Global Microsoft 365 outage disrupts Outlook and Teams as cause stays unconfirmed

A Microsoft 365 outage that began on Thursday 12 November left users around the world unable to reach Outlook email and disrupted Teams, Copilot and other workplace services. More than 19 hours after the first mailbox errors, Microsoft still listed the incident as ongoing, according to UptimeRobot, a monitoring company that tracked Microsoft's service health updates.

Microsoft reversed a recent network configuration change and applied a patch during the night. It said it had seen no evidence of malicious activity. In the reports reviewed for this article, it had not confirmed what caused the failure. It has said it will publish a post-incident report with the root cause once the incident is mitigated, UptimeRobot reported.

This article is based on reports from UptimeRobot and Al Jazeera covering 12 and 13 November. Other outlets have since described further Microsoft statements on the cause and on recovery. NewsWLD has not been able to review the text of those statements, and this article will be updated when they can be checked.

How the outage unfolded

All times are in Coordinated Universal Time (UTC), which matches GMT. US Eastern time is five hours behind.

• 12 Nov, about 16:00: Users begin reporting that they cannot access Outlook, according to Al Jazeera.
• 12 Nov, 16:17: Microsoft opens its first incident. Users cannot connect to Exchange Online mailboxes through Outlook on the web, Outlook desktop, Exchange ActiveSync or REST connections, UptimeRobot reported.
• Within about an hour: Downdetector, which counts user reports rather than confirmed failures, has logged reports from 74 countries and territories, Al Jazeera reported.
• 12 Nov, 18:26: Microsoft opens a second, broader incident covering every Microsoft 365 service that depends on Exchange Online.
• Late on 12 Nov: Microsoft reports only limited recovery as it routes traffic away from affected servers, according to Al Jazeera.
• Overnight: Microsoft begins reverting a recent network configuration change that lined up with the start of the problem.
• 13 Nov, 07:29: Microsoft reports progress after patching part of its infrastructure, UptimeRobot reported.
• Friday morning in Europe: The disruption is still unresolved, and some servers Microsoft had restored are failing again, Al Jazeera reported.
• 13 Nov, 11:30: Microsoft still lists the incident as ongoing.

Microsoft first said it was investigating problems in the Americas. It later said users in any region could be affected. UptimeRobot also reported that recovery had been completed in parts of Asia Pacific, without giving a time.

Which services were hit

The second incident covered services that rely on Exchange Online, Microsoft's hosted email system. UptimeRobot listed calendar and scheduling in Teams, Copilot Chat, parts of SharePoint, Defender and Purview, and some pages of the Microsoft 365 admin center. A separate Teams incident delayed chats and presence status for users in the Americas. Microsoft did not say whether it was related.

The effects reached beyond Microsoft's own products. Al Jazeera reported that the outage hit integrations used by other companies, including the AI developers OpenAI and Anthropic. It also reported disruption to government systems in Japan and Singapore, the Supreme Court of the Philippines, and Australia's spy agency and federal police.

Microsoft has not confirmed how many users were affected, Al Jazeera reported. Walter Pasquarelli, an analyst quoted by Al Jazeera, said about 430 million people use Microsoft services. That is an estimate of the total user base, not a count of people affected.

What Microsoft has said about the cause

Microsoft's updates point to an overload inside its own systems. The company said affected infrastructure was under elevated load across several regions and that a number of servers had become unexpectedly unavailable. It said the load was not caused by an increase in traffic.

According to UptimeRobot, Microsoft said "a process on the affected servers responsible for establishing secure connections becomes overwhelmed." That process handles the encrypted handshake between users' apps and Microsoft's servers. When it stalls, users cannot connect even if the mailbox data is intact.

Microsoft later began reverting a recent network configuration change that it said lined up with the start of the problem. Al Jazeera reported that Microsoft did not say whether that change was to blame. At 07:29 UTC on Friday, Microsoft said: "We're seeing positive results for server stability after applying an upstream authentication/routing configuration component patch to a portion of our infrastructure."

Early on Friday, Microsoft said on its service health page that it had had only "marginal success" in restoring services and was "confirming that developed patches have been applied and working as intended after infrastructure reboots are completed," according to Al Jazeera.

UptimeRobot said that until Microsoft's post-incident report is published, "the cause isn't confirmed."

Microsoft rules out malicious activity

Charles Lamanna, Microsoft's executive vice president of Copilot, Agents and Platform, said "there is no indication this is the result of malicious or cyber activity," Al Jazeera reported. UptimeRobot also reported that Microsoft said it had no evidence of malicious activity.

Rupert Goodwins, a technology analyst and journalist, told Al Jazeera the outage was not unprecedented, but said "the scale is impressive" and called it "very embarrassing for Microsoft."

Delayed email and what to watch next

To reduce the risk of lost messages, Microsoft extended the email timeout window to 48 hours, UptimeRobot reported. That gives senders' servers longer to retry delivery before a message bounces.

The next milestone is Microsoft's post-incident report, which should set out the root cause and explain why the network change and the connection overload led to such a wide failure. Microsoft has not given a date for that report in the sources reviewed.