[ excerpt from developer's site ] Bayespam is a qmail spam filter written in Perl, using Bayesian classification to filter out unsolicited commercial email. It is written with ease of installation and use in mind, and it is encouraged that you give it a try. Bayespam actually learns as you give it more spam to process, so it should become better and better the longer you use it. Bayespam is based on a paper written by Paul Graham called A Plan for Spam. In this paper, Mr. Graham talked about a spam filter he is working on that used Bayesian classification to determine if a particular piece of email is spam or not.