You should go to Administration --> System --> Notification at the TM ART GUI, and set up 1) e-mail address of the system administrator 2) mail server. You'll then get a variety of notifications, including ones that tell when the Execution Server is unavailable.
As you can have some monitors which stop raising results even if the execution is working, what I have done on my side is a monitor which execute a sql query on the TMART database. The query is raising all monitors where the time of the last result is prior to the current time minus 30 minutes (this can be parameter according the different frequency that you are using). The query has to be customized to take in count the exclusions and blackouts periods.