Since you are using AD as your authentication method, it is likely that you will have to add a dummy user to that system in order for the user to be able to log on to the Server. Once you have added the user, you will just need to ensure that this user doesn't have admin rights on the Server so that you can easily vet whether or not the permissions are setup correctly.
Hope this helps,
Yeah, I know about that. Was hoping for a backdoor user