The MSMQ subkey stores configuration data for Message Queuing. This subkey and its contents appear only if you have installed the Message Queuing service.

Message Queuing is a store-and-forward service that enables applications to communicate across heterogeneous networks and operating systems, even when the networks and applications are running at different times. Message Queuing stores messages in queues and forwards them when the destination networks and applications come online. The entries in this subkey apply to all users of the computer.