The basic X.400 messaging service provides notification of message non-delivery. When a message cannot be delivered to a recipient, a non-delivery report is generated and returned to the originator. The content of the non-delivery report contains status information about the subject message.
The MT service also provides notification of delivery as an optional service. If a message originator requests acknowledgement of successful delivery, a delivery report is returned to the originator by the recipient's MTA upon delivery of the subject message.