Learns to classify your email into different categories, so as well as detecting Spam, it can help you sort email into work and personal etc. It uses Bayesian statistics to learn from examples you give it. Initially it regards all email as "Unclassified", you correct it by saying "this one is spam") and it very quickly learn to label your mail.
Pop File works either on a windows PC or under Linux or other operating systems. It can be installed on your client machine (i.e. desktop) or on the email server.
Windows Client Software
Cloudmark Spam Net - Community of users identify spam