Troubleshooting Exchange Server 2007 Event ID 1020
For Exchange Server 2007 users the following error message is a commonplace: “The account ‘Domain\Administrator’ provided valid credentials, but is not authorized to use the server; failing authentication. Event ID: 1020” Elucidation: The aformentioned error event is an indication of missing permissions on the receive connector. If the user account does not have MS-Exch-SMTP-Submit permissions [...]

