SpamLookup is an anti-spam plugin created by lead Movable Type engineer Brad Choate, which identifies spam based on a number of unique characteristics and administrator based tests. It includes:

• IP address blacklist lookups
• Domain name blacklist lookups
• IP address source correlation
• Lookup whitelists
• Link limits
• Email and Link memory tests
• Keyword filtering

This plugin utilizes the feedback rating framework. Each test that is enabled contributes to the final composite score of a feedback item. The final score (which is an average of all tests, including SpamLookup and other plugins) determines whether an item is marked as Junk or not.

Because of its many accurate and customizable tests, SpamLookup is the most successful anti-spam plugin for Movable Type. It is bundled with Movable Type 3.3 and Movable Type Enterprise, and can be configured on both the system level and weblog level (by authors with the appropriate permissions).