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

Announcements Sourav Nandi

14/07/2025 08:50:00 AM

NHSmail Reference: INC46578145

Microsoft Reference: EX1113110

Issue Status: RESOLVED

Issue Description: Users may be unable to access their mailbox using any Exchange Online connection method.

Final Update: 16/07/2025 09:05:00 AM – Microsoft have completed their deployment and confirmed through extended monitoring that the underlying issue is fully resolved.

Scope of impact: Any user may be impacted when attempting to access their mailbox using any Exchange Online connection method.

Root cause: A multi-layered caching issue within our processing infrastructure generated excessive requests to backend components. This led to high resource utilization, which in turn caused mailbox access issues for end users.

Next steps: To help prevent similar impact in the future, Microsoft are assessing optimizations they can make to their monitoring systems to expedite the detection and resolution of service availability issues.