Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to connect to, or experience degraded functionality with Exchange Online – ONGOING
01/09/2026 08:51:00 AM
NHS.net Connect Reference: INC46923137
Microsoft Reference: EX1464935
Issue Status: ONGOING
Issue Description: Users may be unable to connect to, or experience degraded functionality with Exchange Online.
More info: Microsoft has confirmed that the authentication component issue impacts other services beyond Exchange Online. For more information regarding other impact scenarios, please see: MO1465074.
They have opted to keep this post (EX1464935) open as Exchange Online remains the most predominantly impacted service.
Users may experience a variety of symptoms related to this event, including but not limited to:
– Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes.
– Delays or failures when sending or receiving email messages.
– Authentication-related errors when accessing Exchange Online services.
– Difficulties accessing or performing actions within Exchange administration experiences.
– Intermittent failures affecting mailbox operations and message delivery work
Current Update: 01/09/2026 08:52:00 AM – Microsoft’s efforts to restart affected sections infrastructure and re-apply the targeted authentication component fix has yielded progress, and they are observing incremental improvement reflected in the service health telemetry associated with search functionality across a sample of the affected environment. They are continuing this action for additional sections of infrastructure as they monitor closely to ensure widespread remediation.
Scope of impact: This issue may impact users attempting to send or receive email messages through Exchange Online. They are continuing their investigation to determine the full scope of affected scenarios and will provide additional information as it becomes available.
Root cause: An issue within a core authentication configuration used by multiple Microsoft 365 services is resulting in impact.
Next update by: Tuesday, September 1, 2026, at 7:00 AM UTC
