I started to wonder about the algorithm used in the Mail spam filter on Jaguar (Mac OS X 10.2). There is also a tool called bogofilter
(http://www.tuxedo.org/~esr/bogofilter/). This software is based on Bayesian statistics. See article "A Plan for Spam" by Paul Graham
(http://www.paulgraham.com/spam.html).

So far the spam filter of Mail has generated one false positive in 15 mails, and it missed two or three spam messages.