I've just started having a weird problem in Outlook (on an IMAP account) where I receive duplicate messages from everyone, one containing the actual message, and the other a blank e-mail simply with "on behalf of [Sender's name]" in the "From:" field. Does anyone have any idea why this might be happening, and what I can do to stop it? Sporadically it also duplicates the names of the sender(s) and receiver(s) - e.g. under from "John Smith John Smith John Smith John Smith John Smith...".