Microsoft 365 Alert – Service Degradation – Microsoft 365 suite – Users may be unable to access Microsoft 365 services – RESOLVED

22/01/2026 08:58:00 AM

NHSmail Reference: INC46730296

Microsoft Reference: MO1220495

Issue Status: RESOLVED

Issue Description: Users may have been unable to access Microsoft 365 services, including Teams and Outlook.

More info: As this issue was a result of a third-party ISP Autonomous System Number (ASN) routing configuration issue; the impact to Microsoft 365 services may have manifested in a multitude of ways. For example, some users may have been unable to access the services and portals altogether, whereas others may have seen impact more variable, such being intermittently unable to send or receive email.

Final Update: 22/01/2026 08:58:00 AM – Microsoft are determined this issue was a result of a third-party ISP Autonomous System Number (ASN) routing configuration issue, and we’ve identified that the third-party has taken action to remediate the impact to downstream services, such as Microsoft 365, and we’ve confirmed the issue is no longer occurring.

Scope of impact: Your organization was affected by this event, and any of your users hosted in North America may have been impacted.

Root cause: A third-party ISP ASN routing configuration issue caused impact to downstream services, such as Microsoft 365.

Next steps: Microsoft are carefully monitoring our managed service environment to ensure the issue doesn’t reoccur, and we’re reviewing our service resilience practices to identify any necessary improvements so we can reduce the downtime associated with these types of ISP-dependent issues in the future.