Our customer has Exchange Server 2016 CU6 deployed with a hybrid. Archiving is currently not working to Exchange Online Archives for all users (it was working prior to migrating to Exchange 2016), with the following error being received:
Exception: Microsoft.Exchange.MailboxAssistants.Assistants.ELC.ElcEwsException: ELC EWS failed with error type: 'ArchiveExchangeWebServiceNotAvailable'. Message: Archive EWS url is unknown.
I found a link to a Docs article that references Exchange 2013 and states the OAuth authentication must be configured between Exchange on-premises and Exchange Online (found here), but nothing about Exchange 2016. Should I just assume this is the case for Exchange 2016 as well?
I've been through this Docs article and confirmed that OAuth is not configured between on-premises Exchange and Exchange Online.