Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to access their mailbox with any Exchange Online connection methods – RESOLVED

11/08/2026 09:38:00 AM

NHS.net Connect Reference: INC46905822

Microsoft Reference: EX1452407

Issue Status: RESOLVED

Issue Description: Users may have been unable to access their mailbox with any Exchange Online connection methods.

Final Update: 11/08/2026 09:40:00 AM – Microsoft has completed their investigation and identified a networking performance issue on the portion of affected mailbox infrastructure. They have confirmed after monitoring the environment that service health availability has been fully recovered by their automated recovery services and impact has been resolved.

Scope of impact: Any user in Europe may have been impacted and unable to access their mailbox with any Exchange Online connection method.

Root cause: The portion of affected mailbox infrastructure encountered a networking performance issue, which led to impact.

Next steps: To help prevent similar impact in the future, Microsoft is further reviewing why the affected portion of mailbox infrastructure encountered a networking performance issue, and how they can improve their remediation automation for a more expedited recovery.