We have had a report of this error when VPOP3 is trying to access a file share, eg for storing backups or archived messages.

In the case where it was reported, it turned out that a Windows Update had converted a 'local' user account into a 'Microsoft' account and that was preventing VPOP3 from accessing the file share, because VPOP3 was trying to use a local account.

If this happens to you, try converting the account back to a local account on the VPOP3 computer.