Overview
- Users worldwide lost access to Outlook, Exchange Online and other Microsoft 365 apps after many servers failed automated health checks and shifted load onto remaining infrastructure.
- Microsoft halted deployments, redirected traffic, restarted and reconfigured affected servers, and tested reverting recent configuration changes as engineers worked to restore capacity.
- Reports peaked on Thursday, Nov. 12, with outage tracker Downdetector logging roughly 129,000–140,000 Outlook problem reports before counts declined while instability continued.
- The disruption caused cascading effects for third‑party connectors used by OpenAI and Anthropic and forced some organisations, including the US House and private companies, to delay activities.
- Recovery has been partial and uneven because some restored servers became unresponsive under renewed traffic, and Microsoft continues multiple workstreams and an active technical investigation with no confirmed root cause.