There really is no good alternative to this program that I've found anyway.-Midnight Rambler
I used Mailwasher years ago (on Win98...) but didn't much like the then-current version. Bayesian began to seem another term for "false positive," and back then it expected you to empty your mailbox every time you ran your email client, so every time Mailwasher ran, it started from the beginning again. I went back to
Magic Mail Monitor (freeware). It isn't Bayesian, development is glacial if it currently exists, and MMM isn't perfect; it's often been very slow on Yahoo! UK accounts since they changed their system a while back. But it's OK - once you've written enough filters, of course, which is tedious to start with. Another approach I sometimes use is to write filters into the small freeware email client
nPOPuk. It takes a few more keystrokes; you have to wait until it finishes looking at the mailbox, press F5 to apply filters, then say Yes to actioning them. Development is also moribund, but the program does work, and is more reliable on Yahoo! UK than MMM is.
Apparently Verizon or whoever now owns Yahoo! are giving themselves the right to read my emails, with the usual take-it-or-leave-it deal. It's not beyond possibility that I may change away from Yahoo!.