Best Mac spam filter gets better with age. Incredibly accurate, easily trained, integrates with Apple’s Mail, Microsoft’s Entourage, and Address Book. If email spam bothers you, get SpamSieve.

SpamSieve gives you back your inbox by bringing powerful Bayesian spam filtering to Mac e-mail clients. It’s quick and easy to control SpamSieve from within your mail client, and you can customize how it interacts with the rest of your message sorting rules. Other spam filters get worse over time as spammers adapt to their rules; SpamSieve actually gets better over time as it adapts to your mail.

9WR - SpamSieve: Easily configured Bayesian email spam filter for Mail, Entourage.