|I suggest you:
1.add a "copy to" and "move to" to the right click menu for every message so that on can organize messages into folders he defines.
2.For each contact add a "send PM" or "send instant message" if he uses yahoo for example(if at all possibl)
By the way, have you tested opera's built-in email client.It has a feature called views : you can have a message in different views at the same time.a message can be in "unread", "important", and "with attachment" views simultanously.
Is it possible for scribe?