SpamSieve = a BIG improvementDecember 9, 2006
Image spam and all manner of rubbish was getting past the Mail.app spam filter. So, enter screen right, SpamSieve.
Having been using this for less than 2 days, I am mightily impressed. You install it, add a plug-in to your mail client (Mail.app for me), disable jun mail filtering (in Mail.app), add a spam mailbox and then restart the client, get training good email and spam email and bingo! You can check the stats, and it seems to be doing a grand job! No spam has entered the inbox since!