Try deleting your email that is sending duplicates the go into outlook. Under options there should be a tab or something about exchange settings. Open that and in there it gives you an address for your exchange. Copy that and go to readd your email. When it gets to the point about putting in the details yourself, insert that in for the IMAP or whatever settings. Maybe that'll take care of it. I know I had to do that to even get my school's emails to show up on my phone.