Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be intermittently unable to access Exchange Online through any connection method – RESOLVED

Announcements Sourav Nandi

01/08/2025 08:35:00 AM

NHSmail Reference: INC46593295

Microsoft Reference: EX1125355

Issue Status: RESOLVED

Issue Description: Some users may be intermittently unable to access Exchange Online through any connection method.

More info: Examples of potentially impacted connection methods were:
– Outlook on the web
– Outlook desktop client
– Representational State Transfer (REST)
– Exchange ActiveSync (EAS)

Final Update: 01/08/2025 08:35:00 AM – Microsoft have identified a networking issue on a portion of Exchange Online infrastructure that prevented the infrastructure from performing as efficiently as expected and resulted in impact. They’ve rerouted traffic to alternate healthy infrastructure, and confirmed with monitoring telemetry that the issue is resolved.

Scope of impact: This issue intermittently affected some users located in the United Kingdom who were attempting to access Exchange Online through any connection method.

Root cause: A networking issue on a portion of Exchange Online infrastructure prevented the infrastructure from performing as efficiently as expected and resulted in impact.

Next steps: Microsoft are further investigating the source of the network issue on the portion of Exchange Online infrastructure so that they can help prevent similar problems from reoccurring.