Post an MT message response to the client URL (if configured).
This callback is a vibes initiated request to the client to attempt delivery of carrier responses. The delivery of these messages is contingent on the client configuring the *reciptOption* tag on the original submission of the MT message. The client endpoint should properly store/record the response and then return an HttpResponse; 200 to acknowledge receipt. The client process should keep actual processing/logic as small as possible, for throughput and performance.