3.1.5.2.1.1 Nonstream Messages
If the message expires or is purged from the destination queue before reaching the receiving application, the message MUST be moved to the system dead-letter queue. This is achieved by generating the Move Message event (see [MS-MQDMPR] section 3.1.7.1.16) with the following parameters:
iMessagePos: A reference to the MessagePosition in the queue from which the message was deleted (that is, the iPosition argument of the Message Position Deleted event).
iTargetQueue: QueueManager.SystemDeadletterQueue
The dead-letter queues are system-generated and implementation-dependent.<26>