🔍 Read the full analysis: Microsoft 365 Outage Enters Day Two: Questions Users Are Asking on ThorstenMeyerAI.com
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TL;DR
Microsoft 365 remained in a state of service degradation at 08:35 UTC on November 13, after an Exchange Online outage that began the previous day. Microsoft reported better server stability after applying a patch to part of its infrastructure and said it was expanding the patch region by region; it has not identified the root cause.
Microsoft 365 remained degraded at 08:35 UTC on Friday, November 13, as Microsoft worked to restore Exchange Online after an outage that began Thursday. In an update at 08:06 UTC, the company said servers were stable where it had applied a patch and that it was expanding the patch region by region; the root cause has not been disclosed.
The disruption has affected access to Exchange Online mailboxes through Outlook on the web, desktop and mobile, as well as through REST connections, according to the incident information summarized by ThorstenMeyerAI.com. Services that rely on Exchange Online have also been affected, including Teams calendars and meeting scheduling, some SharePoint Online functions, Microsoft 365 Copilot, the Microsoft Defender XDR portal, Purview and Planner. The degree of impact may differ by user and service.
Microsoft’s status page continued to list “Service degradation” for Microsoft 365 on Friday morning. The company’s 08:06 UTC update for incident EX1550543 said a patch had produced stable servers in the portion of infrastructure where it was applied. Microsoft said it had begun expanding the work systematically, starting with regions that were at or entering peak business hours.
The incident record describes repeated attempts to return servers to service. Microsoft said that some servers became unresponsive again after receiving traffic, and that a process responsible for establishing secure connections was becoming overwhelmed. An earlier service-health update said the company had found a core process on affected servers was overwhelmed, reducing capacity. The company also paused deployments, redistributed traffic, restarted servers and changed how server health was checked, according to its updates.
Microsoft 365 outage · Nov 12–13, 2026 · times UTC
Down, rerouted, restarted, down again
How Microsoft described the outage, step by step, in its own status posts.
Server pool (schematic)
servingcarrying extra loadunavailablerestart
What Microsoft said
- 17:54Nov 12Mailbox access fails in the Americas
- 18:07“May affect” users “in any region”
- 18:35“Elevated load across multiple regions”
- 19:12All deployments paused, traffic moved, servers restarted
- 19:31Not more traffic: servers “unexpectedly unavailable”, the rest carry the load
- 21:00New health-check method: some servers back in service
- 23:59Returned servers “can become unresponsive again”
- 08:06Nov 13Patch stable where applied, now expanding region by region; still degraded
Hit
Exchange Online mail in Outlook, Teams calendars, SharePoint features, Microsoft 365 Copilot, Defender XDR portal, Purview and more
AI connectors
OpenAI and Anthropic reported errors in their Microsoft 365 connectors
Earnings call moved
Workhorse Group: from Nov 12 to Nov 16, citing the Microsoft outage
Sources: Microsoft 365 Status on X (Nov 12, 17:54–21:00 UTC); Microsoft service health EX1550543 (Nov 12, 23:59 UTC; Nov 13, 08:06 UTC) and status.cloud.microsoft MO1550821 (Nov 13, 07:29 UTC); Anthropic and OpenAI status pages; Workhorse Group press release, Nov 12, 2026. Server pool is a schematic, not real server counts.
Graphic: Powered by Thorsten Meyer AI
How the outage affects work
The disruption reaches beyond inbox access because Exchange Online supports connected Microsoft 365 functions. If mailboxes or secure connections are unavailable, users may also have trouble with calendar-based work, meeting scheduling and services that depend on Exchange data. That can affect routine coordination across organizations, though the source material does not establish that every listed service or user was affected equally.
There are also reported effects outside Microsoft’s own products. OpenAI and Anthropic reported errors in their Microsoft 365 connectors, according to the source report. Workhorse Group moved its third-quarter earnings call from November 12 to November 16 because of the outage. These examples show how a cloud service disruption can interfere with other companies’ integrations and scheduled business activity, but they do not establish the full scale of downstream impact.
Reports from outage-tracking services indicate substantial user complaints, not a verified count of people unable to work. Reuters, in reporting carried by The Korea Times, said Downdetector recorded more than 130,000 U.S. Outlook problem reports near a peak around 1 p.m. ET Thursday. Business Standard, citing Downdetector, reported complaints from 74 countries. Downdetector counts submissions rather than confirmed affected users, so those figures should not be read as the number of people cut off.
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How the disruption developed
Microsoft’s first public post about the Exchange Online issue appeared at 17:54 UTC on November 12, saying it was investigating mailbox-access problems in the Americas. A copy of the service-health post on Cloud Admin Hub gives the incident start time as 16:17 UTC. At 18:07 UTC, Microsoft said the problem could affect connectivity for users in any region.
In its updates Thursday evening, Microsoft first described elevated load across multiple regions, then said the load was not caused by increased traffic: servers had become unexpectedly unavailable, placing strain on the remaining infrastructure. The company said it was investigating failed automated health checks and a component responsible for processing server health. Later, it reported that restarts and other steps had not provided the expected relief.
On Friday, Microsoft said it had begun reverting a network configuration change that correlated with the start of the impact, but later reported that a change it applied was not taking as expected. It then reported positive stability results after a patch to an upstream authentication and routing configuration component. A separate Teams incident, tracked as TM1550488, was marked fully resolved at 17:09 UTC Thursday. BleepingComputer reported that Microsoft had not said whether that incident was connected to the Exchange outage.
““We’ve initiated its expansion systematically,””
— Microsoft, in its EX1550543 service-health update at 08:06 UTC on November 13, as quoted by ThorstenMeyerAI.com
Root cause and recovery remain open
Microsoft has not named a root cause. Its updates have described unavailable servers, failed health checks and an overwhelmed process for establishing secure connections. The company also said it was reverting a network configuration change that correlated with the start of the outage, but that does not establish that the change caused the incident.
The extent of recovery is also not yet clear. Microsoft reported stable servers where the patch had been applied, but its status page still showed service degradation at 08:35 UTC. The source material does not give a confirmed restoration time, a complete count of affected customers, or a region-by-region account of which services were back to normal. Microsoft said it was not aware of malicious activity and promised a Post-Incident Report after mitigation.
Microsoft’s regional patch rollout
Microsoft said it was expanding the patch region by region, beginning with areas at or approaching peak business hours. Its next status updates should indicate whether the stability gains persist as more servers receive the patch and traffic returns to them. Users and administrators should consult Microsoft’s service-health information for the latest incident status; the source material provides no confirmed time for full restoration.
After the issue is mitigated, Microsoft has said it will publish a Post-Incident Report. That report is expected to provide a fuller account of the cause and response, but no publication date was given in the available information.
Key Questions
Is Microsoft 365 still experiencing an outage?
Yes. As of 08:35 UTC on November 13, Microsoft’s status page still listed service degradation. Microsoft had reported patch-related stability gains in part of its infrastructure, but had not announced full restoration.
Which Microsoft 365 services are affected?
The reported issue centers on Exchange Online mailbox access through Outlook and REST connections. The source report also lists effects on services that rely on Exchange Online, including Teams calendars and scheduling, parts of SharePoint Online, Copilot, Defender XDR, Purview and Planner. The available information does not confirm that all users or functions in each service are affected.
What caused the Microsoft 365 outage?
The root cause has not been confirmed. Microsoft has described servers becoming unavailable, health-check problems and an overwhelmed process responsible for establishing secure connections. It also said it was reverting a network configuration change that correlated with the outage’s start, without confirming that the change caused it.
When will Microsoft 365 be fully restored?
Microsoft has not provided a confirmed restoration time in the available updates. At 08:06 UTC on November 13, it said it was expanding a patch across regions after seeing stable servers where the patch had been applied.
Has Microsoft said the outage was caused by a cyberattack?
No. Microsoft said it was not aware of malicious activity. That statement reports the company’s assessment at the time; its technical investigation and promised Post-Incident Report were still pending.
Source: ThorstenMeyerAI.com
