Rated 5 out of 5 stars

This add-on provides excellent transparency for the junk mail filtering process. First, it provides insight into how well the process is working by showing the spam score for each e-mai. Uncertain cases can be displayed in a special folder (actually, a filtered version of the inbox), and you can then vote them as spam or not using optional "Is Junk" and "Not Junk" buttons. This trains the Baysian filter so it can discriminate better. Beyond that, the add-on provides a number of other helpful features. Well done!