Scanning

There are two mechanisms for invoking SpamAssassin. The first is the spamassassin Perl script. The second is the spamc C program. With the spamassassin script an entire perl process is initiated, all of the rules are read, the regexes compiled, and then the scanning is performed for each email message. This entails a fair amount of overhead. The alternative method is to run a long-running daemon (spamd) so the startup costs of perl and spamassassin are incurred only once in a great while. Then the lightweight spamc program is used to pass the message to the daemon and return the result of the scanning. This document uses the spamc/spamd method.

First the spamd daemon needs to be started. The exact procedure for doing this will certainly vary from OS to OS. The following instructions apply to debian, because that is what I have experience with.

Secondly you will need to instruct exim to pre-process each email with spamassassin. To do this system-wide requires, at the very least, editing your exim.conf file.