JunkMatcher for Mac

From Benjamin Han:

JunkMatcher is a cocktail-styled spam filter for Mail.app on Mac OS X (10.3.x or later). It filters spam by conducting a wealth of tests over emails. Two types of tests are available: property tests can detect general characteristics of spam using techniques such as naive Bayesian filtering (thanks to SpamBayes) and blacklist lookup (checking if a message was sent from a spamming IP address), and pattern tests can spot keywords such as "v1ägra" or "\/Iagr á" by using patterns written in regular expressions, a very powerful language designed just for that - to describe patterns.

JunkMatcher integrates tightly with Mail.app and OS X. You don't need to keep a second app running in order to use it - the filter will automagically spring into action via a rule within Mail.app! You can even use it with Mail.app's built-in filter if you wish, in which case it will become a good teacher to the built-in filter. JunkMatcher also knows your Address Book, and you can train emails as spam/ham (good emails) directly from within Mail.app, etc.

JunkMatcher is extremely configurable. The GUI lets you tweak a gazillion of settings, analyze mis-classified emails, and even design your own pattern tests to catch more spam. You can write patterns to match many "views" of cleanly distilled emails such as the headers, the subject, the body, and even the text rendering for HTML emails (thanks to ELinks). You can also check on what JunkMatcher has done in the past and correct its mistakes if necessary, all from a very friendly GUI.

JunkMatcher evolves, too. In addition to the built-in Bayesian classifier that learns from mistakes, you can also download new pattern updates directly within the JunkMatcher GUI. Best of all? JunkMatcher is completely free (donation is welcome)! In fact, it is an open-source app so you also get the source code!