Microsoft 365 Alert – Service Degradation – Exchange Online – Users may experience errors or failures when accessing their Exchange Online mailbox with any connection method – RESOLVED

05/12/2025 08:26:00 AM

NHSmail Reference: INC46698761

Microsoft Reference: EX1192067

Issue Status: RESOLVED

Issue Description: Users may experience errors or failures when accessing their Exchange Online mailbox with any connection method.

Final Update: 16/12/2025 09:02:00 AM – Microsoft’s continue to see positive results from the affected infrastructure and stable availability of Exchange Online functionality, which confirms that the service has returned to a healthy state after implementation of the targeted fixes to reduce failures and improve performance.

Scope of impact: Impact is specific to some users located in Europe who are unable to access their mailbox with any Exchange Online connection method.

Root cause: A subset of Exchange Online service infrastructure that helps facilitate access to user mailboxes dropped below our manageable service performance thresholds, resulting in impact.

Next Steps: Microsoft are  reviewing the subset of Exchange Online service infrastructure that fell below their manageable service performance thresholds to identify and implement measures to prevent similar future occurrences.