Perl-based spam filter using text analysis

 SpamAssassin is a very powerful and fully configurable spam filter
 with numerous features including automatic white-listing, RBL
 testing, Bayesian analysis, header and body text analysis. It is
 designed to be called from a user's .procmail or .forward file, but
 can also be integrated into a Mail Transport Agent (MTA).
 .
 Included in this package is a daemonized form of spamassassin (spamd)
 which communicates with its client (spamc) via TCP, to reduce the
 overhead of loading perl with each message. To take advantage of
 this, you must install the spamc package.