Outlook prompts for password and duplicate e-mail messages appear
Cause: This can occur if your Outlook profile contains two Internet accounts that both point to the same POP3 server, or for other reasons. We point here to six solutions.
Solution #1: Turn off e-mail reception for one of the POP3 accounts: in Outlook, on the Tools menu, point to Send/Receive Settings, and then click Define Send/Receive Groups. Double-click the group that contains the two POP3 accounts, and under Accounts, click one of the POP3 accounts. Click to clear the Receive mail items checkbox.