You may be receiving duplicate mails because of two accounts created in Microsoft Outlook 2007 that are pointing to the same POP3 server. I have searched and found a few steps to resolve your issue. I suggest that you follow the steps provided below:
- Launch Microsoft Office Outlook 2007.
- On the “Tools” menu, point to “Send/Receive” and then point to “Send/Receive Settings”.
- Click on “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” check box.
If the issue persists, I suggest that you contact your Internet Service Provider since they would be your first point of contact in resolving the issue.