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diff --git a/doc/changes/changes.me b/doc/changes/changes.me deleted file mode 100644 index b963396..0000000 --- a/doc/changes/changes.me +++ /dev/null @@ -1,975 +0,0 @@ -.\" Copyright (c) 1998 Sendmail, Inc. All rights reserved. -.\" Copyright (c) 1994 Eric P. Allman. All rights reserved. -.\" Copyright (c) 1988, 1994 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" By using this file, you agree to the terms and conditions set -.\" forth in the LICENSE file which can be found at the top level of -.\" the sendmail distribution. -.\" -.\" -.\" @(#)changes.me 8.7 (Berkeley) 5/19/1998 -.\" -.\" ditroff -me -Pxx changes.me -.eh '%''Changes in Sendmail Version 8' -.oh 'Changes in Sendmail Version 8''%' -.nr si 3n -.if n .ls 2 -.+c -.(l C -.sz 14 -Changes in Sendmail Version 8* -.sz -.sp -Eric Allman -.sp 0.5 -.i -University of California, Berkeley -Mammoth Project -.)l -.(f -*An earlier version of this paper was printed in the -Proceedings of the 1994 AUUG Queensland Summer Technical Conference, -Gateway Hotel, Brisbane, March 1994. -.)f -.sp -.(l F -.ce -ABSTRACT -.sp \n(psu -Version 8 of -.i sendmail -includes a number of major changes from previous versions. -This paper gives a very short history of -.i sendmail , -a summary of the major differences between version 5 -(the last publically available version) -and version 8, -and some discussion of future directions. -.)l -.sp 2 -.pp -In 1987, the author stopped major work on -.i sendmail -due to other time committments, -only to return to active work in 1991. -This paper explores why work resumed -and what changes have been made. -.pp -Section 1 gives a short history of -.i sendmail -through version 5 and the motivation behind working on version 8. -Section 2 has -a rather detailed description of what has changed -between version 5 and version 8. -The paper finishes off with some thoughts -about what still needs to be done. -.sh 1 "HISTORY" -.pp -As discussed elsewhere, -[Allman83a, Allman83b, Allman&Amos85] -sendmail has existed in various forms since 1980. -It was released under the name -.i delivermail -in 4BSD and 4.1BSD, and as -.i sendmail -in 4.2BSD. -.\"4.0BSD delivermail 1.10 -.\"4.1BSD delivermail 1.10 -.\"4.2BSD sendmail 4.12 -.\"4.3BSD sendmail 5.52 -It quickly became the dominant mail system for networked UNIX systems. -.pp -Prior the release of 4.3BSD in November 1986, -the author had left the University for private industry, -but continued to do some work on -.i sendmail -with activity slowly trailing off -until effectively stopping after February 1987. -There was minimal support done by many people for several years, -until July of 1991 when the original author, -who had returned the University, -started active work on it again. -.pp -There were several reasons for renewed work on -.i sendmail . -There was a desire at Berkeley to convert to a subdomained structure -so that individuals were identified by their subdomain -rather than by their individual workstation; -although possible in the old code, there were some problems, -and the author was the obvious person to address them. -The Computer Systems Research Group (CSRG), -the group that produced the Berkeley Software Distributions, -was working on 4.4BSD, -and wanted an update to the mail system. -Bryan Costales was working on a book on -.i sendmail -that was being reviewed by the author, -which encouraged him to make some revisions. -And the author wanted to try to unify some of the disparate versions of -.i sendmail -that had been permitted to proliferate. -.pp -During the 1987\-91 fallow period, -many vendors and outside volunteers -had produced variants of -.i sendmail . -Perhaps the best known is the IDA version -[IDA87]. -Originally intended to be a new set of configuration files, -IDA expanded into a fairly large set of patches for the code. -Originally produced in Sweden, -IDA development passed to the University of Illinois, -and was widely used by the fairly large set of people -who prefer to get and compile their own source code -rather than use vendor-supplied binaries. -.pp -In about the same time frame, -attempts were made to clean up and extend the Simple Mail Transport Protocol -(SMTP) -[RFC821]. -This involved clarifications of some ambiguities in the protocol, -and correction of some problem areas -[RFC1123], -as well as extensions for additional functionality -(dubbed Extended Simple Mail Transport Protocol, or ESMTP) -[RFC1425, RFC1426, RFC1427] -and a richer set of semantics in the body of messages -(the Multipurpose Internet Mail Extensions, a.k.a. MIME) -[RFC1521, RFC1344]. -Neither the IDA group nor most vendors -were modifying -.i sendmail -to conform to these new standards. -It seemed clear that these were ``good things'' -that should be encouraged. -However, since no one was working on a publically available version of -.i sendmail -with these updates, -they were unlikely to be widely deployed any time in the near future. -.pp -There are, of course, other mail transport agents available, -such as -.i MMDF -.\"[ref], -.i zmailer -.\"[ref], -.i smail -.\"[ref], -and -.i PP -.\"[ref]. -However, none of these seemed to be gaining the prominence of -.i sendmail ; -it appeared that most companies would not convert to another -mail transport agent any time in the forseeable future. -However, they might be persuaded to convert to a newer version of -.i sendmail . -.pp -All of these convinced the author -to work on a updated version of -.i sendmail -for public distribution. -.pp -The new version of -.i sendmail -is referred to as version eight (V8). -Versions six and seven were skipped -because of an agreement -that all files in 4.4BSD would be numbered as -.q 8.1 . -Rather than have an external version number -that differed from the file version numbers, -.i sendmail -just jumped directly to V8. -.sh 1 "CHANGES IN VERSION EIGHT" -.pp -The following is a summary of the changes between the last commonly -available version of sendmail from Berkeley (5.67) and the latest -version (8.6.6). -.pp -Many of these are ideas that had been tried in IDA, -but many of them were generalized in V8. -.sh 2 "Performance Enhancements" -.pp -Instead of closing SMTP connections immediately, open connections are -cached for possible future use. There is a limit to the number of -simultaneous open connections and the idle time of any individual -connection. -.pp -This is of best help during queue processing (since there is the -potential of many different messages going to one site), although -it can also help when processing MX records which aren't handled -by MX Piggybacking. -.pp -If two hosts with different names in a single message happen to -have the same set of MX hosts, they can be sent in the same -transaction. Version 8 notices this and tries to batch the messages. -.pp -For example, if two sites ``foo.com'' and ``bar.com'' are both -served by UUNET, they will have the same set of MX hosts and will -be sent in one transaction. UUNET will then split the message -and send it to the two individual hosts. -.sh 2 "RFC 1123 Changes" -.pp -A number of changes have been made to make sendmail ``conditionally -compliant'' (that is, it satisfies all of the MUST clauses and most -but not all of the SHOULD clauses in RFC 1123). -.pp -The major areas of change are (numbers are RFC 1123 section numbers): -.nr ii 0.75i -.ip \(sc5.2.7 -Response to RCPT command is fast. Previously, sendmail -expanded all aliases as far as it could \*- this could -take a very long time, particularly if there were -name server delays. Version 8 only checks for the -existence of an alias and does the expansion later. -It does still do a DNS lookup if there is an explicit host name -in the RCPT command, -but this time is bounded. -.ip \(sc5.2.8 -Numeric IP addresses are logged in Received: lines. -This helps tracing spoofed messages. -.ip \(sc5.2.17 -Self domain literal is properly handled. Previously, -if someone sent to user@[1.2.3.4], where 1.2.3.4 is -your IP address, the mail would probably be rejected -with a ``configuration error''. -Version 8 can handle these addresses. -.ip \(sc5.3.2 -Better control over individual timeouts. RFC 821 specified -no timeouts. Older versions of sendmail had a single -timeout, typically set to two hours. Version 8 allows -the configuration file to set timeouts for various -SMTP commands individually. -.ip \(sc5.3.3 -Error messages are sent as From:<>. This was urged by -RFC 821 and reiterated by RFC 1123, but older versions -of sendmail never really did it properly. Version 8 -does. However, some systems cannot handle this -perfectly legal address; if necessary, you can create -a special mailer that uses the `g' flag to disable this. -.ip \(sc5.3.3 -Error messages are never sent to <>. Previously, -sendmail was happy to send responses-to-responses which -sometimes resulted in responses-to-responses-to-responses -which resulted in .... you get the idea. -.ip \(sc5.3.3 -Route-addrs (the ugly ``<@hosta,@hostb:user@hostc>'' -syntax) are pruned. RFC 821 urged the use of this -bletcherous syntax. RFC 1123 has seen the light and -officially deprecates them, further urging that you -eliminate all but ``user@hostc'' should you receive -one of these things. Version 8 is slightly more generous -than the standards suggest; instead of stripping off all -the route addressees, it only strips hosts off up to -the one before the last one known to DNS, thus allowing -you to have pseudo-hosts such as foo.BITNET. The `R' -option will turn this off. -.lp -The areas in which sendmail is not ``unconditionally compliant'' are: -.ip \(sc5.2.6 -Sendmail does do header munging. -.ip \(sc5.2.10 -Sendmail doesn't always use the exact SMTP message -text from RFC 821. This is a rather silly requirement. -.ip \(sc5.3.1.1 -Sendmail doesn't guarantee only one connect for each -host on queue runs. Connection caching gives you most -of this, but it does not provide a guarantee. -.ip \(sc5.3.1.1 -Sendmail doesn't always provide an adequate limit -on concurrency. That is, there can be several -independent sendmails running at once. My feeling -is that doing an absolute limit would be a mistake -(it might result in lost mail). However, if you use -the XLA contributed software, most of this will be -guaranteed (but I don't guarantee the guarantee). -.sh 2 "Extended SMTP Support -.pp -Version 8 includes both sending and receiving support for Extended -SMTP support as defined by RFC 1425 (basic) and RFC 1427 (SIZE); -and limited support for RFC 1426 (BODY). -The body support is minimal because the -.q 8BITMIME -body type is not currently advertised. -Although such a body type will be accepted, -it will not be correctly converted to 7 bits -if speaking to a non-8-bit-MIME aware SMTP server. -.pp -.i Sendmail -tries to speak ESMTP if you have the `a' flag set -in the flags for the mailer descriptor, -or if the other end advertises the fact that it speaks ESMTP. -This is a non-standard advertisement: -.i sendmail -announces -.q "ESMTP spoken here" -during the initial connection message, -and client sendmails search for this message. -This creates some problems for some PC-based mailers, -which do not understand two-line greeting messages -as required by RFC 821. -.sh 2 "Eight-Bit Clean -.pp -Previous versions of sendmail used the 0200 bit for quoting. This -version avoids that use. -However, you can set option `7' to get seven bit stripping -for compatibility with RFC 821, -which is a 7-bit protocol. -This option says ``strip to 7 bits on input''. -.pp -Individual mailers can still produce seven bit out put using the -`7' mailer flag. -This flag says ``strip to 7 bits on output''. -.sh 2 "User Database" -.pp -The User Database (UDB) is an as-yet experimental attempt to provide -unified large-site name support. -We are installing it at Berkeley; -future versions may show significant modifications. -Briefly, UDB contains a database that is intended to contain -all the per-user information for your workgroup, -such as people's full names, their .plan information, -their outgoing mail name, and their mail drop. -.pp -The user database allows you to map both incoming and outgoing -addresses, much like IDA. However, the interface is still -better with IDA; -in particular, the alias file with incoming/outgoing marks -provides better locality of information. -.sh 2 "Improved BIND Support" -.pp -The BIND support, particularly for MX records, had a number of -annoying ``features'' which have been removed in this release. In -particular, these more tightly bind (pun intended) the name server -to sendmail, so that the name server resolution rules are incorporated -directly into sendmail. -.pp -The major change has been that the $[ ... $] operator didn't fully -qualify names that were in DNS as A or MX records. Version 8 does -this qualification. -.pp -This has proven to be an annoyance in Sun shops, -who often still run without BIND support. -However, it is really critical that this be supported, -since MX records are mandatory. -In SunOS you can choose either MX support or NIS support, -but not both. -This is fixed in Solaris, -and some -.i sendmail -support to allow this in SunOS should be forthcoming in a future release. -.sh 2 "Keyed Files" -.pp -Generalized keyed files is an idea taken directly from IDA sendmail -(albeit with a completely different implementation). -They can be useful on large sites. -.pp -Version 8 includes the following built-in map classes: -.ip dbm -Support for the ndbm(3) library. -.ip hash -Support for the ``Hash'' type from the new Berkeley db(3) library. -this library provides substantially better database support -than ndbm(3), -including in-memory caching, -arbitrarily long keys and values, -and better disk utilization. -.ip btree -Support for the ``B-Tree'' type from the new Berkeley db(3) library. -B-Trees provide better clustering than Hashed files -if you are fetching lots of records that have similar keys, -such as searching a dictionary for words beginning with ``detr''. -.ip nis -Support for NIS (a.k.a. YP) maps. -NIS+ is not supported in this version. -.ip host -Support for DNS lookups. -.ip dequote -A ``pseudo-map'' (that is, once that does not have any external data) -that allows a configuration file to break apart a quoted string -in the address. -This is necessary primarily for DECnet addresses, -which often have quoted addresses that need to be unwrapped on gateways. -.sh 2 "Multi-Word Classes & Macros in Classes" -.pp -Classes can now be multiple words. For example, -.(b -CShofmann.CS.Berkeley.EDU -.)b -allows you to match the entire string ``hofmann.CS.Berkeley.EDU'' -using the single construct ``$=S''. -.pp -Class definitions are now allowed to include macros \*- for example: -.(b -Cw$k -.)b -is legal. -.sh 2 "IDENT Protocol Support" -.pp -The IDENT protocol as defined in RFC 1413 [RFC1413] is supported. -However, many systems have a TCP/IP bug that renders this useless, -and the feature must be turned off. -Roughly, if one of these system receives a -.q "No route to host" -message (ICMP message ICMP_UNREACH_HOST) on -.i any -connection, all connections to that host are closed. -Some firewalls return this error if you try to connect -to the IDENT port, -so you can't receive email from these hosts on these systems. -It's possible that if the firewall used a more specific message -(such as ICMP_UNREACH_PROTOCOL, ICMP_UNREACH_PORT or ICMP_UNREACH_NET_PROHIB) -it would work, but this hasn't been verified. -.pp -IDENT protocol support cannot be used on -4.3BSD, -Apollo DomainOS, -Apple A/UX, -ConvexOS, -Data General DG/UX, -HP-UX, -Sequent Dynix, -or -Ultrix 4.x, x \(<= 3. -It seems to work on -4.4BSD, -IBM AIX 3.x, -OSF/1, -SGI IRIX, -Solaris, -SunOS, -and Ultrix 4.4. -.sh 2 "Separate Envelope/Header Processing -.pp -Since the From: line is passed in separately from the envelope -sender, these have both been made visible; the $g macro is set to -the envelope sender during processing of mailer argument vectors -and the header sender during processing of headers. -.pp -It is also possible to specify separate per-mailer envelope and -header processing. The SenderRWSet and RecipientRWset arguments -for mailers can be specified as ``envelope/header'' to give different -rewritings for envelope versus header addresses. -.sh 2 "Owner-List Propagates to Envelope -.pp -When an alias has an associated owner-list name, that alias is used -to change the envelope sender address. This will cause downstream -errors to be returned to that owner. -.pp -Some people find this confusing -because the envelope sender is what appears in the first -``From_'' line in UNIX messages -(that is, the line beginning ``From<space>'' -instead of ``From:''; -the latter is the header from, which -.i does -indicate the sender of the message). -In previous versions, -.i sendmail -has tried to avoid changing the envelope sender -for back compatibility with UNIX convention; -at this point that back compatibility is creating too many problems, -and it is necessary to move forward into the 1980s. -.sh 2 "Command Line Flags" -.pp -The -.b \-B -flag has been added to pass in body type information. -.pp -The -.b \-p -flag has been added to pass in protocol information -that was previously passed in by defining the -.b $r -and -.b $s -macros. -.pp -The -.b \-X -flag has been added to allow logging of all protocol in and -out of sendmail for debugging. -You can set -.q "\-X filename" -and a complete transcript will be logged in that file. -This gets big fast: the option is only for debugging. -.pp -The -.b \-q -flag can limit limit a queue run to specific recipients, -senders, or queue ids using \-qRsubstring, \-qSsubstring, or -\-qIsubstring respectively. -.sh 2 "New Configuration Line Types -.pp -The `T' (Trusted users) configuration line has been deleted. It -will still be accepted but will be ignored. -.pp -The `K' line has been added to declare database maps. -.pp -The `V' line has been added to declare the configuration version -level. -.pp -The `M' (mailer) line takes a D= field to specify execution -directory. -.sh 2 "New and Extended Options" -.pp -Several new options have been added, many to support new features, -others to allow tuning that was previously available only by -recompiling. Briefly: -.nr ii 0.5i -.ip A -The alias file specification can now be a list of alias files. -Also, the configuration can specify a class of file. -For example, to search the NIS aliases, use -.q OAnis:mail.aliases . -.ip b -Insist on a minimum number of disk blocks. -.ip C -Delivery checkpoint interval. Checkpoint the queue (to avoid -duplicate deliveries) every C addresses. -.ip E -Default error message. This message (or the contents of the -indicated file) are prepended to error messages. -.ip G -Enable GECOS matching. If you can't find a local user name -and this option is enabled, do a sequential scan of the passwd -file to match against full names. Previously a compile option. -.ip h -Maximum hop count. Previously this was compiled in. -.ip I -This option has been extended to allow setting of resolver parameters. -.ip j -Send errors in MIME-encapsulated format. -.ip J -Forward file path. Where to search for .forward files \*- defaults -to $HOME/.forward. -.ip k -Connection cache size. The total number of connections that will -be kept open at any time. -.ip K -Connection cache lifetime. The amount of time any connection -will be permitted to sit idle. -.ip l -Enable Errors-To: header. These headers violate RFC 1123; -this option is included to provide back compatibility with -old versions of sendmail. -.ip O -Incoming daemon options (e.g., use alternate SMTP port). -.ip p -Privacy options. These can be used to make your SMTP server -less friendly. -.ip r -This option has been extended to allow finer grained control -over timeouts. -For example, you can set the timeout for SMTP commands individually. -.ip R -Don't prune route-addrs. Normally, if version 8 sees an address -like "<@hostA,@hostB:user@hostC>, sendmail will try to strip off -as much as it can (up to user@hostC) as suggested by RFC 1123. -This option disables that behaviour. -.ip T -The -.q "Return To Sender" -timeout has been extended -to allow specification of a warning message interval, -typically something on the order of four hours. -If a message cannot be delivered in that interval, -a warning message is sent back to the sender -but the message continues to be tried. -.ip U -User database spec. This is still experimental. -.ip V -Fallback ``MX'' host. This can be thought of as an MX host -that applies to all addresses that has a very high preference -value (that is, use it only if everything else fails). -.ip w -If set, assume that if you are the best MX host for a host, -you should send directly to that host. This is intended -for compatibility with UIUC sendmail, and may have some -use on firewalls. -.ip 7 -Do not run eight bit clean. Technically, you have to assert -this option to be RFC 821 compatible. -.sh 2 "New Mailer Definitions" -.ip L= -Set the allowable line length. In V5, the L mailer flag implied -a line length limit of 990 characters; this is now settable to -an arbitrary value. -.ip F=a -Try to use ESMTP. It will fall back to SMTP if the initial -EHLO packet is rejected. -.ip F=b -Ensure a blank line at the end of messages. Useful on the -*file* mailer. -.ip F=c -Strip all comments from addresses; this should only be used as -a last resort when dealing with cranky mailers. -.ip F=g -Never use the null sender as the envelope sender, even when -running SMTP. This violates RFC 1123. -.ip F=7 -Strip all output to this mailer to 7 bits. -.ip F=L -Used to set the line limit to 990 bytes for SMTP compatibility. -It now does that only if the L= keyletter is not specified. -This flag is obsolete and should not be used. -.sh 2 "New or Changed Pre-Defined Macros" -.ip $k -UUCP node name from uname(2). -.ip $m -Domain part of our full hostname. -.ip $_ -RFC 1413-provided sender address. -.ip $w -Previously was sometimes the full domain name, sometimes -just the first word. Now guaranteed to be the first word -of the domain name (i.e., the host name). -.ip $j -Previously had to be defined \*- it is now predefined to be -the full domain name, if that can be determined. That is, -it is equivalent to $w.$m. -.sh 2 "New and Changed Classes" -.ip $=k -Initialized to contain $k. -.ip $=w -Now includes -.q [1.2.3.4] -(where 1.2.3.4 is your IP address) -to allow the configuration file to recognize your own IP address. -.sh 2 "New Rewriting Tokens" -.pp -The -.b $& -construct has been adopted from IDA to defer macro evaluation. -Normally, macros in rulesets are bound when the rule is first parsed -during startup. -Some macros change during processing and are uninteresting during startup. -However, that macro can be referenced using -.q $&x -to defer the evaulation of -$x -until the rule is processed. -.pp -The tokens -.b $( -and -.b $) -have been added to allow specification of map rewriting. -.pp -Version 8 allows -.b $@ -on the Left Hand Side of an `R' line to match -zero tokens. -This is intended to be used to match the null input. -.sh 2 "Bigger Defaults -.pp -Version 8 allows up to 100 rulesets instead of 30. It is recommended -that rulesets 0\-9 be reserved for sendmail's dedicated use in future -releases. -.pp -The total number of MX records that can be used has been raised to -20. -.pp -The number of queued messages that can be handled at one time has -been raised from 600 to 1000. -.sh 2 "Different Default Tuning Parameters -.pp -Version 8 has changed the default parameters for tuning queue costs -to make the number of recipients more important than the size of -the message (for small messages). This is reasonable if you are -connected with reasonably fast links. -.sh 2 "Auto-Quoting in Addresses -.pp -Previously, the ``Full Name <email address>'' syntax would generate -incorrect protocol output if ``Full Name'' had special characters -such as dot. This version puts quotes around such names. -.sh 2 "Symbolic Names On Error Mailer -.pp -Several names have been built in to the $@ portion of the $#error -mailer. For example: -.(b -$#error $@NOHOST $: Host unknown -.)b -Prints the indicated message -and sets the exit status of -.i sendmail -to -.sm EX_NOHOST . -.sh 2 "New Built-In Mailers" -.pp -Two new mailers, *file* and *include*, are included to define options -when mailing to a file or a :include: file respectively. Previously -these were overloaded on the local mailer. -.sh 2 "SMTP VRFY Doesn't Expand -.pp -Previous versions of sendmail treated VRFY and EXPN the same. In -this version, VRFY doesn't expand aliases or follow .forward files. -.pp -As an optimization, if you run with your default delivery mode -being queue-only, the RCPT command will also not chase aliases and -\&.forward files. -It will chase them when it processes the queue. -This speeds up RCPT processing. -.sh 2 "[IPC] Mailers Allow Multiple Hosts -.pp -When an address resolves to a mailer that has ``[IPC]'' as its -``Path'', the $@ part (host name) can be a colon-separated list of -hosts instead of a single hostname. This asks sendmail to search -the list for the first entry that is available exactly as though -it were an MX record. The intent is to route internal traffic -through internal networks without publishing an MX record to the -net. MX expansion is still done on the individual items. -.sh 2 "Aliases Extended" -.pp -The implementation has been merged with maps. Among other things, -this supports multiple alias files and NIS-based aliases. For -example: -.(b -OA/etc/aliases,nis:mail.aliases -.)b -will search first the local database -.q /etc/aliases -followed by the NIS map - -.sh 2 "Portability and Security Enhancements -.pp -A number of internal changes have been made to enhance portability. -.pp -Several fixes have been made to increase the paranoia factor. -.pp -In particular, the permissions required for .forward and :include: -files have been tightened up considerably. V5 would pretty much -read any file it could get to as root, which exposed some security -holes. V8 insists that all directories leading up to the .forward -or :include: file be searchable ("x" permission) by the controlling -user" (defined below), that the file itself be readable by the -controlling user, and that .forward files be owned by the user -who is being forwarded to or root. -.pp -The "controlling user" is the user on whose behalf the mail is -being delivered. For example, if you mail to "user1" then the -controlling user for ~user1/.forward and any mailers invoked -by that .forward file, including :include: files. -.pp -Previously, anyone who had a home directory could create a .forward -could forward to a program. Now, sendmail checks to make sure -that they have an "approved shell", that is, a shell listed in -the /etc/shells file. -.sh 2 "Miscellaneous Fixes and Enhancements" -.pp -A number of small bugs having to do with things like backslash-escaped -quotes inside of comments have been fixed. -.pp -The fixed size limit on header lines -(such as -.q To: -and -.q Cc: ) -has been eliminated; -those buffers are dynamically allocated now. -.pp -Sendmail writes a /etc/sendmail.pid file with the current process id -and the current invocation flags. -.pp -Two people using the same program (e.g., submit) are considered -"different" so that duplicate elimination doesn't delete one of -them. For example, two people forwarding their email to -|submit will be treated as two recipients. -.pp -The mailstats program prints mailer names and gets the location of -the sendmail.st file from /etc/sendmail.cf. -.pp -Many minor bugs have been fixed, such as handling of backslashes -inside of quotes. -.pp -A hook has been added to allow rewriting of local addresses after -aliasing. -.sh 1 "FUTURE WORK" -.pp -The previous section describes -.i sendmail -as of version 8.6.6. -There is still much to be done. -Some high points are described below. -This list is by no means exhaustive. -.sh 2 "Full MIME Support" -.pp -Currently -.i sendmail -only supports seven bit MIME messages. -Although it can pass eight bit MIME messages, -it cannot advertise that fact because the standards say -that the mail agent must be able to do 8- to 7-bit conversion -to have full 8-bit support. -This requires far more extensive modification of the message body -than is currently supported. -.pp -The best way to do this would be to support the general concept -of an external -``message filter'' -that could do arbitrary modifications of the message. -This would allow MIME conversion as well as such things as -automatic encryption of messages sent over external links. -This is probably an extremely non-trivial change. -.sh 2 "Service Switch Abstraction" -.pp -Most modern systems include some concept of a -.q "service switch" -\*- for example, to look up host names you can try -DNS, NIS, NIS+, text tables, NetInfo, -or other services in some arbitrary order. -This is currently very clumsy in -.i sendmail , -with only limited control of the services provided. -.sh 2 "More Control of Local Addresses" -.pp -Currently some addresses are declared as -.q local -and are handled specially \*- -for example, they may have .forward files, -may be translated into program calls or file deliveries, -and so forth. -These should be broken out into separate flags -to allow the local system administrator -to have more fine-grained control over operations. -.sh 2 "More Run-Time Configuration Options" -.pp -There are many options that are configured at compile time, -such as the method of file locking -and the use of the IDENT protocol -[RFC1413]. -These should be transfered to run time -by adding new options. -.pp -Similarly, some options are currently overloaded, -that is, a single option controls more than one thing. -These should probably be broken out into separate options. -.pp -This implies that options will change from single characters -to words. -.sh 2 "More Configuration Control Over Errors" -.pp -Currently, -the configuration file can generate an error message during parsing. -However, -it cannot tweak other operations, -such as issuing a warning message to the system postmaster. -Similarly, -some errors should not be triggered if they are in aliases -during an alias file rebuild, -but should be triggered if that alias is actually used. -.sh 2 "Long Term Host State" -.pp -Currently, -.i sendmail -only remembers host status during a single queue run. -This should be converted to long term status -stored on disk -so it can be shared between instantiations of -.i sendmail . -Entries will have to be timestamped -so they can time out. -This will allow -.i sendmail -to implement exponential backoff on queue runs -on a per-host basis. -.sh 2 "Connection Control" -.pp -Modern networks have different types of connectivity -than the past. -In particular, the rising prominence of dialup IP -has created certain challenges for automated servers. -It is not uncommon to try to make a connection to a host -and have it fail, even though if you tried again it would succeed. -The connection management could be a bit cleverer -to try to adapt to such situations. -.sh 2 "Other Caching" -.pp -When you do an MX record lookup, -the name server automatically returns the IP addresses -of the associated MX servers. -This information is currently ignored, -and another query is done to get this information. -It should be cached to avoid excess name server traffic. -.sh 1 "REFERENCES" -.ip [Allman83a] -.q "Sendmail \*- An Internetwork Mail Router." -E. Allman. -In -.ul -Unix Programmers's Manual, -4.2 Berkeley Software Distribution, -volume 2C. -August 1983. -.ip [Allman83b] -.q "Mail Systems and Addressing in 4.2BSD." -E. Allman -In -.ul -UNICOM Conference Proceedings. -San Diego, California. -January 1983. -.ip [Allman&Amos85] -``Sendmail Revisited.'' -E. Allman and M. Amos. -In -.ul -Usenix Summer 1985 Conference Proceedings. -Portland, Oregon. -June 1985. -.ip [IDA87] -.ul 3 -Electronic Mail Addressing in Theory and Practice -with the IDA Sendmail Enhancement Kit -(or The Postmaster's Last Will and Testament). -Lennart Lo\*:vstrand. -Department of Computer and Information Science, -University of Linko\*:ping, -Sweden, -Report no. LiTH-IDA-Ex-8715. -May 1987. -.ip [RFC821] -.ul -Simple Mail Transport Protocol. -J. Postel. -August 1982. -.ip [RFC1123] -.ul -Requirements for Internet Hosts \*- Application and Support. -Internet Engineering Task Force, -R. Braden, Editor. -October 1989. -.ip [RFC1344] -.ul -Implications of MIME for Internet Mail Gateways. -N. Borenstein. -June 1992. -.ip [RFC1413] -.ul -Identification Protocol. -M. St. Johns. -February 1993. -.ip [RFC1425] -.ul -SMTP Service Extensions. -J. Klensin, N. Freed, M. Rose, E. Stefferud, and D. Crocker. -February 1993. -.ip [RFC1426] -.ul -SMTP Service Extension for 8bit-MIMEtransport. -J. Klensin, N. Freed, M. Rose, E. Stefferud, and D. Crocker. -February 1993. -.ip [RFC1427] -.ul -SMTP Service Extension for Message Size Declaration. -J. Klensin, N. Freed, and K. Moore. -February 1993. -.ip [RFC1521] -.ul 3 -MIME (Multipurpose Internet Mail Extensions) Part One: -Mechanisms for Specifying and Describing -the Format of Internet Message Bodies. -N. Borenstein and N. Freed. -September 1993. |