I just upgraded my Office suite to 2010, and was fairly happy. But I now see that Outlook 2010 is duplicating messages. Googling the issues leads me to believe that I need to check the "leave a copy ...

I have about 12,000 emails in my outlook express inbox folder. About 5500 of those are duplcate copies of different emails. That is, there are only 5700 unique emails, 5500 of which has a duplicate ...