From JAM Software:
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).
Native 64 bit support has been integrated.
SpamAssassin version 3.4.1 integrated.
ActivePerl 5.8 replaced by Strawberry Perl 5.22. Support for Windows XP and Server 2003 dropped.
Critical error in DNS-based spam tests removed.
A few minor fixes have been incorporated.