Microsoft outage explained in 5 points, why Outlook and Teams went down for more than 24 hours

Millions of people rely on Microsoft services to get through their working day. But an incident on November 12, caused by a technical failure in the company’s infrastructure, disrupted major services such as Outlook, Teams, Copilot, and several other Microsoft 365 services. This leaves businesses and individuals struggling to access emails and carry out routine work. And what began as a technical problem soon turned into a global disruption, affecting users across more than 70 countries.

Microsoft revealed that the situation is now improving. As of Saturday, November 14, Microsoft says it is seeing sustained recovery and stability across the affected environments, with most disrupted services and features restored. However, it is still monitoring its systems and working through the backlog of delayed emails. The company has apologised for the disruption and promised to reveal a detailed report soon explaining what went wrong.

1. It started with Outlook, but quickly spread across Microsoft 365

The outage first became noticeable as users began reporting problems accessing their Exchange Online mailboxes, the infrastructure that powers Microsoft's email service. Outlook users experienced difficulties opening their inboxes, sending messages and receiving emails. The problem then spread to other services that depend on the same infrastructure.

Microsoft Teams continued to support core messaging and online meetings, but features linked to Exchange Online, such as calendars, meeting invitations and scheduling, were affected. Copilot users also faced problems loading chats and accessing work-related information from emails, calendars and files.

Other affected services included SharePoint Online, Microsoft Planner, To Do, Defender, Purview, Power BI and Windows 365. Not every feature stopped working, though. Microsoft said services that did not depend on Exchange Online continued to function.

Downdetector recorded more than 1.3 lakh reports of Outlook problems at the peak, while disruptions were reported across 74 countries and territories.

2. A network problem left Microsoft's servers struggling to respond

The first clues came from Microsoft's investigation into why so many users were unable to access their mailboxes. Engineers found that a large number of servers had unexpectedly become unavailable, leaving fewer machines to handle incoming requests.

Microsoft later identified a process responsible for establishing secure connections on the affected servers as a key factor. In one of its updates, the company said this process was becoming overwhelmed, causing servers to stop processing requests. Microsoft clarified that the problem was related to reduced server availability, rather than an overall increase in traffic. It said the incident was linked to an issue that emerged during an earlier network capacity upgrade and surfaced after a more recent network change.

Microsoft was also quick to rule out speculation about a cyberattack or an AI-related failure. In a statement, it said, "This was a technical issue not related to cyber or AI / agents." The company has promised a full post-incident report once its investigation is complete.

3. The outage reached airlines, businesses and even AI services

The disruption was not limited to people unable to check their inboxes. Businesses that depend on Microsoft's cloud services also struggled to communicate with customers and access workplace tools.

In India, the impact reached the aviation sector. IndiGo warned that its email support system had been affected and that it might not receive messages sent by customers. In its advisory, IndiGo said, "Due to a global Microsoft service disruption, our email support services are currently impacted, and we may not be able to receive your emails." It asked passengers needing urgent assistance to use its website or app.

Financial services firms also reported difficulties accessing research reports and handling client interactions. The disruption even reached AI companies. OpenAI and Anthropic reported problems with their Microsoft 365 connectors, which allow their services to work with users' emails, calendars and other workplace data.

4. Bringing the servers back online proved harder than expected

Microsoft's recovery efforts took longer because restarting affected servers did not always solve the problem. In some cases, machines that initially returned to service became unresponsive again once they started receiving traffic.

Engineers tried several approaches. They redirected traffic to alternative infrastructure, restarted affected servers, tested configuration changes and worked to increase capacity by scaling up virtual machines. Microsoft also began reversing a recent network configuration change that coincided with the start of the outage.

Rather than restoring everything at once, the company chose to bring services back in stages. Explaining the approach, Microsoft said, "Given the scale of demand, we restored services gradually, validating stability at each stage. While this took longer, it helped ensure a stable restoration."

5. Services are recovering, but Microsoft is still monitoring the impact

By November 14, Microsoft was reporting sustained recovery across the previously affected environments. It said the majority of impacted scenarios had been addressed, while engineers continued to monitor service stability and ensure that delayed emails were successfully processed.

Microsoft has apologised to customers and partners, saying, "We are deeply sorry for the disruption this incident has caused our customers and partners. We know the trust they place in our services and take that responsibility extremely seriously." Its promised post-incident report should offer a clearer account of the failure and the steps it plans to take to prevent a similar outage.