A reference to the original mail message for which this DSN message was sent.
A MailMessage object containing the part of the original e-mail message which was attached to the DSN message, or a null reference (Nothing in Visual Basic) if the original e-mail message was not attached.
Some mail servers may attach the original message (usually, only the header) to the DSN, others don't. The default behavior is not defined. During sending the original message, you may request the mail server (to which you're sending your message) to include the entire message or its header in the bounce in case of non-delivery. You can use properties of DeliveryNotification object to tune this behavior prior to sending the original message.
The example is available in DsnStructure topic.
Result Class | MailBee.BounceMail Namespace