You have to put some condition. The way I read that screenshot is "All conditions must match" and all conditions are empty, so it is like: from is empty and to is empty and subject is empty....
try putting "Any condition" and set the subject to a RegEx like: ".*" or something like that
Mail Scanner is one of the scheduled tasks. All of these tasks are watched by the Cron Watcher. This process will inform you of any scheduled tasks that do not finish in 20 minutes or so (I think there is a global variable for that)