•	If the user has a joint IMAP and POP mailbox, make sure the user is logging on to the mail server using both POP and IMAP clients. If the user is logging on using an IMAP client, but the POP client is set to retrieve mail on a regular basis, the mail may be downloaded to the user's hard disk before the user sees it in the IMAP mailbox.
•	Turn on separate POP and IMAP mailboxes and tell the user to log on using both clients. If the user is only logging on using one client, disable the other protocol.

Related topic

Solving problems with mail services