Dennes Torres gives us a warning:
While making some CETAS tests, I discovered an interesting new behaviour. The following error message was displayed and it was very strange:
Msg 16539, Level 16, State 1, Line 1
Operation failed since the external data source ‘https://euwe01devqigsa01.blob.core.windows.net/dennes/filescsv/’ has underlying storage account that is not in the list of Outbound Firewall Rules on the server. Please add this storage account to the list of Outbound Firewall Rules on your server and retry the operation.
Read on for the cause of this error message.