Automatic emails are generated from event activity or scheduled rules rather than requiring an administrator to send each message manually. Use them for workflows such as confirmations, upcoming-event notices or other repeatable attendee communication.
When troubleshooting, separate message generation from message delivery: first confirm that the expected job/message was created, then review the delivery history or email log for sending status and errors.
Make major template changes before the event reaches a high-volume send window and test with a small audience first.