03-08-2013 12:09 PM
Not really clear if the duplicated e-mails are the result of having morethan one account set up or a single account is making duplicate entries. I'll answer on the basis of the first situation.
This will happen if you have ore than one e-mail account set up and people send you e-mails to each of those accounts. It is not immediately obvious what account an e-mail comes from. You can check iit by scrolling up in each e-mail which will then reveal what e-mail account(s) are involved.