About MSMQ instances

MSMQ (Microsoft Message Queuing) instances are necessary only when connecting sites using non-transactional replication categories and rules that involve the transfer of XML-formatted data.

In such cases, each intranet is defined to have these MSMQ instances:

Inbound Queue: This instance receives requests from either the Replicator service or an ASP page. The Replication Queue Listener service, which monitors the queue, directs the requests to the IDO layer for placement into the target database.
Outbound Queue: This instance stores requests for outbound replication documents until the the documents are successfully sent to the target intranet or a fatal error is encountered.

Note: MSMQ is not used when replicating JSON-formatted data, for instance, when using the Data Lake.