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.