Well you'd only do it on words that are almost certainly spam. Like Viagra or male impotence or...well, you get the picture. It works on the theory of "this word would almost never be used legitimately in a post so it's almost certainly spam"

I use this on my mail server and with 200 users I've yet to ever get a false positive.

> I use this on my mail server and with 200 users > I've yet to ever get a false positive.

How do you know? I don't see how you would measure that; if you can figure out it is a false positive, you have discovered a better filter. You might get user complaints, but the absence of user complaints doesn't prove you have no false positives. (Although the presence of user complains could prove that you do.)

Also: The assertion that everything to do with viagra is spam makes it very difficult to have a discussion about viagra or spam. For example, this posting would be rejected.

If you read my initial post I said specifically that it can't be just a flat out block. What you do is stop it and send an e-mail to the person who posted it asking them to verify they are an actual person.

That's both why it works even if you want to discuss viagra and how you can tell if you are getting too many false positives.