Microsoft 365 outage disrupts Outlook and Teams for hours as servers fail health checks

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Microsoft 365 services including Outlook Teams SharePoint and Copilot were disrupted for thousands of users for more than five hours on Thursday November 12th.

Reports on Downdetector peaked at nearly 130000 for Outlook around 1 p.m. ET and the outage lasted roughly six hours and 42 minutes according to tracking sites before limited recovery was observed.

Microsoft stated that a number of servers became unexpectedly unavailable after failing automated health checks which strained the remaining infrastructure and it had no indication of a cyber-attack.

The Guardian and Reuters reported that the company was shifting traffic to alternate routes and restarting affected servers with some remaining stable as recovery progressed into the evening.

The outage also affected connectors used by OpenAI and Anthropic AI services.

Mark Gregory of RMIT University described it as a potential cascading problem from a network layer configuration issue similar to past telecom outages highlighting the need for better testing of changes.

Microsoft last month faced a separate Azure outage affecting productivity tools and the company said it was assessing whether reverting recent configuration updates could speed recovery.