Microsoft’s cloud-based services, including Microsoft 365, Outlook and Teams, suffered a major global outage on Thursday, November 12, disrupting business operations and communications for users across several countries.
More than 130,000 users reported problems accessing Outlook at the peak of the disruption, according to outage-tracking platform Downdetector, with complaints recorded across 74 countries.
Microsoft attributed the disruption to infrastructure problems affecting multiple regions, particularly its Exchange Online email service.
The company explained that some servers unexpectedly became unreachable and failed to complete automated health checks, placing excessive pressure on the remaining infrastructure and triggering widespread connectivity problems.
Other affected services included Microsoft Teams, SharePoint Online, Microsoft 365 Copilot and Defender XDR, although the level of disruption varied.
On Teams, users experienced difficulties accessing calendars, scheduling meetings and initiating new chats in organisations with certain security restrictions enabled. However, general messaging and participation in online meetings largely remained operational.
Microsoft said it had taken steps to prevent the problem from spreading to additional servers, temporarily suspended new deployments and configuration changes, and began restoring affected infrastructure.
By 5 a.m. Taiwan time on Friday, the company had validated an alternative server health-check method, allowing some affected servers to return online. It subsequently reported a decline in Outlook outage complaints from more than 130,000 to approximately 31,000.
Microsoft also ruled out a cyberattack as the cause of the incident, with Charles Lamanna, the company’s Executive Vice-President of its Copilot business, confirming that there was no indication of malicious activity.
The disruption also affected some third-party services. OpenAI reported connection problems and tool errors involving its Microsoft connector, while Anthropic said an upstream supplier issue had affected its Microsoft 365 connector.
However, Amazon Web Services dismissed reports suggesting that its infrastructure was experiencing a similar disruption, insisting that its services were operating normally.
The outage had consequences for businesses, including electric truck manufacturer Workhorse Group, which postponed its third-quarter earnings announcement from November 12 to November 16 because of business disruptions.
The incident has renewed concerns about the dependence of global businesses on a handful of major cloud service providers and the risks associated with disruptions to critical digital infrastructure.
Microsoft reported in January that it had more than 450 million paid commercial Microsoft 365 seats worldwide, underscoring the scale of potential disruption when its services experience widespread technical failures.
Although no data loss or security breach had been reported in connection with Thursday’s incident, the disruption could raise questions about service reliability, business continuity arrangements and Microsoft’s contractual service commitments to enterprise customers.