How do I make new users receive an email when auto approve is on?

When you select the “Auto Approve” toggle a new toggle becomes available called “Enable User Registration Notification”. 

Once checked auto approved users will receive an email using the email template called “Account Registration -User Notification” . This email template can be updated to suit your needs of for example a welcome email.

To get to the email notification templates you can go to

Admin Dashboard > Portal Settings >Email Notifications