TL;DR
Microsoft 365 remained degraded at 08:35 UTC on Nov. 13, with many users unable to access Exchange Online and related services. Microsoft says a patch has stabilized servers where applied and is expanding region by region; it has not identified the root cause.
Microsoft’s Microsoft 365 outage continued into Friday, Nov. 13, leaving many users unable to reach Exchange Online mailboxes and disrupting connected services. At 08:06 UTC, Microsoft said a patch had stabilized servers where applied and that it was expanding the fix region by region; as of 08:35 UTC, its status page still listed the service as degraded.
Get business pricing on tech for your team
- Business-only prices and quantity discounts
- Tax-exempt purchasing
- Multiple users, one account, clear invoices
The incident began Thursday, Nov. 12. Microsoft first reported at 17:54 UTC that it was investigating mailbox access problems in the Americas through multiple connection methods. At 18:07 UTC, it said the issue might affect Microsoft 365 connectivity in any region. The incident is tracked as EX1550543; Microsoft has not published a root cause.
In updates Thursday, Microsoft initially described elevated load across multiple regions, then said the load was not caused by increased traffic but by servers that had become unexpectedly unavailable. It paused deployments, shifted traffic, restarted servers and changed its method for checking server health. Those steps did not provide a lasting recovery: Microsoft later said some servers became unresponsive again after receiving traffic.
Microsoft reported positive stability results after applying a patch to part of its infrastructure at 07:29 UTC Friday. In its 08:06 UTC update, it said the patch was stable where applied and that expansion was proceeding systematically, beginning with regions at or approaching peak business hours. The service remained degraded in the latest status cited by the source material.
How the Outage Reached Other Tools
The disruption affects more than inbox access because several workplace services depend on Exchange Online. Microsoft listed impacts involving Teams calendars and meeting scheduling, parts of SharePoint Online, Microsoft 365 Copilot, the Defender XDR portal, Purview and Planner. OpenAI and Anthropic also reported errors in their Microsoft 365 connectors, according to their status pages cited in the source material.
The interruption has had operational effects beyond software access. Workhorse Group said it moved its third-quarter earnings call from Nov. 12 to Nov. 16 because of the outage. The episode shows how a failure in a shared cloud service can affect scheduling, collaboration and systems that connect to Microsoft 365. The full scale of those effects is not yet known.
Reports from outage-tracking services offer an indication of user complaints, but not a count of people affected. Reuters, in a report published by The Korea Times, said Downdetector recorded more than 130,000 U.S. Outlook problem reports around 1 p.m. ET Thursday. Business Standard, citing Downdetector, reported reports from 74 countries. Those figures are reports submitted by users, not verified totals of affected users.
Products Worth Considering
DJI Mini 3 Drone with DJI RC and 3‑Axis Mechanical Gimbal
Amazon Kindle Paperwhite (2024, 16 GB) – 7-inch Display, Black
DJI Mini 5 Pro Fly More Combo with DJI RC 2
As an affiliate, we earn on qualifying purchases.
Thursday’s Escalating Status Updates
Microsoft’s first public update about Exchange Online came at 17:54 UTC Thursday. A copy of the service health notice on Cloud Admin Hub gives the incident start time as 16:17 UTC. Microsoft broadened its warning 13 minutes after its first public post, saying connectivity problems might affect users in any region.
Over the following hours, Microsoft described shifting traffic and restarting servers, then reported that some restored servers could become unresponsive when traffic returned. The outage crossed business hours in several regions. CNBC reported that email and other tools were unavailable through much of the Asian business day and into the early European hours.
A separate Teams incident, TM1550488, was marked fully resolved by Microsoft at 17:09 UTC Thursday. BleepingComputer reported that Microsoft had not said whether that incident was related to the Exchange Online outage. The source material does not establish a connection between them.
“Servers are stable where the patch has been applied.”
— Microsoft, in its 08:06 UTC service health update for EX1550543
Root Cause and Recovery Remain Open
Microsoft has not named the root cause or said how long the regional patch rollout will take. Its updates describe overloaded processes and unavailable servers, but do not establish what caused those conditions. The status page still listed the service as degraded at 08:35 UTC Friday.
Microsoft said it was not aware of malicious activity. That is the company’s current assessment, not a published final investigation finding. It has promised a Post-Incident Report after mitigation. It is also unclear whether the separate Teams incident on Thursday was related, how many users were affected, and when all services will return to normal.
Patch Rollout and Incident Report
Microsoft said it was expanding the patch region by region, prioritizing areas in or entering peak business hours. Customers should check Microsoft’s service health updates for changes to EX1550543 and for confirmation that affected services have recovered; the latest information in the source material does not give a completion time.
After the incident is mitigated, Microsoft says it will publish a Post-Incident Report. That report is expected to provide further detail, but its publication date and the findings it will contain have not been specified.
Key Questions
Is the Microsoft 365 outage over?
No. As of 08:35 UTC on Nov. 13, Microsoft’s status page still listed the service as degraded.
Which services are affected?
Microsoft reported Exchange Online mailbox access problems and impacts to connected services, including Teams calendars and scheduling, parts of SharePoint Online, Microsoft 365 Copilot, Defender XDR, Purview and Planner.
What caused the outage?
Microsoft has not identified or published the root cause. It said affected servers became unexpectedly unavailable and described an overwhelmed core process.
What is Microsoft doing to restore service?
Microsoft said a patch had stabilized servers where applied and that it was expanding the patch region by region. It has not given a time for full recovery.
How many people were affected?
The source material does not give a verified number of affected people. Downdetector figures cited in reports count user-submitted problem reports, not confirmed individual users.
Source: Thorsten Meyer AI
