automatic actions on messages. ++ ++This leaves things a bit vague as far as other processing actions such as ++address rewriting are concerned. Exim treats Resent- header lines as follows: ++ ++ * A Resent-From: line that just contains the login id of the submitting user ++ is automatically rewritten in the same way as From: (see below). ++ ++ * If there's a rewriting rule for a particular header line, it is also ++ applied to Resent- header lines of the same type. For example, a rule that ++ rewrites From: also rewrites Resent-From:. ++ ++ * For local messages, if Sender: is removed on input, Resent-Sender: is also ++ removed. ++ ++ * For a locally-submitted message, if there are any Resent- header lines but ++ no Resent-Date:, Resent-From:, or Resent-Message-Id:, they are added as ++ necessary. It is the contents of Resent-Message-Id: (rather than ++ Message-Id:) which are included in log lines in this case. ++ ++ * The logic for adding Sender: is duplicated for Resent-Sender: when any ++ Resent- header lines are present. ++ ++ ++46.6 The Auto-Submitted: header line ++------------------------------------ ++ ++Whenever Exim generates an autoreply, a bounce, or a delay warning message, it ++includes the header line: ++ ++Auto-Submitted: auto-replied ++ ++ ++46.7 The Bcc: header line ++------------------------- ++ ++If Exim is called with the -t option, to take recipient addresses from a ++message's header, it removes any Bcc: header line that may exist (after ++extracting its addresses). If -t is not present on the command line, any ++existing Bcc: is not removed. ++ ++ ++46.8 The Date: header line ++-------------------------- ++ ++If a locally-generated or submission-mode message has no Date: header line, ++Exim adds one, using the current date and time, unless the ++suppress_local_fixups control has been specified. ++ ++ ++46.9 The Delivery-date: header line ++----------------------------------- ++ ++Delivery-date: header lines are not part of the standard RFC 2822 header set. ++Exim can be configured to add them to the final delivery of messages. (See the ++generic delivery_date_add transport option.) They should not be present in ++messages in transit. If the delivery_date_remove configuration option is set ++(the default), Exim removes Delivery-date: header lines from incoming messages. ++ ++ ++46.10 The Envelope-to: header line ++---------------------------------- ++ ++Envelope-to: header lines are not part of the standard RFC 2822 header set. ++Exim can be configured to add them to the final delivery of messages. (See the ++generic envelope_to_add transport option.) They should not be present in ++messages in transit. If the envelope_to_remove configuration option is set (the ++default), Exim removes Envelope-to: header lines from incoming messages. ++ ++ ++46.11 The From: header line ++--------------------------- ++ ++If a submission-mode message does not contain a From: header line, Exim adds ++one if either of the following conditions is true: ++ ++ * The envelope sender address is not empty (that is, this is not a bounce ++ message). The added header line copies the envelope sender address. ++ ++ * The SMTP session is authenticated and $authenticated_id is not empty. ++ ++ 1. If no domain is specified by the submission control, the local part is ++ $authenticated_id and the domain is $qualify_domain. ++ ++ 2. If a non-empty domain is specified by the submission control, the local ++ part is $authenticated_id, and the domain is the specified domain. ++ ++ 3. If an empty domain is specified by the submission control, ++ $authenticated_id is assumed to be the complete address. ++ ++A non-empty envelope sender takes precedence. ++ ++If a locally-generated incoming message does not contain a From: header line, ++and the suppress_local_fixups control is not set, Exim adds one containing the ++sender's address. The calling user's login name and full name are used to ++construct the address, as described in section 46.18. They are obtained from ++the password data by calling getpwuid() (but see the unknown_login ++configuration option). The address is qualified with qualify_domain. ++ ++For compatibility with Sendmail, if an incoming, non-SMTP message has a From: ++header line containing just the unqualified login name of the calling user, ++this is replaced by an address containing the user's login name and full name ++as described in section 46.18. ++ ++ ++46.12 The Message-ID: header line ++--------------------------------- ++ ++If a locally-generated or submission-mode incoming message does not contain a ++Message-ID: or Resent-Message-ID: header line, and the suppress_local_fixups ++control is not set, Exim adds a suitable header line to the message. If there ++are any Resent-: headers in the message, it creates Resent-Message-ID:. The id ++is constructed from Exim's internal message id, preceded by the letter E to ++ensure it starts with a letter, and followed by @ and the primary host name. ++Additional information can be included in this header line by setting the ++message_id_header_text and/or message_id_header_domain options. ++ ++ ++46.13 The Received: header line ++------------------------------- ++ ++A Received: header line is added at the start of every message. The contents ++are defined by the received_header_text configuration option, and Exim ++automatically adds a semicolon and a timestamp to the configured string. ++ ++The Received: header is generated as soon as the message's header lines have ++been received. At this stage, the timestamp in the Received: header line is the ++time that the message started to be received. This is the value that is seen by ++the DATA ACL and by the local_scan() function. ++ ++Once a message is accepted, the timestamp in the Received: header line is ++changed to the time of acceptance, which is (apart from a small delay while the ++-H spool file is written) the earliest time at which delivery could start. ++ ++ ++46.14 The References: header line ++--------------------------------- ++ ++Messages created by the autoreply transport include a References: header line. ++This is constructed according to the rules that are described in section 3.64 ++of RFC 2822 (which states that replies should contain such a header line), and ++section 3.14 of RFC 3834 (which states that automatic responses are not ++different in this respect). However, because some mail processing software does ++not cope well with very long header lines, no more than 12 message IDs are ++copied from the References: header line in the incoming message. If there are ++more than 12, the first one and then the final 11 are copied, before adding the ++message ID of the incoming message. ++ ++ ++46.15 The Return-path: header line ++---------------------------------- ++ ++Return-path: header lines are defined as something an MTA may insert when it ++does the final delivery of messages. (See the generic return_path_add transport ++option.) Therefore, they should not be present in messages in transit. If the ++return_path_remove configuration option is set (the default), Exim removes ++Return-path: header lines from incoming messages. ++ ++ ++46.16 The Sender: header line ++----------------------------- ++ ++For a locally-originated message from an untrusted user, Exim may remove an ++existing Sender: header line, and it may add a new one. You can modify these ++actions by setting the local_sender_retain option true, the local_from_check ++option false, or by using the suppress_local_fixups control setting. ++ ++When a local message is received from an untrusted user and local_from_check is ++true (the default), and the suppress_local_fixups control has not been set, a ++check is made to see if the address given in the From: header line is the ++correct (local) sender of the message. The address that is expected has the ++login name as the local part and the value of qualify_domain as the domain. ++Prefixes and suffixes for the local part can be permitted by setting ++local_from_prefix and local_from_suffix appropriately. If From: does not ++contain the correct sender, a Sender: line is added to the message. ++ ++If you set local_from_check false, this checking does not occur. However, the ++removal of an existing Sender: line still happens, unless you also set ++local_sender_retain to be true. It is not possible to set both of these options ++true at the same time. ++ ++By default, no processing of Sender: header lines is done for messages received ++over TCP/IP or for messages submitted by trusted users. However, when a message ++is received over TCP/IP in submission mode, and sender_retain is not specified ++on the submission control, the following processing takes place: ++ ++First, any existing Sender: lines are removed. Then, if the SMTP session is ++authenticated, and $authenticated_id is not empty, a sender address is created ++as follows: ++ ++ * If no domain is specified by the submission control, the local part is ++ $authenticated_id and the domain is $qualify_domain. ++ ++ * If a non-empty domain is specified by the submission control, the local ++ part is $authenticated_id, and the domain is the specified domain. ++ ++ * If an empty domain is specified by the submission control, ++ $authenticated_id is assumed to be the complete address. ++ ++This address is compared with the address in the From: header line. If they are ++different, a Sender: header line containing the created address is added. ++Prefixes and suffixes for the local part in From: can be permitted by setting ++local_from_prefix and local_from_suffix appropriately. ++ ++Note: Whenever a Sender: header line is created, the return path for the ++message (the envelope sender address) is changed to be the same address, except ++in the case of submission mode when sender_retain is specified. ++ ++ ++46.17 Adding and removing header lines in routers and transports ++---------------------------------------------------------------- ++ ++When a message is delivered, the addition and removal of header lines can be ++specified in a system filter, or on any of the routers and transports that ++process the message. Section 45.6 contains details about modifying headers in a ++system filter. Header lines can also be added in an ACL as a message is ++received (see section 42.23). ++ ++In contrast to what happens in a system filter, header modifications that are ++specified on routers and transports apply only to the particular recipient ++addresses that are being processed by those routers and transports. These ++changes do not actually take place until a copy of the message is being ++transported. Therefore, they do not affect the basic set of header lines, and ++they do not affect the values of the variables that refer to header lines. ++ ++Note: In particular, this means that any expansions in the configuration of the ++transport cannot refer to the modified header lines, because such expansions ++all occur before the message is actually transported. ++ ++For both routers and transports, the result of expanding a headers_add option ++must be in the form of one or more RFC 2822 header lines, separated by newlines ++(coded as "\n"). For example: ++ ++headers_add = X-added-header: added by $primary_hostname\n\ ++ X-added-second: another added header line ++ ++Exim does not check the syntax of these added header lines. ++ ++Multiple headers_add options for a single router or transport can be specified; ++the values will be concatenated (with a separating newline added) before ++expansion. ++ ++The result of expanding headers_remove must consist of a colon-separated list ++of header names. This is confusing, because header names themselves are often ++terminated by colons. In this case, the colons are the list separators, not ++part of the names. For example: ++ ++headers_remove = return-receipt-to:acknowledge-to ++ ++Multiple headers_remove options for a single router or transport can be ++specified; the values will be concatenated (with a separating colon added) ++before expansion. ++ ++When headers_add or headers_remove is specified on a router, its value is ++expanded at routing time, and then associated with all addresses that are ++accepted by that router, and also with any new addresses that it generates. If ++an address passes through several routers as a result of aliasing or ++forwarding, the changes are cumulative. ++ ++However, this does not apply to multiple routers that result from the use of ++the unseen option. Any header modifications that were specified by the "unseen" ++router or its predecessors apply only to the "unseen" delivery. ++ ++Addresses that end up with different headers_add or headers_remove settings ++cannot be delivered together in a batch, so a transport is always dealing with ++a set of addresses that have the same header-processing requirements. ++ ++The transport starts by writing the original set of header lines that arrived ++with the message, possibly modified by the system filter. As it writes out ++these lines, it consults the list of header names that were attached to the ++recipient address(es) by headers_remove options in routers, and it also ++consults the transport's own headers_remove option. Header lines whose names ++are on either of these lists are not written out. If there are multiple ++instances of any listed header, they are all skipped. ++ ++After the remaining original header lines have been written, new header lines ++that were specified by routers' headers_add options are written, in the order ++in which they were attached to the address. These are followed by any header ++lines specified by the transport's headers_add option. ++ ++This way of handling header line modifications in routers and transports has ++the following consequences: ++ ++ * The original set of header lines, possibly modified by the system filter, ++ remains "visible", in the sense that the $header_xxx variables refer to it, ++ at all times. ++ ++ * Header lines that are added by a router's headers_add option are not ++ accessible by means of the $header_xxx expansion syntax in subsequent ++ routers or the transport. ++ ++ * Conversely, header lines that are specified for removal by headers_remove ++ in a router remain visible to subsequent routers and the transport. ++ ++ * Headers added to an address by headers_add in a router cannot be removed by ++ a later router or by a transport. ++ ++ * An added header can refer to the contents of an original header that is to ++ be removed, even it has the same name as the added header. For example: ++ ++ headers_remove = subject ++ headers_add = Subject: new subject (was: $h_subject:) ++ ++Warning: The headers_add and headers_remove options cannot be used for a ++redirect router that has the one_time option set. ++ ++ ++46.18 Constructed addresses ++--------------------------- ++ ++When Exim constructs a sender address for a locally-generated message, it uses ++the form ++ ++<user name> <login@qualify_domain> ++ ++For example: ++ ++Zaphod Beeblebrox <zaphod@end.univ.example> ++ ++The user name is obtained from the -F command line option if set, or otherwise ++by looking up the calling user by getpwuid() and extracting the "gecos" field ++from the password entry. If the "gecos" field contains an ampersand character, ++this is replaced by the login name with the first letter upper cased, as is ++conventional in a number of operating systems. See the gecos_name option for a ++way to tailor the handling of the "gecos" field. The unknown_username option ++can be used to specify user names in cases when there is no password file ++entry. ++ ++In all cases, the user name is made to conform to RFC 2822 by quoting all or ++parts of it if necessary. In addition, if it contains any non-printing ++characters, it is encoded as described in RFC 2047, which defines a way of ++including non-ASCII characters in header lines. The value of the ++headers_charset option specifies the name of the encoding that is used (the ++characters are assumed to be in this encoding). The setting of ++print_topbitchars controls whether characters with the top bit set (that is, ++with codes greater than 127) count as printing characters or not. ++ ++ ++46.19 Case of local parts ++------------------------- ++ ++RFC 2822 states that the case of letters in the local parts of addresses cannot ++be assumed to be non-significant. Exim preserves the case of local parts of ++addresses, but by default it uses a lower-cased form when it is routing, ++because on most Unix systems, usernames are in lower case and case-insensitive ++routing is required. However, any particular router can be made to use the ++original case for local parts by setting the caseful_local_part generic router ++option. ++ ++If you must have mixed-case user names on your system, the best way to proceed, ++assuming you want case-independent handling of incoming email, is to set up ++your first router to convert incoming local parts in your domains to the ++correct case by means of a file lookup. For example: ++ ++correct_case: ++ driver = redirect ++ domains = +local_domains ++ data = ${lookup{$local_part}cdb\ ++ {/etc/usercased.cdb}{$value}fail}\ ++ @$domain ++ ++For this router, the local part is forced to lower case by the default action ( ++caseful_local_part is not set). The lower-cased local part is used to look up a ++new local part in the correct case. If you then set caseful_local_part on any ++subsequent routers which process your domains, they will operate on local parts ++with the correct case in a case-sensitive manner. ++ ++ ++46.20 Dots in local parts ++------------------------- ++ ++RFC 2822 forbids empty components in local parts. That is, an unquoted local ++part may not begin or end with a dot, nor have two consecutive dots in the ++middle. However, it seems that many MTAs do not enforce this, so Exim permits ++empty components for compatibility. ++ ++ ++46.21 Rewriting addresses ++------------------------- ++ ++Rewriting of sender and recipient addresses, and addresses in headers, can ++happen automatically, or as the result of configuration options, as described ++in chapter 31. The headers that may be affected by this are Bcc:, Cc:, From:, ++Reply-To:, Sender:, and To:. ++ ++Automatic rewriting includes qualification, as mentioned above. The other case ++in which it can happen is when an incomplete non-local domain is given. The ++routing process may cause this to be expanded into the full domain name. For ++example, a header such as ++ ++To: hare@teaparty ++ ++might get rewritten as ++ ++To: hare@teaparty.wonderland.fict.example ++ ++Rewriting as a result of routing is the one kind of message processing that ++does not happen at input time, as it cannot be done until the address has been ++routed. ++ ++Strictly, one should not do any deliveries of a message until all its addresses ++have been routed, in case any of the headers get changed as a result of ++routing. However, doing this in practice would hold up many deliveries for ++unreasonable amounts of time, just because one address could not immediately be ++routed. Exim therefore does not delay other deliveries when routing of one or ++more addresses is deferred. ++ ++ ++ ++=============================================================================== ++47. SMTP PROCESSING ++ ++Exim supports a number of different ways of using the SMTP protocol, and its ++LMTP variant, which is an interactive protocol for transferring messages into a ++closed mail store application. This chapter contains details of how SMTP is ++processed. For incoming mail, the following are available: ++ ++ * SMTP over TCP/IP (Exim daemon or inetd); ++ ++ * SMTP over the standard input and output (the -bs option); ++ ++ * Batched SMTP on the standard input (the -bS option). ++ ++For mail delivery, the following are available: ++ ++ * SMTP over TCP/IP (the smtp transport); ++ ++ * LMTP over TCP/IP (the smtp transport with the protocol option set to ++ "lmtp"); ++ ++ * LMTP over a pipe to a process running in the local host (the lmtp ++ transport); ++ ++ * Batched SMTP to a file or pipe (the appendfile and pipe transports with the ++ use_bsmtp option set). ++ ++Batched SMTP is the name for a process in which batches of messages are stored ++in or read from files (or pipes), in a format in which SMTP commands are used ++to contain the envelope information. ++ ++ ++47.1 Outgoing SMTP and LMTP over TCP/IP ++--------------------------------------- ++ ++Outgoing SMTP and LMTP over TCP/IP is implemented by the smtp transport. The ++protocol option selects which protocol is to be used, but the actual processing ++is the same in both cases. ++ ++If, in response to its EHLO command, Exim is told that the SIZE parameter is ++supported, it adds SIZE=<n> to each subsequent MAIL command. The value of <n> ++is the message size plus the value of the size_addition option (default 1024) ++to allow for additions to the message such as per-transport header lines, or ++changes made in a transport filter. If size_addition is set negative, the use ++of SIZE is suppressed. ++ ++If the remote server advertises support for PIPELINING, Exim uses the ++pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets ++required for the transaction. ++ ++If the remote server advertises support for the STARTTLS command, and Exim was ++built to support TLS encryption, it tries to start a TLS session unless the ++server matches hosts_avoid_tls. See chapter 41 for more details. Either a match ++in that or hosts_verify_avoid_tls apply when the transport is called for ++verification. ++ ++If the remote server advertises support for the AUTH command, Exim scans the ++authenticators configuration for any suitable client settings, as described in ++chapter 33. ++ ++Responses from the remote host are supposed to be terminated by CR followed by ++LF. However, there are known to be hosts that do not send CR characters, so in ++order to be able to interwork with such hosts, Exim treats LF on its own as a ++line terminator. ++ ++If a message contains a number of different addresses, all those with the same ++characteristics (for example, the same envelope sender) that resolve to the ++same set of hosts, in the same order, are sent in a single SMTP transaction, ++even if they are for different domains, unless there are more than the setting ++of the max_rcpts option in the smtp transport allows, in which case they are ++split into groups containing no more than max_rcpts addresses each. If ++remote_max_parallel is greater than one, such groups may be sent in parallel ++sessions. The order of hosts with identical MX values is not significant when ++checking whether addresses can be batched in this way. ++ ++When the smtp transport suffers a temporary failure that is not ++message-related, Exim updates its transport-specific database, which contains ++records indexed by host name that remember which messages are waiting for each ++particular host. It also updates the retry database with new retry times. ++ ++Exim's retry hints are based on host name plus IP address, so if one address of ++a multi-homed host is broken, it will soon be skipped most of the time. See the ++next section for more detail about error handling. ++ ++When a message is successfully delivered over a TCP/IP SMTP connection, Exim ++looks in the hints database for the transport to see if there are any queued ++messages waiting for the host to which it is connected. If it finds one, it ++creates a new Exim process using the -MC option (which can only be used by a ++process running as root or the Exim user) and passes the TCP/IP socket to it so ++that it can deliver another message using the same socket. The new process does ++only those deliveries that are routed to the connected host, and may in turn ++pass the socket on to a third process, and so on. ++ ++The connection_max_messages option of the smtp transport can be used to limit ++the number of messages sent down a single TCP/IP connection. ++ ++The second and subsequent messages delivered down an existing connection are ++identified in the main log by the addition of an asterisk after the closing ++square bracket of the IP address. ++ ++ ++47.2 Errors in outgoing SMTP ++---------------------------- ++ ++Three different kinds of error are recognized for outgoing SMTP: host errors, ++message errors, and recipient errors. ++ ++Host errors ++ ++ A host error is not associated with a particular message or with a ++ particular recipient of a message. The host errors are: ++ ++ + Connection refused or timed out, ++ ++ + Any error response code on connection, ++ ++ + Any error response code to EHLO or HELO, ++ ++ + Loss of connection at any time, except after ".", ++ ++ + I/O errors at any time, ++ ++ + Timeouts during the session, other than in response to MAIL, RCPT or ++ the "." at the end of the data. ++ ++ For a host error, a permanent error response on connection, or in response ++ to EHLO, causes all addresses routed to the host to be failed. Any other ++ host error causes all addresses to be deferred, and retry data to be ++ created for the host. It is not tried again, for any message, until its ++ retry time arrives. If the current set of addresses are not all delivered ++ in this run (to some alternative host), the message is added to the list of ++ those waiting for this host, so if it is still undelivered when a ++ subsequent successful delivery is made to the host, it will be sent down ++ the same SMTP connection. ++ ++Message errors ++ ++ A message error is associated with a particular message when sent to a ++ particular host, but not with a particular recipient of the message. The ++ message errors are: ++ ++ + Any error response code to MAIL, DATA, or the "." that terminates the ++ data, ++ ++ + Timeout after MAIL, ++ ++ + Timeout or loss of connection after the "." that terminates the data. A ++ timeout after the DATA command itself is treated as a host error, as is ++ loss of connection at any other time. ++ ++ For a message error, a permanent error response (5xx) causes all addresses ++ to be failed, and a delivery error report to be returned to the sender. A ++ temporary error response (4xx), or one of the timeouts, causes all ++ addresses to be deferred. Retry data is not created for the host, but ++ instead, a retry record for the combination of host plus message id is ++ created. The message is not added to the list of those waiting for this ++ host. This ensures that the failing message will not be sent to this host ++ again until the retry time arrives. However, other messages that are routed ++ to the host are not affected, so if it is some property of the message that ++ is causing the error, it will not stop the delivery of other mail. ++ ++ If the remote host specified support for the SIZE parameter in its response ++ to EHLO, Exim adds SIZE=nnn to the MAIL command, so an over-large message ++ will cause a message error because the error arrives as a response to MAIL. ++ ++Recipient errors ++ ++ A recipient error is associated with a particular recipient of a message. ++ The recipient errors are: ++ ++ + Any error response to RCPT, ++ ++ + Timeout after RCPT. ++ ++ For a recipient error, a permanent error response (5xx) causes the ++ recipient address to be failed, and a bounce message to be returned to the ++ sender. A temporary error response (4xx) or a timeout causes the failing ++ address to be deferred, and routing retry data to be created for it. This ++ is used to delay processing of the address in subsequent queue runs, until ++ its routing retry time arrives. This applies to all messages, but because ++ it operates only in queue runs, one attempt will be made to deliver a new ++ message to the failing address before the delay starts to operate. This ++ ensures that, if the failure is really related to the message rather than ++ the recipient ("message too big for this recipient" is a possible example), ++ other messages have a chance of getting delivered. If a delivery to the ++ address does succeed, the retry information gets cleared, so all stuck ++ messages get tried again, and the retry clock is reset. ++ ++ The message is not added to the list of those waiting for this host. Use of ++ the host for other messages is unaffected, and except in the case of a ++ timeout, other recipients are processed independently, and may be ++ successfully delivered in the current SMTP session. After a timeout it is ++ of course impossible to proceed with the session, so all addresses get ++ deferred. However, those other than the one that failed do not suffer any ++ subsequent retry delays. Therefore, if one recipient is causing trouble, ++ the others have a chance of getting through when a subsequent delivery ++ attempt occurs before the failing recipient's retry time. ++ ++In all cases, if there are other hosts (or IP addresses) available for the ++current set of addresses (for example, from multiple MX records), they are ++tried in this run for any undelivered addresses, subject of course to their own ++retry data. In other words, recipient error retry data does not take effect ++until the next delivery attempt. ++ ++Some hosts have been observed to give temporary error responses to every MAIL ++command at certain times ("insufficient space" has been seen). It would be nice ++if such circumstances could be recognized, and defer data for the host itself ++created, but this is not possible within the current Exim design. What actually ++happens is that retry data for every (host, message) combination is created. ++ ++The reason that timeouts after MAIL and RCPT are treated specially is that ++these can sometimes arise as a result of the remote host's verification ++procedures. Exim makes this assumption, and treats them as if a temporary error ++response had been received. A timeout after "." is treated specially because it ++is known that some broken implementations fail to recognize the end of the ++message if the last character of the last line is a binary zero. Thus, it is ++helpful to treat this case as a message error. ++ ++Timeouts at other times are treated as host errors, assuming a problem with the ++host, or the connection to it. If a timeout after MAIL, RCPT, or "." is really ++a connection problem, the assumption is that at the next try the timeout is ++likely to occur at some other point in the dialogue, causing it then to be ++treated as a host error. ++ ++There is experimental evidence that some MTAs drop the connection after the ++terminating "." if they do not like the contents of the message for some ++reason, in contravention of the RFC, which indicates that a 5xx response should ++be given. That is why Exim treats this case as a message rather than a host ++error, in order not to delay other messages to the same host. ++ ++ ++47.3 Incoming SMTP messages over TCP/IP ++--------------------------------------- ++ ++Incoming SMTP messages can be accepted in one of two ways: by running a ++listening daemon, or by using inetd. In the latter case, the entry in /etc/ ++inetd.conf should be like this: ++ ++smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs ++ ++Exim distinguishes between this case and the case of a locally running user ++agent using the -bs option by checking whether or not the standard input is a ++socket. When it is, either the port must be privileged (less than 1024), or the ++caller must be root or the Exim user. If any other user passes a socket with an ++unprivileged port number, Exim prints a message on the standard error stream ++and exits with an error code. ++ ++By default, Exim does not make a log entry when a remote host connects or ++disconnects (either via the daemon or inetd), unless the disconnection is ++unexpected. It can be made to write such log entries by setting the ++smtp_connection log selector. ++ ++Commands from the remote host are supposed to be terminated by CR followed by ++LF. However, there are known to be hosts that do not send CR characters. In ++order to be able to interwork with such hosts, Exim treats LF on its own as a ++line terminator. Furthermore, because common code is used for receiving ++messages from all sources, a CR on its own is also interpreted as a line ++terminator. However, the sequence "CR, dot, CR" does not terminate incoming ++SMTP data. ++ ++One area that sometimes gives rise to problems concerns the EHLO or HELO ++commands. Some clients send syntactically invalid versions of these commands, ++which Exim rejects by default. (This is nothing to do with verifying the data ++that is sent, so helo_verify_hosts is not relevant.) You can tell Exim not to ++apply a syntax check by setting helo_accept_junk_hosts to match the broken ++hosts that send invalid commands. ++ ++The amount of disk space available is checked whenever SIZE is received on a ++MAIL command, independently of whether message_size_limit or check_spool_space ++is configured, unless smtp_check_spool_space is set false. A temporary error is ++given if there is not enough space. If check_spool_space is set, the check is ++for that amount of space plus the value given with SIZE, that is, it checks ++that the addition of the incoming message will not reduce the space below the ++threshold. ++ ++When a message is successfully received, Exim includes the local message id in ++its response to the final "." that terminates the data. If the remote host logs ++this text it can help with tracing what has happened to a message. ++ ++The Exim daemon can limit the number of simultaneous incoming connections it is ++prepared to handle (see the smtp_accept_max option). It can also limit the ++number of simultaneous incoming connections from a single remote host (see the ++smtp_accept_max_per_host option). Additional connection attempts are rejected ++using the SMTP temporary error code 421. ++ ++The Exim daemon does not rely on the SIGCHLD signal to detect when a subprocess ++has finished, as this can get lost at busy times. Instead, it looks for ++completed subprocesses every time it wakes up. Provided there are other things ++happening (new incoming calls, starts of queue runs), completed processes will ++be noticed and tidied away. On very quiet systems you may sometimes see a ++"defunct" Exim process hanging about. This is not a problem; it will be noticed ++when the daemon next wakes up. ++ ++When running as a daemon, Exim can reserve some SMTP slots for specific hosts, ++and can also be set up to reject SMTP calls from non-reserved hosts at times of ++high system load - for details see the smtp_accept_reserve, smtp_load_reserve, ++and smtp_reserve_hosts options. The load check applies in both the daemon and ++inetd cases. ++ ++Exim normally starts a delivery process for each message received, though this ++can be varied by means of the -odq command line option and the queue_only, ++queue_only_file, and queue_only_load options. The number of simultaneously ++running delivery processes started in this way from SMTP input can be limited ++by the smtp_accept_queue and smtp_accept_queue_per_connection options. When ++either limit is reached, subsequently received messages are just put on the ++input queue without starting a delivery process. ++ ++The controls that involve counts of incoming SMTP calls (smtp_accept_max, ++smtp_accept_queue, smtp_accept_reserve) are not available when Exim is started ++up from the inetd daemon, because in that case each connection is handled by an ++entirely independent Exim process. Control by load average is, however, ++available with inetd. ++ ++Exim can be configured to verify addresses in incoming SMTP commands as they ++are received. See chapter 42 for details. It can also be configured to rewrite ++addresses at this time - before any syntax checking is done. See section 31.9. ++ ++Exim can also be configured to limit the rate at which a client host submits ++MAIL and RCPT commands in a single SMTP session. See the smtp_ratelimit_hosts ++option. ++ ++ ++47.4 Unrecognized SMTP commands ++------------------------------- ++ ++If Exim receives more than smtp_max_unknown_commands unrecognized SMTP commands ++during a single SMTP connection, it drops the connection after sending the ++error response to the last command. The default value for ++smtp_max_unknown_commands is 3. This is a defence against some kinds of abuse ++that subvert web servers into making connections to SMTP ports; in these ++circumstances, a number of non-SMTP lines are sent first. ++ ++ ++47.5 Syntax and protocol errors in SMTP commands ++------------------------------------------------ ++ ++A syntax error is detected if an SMTP command is recognized, but there is ++something syntactically wrong with its data, for example, a malformed email ++address in a RCPT command. Protocol errors include invalid command sequencing ++such as RCPT before MAIL. If Exim receives more than smtp_max_synprot_errors ++such commands during a single SMTP connection, it drops the connection after ++sending the error response to the last command. The default value for ++smtp_max_synprot_errors is 3. This is a defence against broken clients that ++loop sending bad commands (yes, it has been seen). ++ ++ ++47.6 Use of non-mail SMTP commands ++---------------------------------- ++ ++The "non-mail" SMTP commands are those other than MAIL, RCPT, and DATA. Exim ++counts such commands, and drops the connection if there are too many of them in ++a single SMTP session. This action catches some denial-of-service attempts and ++things like repeated failing AUTHs, or a mad client looping sending EHLO. The ++global option smtp_accept_max_nonmail defines what "too many" means. Its ++default value is 10. ++ ++When a new message is expected, one occurrence of RSET is not counted. This ++allows a client to send one RSET between messages (this is not necessary, but ++some clients do it). Exim also allows one uncounted occurrence of HELO or EHLO, ++and one occurrence of STARTTLS between messages. After starting up a TLS ++session, another EHLO is expected, and so it too is not counted. ++ ++The first occurrence of AUTH in a connection, or immediately following STARTTLS ++is also not counted. Otherwise, all commands other than MAIL, RCPT, DATA, and ++QUIT are counted. ++ ++You can control which hosts are subject to the limit set by ++smtp_accept_max_nonmail by setting smtp_accept_max_nonmail_hosts. The default ++value is "*", which makes the limit apply to all hosts. This option means that ++you can exclude any specific badly-behaved hosts that you have to live with. ++ ++ ++47.7 The VRFY and EXPN commands ++------------------------------- ++ ++When Exim receives a VRFY or EXPN command on a TCP/IP connection, it runs the ++ACL specified by acl_smtp_vrfy or acl_smtp_expn (as appropriate) in order to ++decide whether the command should be accepted or not. If no ACL is defined, the ++command is rejected. ++ ++When VRFY is accepted, it runs exactly the same code as when Exim is called ++with the -bv option. ++ ++When EXPN is accepted, a single-level expansion of the address is done. EXPN is ++treated as an "address test" (similar to the -bt option) rather than a ++verification (the -bv option). If an unqualified local part is given as the ++argument to EXPN, it is qualified with qualify_domain. Rejections of VRFY and ++EXPN commands are logged on the main and reject logs, and VRFY verification ++failures are logged on the main log for consistency with RCPT failures. ++ ++ ++47.8 The ETRN command ++--------------------- ++ ++RFC 1985 describes an SMTP command called ETRN that is designed to overcome the ++security problems of the TURN command (which has fallen into disuse). When Exim ++receives an ETRN command on a TCP/IP connection, it runs the ACL specified by ++acl_smtp_etrn in order to decide whether the command should be accepted or not. ++If no ACL is defined, the command is rejected. ++ ++The ETRN command is concerned with "releasing" messages that are awaiting ++delivery to certain hosts. As Exim does not organize its message queue by host, ++the only form of ETRN that is supported by default is the one where the text ++starts with the "#" prefix, in which case the remainder of the text is specific ++to the SMTP server. A valid ETRN command causes a run of Exim with the -R ++option to happen, with the remainder of the ETRN text as its argument. For ++example, ++ ++ETRN #brigadoon ++ ++runs the command ++ ++exim -R brigadoon ++ ++which causes a delivery attempt on all messages with undelivered addresses ++containing the text "brigadoon". When smtp_etrn_serialize is set (the default), ++Exim prevents the simultaneous execution of more than one queue run for the ++same argument string as a result of an ETRN command. This stops a misbehaving ++client from starting more than one queue runner at once. ++ ++Exim implements the serialization by means of a hints database in which a ++record is written whenever a process is started by ETRN, and deleted when the ++process completes. However, Exim does not keep the SMTP session waiting for the ++ETRN process to complete. Once ETRN is accepted, the client is sent a "success" ++return code. Obviously there is scope for hints records to get left lying ++around if there is a system or program crash. To guard against this, Exim ++ignores any records that are more than six hours old. ++ ++For more control over what ETRN does, the smtp_etrn_command option can used. ++This specifies a command that is run whenever ETRN is received, whatever the ++form of its argument. For example: ++ ++smtp_etrn_command = /etc/etrn_command $domain \ ++ $sender_host_address ++ ++The string is split up into arguments which are independently expanded. The ++expansion variable $domain is set to the argument of the ETRN command, and no ++syntax checking is done on the contents of this argument. Exim does not wait ++for the command to complete, so its status code is not checked. Exim runs under ++its own uid and gid when receiving incoming SMTP, so it is not possible for it ++to change them before running the command. ++ ++ ++47.9 Incoming local SMTP ++------------------------ ++ ++Some user agents use SMTP to pass messages to their local MTA using the ++standard input and output, as opposed to passing the envelope on the command ++line and writing the message to the standard input. This is supported by the ++-bs option. This form of SMTP is handled in the same way as incoming messages ++over TCP/IP (including the use of ACLs), except that the envelope sender given ++in a MAIL command is ignored unless the caller is trusted. In an ACL you can ++detect this form of SMTP input by testing for an empty host identification. It ++is common to have this as the first line in the ACL that runs for RCPT ++commands: ++ ++accept hosts = : ++ ++This accepts SMTP messages from local processes without doing any other tests. ++ ++ ++47.10 Outgoing batched SMTP ++--------------------------- ++ ++Both the appendfile and pipe transports can be used for handling batched SMTP. ++Each has an option called use_bsmtp which causes messages to be output in BSMTP ++format. No SMTP responses are possible for this form of delivery. All it is ++doing is using SMTP commands as a way of transmitting the envelope along with ++the message. ++ ++The message is written to the file or pipe preceded by the SMTP commands MAIL ++and RCPT, and followed by a line containing a single dot. Lines in the message ++that start with a dot have an extra dot added. The SMTP command HELO is not ++normally used. If it is required, the message_prefix option can be used to ++specify it. ++ ++Because appendfile and pipe are both local transports, they accept only one ++recipient address at a time by default. However, you can arrange for them to ++handle several addresses at once by setting the batch_max option. When this is ++done for BSMTP, messages may contain multiple RCPT commands. See chapter 25 for ++more details. ++ ++When one or more addresses are routed to a BSMTP transport by a router that ++sets up a host list, the name of the first host on the list is available to the ++transport in the variable $host. Here is an example of such a transport and ++router: ++ ++begin routers ++route_append: ++ driver = manualroute ++ transport = smtp_appendfile ++ route_list = domain.example batch.host.example ++ ++begin transports ++smtp_appendfile: ++ driver = appendfile ++ directory = /var/bsmtp/$host ++ batch_max = 1000 ++ use_bsmtp ++ user = exim ++ ++This causes messages addressed to domain.example to be written in BSMTP format ++to /var/bsmtp/batch.host.example, with only a single copy of each message ++(unless there are more than 1000 recipients). ++ ++ ++47.11 Incoming batched SMTP ++--------------------------- ++ ++The -bS command line option causes Exim to accept one or more messages by ++reading SMTP on the standard input, but to generate no responses. If the caller ++is trusted, the senders in the MAIL commands are believed; otherwise the sender ++is always the caller of Exim. Unqualified senders and receivers are not ++rejected (there seems little point) but instead just get qualified. HELO and ++EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act as NOOP; QUIT quits. ++ ++Minimal policy checking is done for BSMTP input. Only the non-SMTP ACL is run ++in the same way as for non-SMTP local input. ++ ++If an error is detected while reading a message, including a missing "." at the ++end, Exim gives up immediately. It writes details of the error to the standard ++output in a stylized way that the calling program should be able to make some ++use of automatically, for example: ++ ++554 Unexpected end of file ++Transaction started in line 10 ++Error detected in line 14 ++ ++It writes a more verbose version, for human consumption, to the standard error ++file, for example: ++ ++An error was detected while processing a file of BSMTP input. ++The error message was: ++ ++501 '>' missing at end of address ++ ++The SMTP transaction started in line 10. ++The error was detected in line 12. ++The SMTP command at fault was: ++ ++rcpt to:<malformed@in.com.plete ++ ++1 previous message was successfully processed. ++The rest of the batch was abandoned. ++ ++The return code from Exim is zero only if there were no errors. It is 1 if some ++messages were accepted before an error was detected, and 2 if no messages were ++accepted. ++ ++ ++ ++=============================================================================== ++48. CUSTOMIZING BOUNCE AND WARNING MESSAGES ++ ++When a message fails to be delivered, or remains on the queue for more than a ++configured amount of time, Exim sends a message to the original sender, or to ++an alternative configured address. The text of these messages is built into the ++code of Exim, but it is possible to change it, either by adding a single ++string, or by replacing each of the paragraphs by text supplied in a file. ++ ++The From: and To: header lines are automatically generated; you can cause a ++Reply-To: line to be added by setting the errors_reply_to option. Exim also ++adds the line ++ ++Auto-Submitted: auto-generated ++ ++to all warning and bounce messages, ++ ++ ++48.1 Customizing bounce messages ++-------------------------------- ++ ++If bounce_message_text is set, its contents are included in the default message ++immediately after "This message was created automatically by mail delivery ++software." The string is not expanded. It is not used if bounce_message_file is ++set. ++ ++When bounce_message_file is set, it must point to a template file for ++constructing error messages. The file consists of a series of text items, ++separated by lines consisting of exactly four asterisks. If the file cannot be ++opened, default text is used and a message is written to the main and panic ++logs. If any text item in the file is empty, default text is used for that ++item. ++ ++Each item of text that is read from the file is expanded, and there are two ++expansion variables which can be of use here: $bounce_recipient is set to the ++recipient of an error message while it is being created, and ++$bounce_return_size_limit contains the value of the return_size_limit option, ++rounded to a whole number. ++ ++The items must appear in the file in the following order: ++ ++ * The first item is included in the headers, and should include at least a ++ Subject: header. Exim does not check the syntax of these headers. ++ ++ * The second item forms the start of the error message. After it, Exim lists ++ the failing addresses with their error messages. ++ ++ * The third item is used to introduce any text from pipe transports that is ++ to be returned to the sender. It is omitted if there is no such text. ++ ++ * The fourth item is used to introduce the copy of the message that is ++ returned as part of the error report. ++ ++ * The fifth item is added after the fourth one if the returned message is ++ truncated because it is bigger than return_size_limit. ++ ++ * The sixth item is added after the copy of the original message. ++ ++The default state (bounce_message_file unset) is equivalent to the following ++file, in which the sixth item is empty. The Subject: and some other lines have ++been split in order to fit them on the page: ++ ++Subject: Mail delivery failed ++ ${if eq{$sender_address}{$bounce_recipient} ++ {: returning message to sender}} ++**** ++This message was created automatically by mail delivery software. ++ ++A message ${if eq{$sender_address}{$bounce_recipient} ++ {that you sent }{sent by ++ ++<$sender_address> ++ ++}}could not be delivered to all of its recipients. ++This is a permanent error. The following address(es) failed: ++**** ++The following text was generated during the delivery attempt(s): ++**** ++------ This is a copy of the message, including all the headers. ++ ------ ++**** ++------ The body of the message is $message_size characters long; ++ only the first ++------ $bounce_return_size_limit or so are included here. ++**** ++ ++ ++48.2 Customizing warning messages ++--------------------------------- ++ ++The option warn_message_file can be pointed at a template file for use when ++warnings about message delays are created. In this case there are only three ++text sections: ++ ++ * The first item is included in the headers, and should include at least a ++ Subject: header. Exim does not check the syntax of these headers. ++ ++ * The second item forms the start of the warning message. After it, Exim ++ lists the delayed addresses. ++ ++ * The third item then ends the message. ++ ++The default state is equivalent to the following file, except that some lines ++have been split here, in order to fit them on the page: ++ ++Subject: Warning: message $message_exim_id delayed ++ $warn_message_delay ++**** ++This message was created automatically by mail delivery software. ++ ++A message ${if eq{$sender_address}{$warn_message_recipients} ++{that you sent }{sent by ++ ++<$sender_address> ++ ++}}has not been delivered to all of its recipients after ++more than $warn_message_delay on the queue on $primary_hostname. ++ ++The message identifier is: $message_exim_id ++The subject of the message is: $h_subject ++The date of the message is: $h_date ++ ++The following address(es) have not yet been delivered: ++**** ++No action is required on your part. Delivery attempts will ++continue for some time, and this warning may be repeated at ++intervals if the message remains undelivered. Eventually the ++mail delivery software will give up, and when that happens, ++the message will be returned to you. ++ ++However, in the default state the subject and date lines are omitted if no ++appropriate headers exist. During the expansion of this file, ++$warn_message_delay is set to the delay time in one of the forms "<n> minutes" ++or "<n> hours", and $warn_message_recipients contains a list of recipients for ++the warning message. There may be more than one if there are multiple addresses ++with different errors_to settings on the routers that handled them. ++ ++ ++ ++=============================================================================== ++49. SOME COMMON CONFIGURATION SETTINGS ++ ++This chapter discusses some configuration settings that seem to be fairly ++common. More examples and discussion can be found in the Exim book. ++ ++ ++49.1 Sending mail to a smart host ++--------------------------------- ++ ++If you want to send all mail for non-local domains to a "smart host", you ++should replace the default dnslookup router with a router which does the ++routing explicitly: ++ ++send_to_smart_host: ++ driver = manualroute ++ route_list = !+local_domains smart.host.name ++ transport = remote_smtp ++ ++You can use the smart host's IP address instead of the name if you wish. If you ++are using Exim only to submit messages to a smart host, and not for receiving ++incoming messages, you can arrange for it to do the submission synchronously by ++setting the mua_wrapper option (see chapter 50). ++ ++ ++49.2 Using Exim to handle mailing lists ++--------------------------------------- ++ ++Exim can be used to run simple mailing lists, but for large and/or complicated ++requirements, the use of additional specialized mailing list software such as ++Majordomo or Mailman is recommended. ++ ++The redirect router can be used to handle mailing lists where each list is ++maintained in a separate file, which can therefore be managed by an independent ++manager. The domains router option can be used to run these lists in a separate ++domain from normal mail. For example: ++ ++lists: ++ driver = redirect ++ domains = lists.example ++ file = /usr/lists/$local_part ++ forbid_pipe ++ forbid_file ++ errors_to = $local_part-request@lists.example ++ no_more ++ ++This router is skipped for domains other than lists.example. For addresses in ++that domain, it looks for a file that matches the local part. If there is no ++such file, the router declines, but because no_more is set, no subsequent ++routers are tried, and so the whole delivery fails. ++ ++The forbid_pipe and forbid_file options prevent a local part from being ++expanded into a file name or a pipe delivery, which is usually inappropriate in ++a mailing list. ++ ++The errors_to option specifies that any delivery errors caused by addresses ++taken from a mailing list are to be sent to the given address rather than the ++original sender of the message. However, before acting on this, Exim verifies ++the error address, and ignores it if verification fails. ++ ++For example, using the configuration above, mail sent to dicts@lists.example is ++passed on to those addresses contained in /usr/lists/dicts, with error reports ++directed to dicts-request@lists.example, provided that this address can be ++verified. There could be a file called /usr/lists/dicts-request containing the ++address(es) of this particular list's manager(s), but other approaches, such as ++setting up an earlier router (possibly using the local_part_prefix or ++local_part_suffix options) to handle addresses of the form owner-xxx or xxx- ++request, are also possible. ++ ++ ++49.3 Syntax errors in mailing lists ++----------------------------------- ++ ++If an entry in redirection data contains a syntax error, Exim normally defers ++delivery of the original address. That means that a syntax error in a mailing ++list holds up all deliveries to the list. This may not be appropriate when a ++list is being maintained automatically from data supplied by users, and the ++addresses are not rigorously checked. ++ ++If the skip_syntax_errors option is set, the redirect router just skips entries ++that fail to parse, noting the incident in the log. If in addition ++syntax_errors_to is set to a verifiable address, a message is sent to it ++whenever a broken address is skipped. It is usually appropriate to set ++syntax_errors_to to the same address as errors_to. ++ ++ ++49.4 Re-expansion of mailing lists ++---------------------------------- ++ ++Exim remembers every individual address to which a message has been delivered, ++in order to avoid duplication, but it normally stores only the original ++recipient addresses with a message. If all the deliveries to a mailing list ++cannot be done at the first attempt, the mailing list is re-expanded when the ++delivery is next tried. This means that alterations to the list are taken into ++account at each delivery attempt, so addresses that have been added to the list ++since the message arrived will therefore receive a copy of the message, even ++though it pre-dates their subscription. ++ ++If this behaviour is felt to be undesirable, the one_time option can be set on ++the redirect router. If this is done, any addresses generated by the router ++that fail to deliver at the first attempt are added to the message as "top ++level" addresses, and the parent address that generated them is marked ++"delivered". Thus, expansion of the mailing list does not happen again at the ++subsequent delivery attempts. The disadvantage of this is that if any of the ++failing addresses are incorrect, correcting them in the file has no effect on ++pre-existing messages. ++ ++The original top-level address is remembered with each of the generated ++addresses, and is output in any log messages. However, any intermediate parent ++addresses are not recorded. This makes a difference to the log only if the ++all_parents selector is set, but for mailing lists there is normally only one ++level of expansion anyway. ++ ++ ++49.5 Closed mailing lists ++------------------------- ++ ++The examples so far have assumed open mailing lists, to which anybody may send ++mail. It is also possible to set up closed lists, where mail is accepted from ++specified senders only. This is done by making use of the generic senders ++option to restrict the router that handles the list. ++ ++The following example uses the same file as a list of recipients and as a list ++of permitted senders. It requires three routers: ++ ++lists_request: ++ driver = redirect ++ domains = lists.example ++ local_part_suffix = -request ++ file = /usr/lists/$local_part$local_part_suffix ++ no_more ++ ++lists_post: ++ driver = redirect ++ domains = lists.example ++ senders = ${if exists {/usr/lists/$local_part}\ ++ {lsearch;/usr/lists/$local_part}{*}} ++ file = /usr/lists/$local_part ++ forbid_pipe ++ forbid_file ++ errors_to = $local_part-request@lists.example ++ no_more ++ ++lists_closed: ++ driver = redirect ++ domains = lists.example ++ allow_fail ++ data = :fail: $local_part@lists.example is a closed mailing list ++ ++All three routers have the same domains setting, so for any other domains, they ++are all skipped. The first router runs only if the local part ends in -request. ++It handles messages to the list manager(s) by means of an open mailing list. ++ ++The second router runs only if the senders precondition is satisfied. It checks ++for the existence of a list that corresponds to the local part, and then checks ++that the sender is on the list by means of a linear search. It is necessary to ++check for the existence of the file before trying to search it, because ++otherwise Exim thinks there is a configuration error. If the file does not ++exist, the expansion of senders is *, which matches all senders. This means ++that the router runs, but because there is no list, declines, and no_more ++ensures that no further routers are run. The address fails with an "unrouteable ++address" error. ++ ++The third router runs only if the second router is skipped, which happens when ++a mailing list exists, but the sender is not on it. This router forcibly fails ++the address, giving a suitable error message. ++ ++ ++49.6 Variable Envelope Return Paths (VERP) ++------------------------------------------ ++ ++Variable Envelope Return Paths - see http://cr.yp.to/proto/verp.txt - are a way ++of helping mailing list administrators discover which subscription address is ++the cause of a particular delivery failure. The idea is to encode the original ++recipient address in the outgoing envelope sender address, so that if the ++message is forwarded by another host and then subsequently bounces, the ++original recipient can be extracted from the recipient address of the bounce. ++ ++Envelope sender addresses can be modified by Exim using two different ++facilities: the errors_to option on a router (as shown in previous mailing list ++examples), or the return_path option on a transport. The second of these is ++effective only if the message is successfully delivered to another host; it is ++not used for errors detected on the local host (see the description of ++return_path in chapter 24). Here is an example of the use of return_path to ++implement VERP on an smtp transport: ++ ++verp_smtp: ++ driver = smtp ++ max_rcpt = 1 ++ return_path = \ ++ ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\ ++ {$1-request+$local_part=$domain@your.dom.example}fail} ++ ++This has the effect of rewriting the return path (envelope sender) on outgoing ++SMTP messages, if the local part of the original return path ends in ++"-request", and the domain is your.dom.example. The rewriting inserts the local ++part and domain of the recipient into the return path. Suppose, for example, ++that a message whose return path has been set to ++somelist-request@your.dom.example is sent to subscriber@other.dom.example. In ++the transport, the return path is rewritten as ++ ++somelist-request+subscriber=other.dom.example@your.dom.example ++ ++For this to work, you must tell Exim to send multiple copies of messages that ++have more than one recipient, so that each copy has just one recipient. This is ++achieved by setting max_rcpt to 1. Without this, a single copy of a message ++might be sent to several different recipients in the same domain, in which case ++$local_part is not available in the transport, because it is not unique. ++ ++Unless your host is doing nothing but mailing list deliveries, you should ++probably use a separate transport for the VERP deliveries, so as not to use ++extra resources in making one-per-recipient copies for other deliveries. This ++can easily be done by expanding the transport option in the router: ++ ++dnslookup: ++ driver = dnslookup ++ domains = ! +local_domains ++ transport = \ ++ ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\ ++ {verp_smtp}{remote_smtp}} ++ no_more ++ ++If you want to change the return path using errors_to in a router instead of ++using return_path in the transport, you need to set errors_to on all routers ++that handle mailing list addresses. This will ensure that all delivery errors, ++including those detected on the local host, are sent to the VERP address. ++ ++On a host that does no local deliveries and has no manual routing, only the ++dnslookup router needs to be changed. A special transport is not needed for ++SMTP deliveries. Every mailing list recipient has its own return path value, ++and so Exim must hand them to the transport one at a time. Here is an example ++of a dnslookup router that implements VERP: ++ ++verp_dnslookup: ++ driver = dnslookup ++ domains = ! +local_domains ++ transport = remote_smtp ++ errors_to = \ ++ ${if match {$return_path}{^(.+?)-request@your.dom.example\$}} ++ {$1-request+$local_part=$domain@your.dom.example}fail} ++ no_more ++ ++Before you start sending out messages with VERPed return paths, you must also ++configure Exim to accept the bounce messages that come back to those paths. ++Typically this is done by setting a local_part_suffix option for a router, and ++using this to route the messages to wherever you want to handle them. ++ ++The overhead incurred in using VERP depends very much on the size of the ++message, the number of recipient addresses that resolve to the same remote ++host, and the speed of the connection over which the message is being sent. If ++a lot of addresses resolve to the same host and the connection is slow, sending ++a separate copy of the message for each address may take substantially longer ++than sending a single copy with many recipients (for which VERP cannot be ++used). ++ ++ ++49.7 Virtual domains ++-------------------- ++ ++The phrase virtual domain is unfortunately used with two rather different ++meanings: ++ ++ * A domain for which there are no real mailboxes; all valid local parts are ++ aliases for other email addresses. Common examples are organizational ++ top-level domains and "vanity" domains. ++ ++ * One of a number of independent domains that are all handled by the same ++ host, with mailboxes on that host, but where the mailbox owners do not ++ necessarily have login accounts on that host. ++ ++The first usage is probably more common, and does seem more "virtual" than the ++second. This kind of domain can be handled in Exim with a straightforward ++aliasing router. One approach is to create a separate alias file for each ++virtual domain. Exim can test for the existence of the alias file to determine ++whether the domain exists. The dsearch lookup type is useful here, leading to a ++router of this form: ++ ++virtual: ++ driver = redirect ++ domains = dsearch;/etc/mail/virtual ++ data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}} ++ no_more ++ ++The domains option specifies that the router is to be skipped, unless there is ++a file in the /etc/mail/virtual directory whose name is the same as the domain ++that is being processed. When the router runs, it looks up the local part in ++the file to find a new address (or list of addresses). The no_more setting ++ensures that if the lookup fails (leading to data being an empty string), Exim ++gives up on the address without trying any subsequent routers. ++ ++This one router can handle all the virtual domains because the alias file names ++follow a fixed pattern. Permissions can be arranged so that appropriate people ++can edit the different alias files. A successful aliasing operation results in ++a new envelope recipient address, which is then routed from scratch. ++ ++The other kind of "virtual" domain can also be handled in a straightforward ++way. One approach is to create a file for each domain containing a list of ++valid local parts, and use it in a router like this: ++ ++my_domains: ++ driver = accept ++ domains = dsearch;/etc/mail/domains ++ local_parts = lsearch;/etc/mail/domains/$domain ++ transport = my_mailboxes ++ ++The address is accepted if there is a file for the domain, and the local part ++can be found in the file. The domains option is used to check for the file's ++existence because domains is tested before the local_parts option (see section ++3.12). You cannot use require_files, because that option is tested after ++local_parts. The transport is as follows: ++ ++my_mailboxes: ++ driver = appendfile ++ file = /var/mail/$domain/$local_part ++ user = mail ++ ++This uses a directory of mailboxes for each domain. The user setting is ++required, to specify which uid is to be used for writing to the mailboxes. ++ ++The configuration shown here is just one example of how you might support this ++requirement. There are many other ways this kind of configuration can be set ++up, for example, by using a database instead of separate files to hold all the ++information about the domains. ++ ++ ++49.8 Multiple user mailboxes ++---------------------------- ++ ++Heavy email users often want to operate with multiple mailboxes, into which ++incoming mail is automatically sorted. A popular way of handling this is to ++allow users to use multiple sender addresses, so that replies can easily be ++identified. Users are permitted to add prefixes or suffixes to their local ++parts for this purpose. The wildcard facility of the generic router options ++local_part_prefix and local_part_suffix can be used for this. For example, ++consider this router: ++ ++userforward: ++ driver = redirect ++ check_local_user ++ file = $home/.forward ++ local_part_suffix = -* ++ local_part_suffix_optional ++ allow_filter ++ ++It runs a user's .forward file for all local parts of the form username-*. ++Within the filter file the user can distinguish different cases by testing the ++variable $local_part_suffix. For example: ++ ++if $local_part_suffix contains -special then ++save /home/$local_part/Mail/special ++endif ++ ++If the filter file does not exist, or does not deal with such addresses, they ++fall through to subsequent routers, and, assuming no subsequent use of the ++local_part_suffix option is made, they presumably fail. Thus, users have ++control over which suffixes are valid. ++ ++Alternatively, a suffix can be used to trigger the use of a different .forward ++file - which is the way a similar facility is implemented in another MTA: ++ ++userforward: ++ driver = redirect ++ check_local_user ++ file = $home/.forward$local_part_suffix ++ local_part_suffix = -* ++ local_part_suffix_optional ++ allow_filter ++ ++If there is no suffix, .forward is used; if the suffix is -special, for ++example, .forward-special is used. Once again, if the appropriate file does not ++exist, or does not deal with the address, it is passed on to subsequent ++routers, which could, if required, look for an unqualified .forward file to use ++as a default. ++ ++ ++49.9 Simplified vacation processing ++----------------------------------- ++ ++The traditional way of running the vacation program is for a user to set up a ++pipe command in a .forward file (see section 22.6 for syntax details). This is ++prone to error by inexperienced users. There are two features of Exim that can ++be used to make this process simpler for users: ++ ++ * A local part prefix such as "vacation-" can be specified on a router which ++ can cause the message to be delivered directly to the vacation program, or ++ alternatively can use Exim's autoreply transport. The contents of a user's ++ .forward file are then much simpler. For example: ++ ++ spqr, vacation-spqr ++ ++ * The require_files generic router option can be used to trigger a vacation ++ delivery by checking for the existence of a certain file in the user's home ++ directory. The unseen generic option should also be used, to ensure that ++ the original delivery also proceeds. In this case, all the user has to do ++ is to create a file called, say, .vacation, containing a vacation message. ++ ++Another advantage of both these methods is that they both work even when the ++use of arbitrary pipes by users is locked out. ++ ++ ++49.10 Taking copies of mail ++--------------------------- ++ ++Some installations have policies that require archive copies of all messages to ++be made. A single copy of each message can easily be taken by an appropriate ++command in a system filter, which could, for example, use a different file for ++each day's messages. ++ ++There is also a shadow transport mechanism that can be used to take copies of ++messages that are successfully delivered by local transports, one copy per ++delivery. This could be used, inter alia, to implement automatic notification ++of delivery by sites that insist on doing such things. ++ ++ ++49.11 Intermittently connected hosts ++------------------------------------ ++ ++It has become quite common (because it is cheaper) for hosts to connect to the ++Internet periodically rather than remain connected all the time. The normal ++arrangement is that mail for such hosts accumulates on a system that is ++permanently connected. ++ ++Exim was designed for use on permanently connected hosts, and so it is not ++particularly well-suited to use in an intermittently connected environment. ++Nevertheless there are some features that can be used. ++ ++ ++49.12 Exim on the upstream server host ++-------------------------------------- ++ ++It is tempting to arrange for incoming mail for the intermittently connected ++host to remain on Exim's queue until the client connects. However, this ++approach does not scale very well. Two different kinds of waiting message are ++being mixed up in the same queue - those that cannot be delivered because of ++some temporary problem, and those that are waiting for their destination host ++to connect. This makes it hard to manage the queue, as well as wasting ++resources, because each queue runner scans the entire queue. ++ ++A better approach is to separate off those messages that are waiting for an ++intermittently connected host. This can be done by delivering these messages ++into local files in batch SMTP, "mailstore", or other envelope-preserving ++format, from where they are transmitted by other software when their ++destination connects. This makes it easy to collect all the mail for one host ++in a single directory, and to apply local timeout rules on a per-message basis ++if required. ++ ++On a very small scale, leaving the mail on Exim's queue can be made to work. If ++you are doing this, you should configure Exim with a long retry period for the ++intermittent host. For example: ++ ++cheshire.wonderland.fict.example * F,5d,24h ++ ++This stops a lot of failed delivery attempts from occurring, but Exim remembers ++which messages it has queued up for that host. Once the intermittent host comes ++online, forcing delivery of one message (either by using the -M or -R options, ++or by using the ETRN SMTP command (see section 47.8) causes all the queued up ++messages to be delivered, often down a single SMTP connection. While the host ++remains connected, any new messages get delivered immediately. ++ ++If the connecting hosts do not have fixed IP addresses, that is, if a host is ++issued with a different IP address each time it connects, Exim's retry ++mechanisms on the holding host get confused, because the IP address is normally ++used as part of the key string for holding retry information. This can be ++avoided by unsetting retry_include_ip_address on the smtp transport. Since this ++has disadvantages for permanently connected hosts, it is best to arrange a ++separate transport for the intermittently connected ones. ++ ++ ++49.13 Exim on the intermittently connected client host ++------------------------------------------------------ ++ ++The value of smtp_accept_queue_per_connection should probably be increased, or ++even set to zero (that is, disabled) on the intermittently connected host, so ++that all incoming messages down a single connection get delivered immediately. ++ ++Mail waiting to be sent from an intermittently connected host will probably not ++have been routed, because without a connection DNS lookups are not possible. ++This means that if a normal queue run is done at connection time, each message ++is likely to be sent in a separate SMTP session. This can be avoided by ++starting the queue run with a command line option beginning with -qq instead of ++-q. In this case, the queue is scanned twice. In the first pass, routing is ++done but no deliveries take place. The second pass is a normal queue run; since ++all the messages have been previously routed, those destined for the same host ++are likely to get sent as multiple deliveries in a single SMTP connection. ++ ++ ++ ++=============================================================================== ++50. USING EXIM AS A NON-QUEUEING CLIENT ++ ++On a personal computer, it is a common requirement for all email to be sent to ++a "smart host". There are plenty of MUAs that can be configured to operate that ++way, for all the popular operating systems. However, there are some MUAs for ++Unix-like systems that cannot be so configured: they submit messages using the ++command line interface of /usr/sbin/sendmail. Furthermore, utility programs ++such as cron submit messages this way. ++ ++If the personal computer runs continuously, there is no problem, because it can ++run a conventional MTA that handles delivery to the smart host, and deal with ++any delays via its queueing mechanism. However, if the computer does not run ++continuously or runs different operating systems at different times, queueing ++email is not desirable. ++ ++There is therefore a requirement for something that can provide the /usr/sbin/ ++sendmail interface but deliver messages to a smart host without any queueing or ++retrying facilities. Furthermore, the delivery to the smart host should be ++synchronous, so that if it fails, the sending MUA is immediately informed. In ++other words, we want something that extends an MUA that submits to a local MTA ++via the command line so that it behaves like one that submits to a remote smart ++host using TCP/SMTP. ++ ++There are a number of applications (for example, there is one called ssmtp) ++that do this job. However, people have found them to be lacking in various ++ways. For instance, you might want to allow aliasing and forwarding to be done ++before sending a message to the smart host. ++ ++Exim already had the necessary infrastructure for doing this job. Just a few ++tweaks were needed to make it behave as required, though it is somewhat of an ++overkill to use a fully-featured MTA for this purpose. ++ ++There is a Boolean global option called mua_wrapper, defaulting false. Setting ++mua_wrapper true causes Exim to run in a special mode where it assumes that it ++is being used to "wrap" a command-line MUA in the manner just described. As ++well as setting mua_wrapper, you also need to provide a compatible router and ++transport configuration. Typically there will be just one router and one ++transport, sending everything to a smart host. ++ ++When run in MUA wrapping mode, the behaviour of Exim changes in the following ++ways: ++ ++ * A daemon cannot be run, nor will Exim accept incoming messages from inetd. ++ In other words, the only way to submit messages is via the command line. ++ ++ * Each message is synchronously delivered as soon as it is received (-odi is ++ assumed). All queueing options (queue_only, queue_smtp_domains, control in ++ an ACL, etc.) are quietly ignored. The Exim reception process does not ++ finish until the delivery attempt is complete. If the delivery is ++ successful, a zero return code is given. ++ ++ * Address redirection is permitted, but the final routing for all addresses ++ must be to the same remote transport, and to the same list of hosts. ++ Furthermore, the return address (envelope sender) must be the same for all ++ recipients, as must any added or deleted header lines. In other words, it ++ must be possible to deliver the message in a single SMTP transaction, ++ however many recipients there are. ++ ++ * If these conditions are not met, or if routing any address results in a ++ failure or defer status, or if Exim is unable to deliver all the recipients ++ successfully to one of the smart hosts, delivery of the entire message ++ fails. ++ ++ * Because no queueing is allowed, all failures are treated as permanent; ++ there is no distinction between 4xx and 5xx SMTP response codes from the ++ smart host. Furthermore, because only a single yes/no response can be given ++ to the caller, it is not possible to deliver to some recipients and not ++ others. If there is an error (temporary or permanent) for any recipient, ++ all are failed. ++ ++ * If more than one smart host is listed, Exim will try another host after a ++ connection failure or a timeout, in the normal way. However, if this kind ++ of failure happens for all the hosts, the delivery fails. ++ ++ * When delivery fails, an error message is written to the standard error ++ stream (as well as to Exim's log), and Exim exits to the caller with a ++ return code value 1. The message is expunged from Exim's spool files. No ++ bounce messages are ever generated. ++ ++ * No retry data is maintained, and any retry rules are ignored. ++ ++ * A number of Exim options are overridden: deliver_drop_privilege is forced ++ true, max_rcpt in the smtp transport is forced to "unlimited", ++ remote_max_parallel is forced to one, and fallback hosts are ignored. ++ ++The overall effect is that Exim makes a single synchronous attempt to deliver ++the message, failing if there is any kind of problem. Because no local ++deliveries are done and no daemon can be run, Exim does not need root ++privilege. It should be possible to run it setuid to exim instead of setuid to ++root. See section 54.3 for a general discussion about the advantages and ++disadvantages of running without root privilege. ++ ++ ++ ++=============================================================================== ++51. LOG FILES ++ ++Exim writes three different logs, referred to as the main log, the reject log, ++and the panic log: ++ ++ * The main log records the arrival of each message and each delivery in a ++ single line in each case. The format is as compact as possible, in an ++ attempt to keep down the size of log files. Two-character flag sequences ++ make it easy to pick out these lines. A number of other events are recorded ++ in the main log. Some of them are optional, in which case the log_selector ++ option controls whether they are included or not. A Perl script called ++ eximstats, which does simple analysis of main log files, is provided in the ++ Exim distribution (see section 52.7). ++ ++ * The reject log records information from messages that are rejected as a ++ result of a configuration option (that is, for policy reasons). The first ++ line of each rejection is a copy of the line that is also written to the ++ main log. Then, if the message's header has been read at the time the log ++ is written, its contents are written to this log. Only the original header ++ lines are available; header lines added by ACLs are not logged. You can use ++ the reject log to check that your policy controls are working correctly; on ++ a busy host this may be easier than scanning the main log for rejection ++ messages. You can suppress the writing of the reject log by setting ++ write_rejectlog false. ++ ++ * When certain serious errors occur, Exim writes entries to its panic log. If ++ the error is sufficiently disastrous, Exim bombs out afterwards. Panic log ++ entries are usually written to the main log as well, but can get lost amid ++ the mass of other entries. The panic log should be empty under normal ++ circumstances. It is therefore a good idea to check it (or to have a cron ++ script check it) regularly, in order to become aware of any problems. When ++ Exim cannot open its panic log, it tries as a last resort to write to the ++ system log (syslog). This is opened with LOG_PID+LOG_CONS and the facility ++ code of LOG_MAIL. The message itself is written at priority LOG_CRIT. ++ ++Every log line starts with a timestamp, in the format shown in the following ++example. Note that many of the examples shown in this chapter are line-wrapped. ++In the log file, this would be all on one line: ++ ++2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed ++ by QUIT ++ ++By default, the timestamps are in the local timezone. There are two ways of ++changing this: ++ ++ * You can set the timezone option to a different time zone; in particular, if ++ you set ++ ++ timezone = UTC ++ ++ the timestamps will be in UTC (aka GMT). ++ ++ * If you set log_timezone true, the time zone is added to the timestamp, for ++ example: ++ ++ 2003-04-25 11:17:07 +0100 Start queue run: pid=12762 ++ ++Exim does not include its process id in log lines by default, but you can ++request that it does so by specifying the "pid" log selector (see section 51.15 ++). When this is set, the process id is output, in square brackets, immediately ++after the time and date. ++ ++ ++51.1 Where the logs are written ++------------------------------- ++ ++The logs may be written to local files, or to syslog, or both. However, it ++should be noted that many syslog implementations use UDP as a transport, and ++are therefore unreliable in the sense that messages are not guaranteed to ++arrive at the loghost, nor is the ordering of messages necessarily maintained. ++It has also been reported that on large log files (tens of megabytes) you may ++need to tweak syslog to prevent it syncing the file with each write - on Linux ++this has been seen to make syslog take 90% plus of CPU time. ++ ++The destination for Exim's logs is configured by setting LOG_FILE_PATH in Local ++/Makefile or by setting log_file_path in the run time configuration. This ++latter string is expanded, so it can contain, for example, references to the ++host name: ++ ++log_file_path = /var/log/$primary_hostname/exim_%slog ++ ++It is generally advisable, however, to set the string in Local/Makefile rather ++than at run time, because then the setting is available right from the start of ++Exim's execution. Otherwise, if there's something it wants to log before it has ++read the configuration file (for example, an error in the configuration file) ++it will not use the path you want, and may not be able to log at all. ++ ++The value of LOG_FILE_PATH or log_file_path is a colon-separated list, ++currently limited to at most two items. This is one option where the facility ++for changing a list separator may not be used. The list must always be ++colon-separated. If an item in the list is "syslog" then syslog is used; ++otherwise the item must either be an absolute path, containing "%s" at the ++point where "main", "reject", or "panic" is to be inserted, or be empty, ++implying the use of a default path. ++ ++When Exim encounters an empty item in the list, it searches the list defined by ++LOG_FILE_PATH, and uses the first item it finds that is neither empty nor ++"syslog". This means that an empty item in log_file_path can be used to mean ++"use the path specified at build time". It no such item exists, log files are ++written in the log subdirectory of the spool directory. This is equivalent to ++the setting: ++ ++log_file_path = $spool_directory/log/%slog ++ ++If you do not specify anything at build time or run time, that is where the ++logs are written. ++ ++A log file path may also contain "%D" or "%M" if datestamped log file names are ++in use - see section 51.3 below. ++ ++Here are some examples of possible settings: ++ ++LOG_FILE_PATH=syslog syslog only ++LOG_FILE_PATH=:syslog syslog and default path ++LOG_FILE_PATH=syslog : /usr/log/exim_%s syslog and specified path ++LOG_FILE_PATH=/usr/log/exim_%s specified path only ++ ++If there are more than two paths in the list, the first is used and a panic ++error is logged. ++ ++ ++51.2 Logging to local files that are periodically "cycled" ++---------------------------------------------------------- ++ ++Some operating systems provide centralized and standardized methods for cycling ++log files. For those that do not, a utility script called exicyclog is provided ++(see section 52.6). This renames and compresses the main and reject logs each ++time it is called. The maximum number of old logs to keep can be set. It is ++suggested this script is run as a daily cron job. ++ ++An Exim delivery process opens the main log when it first needs to write to it, ++and it keeps the file open in case subsequent entries are required - for ++example, if a number of different deliveries are being done for the same ++message. However, remote SMTP deliveries can take a long time, and this means ++that the file may be kept open long after it is renamed if exicyclog or ++something similar is being used to rename log files on a regular basis. To ++ensure that a switch of log files is noticed as soon as possible, Exim calls ++stat() on the main log's name before reusing an open file, and if the file does ++not exist, or its inode has changed, the old file is closed and Exim tries to ++open the main log from scratch. Thus, an old log file may remain open for quite ++some time, but no Exim processes should write to it once it has been renamed. ++ ++ ++51.3 Datestamped log files ++-------------------------- ++ ++Instead of cycling the main and reject log files by renaming them periodically, ++some sites like to use files whose names contain a datestamp, for example, ++mainlog-20031225. The datestamp is in the form yyyymmdd or yyyymm. Exim has ++support for this way of working. It is enabled by setting the log_file_path ++option to a path that includes "%D" or "%M" at the point where the datestamp is ++required. For example: ++ ++log_file_path = /var/spool/exim/log/%slog-%D ++log_file_path = /var/log/exim-%s-%D.log ++log_file_path = /var/spool/exim/log/%D-%slog ++log_file_path = /var/log/exim/%s.%M ++ ++As before, "%s" is replaced by "main" or "reject"; the following are examples ++of names generated by the above examples: ++ ++/var/spool/exim/log/mainlog-20021225 ++/var/log/exim-reject-20021225.log ++/var/spool/exim/log/20021225-mainlog ++/var/log/exim/main.200212 ++ ++When this form of log file is specified, Exim automatically switches to new ++files at midnight. It does not make any attempt to compress old logs; you will ++need to write your own script if you require this. You should not run exicyclog ++with this form of logging. ++ ++The location of the panic log is also determined by log_file_path, but it is ++not datestamped, because rotation of the panic log does not make sense. When ++generating the name of the panic log, "%D" or "%M" are removed from the string. ++In addition, if it immediately follows a slash, a following non-alphanumeric ++character is removed; otherwise a preceding non-alphanumeric character is ++removed. Thus, the four examples above would give these panic log names: ++ ++/var/spool/exim/log/paniclog ++/var/log/exim-panic.log ++/var/spool/exim/log/paniclog ++/var/log/exim/panic ++ ++ ++51.4 Logging to syslog ++---------------------- ++ ++The use of syslog does not change what Exim logs or the format of its messages, ++except in one respect. If syslog_timestamp is set false, the timestamps on ++Exim's log lines are omitted when these lines are sent to syslog. Apart from ++that, the same strings are written to syslog as to log files. The syslog ++"facility" is set to LOG_MAIL, and the program name to "exim" by default, but ++you can change these by setting the syslog_facility and syslog_processname ++options, respectively. If Exim was compiled with SYSLOG_LOG_PID set in Local/ ++Makefile (this is the default in src/EDITME), then, on systems that permit it ++(all except ULTRIX), the LOG_PID flag is set so that the syslog() call adds the ++pid as well as the time and host name to each line. The three log streams are ++mapped onto syslog priorities as follows: ++ ++ * mainlog is mapped to LOG_INFO ++ ++ * rejectlog is mapped to LOG_NOTICE ++ ++ * paniclog is mapped to LOG_ALERT ++ ++Many log lines are written to both mainlog and rejectlog, and some are written ++to both mainlog and paniclog, so there will be duplicates if these are routed ++by syslog to the same place. You can suppress this duplication by setting ++syslog_duplication false. ++ ++Exim's log lines can sometimes be very long, and some of its rejectlog entries ++contain multiple lines when headers are included. To cope with both these ++cases, entries written to syslog are split into separate syslog() calls at each ++internal newline, and also after a maximum of 870 data characters. (This allows ++for a total syslog line length of 1024, when additions such as timestamps are ++added.) If you are running a syslog replacement that can handle lines longer ++than the 1024 characters allowed by RFC 3164, you should set ++ ++SYSLOG_LONG_LINES=yes ++ ++in Local/Makefile before building Exim. That stops Exim from splitting long ++lines, but it still splits at internal newlines in reject log entries. ++ ++To make it easy to re-assemble split lines later, each component of a split ++entry starts with a string of the form [<n>/<m>] or [<n>\<m>] where <n> is the ++component number and <m> is the total number of components in the entry. The / ++delimiter is used when the line was split because it was too long; if it was ++split because of an internal newline, the \ delimiter is used. For example, ++supposing the length limit to be 50 instead of 870, the following would be the ++result of a typical rejection message to mainlog (LOG_INFO), each line in ++addition being preceded by the time, host name, and pid as added by syslog: ++ ++[1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from ++[2/5] [127.0.0.1] (ph10): syntax error in 'From' header ++[3/5] when scanning for sender: missing or malformed lo ++[4/5] cal part in "<>" (envelope sender is <ph10@cam.exa ++[5/5] mple>) ++ ++The same error might cause the following lines to be written to "rejectlog" ++(LOG_NOTICE): ++ ++[1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro ++[2/18] m [127.0.0.1] (ph10): syntax error in 'From' head ++[3/18] er when scanning for sender: missing or malformed ++[4/18] local part in "<>" (envelope sender is <ph10@cam ++[5\18] .example>) ++[6\18] Recipients: ph10@some.domain.cam.example ++[7\18] P Received: from [127.0.0.1] (ident=ph10) ++[8\18] by xxxxx.cam.example with smtp (Exim 4.00) ++[9\18] id 16RdAL-0006pc-00 ++[10/18] for ph10@cam.example; Mon, 16 Sep 2002 16: ++[11\18] 09:43 +0100 ++[12\18] F From: <> ++[13\18] Subject: this is a test header ++[18\18] X-something: this is another header ++[15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp ++[16\18] le> ++[17\18] B Bcc: ++[18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100 ++ ++Log lines that are neither too long nor contain newlines are written to syslog ++without modification. ++ ++If only syslog is being used, the Exim monitor is unable to provide a log tail ++display, unless syslog is routing mainlog to a file on the local host and the ++environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor where it ++is. ++ ++ ++51.5 Log line flags ++------------------- ++ ++One line is written to the main log for each message received, and for each ++successful, unsuccessful, and delayed delivery. These lines can readily be ++picked out by the distinctive two-character flags that immediately follow the ++timestamp. The flags are: ++ ++<= message arrival ++=> normal message delivery ++-> additional address in same delivery ++>> cutthrough message delivery ++*> delivery suppressed by -N ++** delivery failed; address bounced ++== delivery deferred; temporary problem ++ ++ ++51.6 Logging message reception ++------------------------------ ++ ++The format of the single-line entry in the main log that is written for every ++message received is shown in the basic example below, which is split over ++several lines in order to fit it on the page: ++ ++2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example ++ H=mailer.fict.example [192.168.123.123] U=exim ++ P=smtp S=5678 id=<incoming message id> ++ ++The address immediately following "<=" is the envelope sender address. A bounce ++message is shown with the sender address "<>", and if it is locally generated, ++this is followed by an item of the form ++ ++R=<message id> ++ ++which is a reference to the message that caused the bounce to be sent. ++ ++For messages from other hosts, the H and U fields identify the remote host and ++record the RFC 1413 identity of the user that sent the message, if one was ++received. The number given in square brackets is the IP address of the sending ++host. If there is a single, unparenthesized host name in the H field, as above, ++it has been verified to correspond to the IP address (see the host_lookup ++option). If the name is in parentheses, it was the name quoted by the remote ++host in the SMTP HELO or EHLO command, and has not been verified. If ++verification yields a different name to that given for HELO or EHLO, the ++verified name appears first, followed by the HELO or EHLO name in parentheses. ++ ++Misconfigured hosts (and mail forgers) sometimes put an IP address, with or ++without brackets, in the HELO or EHLO command, leading to entries in the log ++containing text like these examples: ++ ++H=(10.21.32.43) [192.168.8.34] ++H=([10.21.32.43]) [192.168.8.34] ++ ++This can be confusing. Only the final address in square brackets can be relied ++on. ++ ++For locally generated messages (that is, messages not received over TCP/IP), ++the H field is omitted, and the U field contains the login name of the caller ++of Exim. ++ ++For all messages, the P field specifies the protocol used to receive the ++message. This is the value that is stored in $received_protocol. In the case of ++incoming SMTP messages, the value indicates whether or not any SMTP extensions ++(ESMTP), encryption, or authentication were used. If the SMTP session was ++encrypted, there is an additional X field that records the cipher suite that ++was used. ++ ++The protocol is set to "esmtpsa" or "esmtpa" for messages received from hosts ++that have authenticated themselves using the SMTP AUTH command. The first value ++is used when the SMTP connection was encrypted ("secure"). In this case there ++is an additional item A= followed by the name of the authenticator that was ++used. If an authenticated identification was set up by the authenticator's ++server_set_id option, this is logged too, separated by a colon from the ++authenticator name. ++ ++The id field records the existing message id, if present. The size of the ++received message is given by the S field. When the message is delivered, ++headers may be removed or added, so that the size of delivered copies of the ++message may not correspond with this value (and indeed may be different to each ++other). ++ ++The log_selector option can be used to request the logging of additional data ++when a message is received. See section 51.15 below. ++ ++ ++51.7 Logging deliveries ++----------------------- ++ ++The format of the single-line entry in the main log that is written for every ++delivery is shown in one of the examples below, for local and remote ++deliveries, respectively. Each example has been split into two lines in order ++to fit it on the page: ++ ++2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv ++ <marv@hitch.fict.example> R=localuser T=local_delivery ++2002-10-31 09:00:10 16ZCW1-0005MB-00 => ++ monk@holistic.fict.example R=dnslookup T=remote_smtp ++ H=holistic.fict.example [192.168.234.234] ++ ++For ordinary local deliveries, the original address is given in angle brackets ++after the final delivery address, which might be a pipe or a file. If ++intermediate address(es) exist between the original and the final address, the ++last of these is given in parentheses after the final address. The R and T ++fields record the router and transport that were used to process the address. ++ ++If SMTP AUTH was used for the delivery there is an additional item A= followed ++by the name of the authenticator that was used. If an authenticated ++identification was set up by the authenticator's client_set_id option, this is ++logged too, separated by a colon from the authenticator name. ++ ++If a shadow transport was run after a successful local delivery, the log line ++for the successful delivery has an item added on the end, of the form ++ ++ST=<shadow transport name> ++ ++If the shadow transport did not succeed, the error message is put in ++parentheses afterwards. ++ ++When more than one address is included in a single delivery (for example, two ++SMTP RCPT commands in one transaction) the second and subsequent addresses are ++flagged with "->" instead of "=>". When two or more messages are delivered down ++a single SMTP connection, an asterisk follows the IP address in the log lines ++for the second and subsequent messages. ++ ++When delivery is done in cutthrough mode it is flagged with ">>" and the log ++line precedes the reception line, since cutthrough waits for a possible ++rejection from the destination in case it can reject the sourced item. ++ ++The generation of a reply message by a filter file gets logged as a "delivery" ++to the addressee, preceded by ">". ++ ++The log_selector option can be used to request the logging of additional data ++when a message is delivered. See section 51.15 below. ++ ++ ++51.8 Discarded deliveries ++------------------------- ++ ++When a message is discarded as a result of the command "seen finish" being ++obeyed in a filter file which generates no deliveries, a log entry of the form ++ ++2002-12-10 00:50:49 16auJc-0001UB-00 => discarded ++ <low.club@bridge.example> R=userforward ++ ++is written, to record why no deliveries are logged. When a message is discarded ++because it is aliased to ":blackhole:" the log line is like this: ++ ++1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole: ++ <hole@nowhere.example> R=blackhole_router ++ ++ ++51.9 Deferred deliveries ++------------------------ ++ ++When a delivery is deferred, a line of the following form is logged: ++ ++2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example ++ R=dnslookup T=smtp defer (146): Connection refused ++ ++In the case of remote deliveries, the error is the one that was given for the ++last IP address that was tried. Details of individual SMTP failures are also ++written to the log, so the above line would be preceded by something like ++ ++2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to ++ mail1.endrest.example [192.168.239.239]: Connection refused ++ ++When a deferred address is skipped because its retry time has not been reached, ++a message is written to the log, but this can be suppressed by setting an ++appropriate value in log_selector. ++ ++ ++51.10 Delivery failures ++----------------------- ++ ++If a delivery fails because an address cannot be routed, a line of the ++following form is logged: ++ ++1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example ++ <jim@trek99.example>: unknown mail domain ++ ++If a delivery fails at transport time, the router and transport are shown, and ++the response from the remote host is included, as in this example: ++ ++2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example ++ R=dnslookup T=remote_smtp: SMTP error from remote mailer ++ after pipelined RCPT TO:<ace400@pb.example>: host ++ pbmail3.py.example [192.168.63.111]: 553 5.3.0 ++ <ace400@pb.example>...Addressee unknown ++ ++The word "pipelined" indicates that the SMTP PIPELINING extension was being ++used. See hosts_avoid_esmtp in the smtp transport for a way of disabling ++PIPELINING. The log lines for all forms of delivery failure are flagged with ++"**". ++ ++ ++51.11 Fake deliveries ++--------------------- ++ ++If a delivery does not actually take place because the -N option has been used ++to suppress it, a normal delivery line is written to the log, except that "=>" ++is replaced by "*>". ++ ++ ++51.12 Completion ++---------------- ++ ++A line of the form ++ ++2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed ++ ++is written to the main log when a message is about to be removed from the spool ++at the end of its processing. ++ ++ ++51.13 Summary of Fields in Log Lines ++------------------------------------ ++ ++A summary of the field identifiers that are used in log lines is shown in the ++following table: ++ ++A authenticator name (and optional id and sender) ++C SMTP confirmation on delivery ++ command list for "no mail in SMTP session" ++CV certificate verification status ++D duration of "no mail in SMTP session" ++DN distinguished name from peer certificate ++DT on => lines: time taken for a delivery ++F sender address (on delivery lines) ++H host name and IP address ++I local interface used ++id message id for incoming message ++P on <= lines: protocol used ++ on => and ** lines: return path ++QT on => lines: time spent on queue so far ++ on "Completed" lines: time spent on queue ++R on <= lines: reference for local bounce ++ on => ** and == lines: router name ++S size of message ++ST shadow transport name ++T on <= lines: message subject (topic) ++ on => ** and == lines: transport name ++U local user or RFC 1413 identity ++X TLS cipher suite ++ ++ ++51.14 Other log entries ++----------------------- ++ ++Various other types of log entry are written from time to time. Most should be ++self-explanatory. Among the more common are: ++ ++ * retry time not reached An address previously suffered a temporary error ++ during routing or local delivery, and the time to retry has not yet ++ arrived. This message is not written to an individual message log file ++ unless it happens during the first delivery attempt. ++ ++ * retry time not reached for any host An address previously suffered ++ temporary errors during remote delivery, and the retry time has not yet ++ arrived for any of the hosts to which it is routed. ++ ++ * spool file locked An attempt to deliver a message cannot proceed because ++ some other Exim process is already working on the message. This can be ++ quite common if queue running processes are started at frequent intervals. ++ The exiwhat utility script can be used to find out what Exim processes are ++ doing. ++ ++ * error ignored There are several circumstances that give rise to this ++ message: ++ ++ 1. Exim failed to deliver a bounce message whose age was greater than ++ ignore_bounce_errors_after. The bounce was discarded. ++ ++ 2. A filter file set up a delivery using the "noerror" option, and the ++ delivery failed. The delivery was discarded. ++ ++ 3. A delivery set up by a router configured with ++ ++ errors_to = <> ++ ++ failed. The delivery was discarded. ++ ++ ++51.15 Reducing or increasing what is logged ++------------------------------------------- ++ ++By setting the log_selector global option, you can disable some of Exim's ++default logging, or you can request additional logging. The value of ++log_selector is made up of names preceded by plus or minus characters. For ++example: ++ ++log_selector = +arguments -retry_defer ++ ++The list of optional log items is in the following table, with the default ++selection marked by asterisks: ++ ++ 8bitmime received 8BITMIME status ++*acl_warn_skipped skipped warn statement in ACL ++ address_rewrite address rewriting ++ all_parents all parents in => lines ++ arguments command line arguments ++*connection_reject connection rejections ++*delay_delivery immediate delivery delayed ++ deliver_time time taken to perform delivery ++ delivery_size add S=nnn to => lines ++*dnslist_defer defers of DNS list (aka RBL) lookups ++*etrn ETRN commands ++*host_lookup_failed as it says ++ ident_timeout timeout for ident connection ++ incoming_interface incoming interface on <= lines ++ incoming_port incoming port on <= lines ++*lost_incoming_connection as it says (includes timeouts) ++ outgoing_port add remote port to => lines ++*queue_run start and end queue runs ++ queue_time time on queue for one recipient ++ queue_time_overall time on queue for whole message ++ pid Exim process id ++ received_recipients recipients on <= lines ++ received_sender sender on <= lines ++*rejected_header header contents on reject log ++*retry_defer "retry time not reached" ++ return_path_on_delivery put return path on => and ** lines ++ sender_on_delivery add sender to => lines ++*sender_verify_fail sender verification failures ++*size_reject rejection because too big ++*skip_delivery delivery skipped in a queue run ++*smtp_confirmation SMTP confirmation on => lines ++ smtp_connection SMTP connections ++ smtp_incomplete_transaction incomplete SMTP transactions ++ smtp_mailauth AUTH argument to MAIL commands ++ smtp_no_mail session with no MAIL commands ++ smtp_protocol_error SMTP protocol errors ++ smtp_syntax_error SMTP syntax errors ++ subject contents of Subject: on <= lines ++ tls_certificate_verified certificate verification status ++*tls_cipher TLS cipher suite on <= and => lines ++ tls_peerdn TLS peer DN on <= and => lines ++ tls_sni TLS SNI on <= lines ++ unknown_in_list DNS lookup failed in list match ++ ++ all all of the above ++ ++More details on each of these items follows: ++ ++ * 8bitmime: This causes Exim to log any 8BITMIME status of received messages, ++ which may help in tracking down interoperability issues with ancient MTAs ++ that are not 8bit clean. This is added to the "<=" line, tagged with "M8S=" ++ and a value of "0", "7" or "8", corresponding to "not given", "7BIT" and ++ "8BITMIME" respectively. ++ ++ * acl_warn_skipped: When an ACL warn statement is skipped because one of its ++ conditions cannot be evaluated, a log line to this effect is written if ++ this log selector is set. ++ ++ * address_rewrite: This applies both to global rewrites and per-transport ++ rewrites, but not to rewrites in filters run as an unprivileged user ++ (because such users cannot access the log). ++ ++ * all_parents: Normally only the original and final addresses are logged on ++ delivery lines; with this selector, intermediate parents are given in ++ parentheses between them. ++ ++ * arguments: This causes Exim to write the arguments with which it was called ++ to the main log, preceded by the current working directory. This is a ++ debugging feature, added to make it easier to find out how certain MUAs ++ call /usr/sbin/sendmail. The logging does not happen if Exim has given up ++ root privilege because it was called with the -C or -D options. Arguments ++ that are empty or that contain white space are quoted. Non-printing ++ characters are shown as escape sequences. This facility cannot log ++ unrecognized arguments, because the arguments are checked before the ++ configuration file is read. The only way to log such cases is to interpose ++ a script such as util/logargs.sh between the caller and Exim. ++ ++ * connection_reject: A log entry is written whenever an incoming SMTP ++ connection is rejected, for whatever reason. ++ ++ * delay_delivery: A log entry is written whenever a delivery process is not ++ started for an incoming message because the load is too high or too many ++ messages were received on one connection. Logging does not occur if no ++ delivery process is started because queue_only is set or -odq was used. ++ ++ * deliver_time: For each delivery, the amount of real time it has taken to ++ perform the actual delivery is logged as DT=<time>, for example, "DT=1s". ++ ++ * delivery_size: For each delivery, the size of message delivered is added to ++ the "=>" line, tagged with S=. ++ ++ * dnslist_defer: A log entry is written if an attempt to look up a host in a ++ DNS black list suffers a temporary error. ++ ++ * etrn: Every valid ETRN command that is received is logged, before the ACL ++ is run to determine whether or not it is actually accepted. An invalid ETRN ++ command, or one received within a message transaction is not logged by this ++ selector (see smtp_syntax_error and smtp_protocol_error). ++ ++ * host_lookup_failed: When a lookup of a host's IP addresses fails to find ++ any addresses, or when a lookup of an IP address fails to find a host name, ++ a log line is written. This logging does not apply to direct DNS lookups ++ when routing email addresses, but it does apply to "byname" lookups. ++ ++ * ident_timeout: A log line is written whenever an attempt to connect to a ++ client's ident port times out. ++ ++ * incoming_interface: The interface on which a message was received is added ++ to the "<=" line as an IP address in square brackets, tagged by I= and ++ followed by a colon and the port number. The local interface and port are ++ also added to other SMTP log lines, for example "SMTP connection from", and ++ to rejection lines. ++ ++ * incoming_port: The remote port number from which a message was received is ++ added to log entries and Received: header lines, following the IP address ++ in square brackets, and separated from it by a colon. This is implemented ++ by changing the value that is put in the $sender_fullhost and ++ $sender_rcvhost variables. Recording the remote port number has become more ++ important with the widening use of NAT (see RFC 2505). ++ ++ * lost_incoming_connection: A log line is written when an incoming SMTP ++ connection is unexpectedly dropped. ++ ++ * outgoing_port: The remote port number is added to delivery log lines (those ++ containing => tags) following the IP address. This option is not included ++ in the default setting, because for most ordinary configurations, the ++ remote port number is always 25 (the SMTP port). ++ ++ * pid: The current process id is added to every log line, in square brackets, ++ immediately after the time and date. ++ ++ * queue_run: The start and end of every queue run are logged. ++ ++ * queue_time: The amount of time the message has been in the queue on the ++ local host is logged as QT=<time> on delivery ("=>") lines, for example, ++ "QT=3m45s". The clock starts when Exim starts to receive the message, so it ++ includes reception time as well as the delivery time for the current ++ address. This means that it may be longer than the difference between the ++ arrival and delivery log line times, because the arrival log line is not ++ written until the message has been successfully received. ++ ++ * queue_time_overall: The amount of time the message has been in the queue on ++ the local host is logged as QT=<time> on "Completed" lines, for example, ++ "QT=3m45s". The clock starts when Exim starts to receive the message, so it ++ includes reception time as well as the total delivery time. ++ ++ * received_recipients: The recipients of a message are listed in the main log ++ as soon as the message is received. The list appears at the end of the log ++ line that is written when a message is received, preceded by the word ++ "for". The addresses are listed after they have been qualified, but before ++ any rewriting has taken place. Recipients that were discarded by an ACL for ++ MAIL or RCPT do not appear in the list. ++ ++ * received_sender: The unrewritten original sender of a message is added to ++ the end of the log line that records the message's arrival, after the word ++ "from" (before the recipients if received_recipients is also set). ++ ++ * rejected_header: If a message's header has been received at the time a ++ rejection is written to the reject log, the complete header is added to the ++ log. Header logging can be turned off individually for messages that are ++ rejected by the local_scan() function (see section 44.2). ++ ++ * retry_defer: A log line is written if a delivery is deferred because a ++ retry time has not yet been reached. However, this "retry time not reached" ++ message is always omitted from individual message logs after the first ++ delivery attempt. ++ ++ * return_path_on_delivery: The return path that is being transmitted with the ++ message is included in delivery and bounce lines, using the tag P=. This is ++ omitted if no delivery actually happens, for example, if routing fails, or ++ if delivery is to /dev/null or to ":blackhole:". ++ ++ * sender_on_delivery: The message's sender address is added to every delivery ++ and bounce line, tagged by F= (for "from"). This is the original sender ++ that was received with the message; it is not necessarily the same as the ++ outgoing return path. ++ ++ * sender_verify_fail: If this selector is unset, the separate log line that ++ gives details of a sender verification failure is not written. Log lines ++ for the rejection of SMTP commands contain just "sender verify failed", so ++ some detail is lost. ++ ++ * size_reject: A log line is written whenever a message is rejected because ++ it is too big. ++ ++ * skip_delivery: A log line is written whenever a message is skipped during a ++ queue run because it is frozen or because another process is already ++ delivering it. The message that is written is "spool file is locked". ++ ++ * smtp_confirmation: The response to the final "." in the SMTP dialogue for ++ outgoing messages is added to delivery log lines in the form "C="<text>. A ++ number of MTAs (including Exim) return an identifying string in this ++ response. ++ ++ * smtp_connection: A log line is written whenever an SMTP connection is ++ established or closed, unless the connection is from a host that matches ++ hosts_connection_nolog. (In contrast, lost_incoming_connection applies only ++ when the closure is unexpected.) This applies to connections from local ++ processes that use -bs as well as to TCP/IP connections. If a connection is ++ dropped in the middle of a message, a log line is always written, whether ++ or not this selector is set, but otherwise nothing is written at the start ++ and end of connections unless this selector is enabled. ++ ++ For TCP/IP connections to an Exim daemon, the current number of connections ++ is included in the log message for each new connection, but note that the ++ count is reset if the daemon is restarted. Also, because connections are ++ closed (and the closure is logged) in subprocesses, the count may not ++ include connections that have been closed but whose termination the daemon ++ has not yet noticed. Thus, while it is possible to match up the opening and ++ closing of connections in the log, the value of the logged counts may not ++ be entirely accurate. ++ ++ * smtp_incomplete_transaction: When a mail transaction is aborted by RSET, ++ QUIT, loss of connection, or otherwise, the incident is logged, and the ++ message sender plus any accepted recipients are included in the log line. ++ This can provide evidence of dictionary attacks. ++ ++ * smtp_no_mail: A line is written to the main log whenever an accepted SMTP ++ connection terminates without having issued a MAIL command. This includes ++ both the case when the connection is dropped, and the case when QUIT is ++ used. It does not include cases where the connection is rejected right at ++ the start (by an ACL, or because there are too many connections, or ++ whatever). These cases already have their own log lines. ++ ++ The log line that is written contains the identity of the client in the ++ usual way, followed by D= and a time, which records the duration of the ++ connection. If the connection was authenticated, this fact is logged ++ exactly as it is for an incoming message, with an A= item. If the ++ connection was encrypted, CV=, DN=, and X= items may appear as they do for ++ an incoming message, controlled by the same logging options. ++ ++ Finally, if any SMTP commands were issued during the connection, a C= item ++ is added to the line, listing the commands that were used. For example, ++ ++ C=EHLO,QUIT ++ ++ shows that the client issued QUIT straight after EHLO. If there were fewer ++ than 20 commands, they are all listed. If there were more than 20 commands, ++ the last 20 are listed, preceded by "...". However, with the default ++ setting of 10 for smtp_accep_max_nonmail, the connection will in any case ++ have been aborted before 20 non-mail commands are processed. ++ ++ * smtp_mailauth: A third subfield with the authenticated sender, ++ colon-separated, is appended to the A= item for a message arrival or ++ delivery log line, if an AUTH argument to the SMTP MAIL command (see 33.2) ++ was accepted or used. ++ ++ * smtp_protocol_error: A log line is written for every SMTP protocol error ++ encountered. Exim does not have perfect detection of all protocol errors ++ because of transmission delays and the use of pipelining. If PIPELINING has ++ been advertised to a client, an Exim server assumes that the client will ++ use it, and therefore it does not count "expected" errors (for example, ++ RCPT received after rejecting MAIL) as protocol errors. ++ ++ * smtp_syntax_error: A log line is written for every SMTP syntax error ++ encountered. An unrecognized command is treated as a syntax error. For an ++ external connection, the host identity is given; for an internal connection ++ using -bs the sender identification (normally the calling user) is given. ++ ++ * subject: The subject of the message is added to the arrival log line, ++ preceded by "T=" (T for "topic", since S is already used for "size"). Any ++ MIME "words" in the subject are decoded. The print_topbitchars option ++ specifies whether characters with values greater than 127 should be logged ++ unchanged, or whether they should be rendered as escape sequences. ++ ++ * tls_certificate_verified: An extra item is added to <= and => log lines ++ when TLS is in use. The item is "CV=yes" if the peer's certificate was ++ verified, and "CV=no" if not. ++ ++ * tls_cipher: When a message is sent or received over an encrypted ++ connection, the cipher suite used is added to the log line, preceded by X=. ++ ++ * tls_peerdn: When a message is sent or received over an encrypted ++ connection, and a certificate is supplied by the remote host, the peer DN ++ is added to the log line, preceded by DN=. ++ ++ * tls_sni: When a message is received over an encrypted connection, and the ++ remote host provided the Server Name Indication extension, the SNI is added ++ to the log line, preceded by SNI=. ++ ++ * unknown_in_list: This setting causes a log entry to be written when the ++ result of a list match is failure because a DNS lookup failed. ++ ++ ++51.16 Message log ++----------------- ++ ++In addition to the general log files, Exim writes a log file for each message ++that it handles. The names of these per-message logs are the message ids, and ++they are kept in the msglog sub-directory of the spool directory. Each message ++log contains copies of the log lines that apply to the message. This makes it ++easier to inspect the status of an individual message without having to search ++the main log. A message log is deleted when processing of the message is ++complete, unless preserve_message_logs is set, but this should be used only ++with great care because they can fill up your disk very quickly. ++ ++On a heavily loaded system, it may be desirable to disable the use of ++per-message logs, in order to reduce disk I/O. This can be done by setting the ++message_logs option false. ++ ++ ++ ++=============================================================================== ++52. EXIM UTILITIES ++ ++A number of utility scripts and programs are supplied with Exim and are ++described in this chapter. There is also the Exim Monitor, which is covered in ++the next chapter. The utilities described here are: ++ ++ 52.1 exiwhat list what Exim processes are doing ++ 52.2 exiqgrep grep the queue ++ 52.3 exiqsumm summarize the queue ++ 52.4 exigrep search the main log ++ 52.5 exipick select messages on various criteria ++ 52.6 exicyclog cycle (rotate) log files ++ 52.7 eximstats extract statistics from the log ++ 52.8 exim_checkaccess check address acceptance from given IP ++ 52.9 exim_dbmbuild build a DBM file ++ 52.10 exinext extract retry information ++ 52.11 exim_dumpdb dump a hints database ++ 52.11 exim_tidydb clean up a hints database ++ 52.11 exim_fixdb patch a hints database ++ 52.15 exim_lock lock a mailbox file ++ ++Another utility that might be of use to sites with many MTAs is Tom Kistner's ++exilog. It provides log visualizations across multiple Exim servers. See http:/ ++/duncanthrax.net/exilog/ for details. ++ ++ ++52.1 Finding out what Exim processes are doing (exiwhat) ++-------------------------------------------------------- ++ ++On operating systems that can restart a system call after receiving a signal ++(most modern OS), an Exim process responds to the SIGUSR1 signal by writing a ++line describing what it is doing to the file exim-process.info in the Exim ++spool directory. The exiwhat script sends the signal to all Exim processes it ++can find, having first emptied the file. It then waits for one second to allow ++the Exim processes to react before displaying the results. In order to run ++exiwhat successfully you have to have sufficient privilege to send the signal ++to the Exim processes, so it is normally run as root. ++ ++Warning: This is not an efficient process. It is intended for occasional use by ++system administrators. It is not sensible, for example, to set up a script that ++sends SIGUSR1 signals to Exim processes at short intervals. ++ ++Unfortunately, the ps command that exiwhat uses to find Exim processes varies ++in different operating systems. Not only are different options used, but the ++format of the output is different. For this reason, there are some system ++configuration options that configure exactly how exiwhat works. If it doesn't ++seem to be working for you, check the following compile-time options: ++ ++EXIWHAT_PS_CMD the command for running ps ++EXIWHAT_PS_ARG the argument for ps ++EXIWHAT_EGREP_ARG the argument for egrep to select from ps output ++EXIWHAT_KILL_ARG the argument for the kill command ++ ++An example of typical output from exiwhat is ++ ++164 daemon: -q1h, listening on port 25 ++10483 running queue: waiting for 0tAycK-0002ij-00 (10492) ++10492 delivering 0tAycK-0002ij-00 to mail.ref.example ++ [10.19.42.42] (editor@ref.example) ++10592 handling incoming call from [192.168.243.242] ++10628 accepting a local non-SMTP message ++ ++The first number in the output line is the process number. The third line has ++been split here, in order to fit it on the page. ++ ++ ++52.2 Selective queue listing (exiqgrep) ++--------------------------------------- ++ ++This utility is a Perl script contributed by Matt Hubbard. It runs ++ ++exim -bpu ++ ++to obtain a queue listing with undelivered recipients only, and then greps the ++output to select messages that match given criteria. The following selection ++options are available: ++ ++-f <regex> ++ ++ Match the sender address using a case-insensitive search. The field that is ++ tested is enclosed in angle brackets, so you can test for bounce messages ++ with ++ ++ exiqgrep -f '^<>$' ++ ++-r <regex> ++ ++ Match a recipient address using a case-insensitve search. The field that is ++ tested is not enclosed in angle brackets. ++ ++-s <regex> ++ ++ Match against the size field. ++ ++-y <seconds> ++ ++ Match messages that are younger than the given time. ++ ++-o <seconds> ++ ++ Match messages that are older than the given time. ++ ++-z ++ ++ Match only frozen messages. ++ ++-x ++ ++ Match only non-frozen messages. ++ ++The following options control the format of the output: ++ ++-c ++ ++ Display only the count of matching messages. ++ ++-l ++ ++ Long format - display the full message information as output by Exim. This ++ is the default. ++ ++-i ++ ++ Display message ids only. ++ ++-b ++ ++ Brief format - one line per message. ++ ++-R ++ ++ Display messages in reverse order. ++ ++There is one more option, -h, which outputs a list of options. ++ ++ ++52.3 Summarizing the queue (exiqsumm) ++------------------------------------- ++ ++The exiqsumm utility is a Perl script which reads the output of "exim -bp" and ++produces a summary of the messages on the queue. Thus, you use it by running a ++command such as ++ ++exim -bp | exiqsumm ++ ++The output consists of one line for each domain that has messages waiting for ++it, as in the following example: ++ ++3 2322 74m 66m msn.com.example ++ ++Each line lists the number of pending deliveries for a domain, their total ++volume, and the length of time that the oldest and the newest messages have ++been waiting. Note that the number of pending deliveries is greater than the ++number of messages when messages have more than one recipient. ++ ++A summary line is output at the end. By default the output is sorted on the ++domain name, but exiqsumm has the options -a and -c, which cause the output to ++be sorted by oldest message and by count of messages, respectively. There are ++also three options that split the messages for each domain into two or more ++subcounts: -b separates bounce messages, -f separates frozen messages, and -s ++separates messages according to their sender. ++ ++The output of exim -bp contains the original addresses in the message, so this ++also applies to the output from exiqsumm. No domains from addresses generated ++by aliasing or forwarding are included (unless the one_time option of the ++redirect router has been used to convert them into "top level" addresses). ++ ++ ++52.4 Extracting specific information from the log (exigrep) ++----------------------------------------------------------- ++ ++The exigrep utility is a Perl script that searches one or more main log files ++for entries that match a given pattern. When it finds a match, it extracts all ++the log entries for the relevant message, not just those that match the ++pattern. Thus, exigrep can extract complete log entries for a given message, or ++all mail for a given user, or for a given host, for example. The input files ++can be in Exim log format or syslog format. If a matching log line is not ++associated with a specific message, it is included in exigrep's output without ++any additional lines. The usage is: ++ ++exigrep [-t<n>] [-I] [-l] [-v] <pattern> [<log file>] ... ++ ++If no log file names are given on the command line, the standard input is read. ++ ++The -t argument specifies a number of seconds. It adds an additional condition ++for message selection. Messages that are complete are shown only if they spent ++more than <n> seconds on the queue. ++ ++By default, exigrep does case-insensitive matching. The -I option makes it ++case-sensitive. This may give a performance improvement when searching large ++log files. Without -I, the Perl pattern matches use Perl's "/i" option; with -I ++they do not. In both cases it is possible to change the case sensitivity within ++the pattern by using "(?i)" or "(?-i)". ++ ++The -l option means "literal", that is, treat all characters in the pattern as ++standing for themselves. Otherwise the pattern must be a Perl regular ++expression. ++ ++The -v option inverts the matching condition. That is, a line is selected if it ++does not match the pattern. ++ ++If the location of a zcat command is known from the definition of ZCAT_COMMAND ++in Local/Makefile, exigrep automatically passes any file whose name ends in ++COMPRESS_SUFFIX through zcat as it searches it. ++ ++ ++52.5 Selecting messages by various criteria (exipick) ++----------------------------------------------------- ++ ++John Jetmore's exipick utility is included in the Exim distribution. It lists ++messages from the queue according to a variety of criteria. For details of ++exipick's facilities, visit the web page at http://www.exim.org/eximwiki/ ++ToolExipickManPage or run exipick with the --help option. ++ ++ ++52.6 Cycling log files (exicyclog) ++---------------------------------- ++ ++The exicyclog script can be used to cycle (rotate) mainlog and rejectlog files. ++This is not necessary if only syslog is being used, or if you are using log ++files with datestamps in their names (see section 51.3). Some operating systems ++have their own standard mechanisms for log cycling, and these can be used ++instead of exicyclog if preferred. There are two command line options for ++exicyclog: ++ ++ * -k <count> specifies the number of log files to keep, overriding the ++ default that is set when Exim is built. The default default is 10. ++ ++ * -l <path> specifies the log file path, in the same format as Exim's ++ log_file_path option (for example, "/var/log/exim_%slog"), again overriding ++ the script's default, which is to find the setting from Exim's ++ configuration. ++ ++Each time exicyclog is run the file names get "shuffled down" by one. If the ++main log file name is mainlog (the default) then when exicyclog is run mainlog ++becomes mainlog.01, the previous mainlog.01 becomes mainlog.02 and so on, up to ++the limit that is set in the script or by the -k option. Log files whose ++numbers exceed the limit are discarded. Reject logs are handled similarly. ++ ++If the limit is greater than 99, the script uses 3-digit numbers such as ++mainlog.001, mainlog.002, etc. If you change from a number less than 99 to one ++that is greater, or vice versa, you will have to fix the names of any existing ++log files. ++ ++If no mainlog file exists, the script does nothing. Files that "drop off" the ++end are deleted. All files with numbers greater than 01 are compressed, using a ++compression command which is configured by the COMPRESS_COMMAND setting in ++Local/Makefile. It is usual to run exicyclog daily from a root crontab entry of ++the form ++ ++1 0 * * * su exim -c /usr/exim/bin/exicyclog ++ ++assuming you have used the name "exim" for the Exim user. You can run exicyclog ++as root if you wish, but there is no need. ++ ++ ++52.7 Mail statistics (eximstats) ++-------------------------------- ++ ++A Perl script called eximstats is provided for extracting statistical ++information from log files. The output is either plain text, or HTML. Exim log ++files are also supported by the Lire system produced by the LogReport ++Foundation http://www.logreport.org. ++ ++The eximstats script has been hacked about quite a bit over time. The latest ++version is the result of some extensive revision by Steve Campbell. A lot of ++information is given by default, but there are options for suppressing various ++parts of it. Following any options, the arguments to the script are a list of ++files, which should be main log files. For example: ++ ++eximstats -nr /var/spool/exim/log/mainlog.01 ++ ++By default, eximstats extracts information about the number and volume of ++messages received from or delivered to various hosts. The information is sorted ++both by message count and by volume, and the top fifty hosts in each category ++are listed on the standard output. Similar information, based on email ++addresses or domains instead of hosts can be requested by means of various ++options. For messages delivered and received locally, similar statistics are ++also produced per user. ++ ++The output also includes total counts and statistics about delivery errors, and ++histograms showing the number of messages received and deliveries made in each ++hour of the day. A delivery with more than one address in its envelope (for ++example, an SMTP transaction with more than one RCPT command) is counted as a ++single delivery by eximstats. ++ ++Though normally more deliveries than receipts are reported (as messages may ++have multiple recipients), it is possible for eximstats to report more messages ++received than delivered, even though the queue is empty at the start and end of ++the period in question. If an incoming message contains no valid recipients, no ++deliveries are recorded for it. A bounce message is handled as an entirely ++separate message. ++ ++eximstats always outputs a grand total summary giving the volume and number of ++messages received and deliveries made, and the number of hosts involved in each ++case. It also outputs the number of messages that were delayed (that is, not ++completely delivered at the first attempt), and the number that had at least ++one address that failed. ++ ++The remainder of the output is in sections that can be independently disabled ++or modified by various options. It consists of a summary of deliveries by ++transport, histograms of messages received and delivered per time interval ++(default per hour), information about the time messages spent on the queue, a ++list of relayed messages, lists of the top fifty sending hosts, local senders, ++destination hosts, and destination local users by count and by volume, and a ++list of delivery errors that occurred. ++ ++The relay information lists messages that were actually relayed, that is, they ++came from a remote host and were directly delivered to some other remote host, ++without being processed (for example, for aliasing or forwarding) locally. ++ ++There are quite a few options for eximstats to control exactly what it outputs. ++These are documented in the Perl script itself, and can be extracted by running ++the command perldoc on the script. For example: ++ ++perldoc /usr/exim/bin/eximstats ++ ++ ++52.8 Checking access policy (exim_checkaccess) ++---------------------------------------------- ++ ++The -bh command line argument allows you to run a fake SMTP session with ++debugging output, in order to check what Exim is doing when it is applying ++policy controls to incoming SMTP mail. However, not everybody is sufficiently ++familiar with the SMTP protocol to be able to make full use of -bh, and ++sometimes you just want to answer the question "Does this address have access?" ++without bothering with any further details. ++ ++The exim_checkaccess utility is a "packaged" version of -bh. It takes two ++arguments, an IP address and an email address: ++ ++exim_checkaccess 10.9.8.7 A.User@a.domain.example ++ ++The utility runs a call to Exim with the -bh option, to test whether the given ++email address would be accepted in a RCPT command in a TCP/IP connection from ++the host with the given IP address. The output of the utility is either the ++word "accepted", or the SMTP error response, for example: ++ ++Rejected: ++550 Relay not permitted ++ ++When running this test, the utility uses "<>" as the envelope sender address ++for the MAIL command, but you can change this by providing additional options. ++These are passed directly to the Exim command. For example, to specify that the ++test is to be run with the sender address himself@there.example you can use: ++ ++exim_checkaccess 10.9.8.7 A.User@a.domain.example \ ++ -f himself@there.example ++ ++Note that these additional Exim command line items must be given after the two ++mandatory arguments. ++ ++Because the exim_checkaccess uses -bh, it does not perform callouts while ++running its checks. You can run checks that include callouts by using -bhc, but ++this is not yet available in a "packaged" form. ++ ++ ++52.9 Making DBM files (exim_dbmbuild) ++------------------------------------- ++ ++The exim_dbmbuild program reads an input file containing keys and data in the ++format used by the lsearch lookup (see section 9.3). It writes a DBM file using ++the lower-cased alias names as keys and the remainder of the information as ++data. The lower-casing can be prevented by calling the program with the -nolc ++option. ++ ++A terminating zero is included as part of the key string. This is expected by ++the dbm lookup type. However, if the option -nozero is given, exim_dbmbuild ++creates files without terminating zeroes in either the key strings or the data ++strings. The dbmnz lookup type can be used with such files. ++ ++The program requires two arguments: the name of the input file (which can be a ++single hyphen to indicate the standard input), and the name of the output file. ++It creates the output under a temporary name, and then renames it if all went ++well. ++ ++If the native DB interface is in use (USE_DB is set in a compile-time ++configuration file - this is common in free versions of Unix) the two file ++names must be different, because in this mode the Berkeley DB functions create ++a single output file using exactly the name given. For example, ++ ++exim_dbmbuild /etc/aliases /etc/aliases.db ++ ++reads the system alias file and creates a DBM version of it in /etc/aliases.db. ++ ++In systems that use the ndbm routines (mostly proprietary versions of Unix), ++two files are used, with the suffixes .dir and .pag. In this environment, the ++suffixes are added to the second argument of exim_dbmbuild, so it can be the ++same as the first. This is also the case when the Berkeley functions are used ++in compatibility mode (though this is not recommended), because in that case it ++adds a .db suffix to the file name. ++ ++If a duplicate key is encountered, the program outputs a warning, and when it ++finishes, its return code is 1 rather than zero, unless the -noduperr option is ++used. By default, only the first of a set of duplicates is used - this makes it ++compatible with lsearch lookups. There is an option -lastdup which causes it to ++use the data for the last duplicate instead. There is also an option -nowarn, ++which stops it listing duplicate keys to stderr. For other errors, where it ++doesn't actually make a new file, the return code is 2. ++ ++ ++52.10 Finding individual retry times (exinext) ++---------------------------------------------- ++ ++A utility called exinext (mostly a Perl script) provides the ability to fish ++specific information out of the retry database. Given a mail domain (or a ++complete address), it looks up the hosts for that domain, and outputs any retry ++information for the hosts or for the domain. At present, the retry information ++is obtained by running exim_dumpdb (see below) and post-processing the output. ++For example: ++ ++$ exinext piglet@milne.fict.example ++kanga.milne.example:192.168.8.1 error 146: Connection refused ++ first failed: 21-Feb-1996 14:57:34 ++ last tried: 21-Feb-1996 14:57:34 ++ next try at: 21-Feb-1996 15:02:34 ++roo.milne.example:192.168.8.3 error 146: Connection refused ++ first failed: 20-Jan-1996 13:12:08 ++ last tried: 21-Feb-1996 11:42:03 ++ next try at: 21-Feb-1996 19:42:03 ++ past final cutoff time ++ ++You can also give exinext a local part, without a domain, and it will give any ++retry information for that local part in your default domain. A message id can ++be used to obtain retry information pertaining to a specific message. This ++exists only when an attempt to deliver a message to a remote host suffers a ++message-specific error (see section 47.2). exinext is not particularly ++efficient, but then it is not expected to be run very often. ++ ++The exinext utility calls Exim to find out information such as the location of ++the spool directory. The utility has -C and -D options, which are passed on to ++the exim commands. The first specifies an alternate Exim configuration file, ++and the second sets macros for use within the configuration file. These ++features are mainly to help in testing, but might also be useful in ++environments where more than one configuration file is in use. ++ ++ ++52.11 Hints database maintenance ++-------------------------------- ++ ++Three utility programs are provided for maintaining the DBM files that Exim ++uses to contain its delivery hint information. Each program requires two ++arguments. The first specifies the name of Exim's spool directory, and the ++second is the name of the database it is to operate on. These are as follows: ++ ++ * retry: the database of retry information ++ ++ * wait-<transport name>: databases of information about messages waiting for ++ remote hosts ++ ++ * callout: the callout cache ++ ++ * ratelimit: the data for implementing the ratelimit ACL condition ++ ++ * misc: other hints data ++ ++The misc database is used for ++ ++ * Serializing ETRN runs (when smtp_etrn_serialize is set) ++ ++ * Serializing delivery to a specific host (when serialize_hosts is set in an ++ smtp transport) ++ ++ ++52.12 exim_dumpdb ++----------------- ++ ++The entire contents of a database are written to the standard output by the ++exim_dumpdb program, which has no options or arguments other than the spool and ++database names. For example, to dump the retry database: ++ ++exim_dumpdb /var/spool/exim retry ++ ++Two lines of output are produced for each entry: ++ ++T:mail.ref.example:192.168.242.242 146 77 Connection refused ++31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 * ++ ++The first item on the first line is the key of the record. It starts with one ++of the letters R, or T, depending on whether it refers to a routing or ++transport retry. For a local delivery, the next part is the local address; for ++a remote delivery it is the name of the remote host, followed by its failing IP ++address (unless retry_include_ip_address is set false on the smtp transport). ++If the remote port is not the standard one (port 25), it is added to the IP ++address. Then there follows an error code, an additional error code, and a ++textual description of the error. ++ ++The three times on the second line are the time of first failure, the time of ++the last delivery attempt, and the computed time for the next attempt. The line ++ends with an asterisk if the cutoff time for the last retry rule has been ++exceeded. ++ ++Each output line from exim_dumpdb for the wait-xxx databases consists of a host ++name followed by a list of ids for messages that are or were waiting to be ++delivered to that host. If there are a very large number for any one host, ++continuation records, with a sequence number added to the host name, may be ++seen. The data in these records is often out of date, because a message may be ++routed to several alternative hosts, and Exim makes no effort to keep ++cross-references. ++ ++ ++52.13 exim_tidydb ++----------------- ++ ++The exim_tidydb utility program is used to tidy up the contents of a hints ++database. If run with no options, it removes all records that are more than 30 ++days old. The age is calculated from the date and time that the record was last ++updated. Note that, in the case of the retry database, it is not the time since ++the first delivery failure. Information about a host that has been down for ++more than 30 days will remain in the database, provided that the record is ++updated sufficiently often. ++ ++The cutoff date can be altered by means of the -t option, which must be ++followed by a time. For example, to remove all records older than a week from ++the retry database: ++ ++exim_tidydb -t 7d /var/spool/exim retry ++ ++Both the wait-xxx and retry databases contain items that involve message ids. ++In the former these appear as data in records keyed by host - they were ++messages that were waiting for that host - and in the latter they are the keys ++for retry information for messages that have suffered certain types of error. ++When exim_tidydb is run, a check is made to ensure that message ids in database ++records are those of messages that are still on the queue. Message ids for ++messages that no longer exist are removed from wait-xxx records, and if this ++leaves any records empty, they are deleted. For the retry database, records ++whose keys are non-existent message ids are removed. The exim_tidydb utility ++outputs comments on the standard output whenever it removes information from ++the database. ++ ++Certain records are automatically removed by Exim when they are no longer ++needed, but others are not. For example, if all the MX hosts for a domain are ++down, a retry record is created for each one. If the primary MX host comes back ++first, its record is removed when Exim successfully delivers to it, but the ++records for the others remain because Exim has not tried to use those hosts. ++ ++It is important, therefore, to run exim_tidydb periodically on all the hints ++databases. You should do this at a quiet time of day, because it requires a ++database to be locked (and therefore inaccessible to Exim) while it does its ++work. Removing records from a DBM file does not normally make the file smaller, ++but all the common DBM libraries are able to re-use the space that is released. ++After an initial phase of increasing in size, the databases normally reach a ++point at which they no longer get any bigger, as long as they are regularly ++tidied. ++ ++Warning: If you never run exim_tidydb, the space used by the hints databases is ++likely to keep on increasing. ++ ++ ++52.14 exim_fixdb ++---------------- ++ ++The exim_fixdb program is a utility for interactively modifying databases. Its ++main use is for testing Exim, but it might also be occasionally useful for ++getting round problems in a live system. It has no options, and its interface ++is somewhat crude. On entry, it prompts for input with a right angle-bracket. A ++key of a database record can then be entered, and the data for that record is ++displayed. ++ ++If "d" is typed at the next prompt, the entire record is deleted. For all ++except the retry database, that is the only operation that can be carried out. ++For the retry database, each field is output preceded by a number, and data for ++individual fields can be changed by typing the field number followed by new ++data, for example: ++ ++> 4 951102:1000 ++ ++resets the time of the next delivery attempt. Time values are given as a ++sequence of digit pairs for year, month, day, hour, and minute. Colons can be ++used as optional separators. ++ ++ ++52.15 Mailbox maintenance (exim_lock) ++------------------------------------- ++ ++The exim_lock utility locks a mailbox file using the same algorithm as Exim. ++For a discussion of locking issues, see section 26.3. Exim_lock can be used to ++prevent any modification of a mailbox by Exim or a user agent while ++investigating a problem. The utility requires the name of the file as its first ++argument. If the locking is successful, the second argument is run as a command ++(using C's system() function); if there is no second argument, the value of the ++SHELL environment variable is used; if this is unset or empty, /bin/sh is run. ++When the command finishes, the mailbox is unlocked and the utility ends. The ++following options are available: ++ ++-fcntl ++ ++ Use fcntl() locking on the open mailbox. ++ ++-flock ++ ++ Use flock() locking on the open mailbox, provided the operating system ++ supports it. ++ ++-interval ++ ++ This must be followed by a number, which is a number of seconds; it sets ++ the interval to sleep between retries (default 3). ++ ++-lockfile ++ ++ Create a lock file before opening the mailbox. ++ ++-mbx ++ ++ Lock the mailbox using MBX rules. ++ ++-q ++ ++ Suppress verification output. ++ ++-retries ++ ++ This must be followed by a number; it sets the number of times to try to ++ get the lock (default 10). ++ ++-restore_time ++ ++ This option causes exim_lock to restore the modified and read times to the ++ locked file before exiting. This allows you to access a locked mailbox (for ++ example, to take a backup copy) without disturbing the times that the user ++ subsequently sees. ++ ++-timeout ++ ++ This must be followed by a number, which is a number of seconds; it sets a ++ timeout to be used with a blocking fcntl() lock. If it is not set (the ++ default), a non-blocking call is used. ++ ++-v ++ ++ Generate verbose output. ++ ++If none of -fcntl, -flock, -lockfile or -mbx are given, the default is to ++create a lock file and also to use fcntl() locking on the mailbox, which is the ++same as Exim's default. The use of -flock or -fcntl requires that the file be ++writeable; the use of -lockfile requires that the directory containing the file ++be writeable. Locking by lock file does not last for ever; Exim assumes that a ++lock file is expired if it is more than 30 minutes old. ++ ++The -mbx option can be used with either or both of -fcntl or -flock. It assumes ++-fcntl by default. MBX locking causes a shared lock to be taken out on the open ++mailbox, and an exclusive lock on the file /tmp/.n.m where n and m are the ++device number and inode number of the mailbox file. When the locking is ++released, if an exclusive lock can be obtained for the mailbox, the file in / ++tmp is deleted. ++ ++The default output contains verification of the locking that takes place. The ++-v option causes some additional information to be given. The -q option ++suppresses all output except error messages. ++ ++A command such as ++ ++exim_lock /var/spool/mail/spqr ++ ++runs an interactive shell while the file is locked, whereas ++ ++exim_lock -q /var/spool/mail/spqr <<End ++<some commands> ++End ++ ++runs a specific non-interactive sequence of commands while the file is locked, ++suppressing all verification output. A single command can be run by a command ++such as ++ ++exim_lock -q /var/spool/mail/spqr \ ++ "cp /var/spool/mail/spqr /some/where" ++ ++Note that if a command is supplied, it must be entirely contained within the ++second argument - hence the quotes. ++ ++ ++ ++=============================================================================== ++53. THE EXIM MONITOR ++ ++The Exim monitor is an application which displays in an X window information ++about the state of Exim's queue and what Exim is doing. An admin user can ++perform certain operations on messages from this GUI interface; however all ++such facilities are also available from the command line, and indeed, the ++monitor itself makes use of the command line to perform any actions requested. ++ ++ ++53.1 Running the monitor ++------------------------ ++ ++The monitor is started by running the script called eximon. This is a shell ++script that sets up a number of environment variables, and then runs the binary ++called eximon.bin. The default appearance of the monitor window can be changed ++by editing the Local/eximon.conf file created by editing exim_monitor/EDITME. ++Comments in that file describe what the various parameters are for. ++ ++The parameters that get built into the eximon script can be overridden for a ++particular invocation by setting up environment variables of the same names, ++preceded by "EXIMON_". For example, a shell command such as ++ ++EXIMON_LOG_DEPTH=400 eximon ++ ++(in a Bourne-compatible shell) runs eximon with an overriding setting of the ++LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it ++overrides the Exim log file configuration. This makes it possible to have ++eximon tailing log data that is written to syslog, provided that MAIL.INFO ++syslog messages are routed to a file on the local host. ++ ++X resources can be used to change the appearance of the window in the normal ++way. For example, a resource setting of the form ++ ++Eximon*background: gray94 ++ ++changes the colour of the background to light grey rather than white. The ++stripcharts are drawn with both the data lines and the reference lines in ++black. This means that the reference lines are not visible when on top of the ++data. However, their colour can be changed by setting a resource called ++"highlight" (an odd name, but that's what the Athena stripchart widget uses). ++For example, if your X server is running Unix, you could set up lighter ++reference lines in the stripcharts by obeying ++ ++xrdb -merge <<End ++Eximon*highlight: gray ++End ++ ++In order to see the contents of messages on the queue, and to operate on them, ++eximon must either be run as root or by an admin user. ++ ++The command-line parameters of eximon are passed to eximon.bin and may contain ++X11 resource parameters interpreted by the X11 library. In addition, if the ++first parameter starts with the string "gdb" then it is removed and the binary ++is invoked under gdb (the parameter is used as the gdb command-name, so ++versioned variants of gdb can be invoked). ++ ++The monitor's window is divided into three parts. The first contains one or ++more stripcharts and two action buttons, the second contains a "tail" of the ++main log file, and the third is a display of the queue of messages awaiting ++delivery, with two more action buttons. The following sections describe these ++different parts of the display. ++ ++ ++53.2 The stripcharts ++-------------------- ++ ++The first stripchart is always a count of messages on the queue. Its name can ++be configured by setting QUEUE_STRIPCHART_NAME in the Local/eximon.conf file. ++The remaining stripcharts are defined in the configuration script by regular ++expression matches on log file entries, making it possible to display, for ++example, counts of messages delivered to certain hosts or using certain ++transports. The supplied defaults display counts of received and delivered ++messages, and of local and SMTP deliveries. The default period between ++stripchart updates is one minute; this can be adjusted by a parameter in the ++Local/eximon.conf file. ++ ++The stripchart displays rescale themselves automatically as the value they are ++displaying changes. There are always 10 horizontal lines in each chart; the ++title string indicates the value of each division when it is greater than one. ++For example, "x2" means that each division represents a value of 2. ++ ++It is also possible to have a stripchart which shows the percentage fullness of ++a particular disk partition, which is useful when local deliveries are confined ++to a single partition. ++ ++This relies on the availability of the statvfs() function or equivalent in the ++operating system. Most, but not all versions of Unix that support Exim have ++this. For this particular stripchart, the top of the chart always represents ++100%, and the scale is given as "x10%". This chart is configured by setting ++SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the Local/eximon.conf ++file. ++ ++ ++53.3 Main action buttons ++------------------------ ++ ++Below the stripcharts there is an action button for quitting the monitor. Next ++to this is another button marked "Size". They are placed here so that shrinking ++the window to its default minimum size leaves just the queue count stripchart ++and these two buttons visible. Pressing the "Size" button causes the window to ++expand to its maximum size, unless it is already at the maximum, in which case ++it is reduced to its minimum. ++ ++When expanding to the maximum, if the window cannot be fully seen where it ++currently is, it is moved back to where it was the last time it was at full ++size. When it is expanding from its minimum size, the old position is ++remembered, and next time it is reduced to the minimum it is moved back there. ++ ++The idea is that you can keep a reduced window just showing one or two ++stripcharts at a convenient place on your screen, easily expand it to show the ++full window when required, and just as easily put it back to what it was. The ++idea is copied from what the twm window manager does for its f.fullzoom action. ++The minimum size of the window can be changed by setting the MIN_HEIGHT and ++MIN_WIDTH values in Local/eximon.conf. ++ ++Normally, the monitor starts up with the window at its full size, but it can be ++built so that it starts up with the window at its smallest size, by setting ++START_SMALL=yes in Local/eximon.conf. ++ ++ ++53.4 The log display ++-------------------- ++ ++The second section of the window is an area in which a display of the tail of ++the main log is maintained. To save space on the screen, the timestamp on each ++log line is shortened by removing the date and, if log_timezone is set, the ++timezone. The log tail is not available when the only destination for logging ++data is syslog, unless the syslog lines are routed to a local file whose name ++is passed to eximon via the EXIMON_LOG_FILE_PATH environment variable. ++ ++The log sub-window has a scroll bar at its lefthand side which can be used to ++move back to look at earlier text, and the up and down arrow keys also have a ++scrolling effect. The amount of log that is kept depends on the setting of ++LOG_BUFFER in Local/eximon.conf, which specifies the amount of memory to use. ++When this is full, the earlier 50% of data is discarded - this is much more ++efficient than throwing it away line by line. The sub-window also has a ++horizontal scroll bar for accessing the ends of long log lines. This is the ++only means of horizontal scrolling; the right and left arrow keys are not ++available. Text can be cut from this part of the window using the mouse in the ++normal way. The size of this subwindow is controlled by parameters in the ++configuration file Local/eximon.conf. ++ ++Searches of the text in the log window can be carried out by means of the ^R ++and ^S keystrokes, which default to a reverse and a forward search, ++respectively. The search covers only the text that is displayed in the window. ++It cannot go further back up the log. ++ ++The point from which the search starts is indicated by a caret marker. This is ++normally at the end of the text in the window, but can be positioned explicitly ++by pointing and clicking with the left mouse button, and is moved automatically ++by a successful search. If new text arrives in the window when it is scrolled ++back, the caret remains where it is, but if the window is not scrolled back, ++the caret is moved to the end of the new text. ++ ++Pressing ^R or ^S pops up a window into which the search text can be typed. ++There are buttons for selecting forward or reverse searching, for carrying out ++the search, and for cancelling. If the "Search" button is pressed, the search ++happens and the window remains so that further searches can be done. If the ++"Return" key is pressed, a single search is done and the window is closed. If ^ ++C is typed the search is cancelled. ++ ++The searching facility is implemented using the facilities of the Athena text ++widget. By default this pops up a window containing both "search" and "replace" ++options. In order to suppress the unwanted "replace" portion for eximon, a ++modified version of the TextPop widget is distributed with Exim. However, the ++linkers in BSDI and HP-UX seem unable to handle an externally provided version ++of TextPop when the remaining parts of the text widget come from the standard ++libraries. The compile-time option EXIMON_TEXTPOP can be unset to cut out the ++modified TextPop, making it possible to build Eximon on these systems, at the ++expense of having unwanted items in the search popup window. ++ ++ ++53.5 The queue display ++---------------------- ++ ++The bottom section of the monitor window contains a list of all messages that ++are on the queue, which includes those currently being received or delivered, ++as well as those awaiting delivery. The size of this subwindow is controlled by ++parameters in the configuration file Local/eximon.conf, and the frequency at ++which it is updated is controlled by another parameter in the same file - the ++default is 5 minutes, since queue scans can be quite expensive. However, there ++is an "Update" action button just above the display which can be used to force ++an update of the queue display at any time. ++ ++When a host is down for some time, a lot of pending mail can build up for it, ++and this can make it hard to deal with other messages on the queue. To help ++with this situation there is a button next to "Update" called "Hide". If ++pressed, a dialogue box called "Hide addresses ending with" is put up. If you ++type anything in here and press "Return", the text is added to a chain of such ++texts, and if every undelivered address in a message matches at least one of ++the texts, the message is not displayed. ++ ++If there is an address that does not match any of the texts, all the addresses ++are displayed as normal. The matching happens on the ends of addresses so, for ++example, cam.ac.uk specifies all addresses in Cambridge, while ++xxx@foo.com.example specifies just one specific address. When any hiding has ++been set up, a button called "Unhide" is displayed. If pressed, it cancels all ++hiding. Also, to ensure that hidden messages do not get forgotten, a hide ++request is automatically cancelled after one hour. ++ ++While the dialogue box is displayed, you can't press any buttons or do anything ++else to the monitor window. For this reason, if you want to cut text from the ++queue display to use in the dialogue box, you have to do the cutting before ++pressing the "Hide" button. ++ ++The queue display contains, for each unhidden queued message, the length of ++time it has been on the queue, the size of the message, the message id, the ++message sender, and the first undelivered recipient, all on one line. If it is ++a bounce message, the sender is shown as "<>". If there is more than one ++recipient to which the message has not yet been delivered, subsequent ones are ++listed on additional lines, up to a maximum configured number, following which ++an ellipsis is displayed. Recipients that have already received the message are ++not shown. ++ ++If a message is frozen, an asterisk is displayed at the left-hand side. ++ ++The queue display has a vertical scroll bar, and can also be scrolled by means ++of the arrow keys. Text can be cut from it using the mouse in the normal way. ++The text searching facilities, as described above for the log window, are also ++available, but the caret is always moved to the end of the text when the queue ++display is updated. ++ ++ ++53.6 The queue menu ++------------------- ++ ++If the shift key is held down and the left button is clicked when the mouse ++pointer is over the text for any message, an action menu pops up, and the first ++line of the queue display for the message is highlighted. This does not affect ++any selected text. ++ ++If you want to use some other event for popping up the menu, you can set the ++MENU_EVENT parameter in Local/eximon.conf to change the default, or set ++EXIMON_MENU_EVENT in the environment before starting the monitor. The value set ++in this parameter is a standard X event description. For example, to run eximon ++using ctrl rather than shift you could use ++ ++EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon ++ ++The title of the menu is the message id, and it contains entries which act as ++follows: ++ ++ * message log: The contents of the message log for the message are displayed ++ in a new text window. ++ ++ * headers: Information from the spool file that contains the envelope ++ information and headers is displayed in a new text window. See chapter 55 ++ for a description of the format of spool files. ++ ++ * body: The contents of the spool file containing the body of the message are ++ displayed in a new text window. There is a default limit of 20,000 bytes to ++ the amount of data displayed. This can be changed by setting the BODY_MAX ++ option at compile time, or the EXIMON_BODY_MAX option at run time. ++ ++ * deliver message: A call to Exim is made using the -M option to request ++ delivery of the message. This causes an automatic thaw if the message is ++ frozen. The -v option is also set, and the output from Exim is displayed in ++ a new text window. The delivery is run in a separate process, to avoid ++ holding up the monitor while the delivery proceeds. ++ ++ * freeze message: A call to Exim is made using the -Mf option to request that ++ the message be frozen. ++ ++ * thaw message: A call to Exim is made using the -Mt option to request that ++ the message be thawed. ++ ++ * give up on msg: A call to Exim is made using the -Mg option to request that ++ Exim gives up trying to deliver the message. A bounce message is generated ++ for any remaining undelivered addresses. ++ ++ * remove message: A call to Exim is made using the -Mrm option to request ++ that the message be deleted from the system without generating a bounce ++ message. ++ ++ * add recipient: A dialog box is displayed into which a recipient address can ++ be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter ++ is set in Local/eximon.conf, the address is qualified with that domain. ++ Otherwise it must be entered as a fully qualified address. Pressing RETURN ++ causes a call to Exim to be made using the -Mar option to request that an ++ additional recipient be added to the message, unless the entry box is ++ empty, in which case no action is taken. ++ ++ * mark delivered: A dialog box is displayed into which a recipient address ++ can be typed. If the address is not qualified and the QUALIFY_DOMAIN ++ parameter is set in Local/eximon.conf, the address is qualified with that ++ domain. Otherwise it must be entered as a fully qualified address. Pressing ++ RETURN causes a call to Exim to be made using the -Mmd option to mark the ++ given recipient address as already delivered, unless the entry box is ++ empty, in which case no action is taken. ++ ++ * mark all delivered: A call to Exim is made using the -Mmad option to mark ++ all recipient addresses as already delivered. ++ ++ * edit sender: A dialog box is displayed initialized with the current ++ sender's address. Pressing RETURN causes a call to Exim to be made using ++ the -Mes option to replace the sender address, unless the entry box is ++ empty, in which case no action is taken. If you want to set an empty sender ++ (as in bounce messages), you must specify it as "<>". Otherwise, if the ++ address is not qualified and the QUALIFY_DOMAIN parameter is set in Local/ ++ eximon.conf, the address is qualified with that domain. ++ ++When a delivery is forced, a window showing the -v output is displayed. In ++other cases when a call to Exim is made, if there is any output from Exim (in ++particular, if the command fails) a window containing the command and the ++output is displayed. Otherwise, the results of the action are normally apparent ++from the log and queue displays. However, if you set ACTION_OUTPUT=yes in Local ++/eximon.conf, a window showing the Exim command is always opened, even if no ++output is generated. ++ ++The queue display is automatically updated for actions such as freezing and ++thawing, unless ACTION_QUEUE_UPDATE=no has been set in Local/eximon.conf. In ++this case the "Update" button has to be used to force an update of the display ++after one of these actions. ++ ++In any text window that is displayed as result of a menu action, the normal ++cut-and-paste facility is available, and searching can be carried out using ^R ++and ^S, as described above for the log tail window. ++ ++ ++ ++=============================================================================== ++54. SECURITY CONSIDERATIONS ++ ++This chapter discusses a number of issues concerned with security, some of ++which are also covered in other parts of this manual. ++ ++For reasons that this author does not understand, some people have promoted ++Exim as a "particularly secure" mailer. Perhaps it is because of the existence ++of this chapter in the documentation. However, the intent of the chapter is ++simply to describe the way Exim works in relation to certain security concerns, ++not to make any specific claims about the effectiveness of its security as ++compared with other MTAs. ++ ++What follows is a description of the way Exim is supposed to be. Best efforts ++have been made to try to ensure that the code agrees with the theory, but an ++absence of bugs can never be guaranteed. Any that are reported will get fixed ++as soon as possible. ++ ++ ++54.1 Building a more "hardened" Exim ++------------------------------------ ++ ++There are a number of build-time options that can be set in Local/Makefile to ++create Exim binaries that are "harder" to attack, in particular by a rogue Exim ++administrator who does not have the root password, or by someone who has ++penetrated the Exim (but not the root) account. These options are as follows: ++ ++ * ALT_CONFIG_PREFIX can be set to a string that is required to match the ++ start of any file names used with the -C option. When it is set, these file ++ names are also not allowed to contain the sequence "/../". (However, if the ++ value of the -C option is identical to the value of CONFIGURE_FILE in Local ++ /Makefile, Exim ignores -C and proceeds as usual.) There is no default ++ setting for ALT_CONFIG_PREFIX. ++ ++ If the permitted configuration files are confined to a directory to which ++ only root has access, this guards against someone who has broken into the ++ Exim account from running a privileged Exim with an arbitrary configuration ++ file, and using it to break into other accounts. ++ ++ * If a non-trusted configuration file (i.e. not the default configuration ++ file or one which is trusted by virtue of being listed in the ++ TRUSTED_CONFIG_LIST file) is specified with -C, or if macros are given with ++ -D (but see the next item), then root privilege is retained only if the ++ caller of Exim is root. This locks out the possibility of testing a ++ configuration using -C right through message reception and delivery, even ++ if the caller is root. The reception works, but by that time, Exim is ++ running as the Exim user, so when it re-execs to regain privilege for the ++ delivery, the use of -C causes privilege to be lost. However, root can test ++ reception and delivery using two separate commands. ++ ++ * The WHITELIST_D_MACROS build option declares some macros to be safe to ++ override with -D if the real uid is one of root, the Exim run-time user or ++ the CONFIGURE_OWNER, if defined. The potential impact of this option is ++ limited by requiring the run-time value supplied to -D to match a regex ++ that errs on the restrictive side. Requiring build-time selection of safe ++ macros is onerous but this option is intended solely as a transition ++ mechanism to permit previously-working configurations to continue to work ++ after release 4.73. ++ ++ * If DISABLE_D_OPTION is defined, the use of the -D command line option is ++ disabled. ++ ++ * FIXED_NEVER_USERS can be set to a colon-separated list of users that are ++ never to be used for any deliveries. This is like the never_users runtime ++ option, but it cannot be overridden; the runtime option adds additional ++ users to the list. The default setting is "root"; this prevents a non-root ++ user who is permitted to modify the runtime file from using Exim as a way ++ to get root. ++ ++ ++54.2 Root privilege ++------------------- ++ ++The Exim binary is normally setuid to root, which means that it gains root ++privilege (runs as root) when it starts execution. In some special cases (for ++example, when the daemon is not in use and there are no local deliveries), it ++may be possible to run Exim setuid to some user other than root. This is ++discussed in the next section. However, in most installations, root privilege ++is required for two things: ++ ++ * To set up a socket connected to the standard SMTP port (25) when ++ initialising the listening daemon. If Exim is run from inetd, this ++ privileged action is not required. ++ ++ * To be able to change uid and gid in order to read users' .forward files and ++ perform local deliveries as the receiving user or as specified in the ++ configuration. ++ ++It is not necessary to be root to do any of the other things Exim does, such as ++receiving messages and delivering them externally over SMTP, and it is ++obviously more secure if Exim does not run as root except when necessary. For ++this reason, a user and group for Exim to use must be defined in Local/Makefile ++. These are known as "the Exim user" and "the Exim group". Their values can be ++changed by the run time configuration, though this is not recommended. Often a ++user called exim is used, but some sites use mail or another user name ++altogether. ++ ++Exim uses setuid() whenever it gives up root privilege. This is a permanent ++abdication; the process cannot regain root afterwards. Prior to release 4.00, ++seteuid() was used in some circumstances, but this is no longer the case. ++ ++After a new Exim process has interpreted its command line options, it changes ++uid and gid in the following cases: ++ ++ * If the -C option is used to specify an alternate configuration file, or if ++ the -D option is used to define macro values for the configuration, and the ++ calling process is not running as root, the uid and gid are changed to ++ those of the calling process. However, if DISABLE_D_OPTION is defined in ++ Local/Makefile, the -D option may not be used at all. If WHITELIST_D_MACROS ++ is defined in Local/Makefile, then some macro values can be supplied if the ++ calling process is running as root, the Exim run-time user or ++ CONFIGURE_OWNER, if defined. ++ ++ * If the expansion test option (-be) or one of the filter testing options ( ++ -bf or -bF) are used, the uid and gid are changed to those of the calling ++ process. ++ ++ * If the process is not a daemon process or a queue runner process or a ++ delivery process or a process for testing address routing (started with -bt ++ ), the uid and gid are changed to the Exim user and group. This means that ++ Exim always runs under its own uid and gid when receiving messages. This ++ also applies when testing address verification (the -bv option) and testing ++ incoming message policy controls (the -bh option). ++ ++ * For a daemon, queue runner, delivery, or address testing process, the uid ++ remains as root at this stage, but the gid is changed to the Exim group. ++ ++The processes that initially retain root privilege behave as follows: ++ ++ * A daemon process changes the gid to the Exim group and the uid to the Exim ++ user after setting up one or more listening sockets. The initgroups() ++ function is called, so that if the Exim user is in any additional groups, ++ they will be used during message reception. ++ ++ * A queue runner process retains root privilege throughout its execution. Its ++ job is to fork a controlled sequence of delivery processes. ++ ++ * A delivery process retains root privilege throughout most of its execution, ++ but any actual deliveries (that is, the transports themselves) are run in ++ subprocesses which always change to a non-root uid and gid. For local ++ deliveries this is typically the uid and gid of the owner of the mailbox; ++ for remote deliveries, the Exim uid and gid are used. Once all the delivery ++ subprocesses have been run, a delivery process changes to the Exim uid and ++ gid while doing post-delivery tidying up such as updating the retry ++ database and generating bounce and warning messages. ++ ++ While the recipient addresses in a message are being routed, the delivery ++ process runs as root. However, if a user's filter file has to be processed, ++ this is done in a subprocess that runs under the individual user's uid and ++ gid. A system filter is run as root unless system_filter_user is set. ++ ++ * A process that is testing addresses (the -bt option) runs as root so that ++ the routing is done in the same environment as a message delivery. ++ ++ ++54.3 Running Exim without privilege ++----------------------------------- ++ ++Some installations like to run Exim in an unprivileged state for more of its ++operation, for added security. Support for this mode of operation is provided ++by the global option deliver_drop_privilege. When this is set, the uid and gid ++are changed to the Exim user and group at the start of a delivery process (and ++also queue runner and address testing processes). This means that address ++routing is no longer run as root, and the deliveries themselves cannot change ++to any other uid. ++ ++Leaving the binary setuid to root, but setting deliver_drop_privilege means ++that the daemon can still be started in the usual way, and it can respond ++correctly to SIGHUP because the re-invocation regains root privilege. ++ ++An alternative approach is to make Exim setuid to the Exim user and also setgid ++to the Exim group. If you do this, the daemon must be started from a root ++process. (Calling Exim from a root process makes it behave in the way it does ++when it is setuid root.) However, the daemon cannot restart itself after a ++SIGHUP signal because it cannot regain privilege. ++ ++It is still useful to set deliver_drop_privilege in this case, because it stops ++Exim from trying to re-invoke itself to do a delivery after a message has been ++received. Such a re-invocation is a waste of resources because it has no ++effect. ++ ++If restarting the daemon is not an issue (for example, if mua_wrapper is set, ++or inetd is being used instead of a daemon), having the binary setuid to the ++Exim user seems a clean approach, but there is one complication: ++ ++In this style of operation, Exim is running with the real uid and gid set to ++those of the calling process, and the effective uid/gid set to Exim's values. ++Ideally, any association with the calling process' uid/gid should be dropped, ++that is, the real uid/gid should be reset to the effective values so as to ++discard any privileges that the caller may have. While some operating systems ++have a function that permits this action for a non-root effective uid, quite a ++number of them do not. Because of this lack of standardization, Exim does not ++address this problem at this time. ++ ++For this reason, the recommended approach for "mostly unprivileged" running is ++to keep the Exim binary setuid to root, and to set deliver_drop_privilege. This ++also has the advantage of allowing a daemon to be used in the most ++straightforward way. ++ ++If you configure Exim not to run delivery processes as root, there are a number ++of restrictions on what you can do: ++ ++ * You can deliver only as the Exim user/group. You should explicitly use the ++ user and group options to override routers or local transports that ++ normally deliver as the recipient. This makes sure that configurations that ++ work in this mode function the same way in normal mode. Any implicit or ++ explicit specification of another user causes an error. ++ ++ * Use of .forward files is severely restricted, such that it is usually not ++ worthwhile to include them in the configuration. ++ ++ * Users who wish to use .forward would have to make their home directory and ++ the file itself accessible to the Exim user. Pipe and append-to-file ++ entries, and their equivalents in Exim filters, cannot be used. While they ++ could be enabled in the Exim user's name, that would be insecure and not ++ very useful. ++ ++ * Unless the local user mailboxes are all owned by the Exim user (possible in ++ some POP3 or IMAP-only environments): ++ ++ 1. They must be owned by the Exim group and be writeable by that group. ++ This implies you must set mode in the appendfile configuration, as well ++ as the mode of the mailbox files themselves. ++ ++ 2. You must set no_check_owner, since most or all of the files will not be ++ owned by the Exim user. ++ ++ 3. You must set file_must_exist, because Exim cannot set the owner ++ correctly on a newly created mailbox when unprivileged. This also ++ implies that new mailboxes need to be created manually. ++ ++These restrictions severely restrict what can be done in local deliveries. ++However, there are no restrictions on remote deliveries. If you are running a ++gateway host that does no local deliveries, setting deliver_drop_privilege ++gives more security at essentially no cost. ++ ++If you are using the mua_wrapper facility (see chapter 50), ++deliver_drop_privilege is forced to be true. ++ ++ ++54.4 Delivering to local files ++------------------------------ ++ ++Full details of the checks applied by appendfile before it writes to a file are ++given in chapter 26. ++ ++ ++54.5 Running local commands ++--------------------------- ++ ++There are a number of ways in which an administrator can configure Exim to run ++commands based upon received, untrustworthy, data. Further, in some ++configurations a user who can control a .forward file can also arrange to run ++commands. Configuration to check includes, but is not limited to: ++ ++ * Use of use_shell in the pipe transport: various forms of shell command ++ injection may be possible with this option present. It is dangerous and ++ should be used only with considerable caution. Consider constraints which ++ whitelist allowed characters in a variable which is to be used in a pipe ++ transport that has use_shell enabled. ++ ++ * A number of options such as forbid_filter_run, forbid_filter_perl, ++ forbid_filter_dlfunc and so forth which restrict facilities available to ++ .forward files in a redirect router. If Exim is running on a central mail ++ hub to which ordinary users do not have shell access, but home directories ++ are NFS mounted (for instance) then administrators should review the list ++ of these forbid options available, and should bear in mind that the options ++ that may need forbidding can change as new features are added between ++ releases. ++ ++ * The ${run...} expansion item does not use a shell by default, but ++ administrators can configure use of /bin/sh as part of the command. Such ++ invocations should be viewed with prejudicial suspicion. ++ ++ * Administrators who use embedded Perl are advised to explore how Perl's ++ taint checking might apply to their usage. ++ ++ * Use of ${expand...} is somewhat analagous to shell's eval builtin and ++ administrators are well advised to view its use with suspicion, in case ++ (for instance) it allows a local-part to contain embedded Exim directives. ++ ++ * Use of ${match_local_part...} and friends becomes more dangerous if Exim ++ was built with EXPAND_LISTMATCH_RHS defined: the second string in each can ++ reference arbitrary lists and files, rather than just being a list of ++ opaque strings. The EXPAND_LISTMATCH_RHS option was added and set false by ++ default because of real-world security vulnerabilities caused by its use ++ with untrustworthy data injected in, for SQL injection attacks. Consider ++ the use of the inlisti expansion condition instead. ++ ++ ++54.6 IPv4 source routing ++------------------------ ++ ++Many operating systems suppress IP source-routed packets in the kernel, but ++some cannot be made to do this, so Exim does its own check. It logs incoming ++IPv4 source-routed TCP calls, and then drops them. Things are all different in ++IPv6. No special checking is currently done. ++ ++ ++54.7 The VRFY, EXPN, and ETRN commands in SMTP ++---------------------------------------------- ++ ++Support for these SMTP commands is disabled by default. If required, they can ++be enabled by defining suitable ACLs. ++ ++ ++54.8 Privileged users ++--------------------- ++ ++Exim recognizes two sets of users with special privileges. Trusted users are ++able to submit new messages to Exim locally, but supply their own sender ++addresses and information about a sending host. For other users submitting ++local messages, Exim sets up the sender address from the uid, and doesn't ++permit a remote host to be specified. ++ ++However, an untrusted user is permitted to use the -f command line option in ++the special form -f <> to indicate that a delivery failure for the message ++should not cause an error report. This affects the message's envelope, but it ++does not affect the Sender: header. Untrusted users may also be permitted to ++use specific forms of address with the -f option by setting the ++untrusted_set_sender option. ++ ++Trusted users are used to run processes that receive mail messages from some ++other mail domain and pass them on to Exim for delivery either locally, or over ++the Internet. Exim trusts a caller that is running as root, as the Exim user, ++as any user listed in the trusted_users configuration option, or under any ++group listed in the trusted_groups option. ++ ++Admin users are permitted to do things to the messages on Exim's queue. They ++can freeze or thaw messages, cause them to be returned to their senders, remove ++them entirely, or modify them in various ways. In addition, admin users can run ++the Exim monitor and see all the information it is capable of providing, which ++includes the contents of files on the spool. ++ ++By default, the use of the -M and -q options to cause Exim to attempt delivery ++of messages on its queue is restricted to admin users. This restriction can be ++relaxed by setting the no_prod_requires_admin option. Similarly, the use of -bp ++(and its variants) to list the contents of the queue is also restricted to ++admin users. This restriction can be relaxed by setting ++no_queue_list_requires_admin. ++ ++Exim recognizes an admin user if the calling process is running as root or as ++the Exim user or if any of the groups associated with the calling process is ++the Exim group. It is not necessary actually to be running under the Exim ++group. However, if admin users who are not root or the Exim user are to access ++the contents of files on the spool via the Exim monitor (which runs ++unprivileged), Exim must be built to allow group read access to its spool ++files. ++ ++ ++54.9 Spool files ++---------------- ++ ++Exim's spool directory and everything it contains is owned by the Exim user and ++set to the Exim group. The mode for spool files is defined in the Local/ ++Makefile configuration file, and defaults to 0640. This means that any user who ++is a member of the Exim group can access these files. ++ ++ ++54.10 Use of argv[0] ++-------------------- ++ ++Exim examines the last component of argv[0], and if it matches one of a set of ++specific strings, Exim assumes certain options. For example, calling Exim with ++the last component of argv[0] set to "rsmtp" is exactly equivalent to calling ++it with the option -bS. There are no security implications in this. ++ ++ ++54.11 Use of %f formatting ++-------------------------- ++ ++The only use made of "%f" by Exim is in formatting load average values. These ++are actually stored in integer variables as 1000 times the load average. ++Consequently, their range is limited and so therefore is the length of the ++converted output. ++ ++ ++54.12 Embedded Exim path ++------------------------ ++ ++Exim uses its own path name, which is embedded in the code, only when it needs ++to re-exec in order to regain root privilege. Therefore, it is not root when it ++does so. If some bug allowed the path to get overwritten, it would lead to an ++arbitrary program's being run as exim, not as root. ++ ++ ++54.13 Dynamic module directory ++------------------------------ ++ ++Any dynamically loadable modules must be installed into the directory defined ++in "LOOKUP_MODULE_DIR" in Local/Makefile for Exim to permit loading it. ++ ++ ++54.14 Use of sprintf() ++---------------------- ++ ++A large number of occurrences of "sprintf" in the code are actually calls to ++string_sprintf(), a function that returns the result in malloc'd store. The ++intermediate formatting is done into a large fixed buffer by a function that ++runs through the format string itself, and checks the length of each conversion ++before performing it, thus preventing buffer overruns. ++ ++The remaining uses of sprintf() happen in controlled circumstances where the ++output buffer is known to be sufficiently long to contain the converted string. ++ ++ ++54.15 Use of debug_printf() and log_write() ++------------------------------------------- ++ ++Arbitrary strings are passed to both these functions, but they do their ++formatting by calling the function string_vformat(), which runs through the ++format string itself, and checks the length of each conversion. ++ ++ ++54.16 Use of strcat() and strcpy() ++---------------------------------- ++ ++These are used only in cases where the output buffer is known to be large ++enough to hold the result. ++ ++ ++ ++=============================================================================== ++55. FORMAT OF SPOOL FILES ++ ++A message on Exim's queue consists of two files, whose names are the message id ++followed by -D and -H, respectively. The data portion of the message is kept in ++the -D file on its own. The message's envelope, status, and headers are all ++kept in the -H file, whose format is described in this chapter. Each of these ++two files contains the final component of its own name as its first line. This ++is insurance against disk crashes where the directory is lost but the files ++themselves are recoverable. ++ ++Some people are tempted into editing -D files in order to modify messages. You ++need to be extremely careful if you do this; it is not recommended and you are ++on your own if you do it. Here are some of the pitfalls: ++ ++ * You must ensure that Exim does not try to deliver the message while you are ++ fiddling with it. The safest way is to take out a write lock on the -D ++ file, which is what Exim itself does, using fcntl(). If you update the file ++ in place, the lock will be retained. If you write a new file and rename it, ++ the lock will be lost at the instant of rename. ++ ++ * If you change the number of lines in the file, the value of $body_linecount ++ , which is stored in the -H file, will be incorrect. At present, this value ++ is not used by Exim, but there is no guarantee that this will always be the ++ case. ++ ++ * If the message is in MIME format, you must take care not to break it. ++ ++ * If the message is cryptographically signed, any change will invalidate the ++ signature. ++ ++All in all, modifying -D files is fraught with danger. ++ ++Files whose names end with -J may also be seen in the input directory (or its ++subdirectories when split_spool_directory is set). These are journal files, ++used to record addresses to which the message has been delivered during the ++course of a delivery attempt. If there are still undelivered recipients at the ++end, the -H file is updated, and the -J file is deleted. If, however, there is ++some kind of crash (for example, a power outage) before this happens, the -J ++file remains in existence. When Exim next processes the message, it notices the ++-J file and uses it to update the -H file before starting the next delivery ++attempt. ++ ++ ++55.1 Format of the -H file ++-------------------------- ++ ++The second line of the -H file contains the login name for the uid of the ++process that called Exim to read the message, followed by the numerical uid and ++gid. For a locally generated message, this is normally the user who sent the ++message. For a message received over TCP/IP via the daemon, it is normally the ++Exim user. ++ ++The third line of the file contains the address of the message's sender as ++transmitted in the envelope, contained in angle brackets. The sender address is ++empty for bounce messages. For incoming SMTP mail, the sender address is given ++in the MAIL command. For locally generated mail, the sender address is created ++by Exim from the login name of the current user and the configured ++qualify_domain. However, this can be overridden by the -f option or a leading ++"From " line if the caller is trusted, or if the supplied address is "<>" or an ++address that matches untrusted_set_senders. ++ ++The fourth line contains two numbers. The first is the time that the message ++was received, in the conventional Unix form - the number of seconds since the ++start of the epoch. The second number is a count of the number of messages ++warning of delayed delivery that have been sent to the sender. ++ ++There follow a number of lines starting with a hyphen. These can appear in any ++order, and are omitted when not relevant: ++ ++-acl <number> <length> ++ ++ This item is obsolete, and is not generated from Exim release 4.61 onwards; ++ -aclc and -aclm are used instead. However, -acl is still recognized, to ++ provide backward compatibility. In the old format, a line of this form is ++ present for every ACL variable that is not empty. The number identifies the ++ variable; the acl_cx variables are numbered 0-9 and the acl_mx variables ++ are numbered 10-19. The length is the length of the data string for the ++ variable. The string itself starts at the beginning of the next line, and ++ is followed by a newline character. It may contain internal newlines. ++ ++-aclc <rest-of-name> <length> ++ ++ A line of this form is present for every ACL connection variable that is ++ defined. Note that there is a space between -aclc and the rest of the name. ++ The length is the length of the data string for the variable. The string ++ itself starts at the beginning of the next line, and is followed by a ++ newline character. It may contain internal newlines. ++ ++-aclm <rest-of-name> <length> ++ ++ A line of this form is present for every ACL message variable that is ++ defined. Note that there is a space between -aclm and the rest of the name. ++ The length is the length of the data string for the variable. The string ++ itself starts at the beginning of the next line, and is followed by a ++ newline character. It may contain internal newlines. ++ ++-active_hostname <hostname> ++ ++ This is present if, when the message was received over SMTP, the value of ++ $smtp_active_hostname was different to the value of $primary_hostname. ++ ++-allow_unqualified_recipient ++ ++ This is present if unqualified recipient addresses are permitted in header ++ lines (to stop such addresses from being qualified if rewriting occurs at ++ transport time). Local messages that were input using -bnq and remote ++ messages from hosts that match recipient_unqualified_hosts set this flag. ++ ++-allow_unqualified_sender ++ ++ This is present if unqualified sender addresses are permitted in header ++ lines (to stop such addresses from being qualified if rewriting occurs at ++ transport time). Local messages that were input using -bnq and remote ++ messages from hosts that match sender_unqualified_hosts set this flag. ++ ++-auth_id <text> ++ ++ The id information for a message received on an authenticated SMTP ++ connection - the value of the $authenticated_id variable. ++ ++-auth_sender <address> ++ ++ The address of an authenticated sender - the value of the ++ $authenticated_sender variable. ++ ++-body_linecount <number> ++ ++ This records the number of lines in the body of the message, and is always ++ present. ++ ++-body_zerocount <number> ++ ++ This records the number of binary zero bytes in the body of the message, ++ and is present if the number is greater than zero. ++ ++-deliver_firsttime ++ ++ This is written when a new message is first added to the spool. When the ++ spool file is updated after a deferral, it is omitted. ++ ++-frozen <time> ++ ++ The message is frozen, and the freezing happened at <time>. ++ ++-helo_name <text> ++ ++ This records the host name as specified by a remote host in a HELO or EHLO ++ command. ++ ++-host_address <address>.<port> ++ ++ This records the IP address of the host from which the message was received ++ and the remote port number that was used. It is omitted for locally ++ generated messages. ++ ++-host_auth <text> ++ ++ If the message was received on an authenticated SMTP connection, this ++ records the name of the authenticator - the value of the ++ $sender_host_authenticated variable. ++ ++-host_lookup_failed ++ ++ This is present if an attempt to look up the sending host's name from its ++ IP address failed. It corresponds to the $host_lookup_failed variable. ++ ++-host_name <text> ++ ++ This records the name of the remote host from which the message was ++ received, if the host name was looked up from the IP address when the ++ message was being received. It is not present if no reverse lookup was ++ done. ++ ++-ident <text> ++ ++ For locally submitted messages, this records the login of the originating ++ user, unless it was a trusted user and the -oMt option was used to specify ++ an ident value. For messages received over TCP/IP, this records the ident ++ string supplied by the remote host, if any. ++ ++-interface_address <address>.<port> ++ ++ This records the IP address of the local interface and the port number ++ through which a message was received from a remote host. It is omitted for ++ locally generated messages. ++ ++-local ++ ++ The message is from a local sender. ++ ++-localerror ++ ++ The message is a locally-generated bounce message. ++ ++-local_scan <string> ++ ++ This records the data string that was returned by the local_scan() function ++ when the message was received - the value of the $local_scan_data variable. ++ It is omitted if no data was returned. ++ ++-manual_thaw ++ ++ The message was frozen but has been thawed manually, that is, by an ++ explicit Exim command rather than via the auto-thaw process. ++ ++-N ++ ++ A testing delivery process was started using the -N option to suppress any ++ actual deliveries, but delivery was deferred. At any further delivery ++ attempts, -N is assumed. ++ ++-received_protocol ++ ++ This records the value of the $received_protocol variable, which contains ++ the name of the protocol by which the message was received. ++ ++-sender_set_untrusted ++ ++ The envelope sender of this message was set by an untrusted local caller ++ (used to ensure that the caller is displayed in queue listings). ++ ++-spam_score_int <number> ++ ++ If a message was scanned by SpamAssassin, this is present. It records the ++ value of $spam_score_int. ++ ++-tls_certificate_verified ++ ++ A TLS certificate was received from the client that sent this message, and ++ the certificate was verified by the server. ++ ++-tls_cipher <cipher name> ++ ++ When the message was received over an encrypted connection, this records ++ the name of the cipher suite that was used. ++ ++-tls_peerdn <peer DN> ++ ++ When the message was received over an encrypted connection, and a ++ certificate was received from the client, this records the Distinguished ++ Name from that certificate. ++ ++Following the options there is a list of those addresses to which the message ++is not to be delivered. This set of addresses is initialized from the command ++line when the -t option is used and extract_addresses_remove_arguments is set; ++otherwise it starts out empty. Whenever a successful delivery is made, the ++address is added to this set. The addresses are kept internally as a balanced ++binary tree, and it is a representation of that tree which is written to the ++spool file. If an address is expanded via an alias or forward file, the ++original address is added to the tree when deliveries to all its child ++addresses are complete. ++ ++If the tree is empty, there is a single line in the spool file containing just ++the text "XX". Otherwise, each line consists of two letters, which are either Y ++or N, followed by an address. The address is the value for the node of the ++tree, and the letters indicate whether the node has a left branch and/or a ++right branch attached to it, respectively. If branches exist, they immediately ++follow. Here is an example of a three-node tree: ++ ++YY darcy@austen.fict.example ++NN alice@wonderland.fict.example ++NN editor@thesaurus.ref.example ++ ++After the non-recipients tree, there is a list of the message's recipients. ++This is a simple list, preceded by a count. It includes all the original ++recipients of the message, including those to whom the message has already been ++delivered. In the simplest case, the list contains one address per line. For ++example: ++ ++4 ++editor@thesaurus.ref.example ++darcy@austen.fict.example ++rdo@foundation ++alice@wonderland.fict.example ++ ++However, when a child address has been added to the top-level addresses as a ++result of the use of the one_time option on a redirect router, each line is of ++the following form: ++ ++<top-level address> <errors_to address> <length>,<parent number>#<flag bits> ++ ++The 01 flag bit indicates the presence of the three other fields that follow ++the top-level address. Other bits may be used in future to support additional ++fields. The <parent number> is the offset in the recipients list of the ++original parent of the "one time" address. The first two fields are the ++envelope sender that is associated with this address and its length. If the ++length is zero, there is no special envelope sender (there are then two space ++characters in the line). A non-empty field can arise from a redirect router ++that has an errors_to setting. ++ ++A blank line separates the envelope and status information from the headers ++which follow. A header may occupy several lines of the file, and to save effort ++when reading it in, each header is preceded by a number and an identifying ++character. The number is the number of characters in the header, including any ++embedded newlines and the terminating newline. The character is one of the ++following: ++ ++<blank> header in which Exim has no special interest ++"B" Bcc: header ++"C" Cc: header ++"F" From: header ++"I" Message-id: header ++"P" Received: header - P for "postmark" ++"R" Reply-To: header ++"S" Sender: header ++"T" To: header ++"*" replaced or deleted header ++ ++Deleted or replaced (rewritten) headers remain in the spool file for debugging ++purposes. They are not transmitted when the message is delivered. Here is a ++typical set of headers: ++ ++111P Received: by hobbit.fict.example with local (Exim 4.00) ++id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100 ++049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example> ++038* X-rewrote-sender: bb@hobbit.fict.example ++042* From: Bilbo Baggins <bb@hobbit.fict.example> ++049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example> ++099* To: alice@wonderland.fict.example, rdo@foundation, ++darcy@austen.fict.example, editor@thesaurus.ref.example ++104T To: alice@wonderland.fict.example, rdo@foundation.example, ++darcy@austen.fict.example, editor@thesaurus.ref.example ++038 Date: Fri, 11 May 2001 10:28:59 +0100 ++ ++The asterisked headers indicate that the envelope sender, From: header, and To: ++header have been rewritten, the last one because routing expanded the ++unqualified domain foundation. ++ ++ ++ ++=============================================================================== ++56. SUPPORT FOR DKIM (DOMAINKEYS IDENTIFIED MAIL) ++ ++DKIM is a mechanism by which messages sent by some entity can be provably ++linked to a domain which that entity controls. It permits reputation to be ++tracked on a per-domain basis, rather than merely upon source IP address. DKIM ++is documented in RFC 4871. ++ ++Since version 4.70, DKIM support is compiled into Exim by default. It can be ++disabled by setting DISABLE_DKIM=yes in Local/Makefile. ++ ++Exim's DKIM implementation allows to ++ ++ 1. Sign outgoing messages: This function is implemented in the SMTP transport. ++ It can co-exist with all other Exim features, including transport filters. ++ ++ 2. Verify signatures in incoming messages: This is implemented by an ++ additional ACL (acl_smtp_dkim), which can be called several times per ++ message, with different signature contexts. ++ ++In typical Exim style, the verification implementation does not include any ++default "policy". Instead it enables you to build your own policy using Exim's ++standard controls. ++ ++Please note that verification of DKIM signatures in incoming mail is turned on ++by default for logging purposes. For each signature in incoming email, exim ++will log a line displaying the most important signature details, and the ++signature status. Here is an example (with line-breaks added for clarity): ++ ++2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: ++ d=facebookmail.com s=q1-2009b ++ c=relaxed/relaxed a=rsa-sha1 ++ i=@facebookmail.com t=1252484542 [verification succeeded] ++ ++You might want to turn off DKIM verification processing entirely for internal ++or relay mail sources. To do that, set the dkim_disable_verify ACL control ++modifier. This should typically be done in the RCPT ACL, at points where you ++accept mail from relay sources (internal hosts or authenticated senders). ++ ++ ++56.1 Signing outgoing messages ++------------------------------ ++ ++Signing is implemented by setting private options on the SMTP transport. These ++options take (expandable) strings as arguments. ++ +++--------------------------------------------------+ ++|dkim_domain|Use: smtp|Type: string*|Default: unset| +++--------------------------------------------------+ ++ ++MANDATORY: The domain you want to sign with. The result of this expanded option ++is put into the $dkim_domain expansion variable. ++ +++----------------------------------------------------+ ++|dkim_selector|Use: smtp|Type: string*|Default: unset| +++----------------------------------------------------+ ++ ++MANDATORY: This sets the key selector string. You can use the $dkim_domain ++expansion variable to look up a matching selector. The result is put in the ++expansion variable $dkim_selector which should be used in the dkim_private_key ++option along with $dkim_domain. ++ +++-------------------------------------------------------+ ++|dkim_private_key|Use: smtp|Type: string*|Default: unset| +++-------------------------------------------------------+ ++ ++MANDATORY: This sets the private key to use. You can use the $dkim_domain and ++$dkim_selector expansion variables to determine the private key to use. The ++result can either ++ ++ * be a valid RSA private key in ASCII armor, including line breaks. ++ ++ * start with a slash, in which case it is treated as a file that contains the ++ private key. ++ ++ * be "0", "false" or the empty string, in which case the message will not be ++ signed. This case will not result in an error, even if dkim_strict is set. ++ +++-------------------------------------------------+ ++|dkim_canon|Use: smtp|Type: string*|Default: unset| +++-------------------------------------------------+ ++ ++OPTIONAL: This option sets the canonicalization method used when signing a ++message. The DKIM RFC currently supports two methods: "simple" and "relaxed". ++The option defaults to "relaxed" when unset. Note: the current implementation ++only supports using the same canonicalization method for both headers and body. ++ +++--------------------------------------------------+ ++|dkim_strict|Use: smtp|Type: string*|Default: unset| +++--------------------------------------------------+ ++ ++OPTIONAL: This option defines how Exim behaves when signing a message that ++should be signed fails for some reason. When the expansion evaluates to either ++"1" or "true", Exim will defer. Otherwise Exim will send the message unsigned. ++You can use the $dkim_domain and $dkim_selector expansion variables here. ++ +++--------------------------------------------------------+ ++|dkim_sign_headers|Use: smtp|Type: string*|Default: unset| +++--------------------------------------------------------+ ++ ++OPTIONAL: When set, this option must expand to (or be specified as) a ++colon-separated list of header names. Headers with these names will be included ++in the message signature. When unspecified, the header names recommended in ++RFC4871 will be used. ++ ++ ++56.2 Verifying DKIM signatures in incoming mail ++----------------------------------------------- ++ ++Verification of DKIM signatures in incoming email is implemented via the ++acl_smtp_dkim ACL. By default, this ACL is called once for each syntactically ++(!) correct signature in the incoming message. ++ ++To evaluate the signature in the ACL a large number of expansion variables ++containing the signature status and its details are set up during the runtime ++of the ACL. ++ ++Calling the ACL only for existing signatures is not sufficient to build more ++advanced policies. For that reason, the global option dkim_verify_signers, and ++a global expansion variable $dkim_signers exist. ++ ++The global option dkim_verify_signers can be set to a colon-separated list of ++DKIM domains or identities for which the ACL acl_smtp_dkim is called. It is ++expanded when the message has been received. At this point, the expansion ++variable $dkim_signers already contains a colon-separated list of signer ++domains and identities for the message. When dkim_verify_signers is not ++specified in the main configuration, it defaults as: ++ ++dkim_verify_signers = $dkim_signers ++ ++This leads to the default behaviour of calling acl_smtp_dkim for each DKIM ++signature in the message. Current DKIM verifiers may want to explicitly call ++the ACL for known domains or identities. This would be achieved as follows: ++ ++dkim_verify_signers = paypal.com:ebay.com:$dkim_signers ++ ++This would result in acl_smtp_dkim always being called for "paypal.com" and ++"ebay.com", plus all domains and identities that have signatures in the ++message. You can also be more creative in constructing your policy. For ++example: ++ ++dkim_verify_signers = $sender_address_domain:$dkim_signers ++ ++If a domain or identity is listed several times in the (expanded) value of ++dkim_verify_signers, the ACL is only called once for that domain or identity. ++ ++Inside the acl_smtp_dkim, the following expansion variables are available (from ++most to least important): ++ ++$dkim_cur_signer ++ ++ The signer that is being evaluated in this ACL run. This can be a domain or ++ an identity. This is one of the list items from the expanded main option ++ dkim_verify_signers (see above). ++ ++$dkim_verify_status ++ ++ A string describing the general status of the signature. One of ++ ++ + none: There is no signature in the message for the current domain or ++ identity (as reflected by $dkim_cur_signer). ++ ++ + invalid: The signature could not be verified due to a processing error. ++ More detail is available in $dkim_verify_reason. ++ ++ + fail: Verification of the signature failed. More detail is available in ++ $dkim_verify_reason. ++ ++ + pass: The signature passed verification. It is valid. ++ ++$dkim_verify_reason ++ ++ A string giving a litte bit more detail when $dkim_verify_status is either ++ "fail" or "invalid". One of ++ ++ + pubkey_unavailable (when $dkim_verify_status="invalid"): The public key ++ for the domain could not be retrieved. This may be a temporary problem. ++ ++ + pubkey_syntax (when $dkim_verify_status="invalid"): The public key ++ record for the domain is syntactically invalid. ++ ++ + bodyhash_mismatch (when $dkim_verify_status="fail"): The calculated ++ body hash does not match the one specified in the signature header. ++ This means that the message body was modified in transit. ++ ++ + signature_incorrect (when $dkim_verify_status="fail"): The signature ++ could not be verified. This may mean that headers were modified, ++ re-written or otherwise changed in a way which is incompatible with ++ DKIM verification. It may of course also mean that the signature is ++ forged. ++ ++$dkim_domain ++ ++ The signing domain. IMPORTANT: This variable is only populated if there is ++ an actual signature in the message for the current domain or identity (as ++ reflected by $dkim_cur_signer). ++ ++$dkim_identity ++ ++ The signing identity, if present. IMPORTANT: This variable is only ++ populated if there is an actual signature in the message for the current ++ domain or identity (as reflected by $dkim_cur_signer). ++ ++$dkim_selector ++ ++ The key record selector string. ++ ++$dkim_algo ++ ++ The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'. ++ ++$dkim_canon_body ++ ++ The body canonicalization method. One of 'relaxed' or 'simple'. ++ ++dkim_canon_headers ++ ++ The header canonicalization method. One of 'relaxed' or 'simple'. ++ ++$dkim_copiedheaders ++ ++ A transcript of headers and their values which are included in the ++ signature (copied from the 'z=' tag of the signature). ++ ++$dkim_bodylength ++ ++ The number of signed body bytes. If zero ("0"), the body is unsigned. If no ++ limit was set by the signer, "9999999999999" is returned. This makes sure ++ that this variable always expands to an integer value. ++ ++$dkim_created ++ ++ UNIX timestamp reflecting the date and time when the signature was created. ++ When this was not specified by the signer, "0" is returned. ++ ++$dkim_expires ++ ++ UNIX timestamp reflecting the date and time when the signer wants the ++ signature to be treated as "expired". When this was not specified by the ++ signer, "9999999999999" is returned. This makes it possible to do useful ++ integer size comparisons against this value. ++ ++$dkim_headernames ++ ++ A colon-separated list of names of headers included in the signature. ++ ++$dkim_key_testing ++ ++ "1" if the key record has the "testing" flag set, "0" if not. ++ ++$nosubdomains ++ ++ "1" if the key record forbids subdomaining, "0" otherwise. ++ ++$dkim_key_srvtype ++ ++ Service type (tag s=) from the key record. Defaults to "*" if not specified ++ in the key record. ++ ++$dkim_key_granularity ++ ++ Key granularity (tag g=) from the key record. Defaults to "*" if not ++ specified in the key record. ++ ++$dkim_key_notes ++ ++ Notes from the key record (tag n=). ++ ++In addition, two ACL conditions are provided: ++ ++dkim_signers ++ ++ ACL condition that checks a colon-separated list of domains or identities ++ for a match against the domain or identity that the ACL is currently ++ verifying (reflected by $dkim_cur_signer). This is typically used to ++ restrict an ACL verb to a group of domains or identities. For example: ++ ++ # Warn when Mail purportedly from GMail has no signature at all ++ warn log_message = GMail sender without DKIM signature ++ sender_domains = gmail.com ++ dkim_signers = gmail.com ++ dkim_status = none ++ ++dkim_status ++ ++ ACL condition that checks a colon-separated list of possible DKIM ++ verification results against the actual result of verification. This is ++ typically used to restrict an ACL verb to a list of verification outcomes, ++ for example: ++ ++ deny message = Mail from Paypal with invalid/missing signature ++ sender_domains = paypal.com:paypal.de ++ dkim_signers = paypal.com:paypal.de ++ dkim_status = none:invalid:fail ++ ++ The possible status keywords are: 'none','invalid','fail' and 'pass'. ++ Please see the documentation of the $dkim_verify_status expansion variable ++ above for more information of what they mean. ++ ++ ++ ++=============================================================================== ++57. ADDING NEW DRIVERS OR LOOKUP TYPES ++ ++The following actions have to be taken in order to add a new router, transport, ++authenticator, or lookup type to Exim: ++ ++ 1. Choose a name for the driver or lookup type that does not conflict with any ++ existing name; I will use "newdriver" in what follows. ++ ++ 2. Add to src/EDITME the line: ++ ++ <type>_NEWDRIVER=yes ++ ++ where <type> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the code is not to ++ be included in the binary by default, comment this line out. You should ++ also add any relevant comments about the driver or lookup type. ++ ++ 3. Add to src/config.h.defaults the line: ++ ++ #define <type>_NEWDRIVER ++ ++ 4. Edit src/drtables.c, adding conditional code to pull in the private header ++ and create a table entry as is done for all the other drivers and lookup ++ types. ++ ++ 5. Edit scripts/lookups-Makefile if this is a new lookup; there is a for-loop ++ near the bottom, ranging the "name_mod" variable over a list of all ++ lookups. Add your "NEWDRIVER" to that list. As long as the dynamic module ++ would be named newdriver.so, you can use the simple form that most lookups ++ have. ++ ++ 6. Edit Makefile in the appropriate sub-directory (src/routers, src/transports ++ , src/auths, or src/lookups); add a line for the new driver or lookup type ++ and add it to the definition of OBJ. ++ ++ 7. Create newdriver.h and newdriver.c in the appropriate sub-directory of src. ++ ++ 8. Edit scripts/MakeLinks and add commands to link the .h and .c files as for ++ other drivers and lookups. ++ ++Then all you need to do is write the code! A good way to start is to make a ++proforma by copying an existing module of the same type, globally changing all ++occurrences of the name, and cutting out most of the code. Note that any ++options you create must be listed in alphabetical order, because the tables are ++searched using a binary chop procedure. ++ ++There is a README file in each of the sub-directories of src describing the ++interface that is expected. ++ diff --git a/debian/patches/series b/debian/patches/series index 57dd216..d92ede3 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -8,3 +8,4 @@ 66_enlarge-dh-parameters-size.dpatch 67_unnecessaryCopt.diff 70_remove_exim-users_references.dpatch +80_addmanuallybuiltdocs.diff |