Veeam Explorer for Exchange (VEX) Restore Failure - HTTP Error 501 – Load Balancer

Veeam Backup & Replication
7.x, 8.x, 9.x
Last Modified:


The following KB is only relevant if a Load Balancer is being used.
When attempting to use the “Restore to <email>” function the restore fails with “HTTP Error 501”.
The following will be found in the logs:


Item restore failed: The request failed with HTTP status 501: Invalid Request.
Error: ExplorerManagementService: Failed to handle OnFinishItemRestore event (sessionId = ‘Unique_Identifier’)
Restored item with the specified identifier does not exist
Error: Restored item with the specified identifier does not exist


This happens because when VEX detects the CAS server it sees the load balancer instead of the actual CAS.


Instead of restoring to the original location, select “Restore to” and then manually change the CAS server to the FQDN of the Exchange CAS server.
Alternatively, you can point the load balancer hostname/FQDN to the IP of the exchange with a hosts entry. 


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