Microsoft 365 Outage Spreads Across Multiple Services
A Microsoft 365 outage affecting tens of thousands of users has spread from Exchange Online to Teams, SharePoint, OneDrive, and Microsoft Defender XDR.
The incident began on August 31, 2026, around 5:30 PM UTC and was initially logged as EX1464935 in the Microsoft 365 admin center. However, Microsoft now tracks it under a broader incident identifier, MO1465074, which includes OneDrive for Business, SharePoint Online, Teams, Purview, and Defender XDR alongside Exchange Online.
Users are experiencing issues with sending and receiving email, as well as authentication errors when accessing Exchange services. Teams users are also facing difficulties with calendar functionality and search, while Microsoft Defender XDR users may encounter intermittent authorization failures.
Microsoft has acknowledged the issue but has not yet identified the root cause. The company's preliminary assessment points to an issue within a core authentication configuration used by multiple internal services within the Exchange Online infrastructure.