Microsoft spent Thursday evening trying to contain a widespread failure across Microsoft 365. Businesses on several continents lost reliable access to Outlook, Teams, OneDrive and the Copilot AI assistant. On outage tracker Downdetector, reports for Outlook alone climbed to almost 140,000 at around 18:00 GMT. Users in the US, Japan and Singapore were among those reporting problems.
Microsoft traced the disruption to a group of servers that unexpectedly went offline. That pushed extra load onto the remaining infrastructure until it also began to struggle. The explanation points to a capacity and resilience problem rather than a security breach, and so far there is no indication of a cyberattack. However, Microsoft hasn’t said why those servers failed in the first place, and that’s the answer IT departments will be waiting for.
The impact varied from service to service. Microsoft says messaging and online meetings mostly kept working. Some users couldn’t open files, saw calendar entries with missing details, or found Copilot unreliable. Recovery has been uneven as well. The company posted updates on X saying it was making progress, but warned that restored services could stop responding again and that customers in any region might be hit.
The effects reached beyond Microsoft’s direct customers. AI developers OpenAI and Anthropic, both of which work with Microsoft’s systems, were also affected. OpenAI said it was investigating problems with its connections to Microsoft services that had left some of its tools not working as expected. Electric truck maker Workhorse Group gave a clear example of the business cost. It moved its third-quarter earnings report from 12 November to 16 November and blamed the outage.
This isn’t a one-off stumble. Just last month, an outage on Microsoft’s Azure cloud platform took down its productivity suite and disrupted companies around the world. Two major incidents within weeks raise the question of how much risk organisations take on when email, chat, file storage and, increasingly, AI tools all depend on one provider. When that provider goes down, many teams have nothing to fall back on.
The stakes rise as Microsoft builds Copilot more deeply into everyday work. An outage now means employees lose an assistant they’re being encouraged to rely on, not just their inbox. Customers will want a detailed post-incident report covering what failed, why the backup capacity couldn’t absorb the load, and what will change. Whether Microsoft provides that level of transparency may shape how hard enterprise buyers push on resilience at their next contract renewal.