Creates MDNReceipt .
CreateMDNReceipt may be invoked after ParseRequest to create an MDN-based receipt. The receipt will report success or failure depending on ErrorReportingFlags and the success or failure of ParseRequest.
This method populates MDNReceipt with a new MDNReceipt. The Headers, MDN, and Message parameters can be used to further customize the receipt, or empty string ("") parameters may be set to use the class generated defaults. Headers will set additional transport headers to be sent with the receipt (in the HTTP or SMTP headers of the signed receipt). MDN can be used to append additional headers to the Message Disposition Notification portion of the MDN Receipt. If MDN is set to a value prefixed with an at sign ("@"), the at sign will be removed and the specified MDN will be used in the receipt in place of the component generated value. Message will set the human-readable portion of the receipt, and should describe any error conditions that may have occurred.