Version 2.x only. This problem does not occur with version 3 or later.
This problem can happen if the user's message index database has become damaged. The POP3, Webmail & IMAP4 services get the message summary data from the database, whereas the administrator console gets the message information directly from the message files on the disk, so if the database is corrupted, the administrator console can still see the messages, but the other components can't.
To fix the problem:
This will force VPOP3 to rebuild the message index database. You will not lose any messages doing this, but you will lose any Webmail/IMAP 'read' flags or 'star' flags on the messages.