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Outlook outage passes 16 hours as Microsoft extends email timeout to 48 hours
Outlook, Teams and Copilot stayed disrupted into 13 November after Exchange Online servers failed health checks. Microsoft extended its email timeout to 48 hours so delayed mail is not bounced and reports phased recovery. Hospitals, airlines and governments were hit. It found no sign of an attack.
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Microsoft's email and collaboration services stayed disrupted into Friday, 13 November 2026, after a number of Exchange Online servers became unavailable on Thursday afternoon, and by Friday evening in India the outage had lasted nearly 16 hours. Microsoft said recovery was progressing in phases and that service health remained variable. It extended its email timeout window to 48 hours so that delayed messages from other providers are held and not bounced back, and said it had found no evidence of malicious activity. Outlook was the most visible casualty, with Teams, Copilot and other Microsoft 365 services also affected. This report is for information only and will change as Microsoft publishes more.
What failed and how it was described
Microsoft said a number of servers were unexpectedly unavailable and were failing automatic health checks, and that the elevated load on the rest of its infrastructure was not caused by an increase in traffic but by servers going offline. It said the failed checks may originate from a specific component responsible for processing server health. Users reported that they could not send or receive mail, that Outlook froze or crashed, and that phones would not refresh inboxes.
Downdetector, the outage-tracking site, logged nearly 130,000 reports of Outlook problems shortly after 1 pm US Eastern time on Thursday, and combined US and Canadian reports reached nearly 150,000 at 1:30 pm. Within about an hour it had reports from 74 countries and territories, and at its worst it recorded 19,650 reports a minute across five Microsoft services, against fewer than 15 a minute on a typical Thursday.
The list of affected services grew. The first notices named Exchange Online and Outlook, then Teams, SharePoint Online, Microsoft 365 Copilot, Planner, To Do, Intune and Defender for Office 365. Microsoft's Azure cloud platform was not among the services Microsoft listed as affected in the first reports.
All times are US Eastern unless stated.
| When | What Microsoft said or did |
|---|---|
| Thursday, about 12:50 pm | First post: users having trouble reaching Exchange Online |
| Thursday afternoon | Paused deployments, moved traffic and restarted servers; steps gave no relief |
| Thursday, about 2:50 pm | Tested a configuration change to redistribute traffic |
| Thursday, about 4:40 pm | Restarted affected servers to return them to service |
| Thursday evening | Began returning a portion of servers; warned they could become unresponsive again |
| Early Friday, about 5 am | Reported early stabilisation and phased recovery |
| Friday | Recovery completed across portions of the affected infrastructure in Asia-Pacific, with work moving to other regions |
| Friday | Extended the email timeout to 48 hours; introduced an alternative health-check method that returned some servers to service |
Microsoft said it would publish a post-incident report after mitigation. It classed Outlook as a service degradation. Customers can follow incidents EX1550543 and MO1550821 in the Microsoft 365 admin centre.
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Who was hit
The effects reached well beyond offices. In Canada, Unity Health Toronto, which runs St. Michael's Hospital, declared a code grey after staff could not reliably send or receive email, and said patient care was unaffected. Other hospitals in Toronto and Montreal reported email problems, and in Montreal one reported delayed appointment requests and some delayed operations. Via Rail said passengers might not receive email confirmations, and the City of Toronto warned that some services could be delayed. Reports from the United Kingdom said hospitals, GP surgeries, schools and police were affected.
Governments reported trouble in several places: the State of Michigan's technology department, the US House of Representatives, Japan's government information system, and in Australia the spy agency and the federal police, whose email systems were affected according to the cyber security minister. In New York, NYC Emergency Management warned of delays in agency email and advised residents to call 311 for non-emergency services and 911 in an emergency. Companies were affected too: the European exchange group Euronext said its listing teams had email problems, the insurer Aviva set up backup plans for its earnings calls, Workhorse Group moved its results to 16 November, Richemont briefly delayed a results announcement, and the shipping group Maersk warned customers of delays. In India, IndiGo, Akasa Air and Air India reported email support problems, and some Outlook users began receiving delayed mail slowly on Friday evening.
What is still not confirmed
The first open question is whether service is fully restored. Microsoft's status page still showed degradation on Friday, and the company said capacity had not fully returned to baseline. Anyone relying on Outlook should check the status page and their administrator's notices before assuming mail flow is normal.
The second is the cause. Microsoft has described what failed, servers failing health checks, and has not said what triggered it. It said it saw no evidence of malicious activity, and the company paused deployments as a standard step but has not said that an update was to blame. The third is the mail that was sent during the outage: the 48-hour window is meant to let delayed messages be delivered, but senders whose mail was bounced earlier may need to resend. The post-incident report is where the trigger, the fix and any steps to prevent a repeat should appear.
Sources
About the Author
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Amita Sahani
Staff Writer
Amita Sahani writes for Wirony. Every story under this byline is reviewed and approved by an editor before it is published, and corrections are made openly.
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