If you have lost messages (eg due to a user deleting messages by mistake, or due to a PC failing when you hadn't bothered backing it up), there are several things you may be able to do, depending on your version/edition of VPOP3 and which settings you have.
VPOP3 Enterprise with IMAP4
If you have VPOP3 Enterprise and were using IMAP4 you have the most options.
- If the users' PC has died, then you can simply reconfigure the user's email client and it will resynchronise with the server when it next connects.
- If the user has deleted some messages by mistake, then if you have VPOP3 version 5 or later, you can use the Message Recycle Bin option if the messages were deleted within the past few days, or the Partial Restore function if the messages were deleted longer ago and you have a database backup containing the messages.
Other options
If you have enabled Message Archiving, you may be able to find the messages in the archive, and copy them from there into the users' mailbox. Note that the message archive is not designed principally as a backup method, so restoring large numbers of messages using this method can be time consuming
Or you can do a restore of a backup to a temporary installation of VPOP3 and view/copy the messages from there in your email client.