Their mission, to stop more spam than any algorithm has before. Bayesian filters have hit the net, they work on a principle where they "learn" what is spam and what is not. I've been testing around with one for a bit, but my E-Mail box has been surprisngly quiet lately. So far it looks good. Surprisingly refined and portable over all platforms that can use python scripts (Linux, Windows, Unix etc). Best of all, FREE!
Spambayes:
http://spambayes.sourceforge.net/
Spambayes:
http://spambayes.sourceforge.net/