Someone made the excellent point that the Messenger service that SBS uses to notify users of a server in violation of the licensing restrictions of SBS is slated to be disabled in updates such as XP SP2. This is true for the client side - the service is not yet disabled by default on the server (although in all likelihood it should be). We're certainly looking at better ways to notify admins and users of when the server is going to be shut down in our future releases, but for now it will continue to be the Messenger service.