Nearly all of today's mail system administrators face spam as their
first threat. Because of this, EnderUNIX team has written this small
application to automagically monitor malicious spammer activity in
your mail server logs.

spamGuard is written purely in C, to stop spammers hanging around.
The program supports nearly all mostly used MTAs; qmail (both
multilog and splogger), sendmail and Postfix.

WWW: http://www.enderunix.org/spamguard