The Message Integrity Check(s) (one-way hash) of the outgoing message.
A MIC will be calculated over the outgoing message using the same algorithm in the SignatureAlgorithm configuration used to sign the message. The property will be set when Post (in AS3, Send) is invoked, and the MIC will automatically be checked against the Original-Content-MIC in the MDN for synchronous MDNs.
The format is in RFC 3335, i.e. "w7AguNJEmhF/qIjJw6LnnA==, md5", with a newline at the end.
If you are requesting an asynchronous MDN, you must save this value externally so that it can be loaded when the MDN is received (you may also use AsyncMDNInfoDir).