When users get enrolled into a large number of courses, such as newly created users, they currently receive an email notification for each new enrollment. Most of my users are assigned to roughly 100 courses via smart groups when their new account gets created. That's a lot of email spam and not a great user experience for them. I suggest creating a summarized enrollment email that lists all new enrollments in a single email instead of a separate email for each new enrollment.
cc: Jeannine Orr