Mem Receiving Duplicate Messages on outlook express and outlook

RESOLUTION
To resolve this behavior, rename the Pop3uidl.dbx file, and then restart Outlook Express. Follow these steps:
1. Click Exit on the File menu to quit Outlook Express.
2. Click Start, point to Search, and then click For Files or Folders.
3. In the Search for files or folders named box, type Pop3uidl.dbx, and then click Search Now.
4. Under Search Results, right-click the Pop3uidl.dbx file, and then click Rename.
5. Type Pop3uidl.old, and then press ENTER.
6. To start Outlook Express, click Start, point to Programs, and then click Outlook Express.



this should fix the issue with duplicate messages received whiled downloading the messages on outlook express

If the mem is using microsoft outlook

CAUSE
This problem may occur if you use the Leave a copy of messages on the server option.
To set the Leave a copy of messages on the server option, follow these steps:
1. On the Tools menu, click E-mail Accounts.
2. Click View or change existing e-mail accounts, and then click Next.
3. Click your POP3 e-mail account, and then click Change.
4. Click More Settings.
5. On the Advanced tab, click to select the Leave a copy of messages on the server check box, and then click OK