Anypoint MQ is a multi-tenant, cloud messaging service that enables customers to perform advanced asynchronous messaging scenarios between their applications.

The dead-letter queue (or undelivered-message queue) is the queue to which messages are sent if they cannot be routed to their correct destination.

By the end of the document you get a clear picture of how to configure a Queue, the DLQ (Dead Letter Queues), Assigning a DLQ to the Parent Queue, and how the message gets routed from the Parent Queue to the DLQ after failure.