Reject mail inline using SpamAssassin spamd

This program is very simple. About 700 lines of C code. No configuration file. Only basic functionality. No bells and whistles. This is a design choice. There are plenty of other plugins that provide much more functionality.

In short, if this is all you need, it's probably the easiest and most efficient choice. If it isn't, you'll have to fork and extend the code, or look elsewhere ;)

milter-spamd runs on OpenBSD and is BSD licensed.

Man page

MILTER-SPAMD(8)         OpenBSD System Manager's Manual        MILTER-SPAMD(8)

NAME
     milter-spamd - sendmail milter plugin for SpamAssassin spamd

SYNOPSIS
     milter-spamd [-d] [-i RE] [-p pipe] [-u user] [-U spamd-user]

DESCRIPTION
     The milter-spamd plugin can be used with the milter API of sendmail(8) to
     filter mails based on decisions from SpamAssassin's spamd(1) daemon.
     Mails are piped to the daemon, which decides whether a mail is spam or
     not according to its own configuration.  Spam mails are rejected with an
     SMTP 554 ("Transaction failed") reply, containing the score from spamd.
     This typically causes the remote MTA to generate a bounce message to the
     sender.  Non-spam mails are accepted without any modifications.

     The options are as follows:

     -d         Do not detach from controlling terminal.  Produce verbose out-
                put on stdout for debugging.

     -i RE      Accept mails without invoking spamd for peers whose host names
                or IP addresses match the specified regular expression.  The
                argument is a case-insensitive extended regular expression
                (like an argument of egrep(1) -i).  Example:

                      # milter-spamd -i '(^127\.|^10\.1\.|\.benzedrine\.ch$)'

                would skip filtering for senders whose host names end in .ben-
                zedrine.ch or whose IP addresses start with 127. or 10.1.

     -p pipe    Use the specified pipe to interface sendmail(8).  Default is
                unix:/var/spool/milter-spamd/sock.

     -u user    Run as the specified user instead of the default, _milter-
                spamd.  When milter-spamd is started as root, it calls
                setuid(2) to drop privileges.  The non-privileged user should
                have read access to the configuration file and read-write ac-
                cess to the pipe.

     -U spamd-user
                Pass the specified user to spamd, so that user's SpamAssassin
                settings are used instead of the default system-wide ones.

SENDMAIL CONFIGURATION
     The plugin needs to be registered in the sendmail(8) configuration, by
     adding the following lines to the .mc file

           INPUT_MAIL_FILTER(`milter-spamd',
                   `S=unix:/var/spool/milter-spamd/sock, T=S:30s;R:2m')

     rebuilding /etc/mail/sendmail.cf from the .mc file using m4(1), and
     restarting sendmail(8).

LOGGING
     milter-spamd sends log messages to syslogd(8) using facility daemon and,
     with increasing verbosity, level err, notice, info and debug.  The fol-
     lowing syslog.conf(5) section can be used to log messages to a dedicated
     file:

     !milter-spamd
     daemon.err;daemon.notice        /var/log/milter-spamd

SEE ALSO
     egrep(1), mailstats(1), regex(3), syslog.conf(5), re_format(7),
     sendmail(8), syslogd(8)

     Simple Mail Transfer Protocol, RFC 2821.

     Enhanced Mail System Status Codes, RFC 1893.

HISTORY
     The first version of milter-spamd was written in 2004.

AUTHORS
     Daniel Hartmeier <daniel@benzedrine.ch>

OpenBSD 3.7                   September 24, 2003                             2

Sources

milter-spamd-0.9.tar.gz source tarball MD5 42bc41678b1430c60b3f83baaee9c59a GPG signature
milter-spamd-0.8.tar.gz source tarball MD5 198dbf9ab4f0fc3b13305b43b5db7751 GPG signature
milter-spamd-0.7.tar.gz source tarball MD5 4b3f3dcf2c31ce7b9ed8f2a5102c1e69 GPG signature
milter-spamd-0.6.tar.gz source tarball MD5 449ef09371e48cdc0963a9a5f5b53fd7 GPG signature
mail/milter-spamd OpenBSD port

History

0.9: September 26, 2017

Add -l option to specify maximum log level, defaults to 6 (LOG_INFO), i.e. excludes LOG_DEBUG.

0.8: June 20, 2017

Remove setegid/seteuid calls.

0.7: January 16, 2017

Add pieces to build on Linux. Use make -f Makefile.linux.

0.6: January 16, 2014

SpamAssassin uses the top-most (trusted) Received: header in its score rules. Because sendmail inserts its own Received: header only after the milter plugin has been called, the plugin adds a similar header to the output sent to SpamAssassin. Improve this fake header by adding the authentication parts, when available. Some SpamAssassin rules use these to score favorably. Suggested and tested by Joerg Jung.

0.5: February 20, 2007

Remove man page section about building sendmail with milter support, this is the default since a while.

June 6, 2005

Fixes for multi-receipient mails (state machine).

October 31, 2004

milter-spamd 0.3 has been successfully tested with SpamAssassin 3.0.1. The API changes mentioned in the SpamAssassin upgrade documentation seem to refer to the command line interface, not the TCP interface used by milter-spamd.

0.3: April 4, 2004

Several bugfixes, add -i to exclude specific senders from getting filtered.

0.1: April 3, 2004

First version.