FOULGER Flagit is a great little App which I was happy to buy after the trial period expired. The author is very quick to communicate. HOWEVER - I have a problem whereby "As completed" and "Clear Flags" stay greyed out. Whether this is a result of my using Spamsieve (I can't see how, though) or some other factor, I don't know. What I do know is that this wonderful little app, which should be part of Apple Mail IMHO, has a flaw, which the author, by his own admission will be fixed but he can't say when. For me it has spoiled the basic idea behind Flagit. I hope the author can sort it out sooner rather than later.
(Version 1.2b)