Overview
- Microsoft acknowledged a multi‑hour disruption that began on Monday, August 31, saying users may face delays or failures when sending or receiving email and authentication errors with Exchange Online.
- Crowdsourced trackers logged thousands to tens of thousands of reports of Outlook and Exchange problems, with many users unable to load inboxes, open folders or complete mailbox operations.
- Microsoft identified the fault as an issue in a core authentication configuration that can affect multiple Microsoft 365 services and listed specific symptoms including mailbox operation failures and admin console errors.
- The company developed a remediation strategy and is applying it to a subset of infrastructure to test whether it resolves the issue before rolling the fix out more broadly, and it is monitoring telemetry during the tests.
- Visibility and communications varied during the outage because the public status page lagged behind admin center and Microsoft 365 Status posts, leaving some administrators dependent on the admin center incident notices EX1464935 and MO1465074 for live updates.