Microsoft Outlook Outage Hits 10 Hours. Why Didn’t the Fix Hold?

Microsoft 365 suffered a widespread outage on Thursday, November 12, leaving some users unable to open their Outlook inboxes, delaying email and disrupting features in Teams and Microsoft’s AI assistant, Copilot. Downdetector logged more than 130,000 Outlook problem reports at the US peak. Nearly 10 hours after Microsoft logged the wider outage, it still hadn’t reported a lasting recovery.

Is Outlook working again?

Microsoft had seen partial recovery in some regions by 9:42 a.m. IST on November 13, but the improvement didn’t last. Earlier, it had reported promising results from restarting servers. Some restarted machines stopped responding again once they began taking requests. Microsoft then tried rerouting and limiting some traffic to take pressure off affected servers. In its 9:42 a.m. update, it said it was looking for other ways to stabilise them. Its next update was due by 10:30 a.m. IST.

How big was the outage, and did it stop at the US border?

US Outlook problem reports peaked at more than 130,000 around 1 p.m. US Eastern time on Thursday, or 11:30 p.m. IST, and were still above 25,000 at 9:30 p.m. New York time, or 8 a.m. IST on Friday. Downdetector recorded reports across 74 countries and territories, according to Hindustan Times. These figures count reports and show where people flagged problems. They cannot establish the total number of affected users. Microsoft initially identified mailbox problems in the Americas and later said users in any region could be affected. Australia offered a concrete example of the spillover. Service NSW, which handles transactions for residents and businesses, asked customers to delay visits to its centres because some transactions were unavailable.

What is Microsoft 365, and which part broke?

Microsoft 365 is the company’s subscription bundle for work apps and online services such as Outlook, Teams and SharePoint. The main trouble was with Exchange Online, the service that stores and delivers work email and runs calendars for Microsoft 365 customers. Outlook is the app people use to reach that service. If the service cannot answer, the app can open while the inbox fails to load or a message takes longer to arrive. Microsoft logged mailbox trouble from 9:47 p.m. IST on Thursday and recorded the broader Microsoft 365 incident separately from 11:56 p.m. IST.

What made the servers stop answering?

Microsoft said software that establishes secure connections on the affected servers became overwhelmed. As servers dropped out, fewer machines were left to handle incoming requests. The company said the strain came from lost capacity. It was checking whether a network settings change that coincided with the start of the incident contributed to the failure. Microsoft said in its incident advisory it had found no indication of malicious activity.

Why could Teams take a call but struggle to book one?

Microsoft said Teams’ main chat and online meeting functions remained largely usable during the broader incident. Scheduling a new meeting or opening a calendar could fail because those features use Exchange Online. Microsoft had also fixed a separate Teams messaging incident earlier on Thursday. In the later outage, the Outlook inbox and the Teams calendar could fail together because both relied on the same underlying service.

Why did ChatGPT and Claude get caught up in it?

Their Microsoft 365 connectors, which let the AI assistants access a user’s work data with permission, ran into errors. OpenAI said new connections and some functions might fail. Anthropic said most requests involving mail, calendar and search through its connector were failing at the time of its update. It also flagged problems with Claude inside Outlook. Microsoft’s own Copilot could struggle to access work email, calendars or files.

Is this the first time Outlook and Teams have gone down together?

Both had trouble on January 25, 2023. Microsoft’s investigation traced that disruption to a change on its global network that interfered with connections to Microsoft 365 and its Azure cloud service. Indian users reported problems that day. In October 2025, a separate failure in Azure Front Door, a service that directs internet requests to the right servers, also disrupted Microsoft 365. In each case, customers saw problems in the apps they opened. The failure started in systems those apps relied on.

What do we know about India this time?

Indian users reported Outlook problems into Friday morning. Moneycontrol, citing Downdetector’s India page, reported 1,960 complaints at 8:42 a.m. IST, up from fewer than 500 earlier that morning. Those are reports from people who flagged a problem. Microsoft gave no India-wide count of affected users. India has seen what dependence on a shared provider can mean. In July 2024, airlines at Delhi airport’s Terminal 3 handed out handwritten boarding passes after a faulty CrowdStrike security update disrupted Windows computers. That was a different failure, on the computers themselves. In the November 2026 incident, the confirmed problem was on Microsoft’s servers.

How will Microsoft know the fix has held?

The test is whether repaired servers keep answering as Microsoft restores normal traffic. For a workplace, that means checking whether new messages arrive and calendar invitations go through once Outlook opens again. Microsoft 365 administrators can follow the wider incident under MO1550821 and the mailbox incident under EX1550543. Microsoft has yet to establish what triggered the outage or whether reversing the network change helped.