🔍 Read the full analysis: How To Keep Work Moving During The Microsoft 365 Outage on ThorstenMeyerAI.com
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TL;DR
Microsoft 365 remained degraded at 08:35 UTC on Nov. 13, with Exchange Online outages affecting Outlook and connected services. Microsoft reported stable servers where it applied a patch and was expanding that patch region by region; the root cause remains unknown. Teams can use established backup communication and file-access methods while checking service status and avoiding duplicate or unverified work.
Microsoft 365 was still experiencing service degradation at 08:35 UTC on Friday, Nov. 13, as Microsoft expanded a patch for an outage affecting Exchange Online and connected tools. Microsoft said servers were stable where the patch had been applied, but the disruption was not yet over and its root cause had not been identified.
The incident, tracked as EX1550543, began on Thursday, Nov. 12, and has prevented many users from reaching Exchange Online mailboxes through Outlook on the web, desktop and mobile apps, as well as REST connections. Because other services depend on Exchange Online, Microsoft has also reported effects on Teams calendars and meeting scheduling, parts of SharePoint Online, Microsoft 365 Copilot, the Microsoft Defender XDR portal, Purview and Planner.
In a service-health update at 08:06 UTC, Microsoft said it had begun expanding the patch systematically, prioritizing regions in or entering peak business hours. At 07:29 UTC, it reported positive server-stability results after applying an upstream authentication and routing configuration component patch to part of its infrastructure. The company has not said how long the regional rollout will take or when affected services will return to normal.
For teams trying to keep work moving, the immediate response is operational rather than technical: check Microsoft’s service-health information, tell colleagues which channels are available, and use only approved backup tools and file copies. Assign someone to track urgent messages or decisions that cannot wait, record actions taken outside the usual system, and reconcile those records once Microsoft 365 is working again. These steps do not restore Microsoft’s services, but can reduce confusion and prevent teams from treating delayed messages as delivered.
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
Keeping Teams Coordinated Offline
The disruption matters because email, calendars and collaboration tools are linked in many organizations’ daily workflows. If Outlook is unavailable, a team may miss approvals or customer requests; if calendar functions are affected, colleagues may not be able to confirm meeting details. When connected services also have problems, simply switching from email to another Microsoft 365 app may not work.
During a continuing outage, organizations should favor clear, consistent instructions over improvised workarounds. Managers can identify one approved backup channel, state which tasks should continue and which should wait, and ask staff to avoid sending the same request through several systems. Where work proceeds from local or previously downloaded files, teams should note who changed what and confirm the authoritative version after service returns.
The business effects can extend beyond routine correspondence. Workhorse Group moved its third-quarter earnings call from Nov. 12 to Nov. 16 because of the outage, according to the source report. OpenAI and Anthropic also reported errors in their Microsoft 365 connectors. Those examples show how a disruption can affect scheduled business communication and services that connect to Microsoft’s platform, though they do not establish the total scope of the outage.
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How the Exchange Incident Developed
Microsoft’s first public notice appeared at 17:54 UTC on Nov. 12, saying it was investigating reports of users unable to access Exchange Online mailboxes through multiple connection methods in the Americas. Thirteen minutes later, it said the issue could affect Microsoft 365 connectivity in any region. The incident is separate in the available reporting from a shorter Teams incident, TM1550488, which Microsoft marked fully resolved at 17:09 UTC on Thursday; Microsoft has not said whether the two were related.
Microsoft’s explanations developed as it investigated. It first described elevated load across multiple regions, then said the load was not caused by increased traffic but by servers becoming unexpectedly unavailable. The company paused deployments, redirected traffic, restarted servers and changed its health-check approach. It later said a core process on affected servers was becoming overwhelmed and that servers could become unresponsive again after receiving traffic. An overnight update referred to a process responsible for establishing secure connections; Microsoft also said it was reverting a network configuration change that correlated with the incident’s start.
Reports from Downdetector cited by media outlets indicated a large volume of complaints, including more than 130,000 U.S. Outlook reports at a Thursday peak, as reported by Reuters in The Korea Times. These are user reports, not a count of affected people, and do not establish how many users or organizations lost access. The available figures should be treated as indicators of reported problems rather than a measured total.
““We’ve initiated its expansion systematically,” referring to the patch rollout.”
— Microsoft, EX1550543 service-health update at 08:06 UTC, Nov. 13
Recovery Scope Remains Unclear
The root cause is not known, and Microsoft has not provided a completion time for the patch rollout or a full estimate of the services and customers affected. Its statement that servers were stable where the patch was applied describes a portion of its infrastructure, not necessarily all affected regions. Microsoft also said a recent network configuration change correlated with the incident’s start, but that does not by itself confirm the underlying cause.
Microsoft said it was not aware of malicious activity and promised a Post-Incident Report after mitigation. Until the company publishes further details, it is also unclear whether all affected Microsoft 365 services will recover at the same pace. The outage status was still listed as service degradation at 08:35 UTC.
Watch for Regional Recovery Updates
Microsoft said it was expanding the patch region by region, with priority given to regions in or entering peak business hours. Organizations should check Microsoft’s service-health page and internal IT guidance for updates, and confirm that Outlook and connected services are functioning before resuming time-sensitive workflows. A partial recovery may not mean every application or connection method is back to normal.
Microsoft has said it will publish a Post-Incident Report once the problem is mitigated. That report is expected to provide more information about the cause and response, but no publication time was given in the source material. Until then, teams should keep track of delayed requests, decisions made through backup channels and files edited during the disruption so they can reconcile work after services recover.
Key Questions
Is the Microsoft 365 outage over?
No. Microsoft’s status page still listed service degradation at 08:35 UTC on Nov. 13. The company reported stable servers where it had applied a patch and said it was expanding the rollout.
Which services have been affected?
The reported disruption centers on Exchange Online and Outlook, including mailbox access through web, desktop, mobile and REST connections. Microsoft also reported effects on Teams calendars and meeting scheduling, parts of SharePoint Online, Copilot, Defender XDR, Purview and Planner.
What should teams do while services are disrupted?
Follow your organization’s IT guidance, use an approved backup communication channel, and make clear which messages or files are authoritative. Track urgent decisions and changes made outside Microsoft 365 so they can be reconciled when service returns.
Has Microsoft identified the cause?
No. Microsoft described unavailable servers and overloaded processes and said a network configuration change correlated with the incident’s start, but it had not named a root cause. The company said it would publish a Post-Incident Report after mitigation.
Source: ThorstenMeyerAI.com
