A client of mine just started getting duplicate email in his Outlook 2003 on his computer. Century Link mistakenly delete his account - an old qwest.net account. The have re-established it. He also upgraded his internet speed.
The only solution I have found is to Uncheck "Leave a copy of messages on the server. This will not work since he accesses his account on his phone, iPad and computer so the messages need to be left on. This is also a POP email account. This doesn't cause an issue in my Outlook 2012.
I also noticed he has 2 users, same email address but different Incoming and Outgoing mail servers. The only difference is that one is for Denver and the other Minneapolis. Not sure why this is...see no reason. Could this be causing the issue? I think it was set up this way before.
Would it help to upgrade his Outlook? Resolve the recent issue.
Thanks,
Margaret
Do it for both accounts, not only making sure, the messages are unique in one account, but also unique ACROSS both accounts.
Say I send a test message to one email address, it must be ONE times in that POP box. But still make sure the other POP box doesn't have this message either (otherwise there's a forwarding rule enabled). Send another message again to the other account, making sure it's unique in that mailbox, but also that there's no forwarding rule on this mailbox either.
If you've made sure both email are unique and not forwarding, you can conclude it's really only that PC's fault. Check that Outlook doesn't have any rules enabled, this one is the most likely causes to have duplicate emails. Make sure no other code is running, so try again by sending a test message, and starting Outlook in safe mode (no addons running, also check no VBA code is inserted anywhere).