Using SpamAssassin with postfix

I was working on a Debian stable (woody) machine. This may work for other configs too. SpamAssassin is one of the few packages that should be more up2date than stable. The newer version is MUCH easier to use, and automagicly includes many of the features we all want (like Bayesian filtering). I got 3.0 from backports.org. Add the line:

     deb http://www.backports.org/debian/ woody spamassassin

apt-get install spamassassin

This document assumes you already have postfix running.

1. create a user and group called mailfilt which has no password, and cannot log in. (su from root only)
2. edit /etc/postfix/master.cf as follows:
   Change the line:

   smtp    inet  n       -       -       -       -       smtpd
   

   to

   smtp    inet  n       -       n       -       -       smtpd -o content_filter=spamassassin:
   

   and add the line:

   spamassassin unix - n n - - pipe flags=Rq user=mailfilt argv=/usr/local/bin/sa-filter.sh -f ${sender} ${recipient}
   

   to the end of the file.
3. Create a file like:

   -rwxr-xr--    1 mailfilt mailfilt       71 Oct 25 11:27 /usr/local/bin/sa-filter.sh

   with the contents

   #!/bin/bash
   /usr/bin/spamc | /usr/sbin/sendmail -i "$@"
   exit $?
   

4. Make sure that spamd is running:

   /etc/init.d/spamassassin restart

5. Re-initialize postfix to start using the spamfilter client:

   /etc/init.d/postfix reload

I think that the default SpamAssassin config will do this, but I'm not totally sure. If you don't like the results, look for info on editing the /usr/share/spamassassin/local.cf file.

Aaron Birenboim