The destination is out of order (Destination out of order) -- an equipment/link failure at or near the called party.
Where you see it
In ISUP/BICC REL messages, 2G/3G DTAP Disconnect, and SIP Reason headers (Q.850;cause=…).
What to check
Report to the operator responsible for the destination -- this is a network-side failure, not the subscriber's.
Check the cause location (user, private or public network) to see which side released the call.
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