]
] DSPAM (as in De-Spam) is an extremely scalable,
] open-source statistical-algorithmic hybrid anti-spam
] filter. A majority of users running v2.10 achieve
] filtering rates ranging from 99.92% - 99.98 %, DSPAM is
] currently effective as both a server-side agent for UNIX
] email servers and a developer's library for mail clients,
] other anti-spam tools, and similar projects requiring
] drop-in spam filtering. DSPAM has been implemented on
] many large and small scale systems with the largest
] systems being reported at about 125,000 mailboxes.

This along with crm114 hit slashdot the other day. I'm playing with DSPAM.