The recipient for the Message Disposition Notification (MDN).
MDNTo corresponds to the Disposition-Notification-To header of RequestHeaders. If nonempty, the client has requested an MDN receipt (typically the actual value is irrelevant). This receipt will be generated in a call to ProcessRequest or CreateMDNReceipt, and may be sent by calling SendResponse.
The receipt will be contained in MDNReceipt. If ReceiptDeliveryOption is empty, the receipt should be synchronously delivered in the HTTP response; otherwise, it should be delivered asynchronously to the URL specified. In either case, SendResponse will send the response as appropriate.
According to RFC specifications, MDNReceipt must be sent if requested by the client. If MDNTo is empty the MDN may be sent or not at the option of the server.
This property is read-only.