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On Thursday afternoon, millions of professionals reached for their inbox and found it unavailable. Microsoft Outlook, together with Teams, SharePoint and Copilot, suffered a major outage that began shortly before 1 p.m. Eastern Time and continued into Friday. Here is a summary of what is known, and what organisations can take from it.
What happened
Microsoft first acknowledged the problem on its Microsoft 365 Status account, noting that users were having trouble accessing Exchange Online mailboxes through multiple connection methods in the Americas. The effect spread quickly. Both personal and enterprise accounts were affected, and email and other tools were unavailable through much of the Asian business day and into the early hours in Europe.
At the peak, outage tracker Downdetector recorded more than 120,000 reports for Outlook alone. Businesses and government bodies were among those affected.
The cause, as stated so far
Microsoft’s explanation is notable for what it rules out. The company said the elevated load was not driven by an increase in traffic, but by a number of servers being unexpectedly unavailable, which strained the infrastructure that remained. It also said it had no indication of a cyber attack, a position it repeated to Australia’s Home Affairs Minister, whose country’s cybersecurity chief has begun looking into the incident.
Microsoft’s repair work involved restarting servers and improving traffic flow. Its latest updates reported partial recovery across regions, and it has committed to publishing a full report once the problem is mitigated. Until that report appears, the root cause should be treated as preliminary.
Why it matters
Outages of this size are rare, but their effect is out of proportion to their length. Email is more than a messaging tool. It carries approvals, contracts, invoices, password resets and customer relationships. When it fails alongside Teams and calendars, an organisation loses its main channels for coordination at the same moment.
How to prepare
Establish a second channel. Choose a communication tool that does not depend on the same provider, and make sure staff know how to reach it. A messaging group or a secondary email address held by key managers is often enough.
Document your failure plan. Decide in advance who declares an incident, who informs clients, and what the fallback for urgent approvals is. A one-page plan used on the day is worth more than a long policy no one has read.
Keep critical contacts offline. Maintain an exportable list of key clients, vendors and staff phone numbers that does not require your email system to open.
Communicate early. Clients forgive disruption far more readily when they hear about it from you before they have to ask. A short, honest message beats silence.
Review after the event. Once service is restored, ask what worked, what did not, and what you would change. Then update the plan.
Conclusion
Large cloud platforms offer reliability that most organisations could not match alone, and that remains a strong reason to use them. This week is also a reminder that reliability is not the same as immunity. The businesses that cope best are not those that avoid disruption, but those that decided beforehand what they would do when it arrived.
Sources: CNBC, ABC News, Variety, ABC7, November 12-13, 2026. Details may change as Microsoft publishes its post-incident report.