Mailwasher 6.3 Pro definitely works with Linux - well, with Ubuntu Hardy Heron, anyway! - through Wine.
I missed Mailwasher when I fled from Windows. The amazingly helpful Jeremy helped me through setting up the old Mailwasher Pro for Linux with some long distance hand holding, but I eventually decided to try the latest version for the added functionality and Hey Presto, the "upgrade" went very smoothly indeed!
Keep up the good work guys!