🔍 Read the full analysis: Microsoft 365 Outage: Microsoft’s Update And Your Next Move on ThorstenMeyerAI.com
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TL;DR
Microsoft 365 remained degraded at 08:35 UTC on November 13, after Exchange Online problems that began Thursday disrupted email and other connected services. Microsoft reported improved stability on some servers after applying a patch and said it was expanding the patch region by region; the root cause is still unknown.
Microsoft 365 was still experiencing service degradation at 08:35 UTC Friday, November 13, as Microsoft expanded a patch intended to stabilize Exchange Online servers affected by an outage that began Thursday. In an 08:06 UTC update on incident EX1550543, Microsoft said servers were stable where the patch had been applied and that it was rolling the change out region by region. The company has not identified the outage’s root cause.
The disruption has prevented many users from reaching Exchange Online mailboxes through Outlook on the web, desktop and mobile apps, as well as through REST connections. Because several Microsoft 365 tools rely on Exchange Online, reported knock-on effects include Teams calendars and meeting scheduling, parts of SharePoint Online, Copilot, the Microsoft Defender XDR portal, Purview and Planner.
Microsoft’s updates describe a sequence of operational problems. The company initially cited elevated load across multiple regions, then said that load was not caused by increased traffic: instead, servers had become unexpectedly unavailable, putting strain on the remaining infrastructure. Microsoft paused deployments, shifted traffic, restarted affected servers and changed how server health was checked.
Those measures did not provide lasting relief. Microsoft later said a core process on affected servers was becoming overwhelmed and that returned servers could become unresponsive again after receiving traffic. At 07:29 UTC Friday, it reported positive stability results after applying an upstream authentication and routing configuration component patch to part of its infrastructure. The 08:06 UTC update said the expansion was proceeding 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
How the Outage Affects Workflows
The outage reaches beyond inbox access because email, calendars and meeting scheduling are linked to other workplace services. When Exchange Online is unavailable or unstable, organizations may also have trouble arranging meetings and using connected Microsoft 365 features. The reported impacts therefore affect routine coordination, not just one application.
There are also reported effects outside Microsoft’s own products. OpenAI and Anthropic reported errors with their Microsoft 365 connectors, while Workhorse Group moved its third-quarter earnings call from November 12 to November 16 because of the outage. These examples indicate potential disruption to third-party integrations and business schedules, but they do not establish that every customer or integration was affected.
Reports of the incident’s scale should be read carefully. Reuters, citing Downdetector, reported more than 130,000 U.S. Outlook problem reports around 1 p.m. ET Thursday; Business Standard cited reports from 74 countries. Downdetector records user-submitted reports, not verified counts of affected people. The figures show complaint volume, not the number of users who lost access.
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From Regional Load to Server Instability
Microsoft’s first public notice appeared at 17:54 UTC Thursday, November 12, saying it was investigating Exchange Online access issues in the Americas. The incident record says the disruption began at 16:17 UTC. At 18:07 UTC, Microsoft warned that connectivity problems might affect users in any region.
As its investigation continued, Microsoft said it had not identified a recent change correlated with the start of the impact. It also described a problem with a component responsible for processing server health, and later said a process responsible for establishing secure connections was becoming overwhelmed. Microsoft reported beginning to reverse a recent network configuration change that correlated with the incident, but its updates have not established that change as the root cause.
A separate Teams incident earlier Thursday, tracked as TM1550488, was marked fully resolved at 17:09 UTC. BleepingComputer reported that Microsoft had not said whether it was related to the ongoing Exchange Online incident. News reports also described disruptions continuing across Asian business hours and into early European hours.
“Servers are stable where a patch was applied, and Microsoft is expanding the patch region by region.”
— Microsoft, in its 08:06 UTC service-health update for EX1550543
Root Cause and Recovery Remain Open
Microsoft has not named a root cause, and its updates describe several related symptoms and investigative steps rather than a confirmed explanation. The company said it was not aware of malicious activity. It also reported that a recent network configuration change correlated with the onset of the impact and that it had begun reverting it, but correlation does not establish that the change caused the outage.
The status page still listed service degradation at 08:35 UTC. Microsoft had reported improved stability on patched servers, but it had not announced a full recovery or given a completion time for the regional rollout. The number of affected customers, the extent of service restoration in each region and the relationship, if any, to the separate Teams incident also remained unclear.
Microsoft said it would publish a Post-Incident Report after the problem is mitigated. Until then, the available updates do not provide a final account of what failed or how long the disruption will continue.
Watch Regional Patch Rollout
Microsoft’s next stated step is to continue expanding the patch systematically across regions, prioritizing areas in or approaching peak business hours. The company’s status page and the EX1550543 service-health record are the primary places to check for changes in impact, mitigation and recovery status.
For now, affected users and organizations can check Microsoft’s service status through their normal service-health channels and follow their own continuity procedures if email or connected tools remain unavailable. A server reported stable under the patch is not the same as a confirmed service-wide recovery; users should look for a clear resolution notice before treating the incident as over.
Microsoft has said it plans to issue a Post-Incident Report once mitigation is complete. That report should provide a fuller explanation of the cause and response, though the company has not specified when it will be published. The immediate milestone is whether the regional rollout maintains server stability and allows Microsoft to clear the active degradation notice.
Key Questions
Is the Microsoft 365 outage over?
No. Microsoft’s status page still listed service degradation at 08:35 UTC on November 13. The company reported improved stability on some patched servers, but had not announced full recovery.
Which Microsoft 365 services are affected?
The primary issue is access to Exchange Online mailboxes through Outlook and REST connections. Reported knock-on effects include Teams calendars and meeting scheduling, parts of SharePoint Online, Copilot, the Microsoft Defender XDR portal, Purview and Planner. The impact may vary by service and region.
What should users do while services are disrupted?
Check the organization’s Microsoft 365 service-health information for current status and follow its continuity procedures. Microsoft had not confirmed a single workaround or a time for full recovery in the updates available at 08:35 UTC.
Does Microsoft know what caused the outage?
Not yet, based on the updates provided. Microsoft described unavailable servers and an overwhelmed process, and said a network configuration change correlated with the start of the impact. It has not confirmed a root cause.
When will Microsoft publish a full explanation?
Microsoft said it would publish a Post-Incident Report after mitigation. It had not given a publication date as of the latest status update cited here.
Source: ThorstenMeyerAI.com
