🔍 Read the full analysis: Microsoft 365 Outage: The Latest On The Disruption And Your Options on ThorstenMeyerAI.com
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TL;DR
Microsoft 365 remained degraded as of 08:35 UTC on November 13, with users reporting trouble accessing Exchange Online and connected services. Microsoft says a patch has improved server stability in part of its infrastructure and is expanding it region by region; the root cause has not been identified.
Microsoft 365 remained under service degradation as of 08:35 UTC on Friday, November 13, after an outage that began the previous day disrupted Exchange Online and other connected services. Microsoft said a patch had produced positive results for server stability on part of its infrastructure and that it was expanding the fix region by region, but the company had not identified the root cause.
The incident is tracked as EX1550543. Microsoft’s first public update came at 17:54 UTC on Thursday, November 12, reporting problems accessing Exchange Online mailboxes through multiple connection methods in the Americas. At 18:07 UTC, the company said the disruption could affect Microsoft 365 connectivity in any region. The incident record cited by ThorstenMeyerAI.com says the issue began at 16:17 UTC.
Users have reported trouble reaching Exchange Online through Outlook on the web, desktop and mobile, as well as through REST connections. Because other products depend on Exchange Online, the disruption has also affected functions including Teams calendars and meeting scheduling, parts of SharePoint Online, Microsoft 365 Copilot, the Microsoft Defender XDR portal, Purview and Planner. The extent of impact may vary by service and user.
Microsoft’s response has included pausing deployments, redirecting traffic, restarting affected servers and changing its approach to server health checks. After earlier restarts did not provide lasting relief, Microsoft said affected servers could become unresponsive again under traffic. At 07:29 UTC Friday, it reported better stability after applying a patch to part of its infrastructure. In its 08:06 UTC update for EX1550543, Microsoft said it was expanding the patch systematically, beginning with regions in or entering peak business hours.
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
Disruption Spreads Beyond Email
The disruption matters because Exchange Online supports more than inbox access. When users cannot reliably connect to mail, calendars, meeting scheduling and other linked services can also be affected, interrupting routine coordination for workplaces and organizations. The range of reported service impacts means the outage may reach teams that do not primarily use Outlook to communicate.
There are also reported effects outside Microsoft’s own products. ThorstenMeyerAI.com said OpenAI and Anthropic reported errors with their Microsoft 365 connectors. Workhorse Group moved its third-quarter earnings call from November 12 to November 16 because of the outage. Those examples show possible operational consequences, but they do not establish that every customer or connected application experienced the same level of disruption.
Public outage figures need careful interpretation. Reuters, in a report published by The Korea Times, said Downdetector recorded more than 130,000 U.S. reports of Outlook problems around 1 p.m. ET Thursday. Business Standard, citing Downdetector, reported complaints from 74 countries. Downdetector counts submitted reports, not verified affected users, so these figures indicate the scale and geographic spread of complaints—not the number of people unable to work.
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How Microsoft Traced the Failure
Microsoft’s public explanation changed as its investigation developed. The company first described elevated load across multiple regions, then said the load was not caused by increased traffic but by servers becoming unexpectedly unavailable and placing strain on remaining capacity. It later pointed to an overwhelmed core process on affected servers.
In an overnight service-health update, Microsoft said a process responsible for establishing secure connections was becoming overwhelmed and causing servers to stop processing requests. The company also said it had begun reverting a recent network configuration change that correlated with the start of the impact. It later reported that a change it had applied was not working as expected. These statements describe investigative findings and troubleshooting steps; they do not amount to a confirmed root cause.
A separate, shorter Teams incident, tracked as TM1550488, was marked fully resolved at 17:09 UTC Thursday, according to the source material. BleepingComputer reported that Microsoft had not said whether that incident was related to EX1550543. The two events should therefore be treated as separate unless Microsoft establishes a connection.
“Servers are stable where a patch was applied”
— Microsoft, EX1550543 service-health update at 08:06 UTC on November 13
Cause and Recovery Remain Open
The root cause remains unknown. Microsoft has described unavailable servers, an overwhelmed process and a recent network configuration change that correlated with the start of the incident, but it has not confirmed which underlying failure triggered the outage. The company said it was not aware of malicious activity; that statement is not a complete explanation of what happened.
It is also unclear how quickly the patch will reach every affected region or when Microsoft will declare the incident resolved. The status page still listed a service degradation at 08:35 UTC Friday. The available reports do not give a confirmed count of affected customers or users, and Downdetector submissions should not be read as such a count. Microsoft has promised a Post-Incident Report after mitigation.
Watch for Regional Patch Updates
Microsoft said it was expanding the patch region by region, prioritizing areas in or approaching peak business hours. Users should check Microsoft’s service-health information for updates to EX1550543 and to see whether their organization’s affected services have recovered. A partial improvement in one region or product does not establish that the broader incident is over.
Microsoft has said it will publish a Post-Incident Report once the problem is mitigated. That report is expected to provide a fuller account of the cause and response, though its timing and exact contents have not been specified in the information available as of 08:35 UTC. Until Microsoft changes the incident status, the outage remains ongoing.
Key Questions
Is the Microsoft 365 outage over?
No. As of 08:35 UTC on November 13, Microsoft’s status page still listed a service degradation. The company reported improved stability on patched infrastructure but was still expanding the patch.
Which Microsoft 365 services have been affected?
The main reported issue concerns Exchange Online mailbox access through Outlook and REST connections. Connected functions and services reported as affected include Teams calendars and meeting scheduling, parts of SharePoint Online, Copilot, the Microsoft Defender XDR portal, Purview and Planner. Impact can vary.
What caused the disruption?
Microsoft has not confirmed a root cause. Its updates have referred to unexpectedly unavailable servers, an overwhelmed process and a network configuration change that correlated with the start of the incident. The company said it was not aware of malicious activity.
What can users do while Microsoft works on a fix?
Check Microsoft’s service-health updates for incident EX1550543 and follow any guidance from your organization’s IT team. The reports available do not confirm a workaround that restores access for all affected users or regions.
When will Microsoft publish a full explanation?
Microsoft has promised a Post-Incident Report after mitigation, but has not specified when it will be released. The outage was still listed as ongoing in the status information available at 08:35 UTC Friday.
Source: ThorstenMeyerAI.com
