Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to share their Outlook calendars externally across any Exchange Online connection method – NEW

10/01/2025 07:40:00 AM

NHSmail Reference: INC47951149

Microsoft Reference: EX975862

Issue Status: OPEN

Issue Description: Users may be unable to share their Outlook calendars externally across any Exchange Online connection method.

Current Update: 10/01/2025 07:40:00 AM Microsoft are rolling back the impacting migration as a temporary solution while they work on developing a long-term fix. They anticipate this roll back process will be completed by Tuesday, January 14, 2024.

Scope of impact: Impact may occur for any user attempting to externally share their Outlook calendars across any Exchange Online connection method.

Root cause: A recent migration for a service that supports external calendar sharing is causing a section of Outlook calendar infrastructure to operate below acceptable performance thresholds.

Next Update by: Saturday, January 11, 2025, at 6:30 AM UTC

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