+---------------+----------------------------------------------+
| Member Name   | Description                                  |
+---------------+----------------------------------------------+
| Delay         | Notify if the delivery is delayed.           |
+---------------+----------------------------------------------+
| Never         | A notification should not be generated       |
|               | under any circumstances.                     |
+---------------+----------------------------------------------+
| None          | No notification information will be sent.    |
|               | The mail server will utilize its             |
|               | configured behavior to determine whether     |
|               | it should generate a delivery notification.  |
+---------------+----------------------------------------------+
| OnFailure     | Notify if the delivery is unsuccessful.      |
+---------------+----------------------------------------------+
| OnSuccess     | Notify if the delivery is successful         |
+---------------+----------------------------------------------+

Msg.DeliveryNotificationOptions += DeliveryNotificationOptions.Delay;