I'm copying a question posted in an online computing forum:

"I pay for a POP3 email account and use Outlook 2003 to access it. Outlook
is configured to leave a copy of the messages on the server until they are
deleted.

I have backed up my .pst file on this machine and need to migrate to a new
computer. When I use my current .pst file on the new machine many duplicate
mail messages are received from the server.

Any emails that I have currently in my .pst file are not detected as being
there, and are simply downloaded again from the server. This creates one
big mess.

How can I get around this happening please? There must be something that I
am not backing up, as Outlook on this machine clearly knows which messages
its needs to download, and which ones it does not."
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I'm trying to help the person but I don't know the answer. Can someone
using this newsgroup advise on problem?