Integration into Courier-MTA using maildrop

First, install SpamAssassin and Courier MTA according to their installation docs. Make sure they are functioning on their own. You may want to use spamc/spamd for better performance. What's left is the The connection between Courier and SpamAssassin.

If you have virtual users (as opposed to plain *nix users) you may have to let Spamassassin know where to find per-user preferences. This can be done by passing the username as an option to spamc using Courier's maildroprc config file as shown below, and then using the spamd --virtual-config-dir option. You can omit this if using only system-wide preferences.

is made by using maildrop as the MDA and spamd/spamc to perform the spam checking using Courier's mail filtering language.

To let Courier To let Courier MTA use maildrop as default for delivery, edit /etc/courier/courierd and set DEFAULTDELIVERY to "| /usr/bin/maildrop" (or wherever your maildrop binary is). Then edit the global filter file /etc/courier/maildroprc, the central maildrop script to pipe mail through Spamassassin before delivery:

import USER
if ($LOGNAME ne "")
{
 xfilter "/usr/bin/vendor_perl/spamc -u $LOGNAME"
}
else
{
 xfilter "/usr/bin/vendor_perl/spamc -u $USER"
}

...

You must then decide what to do with any spam mail. For example, an instruction in the the users .mailfilter file:

if(/^X-Spam-Status: YES/)
{
 to "$HOME/Maildir/.Junk/"
}

If you have virtual users (as opposed to plain *nix users) you may want to let Spamassassin know where to find per-user preferences. Do this by passing the username to spamc with the -u option and then using the spamd --virtual-config-dir option. You can omit this if using only system-wide preferences.