A store administrator can enable and disable email notifications directly on the notifications listing page in the store's Admin area.
X-Cart 5.4.x - Store Setup > Email Notifications
X-Cart 5.5.x - Settings > Email Notifications > Notifications
Email notifications are sent separately for every user type enabled in a store. Hence, they can be enabled and disabled on a per-user-type basis.
Set the corresponding toggle either ON or OFF to enable/disable notifications for a user type. If the ON/OFF toggle is in faded green, a notification can not be disabled for this type of user.