That's going to be difficult to determine. If you browse the messages on the queue does the message descriptor not give you an indication from which Q manager it originated?
Once you have that info you may be able to determine which channel is the receiver channel from that QManager.
It could also be a local application placing messages on the queue.
If it's a cluster queue, determine which other QManagers are part of the cluster, it may be one of them, and the messages will be coming in via your cluster channel.
Hope that helps...
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