Saw this error the other day: When you open Exchange Control Panel and view the Mailbox Delegation tab of any user account you get the following: The object <name> has been corrupted, and it’s in an inconsistent state. The following validation errors happened: The access control entry defines the ObjectType ‘9b026da6-0d3c-465c-8bee-5199d7165cba’ that can’t be resolved.. […]