Outlook keeps re-downloading old emails?

Question :
All of a sudden, my email tells me that it wants to download 748 emails.  On closer inspection of said emails, some of them are dated as far back as August 15/10.  These are emails that I have already seen and deleted/dealt with etc.
How do I stop this from happening.  No one else uses my computer or email, so no settings have been changed.  I have turned off and restarted my computer with no success.
 Answer:
Outlook stores the last downloaded information in the pst file. When you create a new profile on a new computer, outlook redownloads everything. This should only happen once for the default account.

Outlook 2010, due to changes in how the "message manager" is handled, may download messages over and over if you deliver multiple accounts to one pst file. To fix, create a separate pst file for each account. In file, account settings, select the account then Change folder button to change the delivery location to a new pst. http://www.slipstick.com/outlook/outlook...-accounts/
Refer some of the below threads:
https://community.spiceworks.com/topic/339770-re-download-all-email-on-pop3-server-to-outlook
http://www.slipstick.com/general/outlook-downloads-duplicate-emails-from-pop3-account/
If you need any assistance in this regard, you can contact us at http://www.hostingraja.in/support/