Still a few bugs left...
A user can't delete custom folders, and if you create them it seems that the first message in your inbox will be replicated in the new folder. That is until you do anything to this "ghost" message (e.g. move, it delte it) where-apon the original message from the inbox will be moved/deleted and the "ghost" message will disappear.
Also messages from the sent folder are delted straight-away (without being moved to the trash folder). I'm assuming that's intentional, although a warning to users would be a good idea (say by the delete button).
Other than that very cool so far