K9 email filter is free. It is an excellent way to deal with spam. And, it
supports perl regular expressions. Set up correctly it can deal with 100%
of spam--silently deleting it without a bother...
Without it, you cannot use usenet, with a valid email address, without being
spammed to death--with it, you don't know the spammers exist...
http://keir.net/k9.html

Regards,
John