Pat,
> Check out
formatting link
> Popfile is an e-mail proxy that filters spam based on how you train
> it. It takes some initial effort to get it over the hump, but it
> achieves over 99% accuracy over the long term.
> I believe they also have an nntp proxy for filtering usenet, too.
> You won't be sorry.
I will second the endorsement of Popfile. I've been using it for over a year now and it works very well. Every once in a great while it misclassified something as spam, but it's seriously easy to reclassify through their web interface.