SpamSquash is a smart Email filter for POP3 Email clients, such as MS OutLook and Pegasus Mail. It uses two methods: a Bayesian filter, you train, and DNS Block Lists. It also includes a white list for Email you don't want blocked, and a black list, for Email you do want blocked.

The license of this software is Free Trial Software, the price is $15, you can free download and get a free trial.