C-Command Software has released a maintenance update to its powerful Bayesian spam filtering software, SpamSieve. Changes include improved compatibility with pre-release versions of Mac OS X, enhanced filtering accuracy, modernized program code, an updated version of the Vietnamese localization, and an updated version of the Apple Mail script for discarding spam. Also, a bug that prevented the Apple Mail command Train as Good from moving Exchange messages back to the Inbox has been fixed, and encoded HTML mail is no longer recognized as spam in the default settings. ($30 new, free update, 3.9 MB)
All I can say after using SpamSieve for over 3 years now is that it is "Truly Awesome"!!! Nothing else is in the ballpark, or even the parking lot.
Yeah, as far as spam filtering on the desktop goes, nothing, but nothing compares with SpamSieve in my experience.