Microsoft's cloud and productivity software services (Microsoft 365) experienced widespread outages across 74 countries worldwide, affecting hundreds of thousands of users including businesses and leading AI platforms. The company is urgently working to fix and gradually restore systems after detecting infrastructure overloaded beyond capacity.
Microsoft faced a major global system outage on Thursday, leaving many users unable to access email service Outlook, as well as Microsoft Teams and Copilot, the company's AI assistant. The issue persisted for several hours, disrupting work for users in multiple countries.
Online system monitoring site Downdetector reported that the outage spread to 74 countries and territories within about an hour, covering the Americas, Europe, Asia, and Africa. Users in the U.S., Japan, Singapore, the U.K., and Australia reported problems.
In the U.S., reports of Outlook issues peaked at over 138,000 on Thursday afternoon local time before dropping to about 34,000–37,000 by evening. Users of Microsoft 365 and Teams also reported problems.
Microsoft stated the initial cause was abnormally high processing loads on servers in multiple regional infrastructures, with some servers unable to provide service. This led to connectivity problems and was not due to increased usage volume.
The company said most issues related to Exchange Online, Outlook's email service. Some users could not open certain file types or view calendar information, and Copilot was also affected. However, most messaging and online meeting services remained operational.
Microsoft announced it halted new system deployments, rerouted traffic away from affected servers, and gradually restarted servers to restore service. It said all efforts are underway to minimize impact and early signs of system recovery have appeared.
However, the company warned that system improvements were not proceeding as expected, and some servers might fail again if usage increases. It is testing additional fixes to support more users without overloading the system.
This outage also affected connectivity services for AI companies OpenAI and Anthropic. OpenAI said it is investigating connection issues with Microsoft services that caused some tools to malfunction, while Anthropic confirmed problems from upstream providers impacting Microsoft 365 connections.
Additionally, U.S. electric truck manufacturer Workhorse Group postponed its Q3 earnings report from 12 to 16 November due to the global Microsoft system outage's impact.
This incident follows a previous Azure cloud outage last month that disrupted software and businesses across multiple industries worldwide, highlighting risks from reliance on major digital infrastructure providers.