Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be unable to access specific archive mailboxes – ONGOING

Announcements Sourav Nandi

24/07/2025 09:00:00 AM

NHSmail Reference: INC46587264

Microsoft Reference: EX1102371

Issue Status: ONGOING

Issue Description: Some users may be unable to access specific archive mailboxes.

More info: Specifically, during an archive mailbox cross-forest migration, some users may be unable to access the online archive mailbox when the primary mailbox is located in a different Active Directory forest from the archive mailbox.

Current Update: 06/08/2025 08:39:00 AM – Microsoft’s server-side fix to update the method that users’ cache is generated upon loading the affected mailboxes has completed and saturated to affected environments, but also revealed additional code discrepancies that will need to be addressed by their supplementary fix. To ensure complete remediation, the internal validations for their secondary fix’s deployment has been delayed to allow for additional review and testing so they can ensure it doesn’t produce any unexpected problems in the service. They aim to provide a timeline for our secondary fix deployment and the remediation of impact at the time of their next scheduled update.

Scope of impact: Some users attempting to access specific archive mailboxes during a migration may be impacted.

Next update by: Monday, August 18, 2025, at 8:30 PM UTC