The “Email me with CRM activity updates (eg. comments, workflows steps, task/event reminders, etc.)” option sends an email notification based on the following criteria.
To the user who created events when the event is accepted from email invitations.
When a user sets you to be “Notified” from the “Notify” feature.
If the “assigned to” user is change or added for a contact, opportunity, project or task.
Event – reminder email (15 mins before).
Task – reminder email (15 mins before).
Workflow – completed email.
Workflow – notify next step email for the assigned to user.
Workflow – workflow step due email is sent to the assigned user of the next step in sequential workflows.
Task – Sends a “Task Assigned” email to the assigned user or when an assigned task is updated.
Liked Stream Items – When a stream item you created is liked