SpamAssassin is also Outlook only... I'm currently using Mailwasher which is working fairly well and automated (its documentation is very loose, so to get it fully automated you have to dig for yourself in its settings). I'm using it with one of the better email programs available for Windows, TheBat.

Just found this last night: http://sourceforge.net/projects/popfile/ Seems interesting. A bit more to configure, but far more control than something as simple as Mailwasher. MW's cool features involve the simple setup and ability to bounce. TheBat actually includes all that's necessary to implement MW's functionality as well, but it's not currently set up to automatically filter remote mail.

Bruno