A few days ago, Microsoft posted updates for the Junkmail tool in Outlook 2003. While the Update for Outlook 2003 Junk Email Filter (KB892236) isn’t going to solve all your problems, it is a good start. Unfortunately, for those running previous versions of Outlook, I believe you are SOL (if I am wrong, please provide a link I can post, for the not so lucky).
For those of you who feel your are more highly evolved, running Entourage on the Mac, but for some crazy reason just don’t have AutoUpdate running, here are your updates (posted months ago): Microsoft Entourage 2004 Junk E-mail Filter Update 1 (11.1.0). Please turn on your AutoUpdates while you’re at it.