Emails alerts about critical events are sent automatically if you entered your email address at setup time.
If you did not specify an email address, see Enable Alerts If Not Defined at Setup.
Mail about...
When...
Frequency
Licensing
1 mail max/ day
Processes
at least one process in dead/loop-crashing/starting status
1 mail max/ hour
Indexing
at least one unavailable/invalid/failing build group status
Search
at least one dead/unavailable search API command