Specifies whether the router should return delivery status notifications
(DSNs) for messages
received over SMTP with null RFC 821 reverse paths.
0 (default) - Don't return a failed DSN. Create the non-delivery report,
but mark it as DEAD.
The Administrator can then delete these messages or release them.
1 - Create and send the delivery status notification.
2 - Do not create a delivery status notification.
RouterDSNForNullReversePath = value