Microsoft's cloud-based services, including Outlook, Teams and Microsoft 365, experienced a major outage on Thursday, disrupting thousands of users and affecting businesses and artificial intelligence platforms for more than five hours.
The disruption began earlier in the day, with outage reports for Outlook reaching approximately 138,058 around 1 pm US Eastern Time, according to Downdetector. Although reports declined to around 34,490 by 6 pm, Microsoft continued working to restore the affected services.
Microsoft attributed the outage to several servers unexpectedly becoming unavailable to handle existing workloads. The company clarified that the disruption was not caused by an unusual increase in traffic.
The incident primarily affected Exchange Online, the cloud-based email service behind Outlook, while users also reported problems accessing Teams and other Microsoft 365 applications. Downdetector recorded nearly 13,000 reports involving Microsoft 365 and 763 reports related to Teams by 5:47 pm.
Microsoft said it was redirecting traffic through alternative routes and restoring affected infrastructure. Previously recovered servers remained stable as efforts continued to bring the remaining systems back online.
The outage also affected AI platforms OpenAI and Anthropic, both of which reported problems with their Microsoft 365 integrations. OpenAI warned that new connections could fail and certain tools might not work properly, while Anthropic identified an issue involving an upstream service provider.
Several businesses also faced operational challenges. US electric truck manufacturer Workhorse Group postponed the announcement of its third-quarter financial results from November 12 to November 16 due to the disruption.
The incident follows another Microsoft Azure outage last month that affected productivity applications and business services across multiple industries.
