On the evening of Thursday 12 November 2026, Microsoft 365 suffered a worldwide outage: Exchange Online email, Outlook, Teams and Copilot were disrupted for more than twenty hours, and on Friday 13 November at around 18:00 Paris time, Microsoft was still reporting intermittent problems. At this stage Microsoft rules out any malicious cause and speaks of servers that became unavailable without warning. Here is what we know about the incident, and what it reminds businesses whose entire office suite relies on a single provider.
A timeline stretching from the afternoon of 12 November to 13 November
The first signs appeared in the afternoon. According to IT-Connect, Teams experienced message-sending failures across the Americas, North and South, from 15:45 to 16:53 Paris time, an initial incident that Microsoft attributed to resource saturation. BleepingComputer specifies that it carried the reference TM1550488 and that the company did not say whether it was related to what followed.
At 18:54 Paris time, the Microsoft 365 Status account reported on X problems accessing Exchange Online mailboxes, initially in the Americas, before indicating that users in all regions could be affected, IT-Connect reports. According to BleepingComputer, Microsoft places the start of the global incident at 13:26 US Eastern time, or 19:26 in France, under the reference MO1550821 visible in admin centres. According to IT-Connect, citing Downdetector, reports came from 74 countries and territories, and nearly 130,000 reports concerned Outlook alone shortly after 19:00. These figures are based on user reports, not on Microsoft data.
A partial recovery was observed during the night, but at midday on 13 November, New York time, Microsoft was still saying that email queues had decreased significantly and were nearing normal levels, but that intermittent access problems or delivery delays remained possible, again according to BleepingComputer.
Servers dropping out, not a surge in traffic
Microsoft’s explanation evolved over the hours. The company first mentioned abnormal load on part of its infrastructure, before specifying that this load did not stem from an increase in traffic: a number of servers had unexpectedly become unavailable, placing excessive load on the rest of the infrastructure.
IT-Connect details the mechanism described by the engineers: servers were failing automated health checks and being removed from the active pool, because a process that handles the opening of secure connections was overwhelmed. Once returned to service, some fell over again as soon as traffic came back. During the night, at around 2:00, Microsoft began rolling back a recent network configuration change whose deployment coincided with the start of the problems, without formally identifying it as the cause.
The measures taken include freezing all deployments, redistributing traffic, restarting the affected servers and adding capacity. Importantly for businesses, BleepingComputer reports that Microsoft extended the expiry time for pending emails to 48 hours in order to preserve delayed messages. Charles Lamanna, executive vice president in charge of Copilot, agents and the platform, told the site he regretted the impact of the outage and said his teams were analysing the incident to prevent it from happening again.
Far more than email: the Exchange domino effect
The list of affected features, published by Microsoft and relayed by IT-Connect, shows how far Exchange Online serves as the foundation of the whole suite:
- mailbox access from Outlook on the web, the desktop app, mobile devices and software connected via API, with emails delivered late;
- in Teams, calls and chats worked, but not scheduling or editing meetings, nor invitations;
- on the security side, Defender for Office 365 could no longer open rewritten links or release quarantined messages;
- Purview (data loss prevention, sensitivity labels, eDiscovery searches) and device enrolment in Intune were also disrupted;
- Copilot could fail to load or lose access to email, calendar and files.
Consumer services such as Outlook.com and OneDrive were also within the scope. In other words, the more tools, particularly AI tools, an organisation plugs into its email system, the further a failure of that system spreads.
What businesses can learn from it
The root cause remains unknown: Microsoft has promised a report once the incident is under control, without giving a date. In the meantime, a few habits are essential:
- check critical emails sent on the evening of 12 November and on 13 November: thanks to the expiry time being extended to 48 hours, delayed messages are not automatically lost, but a quote or a reminder may have arrived late;
- follow incident MO1550821 in the admin centre and keep the root-cause report promised by Microsoft, to document the interruption for management or the insurer;
- plan a backup channel outside Microsoft 365 (phone, a contact list accessible offline, a fallback messaging service) and include it in the business continuity plan;
- check the quarantine: during the outage, releasing quarantined messages could fail and links rewritten by Defender could stop opening; legitimate emails may have remained blocked.
Frequently asked questions
Was the Microsoft 365 outage of 12 November a cyberattack?
No, according to Microsoft at this stage: the company says it has found no evidence of malicious activity. It attributes the incident to servers that became unavailable and the resulting overload on the rest of the infrastructure.
Are emails sent during the outage lost?
Not necessarily. Microsoft extended to 48 hours the retention period for messages awaiting delivery, which allows time to route them once service is restored. It is still wise to check that important emails were received.
When will the exact cause be known?
Microsoft has committed to publishing a root-cause analysis after full resolution, without setting a deadline. A rollback of a network configuration change has been initiated, but the company has not confirmed that it was the origin of the outage.
Sources
- Panne mondiale de Microsoft 365 : Outlook, Teams et Copilot perturbés depuis plus de 11 heures — IT-Connect, 2026-11-13
- Massive Microsoft 365 outage disrupts Outlook, Teams, Copilot worldwide — BleepingComputer, 2026-11-12