Conceptually I am high on this product. Unfortunately I can not make it deliver on the promise. I very much miss this feature (had it in Eudora Pro) since I began using Apple's Mail. I am using Mail v1.2.5 (docs referred to 1.2.3). Three stars for the concept and a hopefully bright future, not higher because implementation is still in progress.

A diamond in the rough, keep your eyes on this one.