Microsoft’s cloud services, including Outlook, Teams, and Copilot, experienced a widespread outage on November 12, disrupting access to email and other Microsoft 365 applications across multiple regions. The disruption continued into November 13, with users in Asia also reporting connectivity issues. 

Microsoft said via its official X account for 365 updates that the outage stemmed from servers becoming unexpectedly unavailable, which placed additional load on the remaining infrastructure. The company said it was not aware of any malicious activity causing the incident and that it will publish a post-incident report detailing the root cause and corrective measures after it resolves the outage.

What happened: Microsoft initially reported that users in the Americas were experiencing issues accessing “Exchange Online mailboxes through multiple connection methods”. The company listed the incident under EX1550543 in its Microsoft 365 admin centre.

As its investigation progressed, Microsoft confirmed that the connectivity problems could affect users in any region. It also identified disruptions to other Microsoft 365 services under incident MO1550821, including Teams, SharePoint Online, Microsoft 365 Copilot, Microsoft Defender XDR, Planner, To Do and Intune.

The company determined that the elevated load across its infrastructure was not driven by an increase in traffic. Instead, a number of servers had become unexpectedly unavailable, placing additional strain on the remaining infrastructure.

The company said affected servers were failing automated health checks, which caused them to become unavailable. Its investigation indicated that a component responsible for processing these checks could be contributing to the failures. Microsoft began testing configuration changes, restarting affected servers and preparing automated recovery systems to detect and restart unresponsive servers.

Microsoft’s recovery efforts: The company paused deployments, redistributed traffic across its global infrastructure and redirected connections to alternative routes. However, the servers it returned to service sometimes became unresponsive again after receiving traffic.

In a later update, Microsoft said “a core process on affected servers was becoming overwhelmed”, reducing capacity. It began testing a configuration change on a subset of servers and restarting affected components before reintroducing traffic to check whether the services remained stable. The company also introduced temporary traffic restrictions in specific locations while monitoring server stability.

Microsoft reported partial recovery in some regions as it brought servers back online and adjusted traffic flows. However, its recovery measures did not initially deliver sustained improvements. The company said it was pursuing multiple workstreams to restore infrastructure capacity and improve stability.

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