Description:

DSPAM (as in De-Spam) is an open-source project to create a new kind
of anti-spam mechanism, and 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.

The DSPAM agent masquerades as the email server's local delivery agent
and filters/learns spams using an advanced Bayesian statistical
approach (based on Bayes's theorem of combined probabilities) which
provides an administratively maintenance-free, easy-learning Anti-Spam
service custom tailored to each individual user's behavior. Advanced
because on top of standard Bayesian filtering is also incorporated the
use of Chained Tokens, de-obfuscation, and other enhancements. DSPAM
works great with Sendmail and Exim, and should work well with any
other MTA that supports an external local delivery agent (postfix,
qmail, etc.)