For email notification it is necessary to activate email notifications addon. After activate email notification add-on go to Support Plus > Add-Ons > Email Notifications.
You can add multiple email notifications for different ticket actions like create ticket,reply ticket,status change email etc. While adding email notification if you check customer in recipient, only ticket creator will receive email notification. If you check company supervisor then only supervisor will get email notifications. If you check company members, all company members will receive email notifications.