Microsoft 365 Alert – Service Degradation – Exchange Online – Some attendees may receive an unexpected cancellation message when a meeting on a shared calendar is updated – RESOLVED

Announcements Arpan Das

07/07/2025 08:43:00 AM

NHSmail Reference: INC46572670

Microsoft Reference: EX1109507

Issue Status: RESOLVED

Issue Description: Attendees may receive an unexpected cancellation message when a meeting on a shared calendar is updated.

More info: Impact is intermittent and specific to updates that are made on behalf of the organizer using classic Outlook for Windows with the calendar sharing improvements enabled.

Final Update: 03/09/2025 15:05:00 PM – Microsoft have confirmed after a period of monitoring that issue has been remediated.

Scope of impact: Some attendees with enabled calendar sharing improvements may be intermittently receiving cancellation messages for updated shared calendar events when the event is still active.

Root cause: Impact occurs due to a code issue triggered when meeting organizers are added as a required meeting attendee.

Next steps: Microsoft are reviewing their coding procedures to better identify similar issues during their development and testing cycles.