Microsoft outage explained: What happened, how businesses were affected and when services will return

Microsoft is struggling to restore its workplace services following a global outage that disrupted Outlook, Teams, Copilot and several other Microsoft 365 applications, affecting businesses, financial institutions, airlines and government operations across multiple countries.

The disruption, which began on Thursday continued into Friday with Microsoft's initial recovery measures failing to deliver sustained improvements. The company is now exploring alternative ways to restore infrastructure capacity and stabilise its services, Microsoft said in a statement.

Here is what happened, how the outage affected users and businesses, and when Microsoft expects services to return to normal.

Quick answers to key questions

•5 QUESTIONS

1

What caused the Microsoft outage?⌵

Microsoft said a core process on affected servers became overwhelmed, causing servers to stop responding and reducing available infrastructure capacity. The loss of server availability shifted more workloads onto the remaining systems, adding pressure.

2

Which Microsoft services were affected by the outage?⌵

The disruption affected services connected to Exchange Online, including Outlook, Teams and Microsoft 365 Copilot. SharePoint, Planner, To Do, Microsoft Defender and some administrative and security tools were also affected.

3

How did the Microsoft outage affect businesses and financial firms?⌵

Financial institutions and trading desks reported communication problems, delayed financing transactions and backed-up trade confirmations. Some staff relied on phone calls, WhatsApp or fax, while airlines reported email and customer-support disruptions.

4

When will Microsoft services be fully restored?⌵

Microsoft has not announced a confirmed timeline for full restoration. It said its initial recovery measures did not deliver sustained improvements and that it was exploring other ways to increase capacity and stabilise services.

5

How can users check the status of the Microsoft outage?⌵

Users can monitor Microsoft's official service-health dashboard. The incident references provided by Microsoft are EX1550543 and MO1550821.

Microsoft's investigation found that a core process running on affected servers was becoming overwhelmed, causing the machines to stop responding and reducing available infrastructure capacity.

The unexpected unavailability of several servers shifted additional workloads onto the remaining infrastructure, creating further pressure on Microsoft's systems.

The disruption affected services connected to Exchange Online and email infrastructure, including Outlook, Teams and Microsoft 365 Copilot. Other affected products and functions included SharePoint, Microsoft Defender, Planner, To Do and certain administrative and security tools.

Microsoft also reported difficulties with traffic routing between backend servers, adding to the challenge of restoring normal operations.

According to a Bloomberg report, financial institutions and trading desks across Asia faced communication difficulties. Traders at UBS, CMC Markets and other financial firms resorted to phone calls, WhatsApp and even fax machines to communicate with clients and colleagues. Some financing transactions were delayed, while trade confirmations backed up, creating settlement difficulties for back-office teams.

In Japan, the Finance Ministry reported that it could not receive emails for much of the day, Associated Press reported. New Zealand immigration authorities paused visa application processing, while some government departments and educational institutions warned of limited communication.

Indian airlines also reported disruptions to customer support. Air India temporarily rerouted its email services, although it said flight operations remained unaffected. IndiGo reported problems with email support, while Akasa Air warned passengers of delays in email responses. Delhi Airport also advised passengers to check their flight status before travelling.

According to Bloomberg, Downdetector received around 200,000 reports of problems across Microsoft services. Outlook-related complaints peaked at 138,058 on Thursday, before declining later in the day.

Microsoft said it was not aware of any malicious activity behind the disruption and was treating the incident as a priority until services were fully restored.

The company initially attempted to restart affected infrastructure, redirect traffic away from malfunctioning servers and redistribute workloads. It also introduced network and traffic-management changes to improve service availability.

However, these measures did not produce the expected results.

In its latest update on November 13, Microsoft said it had monitored the changes introduced to improve serviceability but found that they were not working as expected.

"We're identifying alternate workstreams that can be applied to increase capacity in the face of sustained traffic management imbalances," the company said.

Microsoft is also working to increase server capacity and address machines that remain in an unstable state.

Microsoft has not announced a confirmed timeline for the complete restoration of its affected services.

Although some regions and functions have experienced partial recovery, the company has acknowledged that its recovery efforts have not yet delivered sustained improvements.

Users can monitor developments through Microsoft's official service-health dashboard under incident references EX1550543 and MO1550821.

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