With this feature, Sales reps remain on top of their to-do list. This is completely controlled by individual Sales reps. They can choose whether they’re notified by email when they’re assigned a task.
This helps to manage their tasks easily with email notifications and gives the flexibility to control.
Steps: In personal settings, enter Activity in the Quick Find box, then select Activity Reminders.
In Email Setting choose “Email me when someone assigns me a task”
You can explore other settings in the Reminder Settings to control your Activity Reminders.

Note: Notification emails aren’t sent for tasks that you assign to yourself; or for tasks that are assigned to another user with the status already set to complete.