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

Announcements Arpan Das

07/07/2025 08:43:00 AM

NHSmail Reference: INC46572670

Microsoft Reference: EX1109507

Issue Status: ONGOING

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.

Current Update: 02/09/2025 08:26:00 AM – Microsoft are proceeding to monitor the complete saturation of the aforementioned enabled change to the affected environment in order to validate the service stability.

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 update by: Tuesday, September 2, 2025, at 10:00 AM UTC