Not sure about Outlook because it is normally used in businesses and downloads email from a Microsoft Exchange server.
But if you are receiving them again and again it seems they are still on the server and haven't been deleted.
Is there a setting in Outlook where you can "delete from server once deleted from my computer"?
If not contact the server administrator.
The XP update SP2 affected my Outlook and now when I download my emails (Send and Receive) it will not stop. It continues to download old messages so that I end up with duplicates and triplicate messages. I now have to manually cancel 'send and receive' once I receive my new emails. How can I fix this. I use SBC DSL and they have an update but it didn't work for me.