SpamAssassin is a mail filter which attempts to identify spam using a variety of mechanisms including text analysis, Bayesian filtering, DNS blocklists, and collaborative filtering databases.

SpamAssassin is a project of the Apache Software Foundation (ASF). SpamAssassin was adapted for Windows by JAM Software. In combination with a MTA (e.g. Hamster or MS Exchange) it's a very powerful anti-spam solution.

The freeware contains, beside several modules, the following SpamAssassin components as

executable files for Windows (.exe):
- spamassassin.exe (mail filter)
- spamd.exe (daemonized version of SpamAssassin)
- WinSpamC.exe (client for spamd)
- sa-update.exe (SpamAssassin rule updates)
- sa-learn.exe (trains bayes filter with spam/ham mail)