This status applies only to response messages.
A business operation can defer a message response for later delivery. The response can be picked up and sent back to the original requester by any business host in the production. Between the time when the business operation defers the response, and when the response is finally sent, the response message has a status of Deferred.
The sender of the original message is unaware of the fact that the message was deferred. If the original call was synchronous, the call does not return to the sender until the response is sent.
When the response message is finally sent, it has a status of Completed.