Microsoft 365 Alert – Service Degradation – Microsoft Teams – Admins may be unable to progress mailbox migrations in Exchange Online – ONGOING

17/04/2026 9:20:00 AM

NHSmail Reference: INC46801881

Microsoft Reference: EX1280763

Issue Status: ONGOING

Issue Description: Admins may be unable to progress mailbox migrations in Exchange Online.

More info: All mailbox migrations from on-premises to Exchange Online and tenant-to-tenant remain in a syncing state.

Current Update: 17/04/2026 9:20:00 AM– Microsoft has begun deploying our fix to revert the offending service update to our internal test environment to validate whether it resolves the issue prior to broad deployment. They will anticipate our validations will complete, and broad deployment initiated by our next scheduled communications update and continue reviewing potential short-term mitigation options, but their testing thus far hasn’t revealed any viable actions besides the reversion.

Scope of impact: All admins attempting mailbox migrations from on-premises to Exchange Online are impacted. This information may be updated as our investigation continues.

Root cause: A recent service-side update introduced an issue that is causing migration jobs to fail, resulting in impact.

Next update by: Monday, April 20, 2026, at 6:00 PM UTC