Receive the same mail twice

[Warren Liu]

I'm using Outlook 2003, the same mail arrived twice from a special contact.
Other persons in my office only received once from the same sender. However,
the email from other senders arrived my computer once. Any idea for trouble
shooting? My configuration is:
Client: Outlook 2003
server: MS Exchange 2003
Protocol: POP3

Thanks a lot for advice.