Microsoft 365 Alert – Service Degradation – Exchange Online – Some users’ calendars may not be synced with delegates’ calendars in Exchange Online – RESOLVED

Announcements Sourav Nandi

21/02/2025 09:00:00 AM

NHSmail Reference: INC48819615

Microsoft Reference: EX1012469

Issue Status: RESOLVED

Issue Description: Some users’ calendars may not be synced with delegates’ calendars in Exchange Online.

More info: While Microsoft work towards resolution, affected delegates can mitigate impact by navigating in the Outlook desktop client to File > Account Settings > their delegate account > More Settings > Advanced and turning off the “Turn on shared calendar improvements” setting. This will revert those delegates to using a shared calendar model utilizing Messaging API (MAPI) components to bypass impact.

Final Update: 24/02/2025 08:45:00 AM – Microsoft have determined that the fix deployment completed, and after a period of monitoring, they confirmed impact was remediated.

Root cause: A recent deployment contained a code issue that introduced a compatibility problem that’s preventing calendars from syncing as expected.

Scope of impact: Some users that are attempting to view their calendars synced with delegates’ calendars in Exchange Online may be impacted.

Next steps: Microsoft are reviewing their metrics for testing and validating our changes to help identify areas of improvement and to prevent similar issues from occurring in the future.