In Mail, why do I receive 2 copies of every email
Since signing up in ICloud I receive 2 copies of every email. I have, inter alia, 2 accounts, one for ICloud and one for MobileMe.
Well I think you answered your own question.
IIRC Mobile Me is being shut down and everything is moving over to iCloud. So if you created a second account in iCloud that gets the same mail as your Mobile Me account that is why you are seeing 2 of every email.
Stop downloading emails from the Mobile Me account.