🔍 Read the full analysis: Microsoft 365 Is Still Experiencing An Outage: What Users Can Do on ThorstenMeyerAI.com
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TL;DR
Microsoft still lists a Microsoft 365 service degradation as of 08:35 UTC on November 13, after an outage affecting Exchange Online and connected services began Thursday. The company says a patch has improved server stability in part of its infrastructure and is being expanded region by region; the cause remains unknown.
Microsoft 365 remained in service degradation as of 08:35 UTC on Friday, November 13, with users still reporting problems reaching Exchange Online mailboxes and connected services. Microsoft said its patch had produced positive server-stability results on part of its infrastructure and that it was expanding the patch region by region, but it had not named the outage’s root cause.
The incident began Thursday, November 12, and Microsoft first publicly reported problems at 17:54 UTC, saying users in the Americas were having trouble accessing Exchange Online mailboxes through multiple connection methods. At 18:07 UTC, the company said the issue could affect Microsoft 365 connectivity in any region. The incident is tracked as EX1550543.
Microsoft’s updates describe servers becoming unavailable and placing strain on the remaining infrastructure. The company said the problem was not driven by increased traffic and later identified an overwhelmed core process on affected servers. It tried redistributing traffic, pausing deployments, restarting servers and changing its health-check approach. Those steps did not provide lasting relief: Microsoft reported that some returned servers became unresponsive again when they began receiving traffic.
In an update at 07:29 UTC Friday, Microsoft reported positive stability results after applying a patch to an upstream authentication and routing configuration component on part of its infrastructure. At 08:06 UTC, the company said it had begun expanding that patch systematically, starting with regions in or entering peak business hours. Microsoft continued to list the service degradation at 08:35 UTC.
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
Outage Spreads Beyond Email
The disruption reaches beyond inbox access because several Microsoft 365 services depend on Exchange Online. The source report lists impacts or related problems involving Teams calendars and meeting scheduling, parts of SharePoint Online, Microsoft 365 Copilot, the Microsoft Defender XDR portal, Purview and Planner. Users may therefore face interruptions in communication, scheduling and other work even when a particular app appears available.
The outage has also affected services and business plans outside Microsoft’s own apps. The source report says 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. The duration and breadth of the disruption make Microsoft’s regional patch rollout relevant to organizations that rely on Exchange-connected tools for daily operations.
Reports of problems indicate the disruption has been widely noticed, but they do not establish how many people lost access. Reuters, in a report carried by The Korea Times, said Downdetector recorded more than 130,000 U.S. Outlook problem reports at the peak, around 1 p.m. ET Thursday. Downdetector counts user reports, not verified affected users, so that figure should be read as a measure of reported complaints rather than a confirmed outage headcount.
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From Thursday Reports to Friday Patch
Microsoft’s public updates traced a changing diagnosis. On Thursday evening it first described elevated load across multiple regions, then said the load stemmed from servers becoming unexpectedly unavailable rather than a rise in traffic. The company said it was investigating failed automated health checks and a component responsible for processing server health. Later updates described a core process becoming overwhelmed and servers losing capacity.
In an overnight update, Microsoft said a process responsible for establishing secure connections was becoming overwhelmed and stopping affected servers from processing requests. It also said it had begun reverting a recent network configuration change that correlated with the start of the impact. A subsequent change was not taking effect as expected. By 04:10 UTC Friday, Microsoft said it had no indication the incident resulted from malicious activity. Those statements describe the investigation, not a confirmed root cause.
A separate Teams incident, tracked as TM1550488, was marked fully resolved by Microsoft at 17:09 UTC Thursday. BleepingComputer reported that Microsoft had not said whether that incident was connected to EX1550543. The source report also cites CNBC’s account that email and other tools were unavailable through much of the Asian business day and into early European hours. These reports help describe the disruption’s timing, while Microsoft’s service record remains the primary status reference.
“We have initiated our expansion systematically, beginning with regions that are in or entering peak business hours.”
— Microsoft, in its 08:06 UTC November 13 update for EX1550543
Root Cause Still Undetermined
Microsoft has not identified or announced a root cause. Its updates refer to unavailable servers, failed health checks, an overwhelmed process and a network configuration change that correlated with the beginning of the impact. The company has not established in the supplied updates which issue initiated the outage or how those factors relate.
It is also not yet clear how quickly the patch will reach all affected regions, whether it will restore service consistently under normal traffic, or when Microsoft will declare the incident resolved. The positive stability results apply to only part of the infrastructure. Microsoft said returned servers had previously become unresponsive again when they received traffic, so the latest update does not by itself confirm a full recovery.
Microsoft said it was not aware of malicious activity and promised a Post-Incident Report after mitigation. The relationship, if any, between the separate Teams incident and the Exchange Online outage also remains unconfirmed. Downdetector figures and media reports provide additional indications of impact but do not establish the total number of affected users or organizations.
Watch Regional Patch Rollout
Microsoft’s immediate next step is to continue expanding the patch region by region, with priority given to areas in or entering peak business hours, according to its 08:06 UTC update. The company will need to report whether stability holds as more servers are patched and begin handling user traffic. Until Microsoft changes the service status, the outage should be treated as ongoing.
Users and administrators can check Microsoft’s Microsoft 365 service-health page for updates to incident EX1550543 and confirm whether the affected services are recovering in their region. If mailbox access or connected features remain unavailable, users can try another available connection method, such as Outlook on the web or a mobile app, but Microsoft has not said that any particular workaround will restore access during this incident. Organizations should follow their own continuity procedures and avoid treating a successful sign-in as confirmation that all dependent services are working.
Microsoft has said it will publish a Post-Incident Report once the problem is mitigated. That report may clarify the root cause, the scope of the disruption and the steps taken to prevent a recurrence. No resolution time was provided in the supplied updates.
Key Questions
Is Microsoft 365 still down?
Microsoft still listed service degradation at 08:35 UTC on November 13. The company reported improved stability on part of its infrastructure, but had not declared the outage resolved.
Which Microsoft 365 services are affected?
The central reported issue is access to Exchange Online mailboxes through Outlook on the web, desktop, mobile and REST connections. The source report also lists effects on Teams calendars and scheduling, parts of SharePoint Online, Copilot, the Defender XDR portal, Purview and Planner.
What can users do while the outage continues?
Check Microsoft’s service-health updates for incident EX1550543 and see whether the services you need have recovered. You can try another available access method, but Microsoft has not confirmed a workaround that will restore service for everyone; organizations should use their established continuity procedures.
What caused the outage?
The root cause has not been announced. Microsoft has described unavailable servers, failed health checks and an overwhelmed process, and said a network configuration change correlated with the start of the incident. Those details have not yet established a confirmed cause.
When will Microsoft 365 be fully restored?
Microsoft has not provided a restoration deadline. As of its 08:06 UTC update Friday, it was expanding a patch region by region; the company said it would issue a Post-Incident Report after mitigation.
Source: ThorstenMeyerAI.com
