This occurrence has happened multiple times to me whilst setting up queues and configuring the ForwardTo property.
The queue fails to forward the message to a topic and the message gets dead lettered:
DeadLetterReason: The transfer destination entity does not exist.
DeadLetterErrorDescription: The transfer destination entity 'sb://*namespace*.servicebus.windows.net/*topic name* with ResourceId 0' does not exist.
The destination does exist! If I export the queue in Service Bus Explorer, delete the queue and re-import with no changes, the queue starts forwarding with out issue.
If is difficult for me to identify the issue seeing as recreating the queue with the same configuration fixes the problem, could possibly be related to https://social.msdn.microsoft.com/Forums/azure/en-US/e8731f67-cdda-4702-9bd9-db72b5462211/azure-service-bus-issue-creating-sas-policy-when-forwardto-is-set?forum=servbus ?
Thanks