- Outlook and Exchange Online faced a global outage starting November 12 evening IST
- Microsoft servers went offline, causing heavy load and intermittent service recovery
- Outage affected Outlook mail, Teams features, and Microsoft 365 services unevenly
At around 9:30 p.m. IST on Thursday, November 12, Outlook users began reporting that they couldn't open their inboxes. Microsoft initially investigated a connectivity problem in the Americas. Within an hour, outage tracker Downdetector had logged reports from 74 countries and territories.
The trouble centred on Exchange Online, Microsoft's cloud email and calendar system. The company said several servers had unexpectedly gone offline, leaving the remaining machines under heavier load even though incoming traffic hadn't risen. Engineers brought some of the affected servers back online. When traffic returned, some became unresponsive again.
By Friday afternoon in India, the outage was still disrupting Outlook and parts of Teams and Copilot. IndiGo and Akasa Air warned passengers that customer emails might never reach their support teams. Air India rerouted its messages and said its flight operations “remain unaffected.” Microsoft reported early signs of recovery but gave no timeline for a full fix.
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Outlook Took the Biggest Hit
Users reported being unable to open Outlook mailboxes on the web, in the desktop app and on mobile. Some messages that got through arrived late. Desktop Outlook could still show emails that had already been downloaded, even when it couldn't fetch new ones.
Microsoft's list of affected services included Exchange Online, Teams, SharePoint Online, Microsoft 365 Copilot, Defender XDR, Planner, To Do and Purview. The disruption was uneven because it primarily affected features that relied on Exchange Online. Teams chats and calls largely kept working. A separate Teams outage that had affected users in North and South America earlier on Thursday had already been resolved. Azure, Microsoft's broader cloud platform, reportedly stayed online despite some complaints on Downdetector.
At Thursday's peak, the outage tracker logged more than 130,000 reports of Outlook problems in the US. By about 12:30 p.m. IST on Friday, it was still showing at least 43,000 Outlook reports across 72 countries. Microsoft has yet to say how many people were affected. The figures track complaints submitted to Downdetector.
The Servers Came Back. Then the Traffic Did
Getting a server to respond again was only the first step. It also had to stay up once people and other systems started using it.
When a server fails an automated health check, its requests can be redirected to machines that are still working. That leaves fewer servers handling the same volume of traffic. Once a recovered server reconnects, it can face a backlog of requests all at once. That can overwhelm it again and send the work back to the servers already under strain.
Microsoft said it was rolling back a network change on Friday. It had yet to say whether the change triggered the outage. Charles Lamanna, Microsoft's executive vice-president for Copilot, Agents and Platform, said the company had found no indication of malicious or cyber activity at that stage.
Australian Home Affairs Minister Tony Burke said Microsoft had drawn a comparison with the CrowdStrike incident, when a faulty update caused widespread disruption. Microsoft has yet to publish a root cause for the Exchange Online failure.
From Airline Inboxes to a Cancelled Bond Deal
In India, IndiGo and Akasa Air warned that passengers could face delays or that their emails might fail to reach customer support. Air India said it had temporarily rerouted incoming mail and was continuing to respond within its usual 24-hour window.
The disruption reached government systems in Singapore and Japan, the Supreme Court in the Philippines, and Australia's intelligence agency and federal police. Some US city governments asked residents to call local offices while email was disrupted. In Britain, councils and police forces warned that some online forms could be affected.
In Taiwan, the outage disrupted fund management work at securities firms, life insurers and investment trusts. One firm reportedly cancelled a scheduled bond repurchase. In the US, electric truck maker Workhorse Group moved its quarterly results to November 16. OpenAI and Anthropic reported problems with the connectors that let their products access Microsoft services.
Microsoft Gives Delayed Mail More Time to Arrive
By Friday afternoon, Microsoft was seeing “early stabilization and capacity improvements,” though its service dashboard said capacity remained below normal. Engineers were gradually sending traffic back to restored servers. For users, that meant an inbox might start working again while a calendar, a Teams feature or another connected app still struggled to reconnect.
Microsoft extended Outlook's email timeout window to 48 hours, giving systems longer to retry delivery before delayed messages expire. Organisations can follow EX1550543 for Exchange Online mailbox connectivity and MO1550821 for the wider Microsoft 365 disruption in the Microsoft 365 admin centre.
The outage follows a nearly 10-hour Microsoft 365 disruption in North America in January and an Outlook lockout in late August. Analysts said recurring failures could add to pressure in Europe to reduce reliance on US technology providers, even as existing licensing contracts limit the immediate financial impact on Microsoft.
For people waiting on email Friday afternoon, the measure of recovery was simpler. A mailbox had to open, and the messages that had been waiting since Thursday night had to start coming through.
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