Added a note about support for secured accounts

Author: periclesrocha

articles/synapse-analytics/sql/tutorial-external-tables-using-managed-identity.md

@@ -40,7 +40,7 @@ To enable your managed identity to access data on ADLS Gen2 accounts, you need t
 Your workspace identity is now a member of the Storage Blob Data Contributor role and has access to the source folder.
 
 > [!NOTE]
-> These steps also apply to secure ADLS Gen2 accounts that are configured to restrict public access. To learn more about securing your ADLS Gen2 account, see [Configure Azure Storage firewalls and virtual networks](/azure/storage/common/storage-network-security).
+> These steps also apply to secure ADLS Gen2 accounts that are configured to restrict public access. If your storage account is associated with a secured ADLS Gen2 account or associated with a VNet, you must authenticate using a managed identity. To learn more about securing your ADLS Gen2 account, see [Configure Azure Storage firewalls and virtual networks](/azure/storage/common/storage-network-security). 
 
 ## Ingest data using COPY INTO