Error: The remote server returned an error: (401) Unauthorized
Error: The remote server returned an error: (401) Unauthorized.
The error message is produced when either the wrong target server administrator account has been chosen or the email address is different than the UPN (User Principal Name). You must make sure that provided credentials are the right ones and that they match the UPN. If you are still using the pre-Windows down level logons (DOMAIN\user) you must create a UPN for the purpose of the migration.