Update 8/18/2025: Based on feedback we received and to give customers more time to prepare, we are cancelling the first planned temporary enforcement (August) and will resume the temporary enforcemen...
Updated Aug 20, 2025
Version 11.0
Blog Post
10 MIN READ
Dedicated Hybrid App: temporary enforcements, new HCW and possible hybrid functionality disruptions
Hi,
I'm afraid we have the same problem – Exchange 2019 CU15 Aug25SU. Users with on-prem mailboxes have complained that archiving is no longer working to their Exchange Online-hosted archive mailboxes. When exporting the mailbox diagnostic logs for MRM, we get the same error you mentioned:
"Microsoft.Exchange.MailboxAssistants.Assistants.ELC.ElcEwsException: ELC EWS failed with error type: 'FailedToGetUserConfiguration'. Details: ExchangeImpersonation SOAP header must be present for this type of OAuth token. ---> System.Web.Services.Protocols.SoapException: ExchangeImpersonation SOAP header must be present for this type of OAuth token."
The ELCLastSuccessTimestamp from the mailbox diagnostic logs for any user does not show a timestamp newer than the date the Exchange hybrid app was deployed. ElcFaiSaveStatus shows "SaveFailed."
LukasSMSFT
Microsoft
MicrosoftWe've released a hotfix update to address this issue: Released: September 2025 Exchange Server Hotfix Updates | Microsoft Community Hub
Yeah - many thanks from us, too!! We installed the HU on our first server - I can confirm that archiving subsequently worked for the mailboxes hosted on it.
Thanks LukasSMSFT, great that the team could put out a hot fix to address this.
