mini_sendmail reads its standard input up to an end-of-file and
sends a copy of the message found there to all of the addresses
listed.  The message is sent by connecting to a local SMTP server.

If you want to use mini_sendmail to send email from inside a
chroot(2) area, you might want to use the mini_sendmail_static
package instead to avoid copying libraries.

See the manual entry for more details.