Select the "Mail" tab.
Select your Mail account and click "Properties."
Select the "Advanced" tab.
In the Delivery section at the bottom of the window, check "Leave a
copy of messages on server" if you want to save your Mail messages on
both the Mail server and on your local computer. If you want your
messages to be deleted from the Mail server after you have received
them in Outlook Express, do not check this box
Possibly this is causing the problem and ur mails are being downloaded
twice
Open Tools/Accounts/Mail Tab. Check each account there at
Properties/Advanced Tab and make sure that the "Leave copy of mail on
server" is not selected.