UPI reported Friday that Microsoft was "making progress" toward restoring service. The BBC described effects in at least 74 countries. Both reports show a recovery that was underway but not finished. Here is what is confirmed, what is not, and what it means for Windows and Microsoft 365 administrators.
What broke: Exchange Online, and the services that depend on it
The outage began in Exchange Online. In its first public acknowledgement, the company said it was "investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas. More details can be found in the Microsoft 365 admin center under EX1550543." Deadline reported that Microsoft soon widened that warning, saying the issue "may affect Microsoft 365 service connectivity for users in any region."
Microsoft then opened a second, broader incident. Both the Exchange Online incident (EX1550543) and the broader Microsoft 365 incident (MO1550821) remained open in its service health dashboard. Features of many Microsoft 365 services that interact with Exchange Online and email services are impacted. Elements of those services that do not depend on interaction with Exchange Online remain functional, Microsoft said.
That dependency explains the patchy experience many users reported. The Pennsylvania university mirror of Microsoft's incident feed listed the following affected areas:
- Exchange Online: mailbox access through Outlook on the web, desktop Outlook, Exchange ActiveSync and REST connections, plus delayed mail delivery.
- Teams: Microsoft said most core functions, including calls, meetings, group chats and channel messages, were not affected. Calendar scheduling, invites, meeting edits, Live and Virtual event creation and some Copilot responses that draw on Outlook data did fail.
- Purview: DLP, auto-labeling, Information Protection, eDiscovery search and export, audit searches and portal access.
- Power BI: intermittent failures when exporting reports with MIP sensitivity labels to PDF.
- Windows 365: Cloud PC users in tenants configured with Purview Customer Key might be unable to connect to their Cloud PCs.
- Microsoft To Do: the app might not load.
The Windows 365 item is easy to miss. Admins who rely on Customer Key for Cloud PCs should note that an email-platform incident could affect access to virtual desktops through the Purview dependency.
Section summary: This was an Exchange Online failure with knock-on effects in every service that uses mail, calendar or Purview. Some users had a working Teams chat and a broken calendar at the same moment.
Microsoft's explanation: servers failing, not a traffic surge
Microsoft has ruled out an attack. According to the BBC, the company blamed "elevated load" on its infrastructure, but not in the usual sense. The status notices mirrored by the University of Pennsylvania say the load was not driven by an overall increase in traffic. Instead, a large number of servers became unexpectedly unavailable, which shifted their work onto the remaining machines.
Those notices show the investigation narrowing over time:
- Freeze. Microsoft paused all deployments and configuration changes as a precaution while reviewing recent changes.
- Health checks. SecurityWeek summarized Microsoft's finding that failed server health checks disrupted Outlook and other Microsoft 365 services. Microsoft's updates said the failures might come from a specific component on the affected servers that processes those checks. It began bypassing that component on a subset of servers and also investigated unusually high processor usage.
- Wider rollout. An alternative health-check method returned the test servers to service, and Microsoft began applying it more broadly. It also prepared an automated process to detect and restart unresponsive servers. A review of recent changes found a small number of configuration updates under investigation as possible contributors.
- Rerouting. Microsoft redistributed Outlook connection traffic across its wider worldwide infrastructure and warned this could add some latency. Gulf Business reported that on Friday Microsoft was increasing virtual machine capacity and investigating traffic-routing problems that have prevented a sustained recovery.
The configuration updates are suspects, not a confirmed root cause. Microsoft has promised a full Post-Incident Report covering the root cause and repair items once the incident is mitigated. Until then, any single-cause explanation is guesswork.
Section summary: Microsoft's account is that servers repeatedly failed their health checks and dropped out of service, overloading the rest. Why they started failing remains unconfirmed.
Recovery has been uneven
The incident updates have not moved in a straight line. Deadline reported that one evening update described "positive results with our efforts to restart affected infrastructure and recover server availability." The optimism was short lived. About an hour later, the company announced that their efforts were "not taking as expected."
By Friday the updates were more positive. UPI quoted Microsoft as saying its latest traffic-optimization actions were improving stability and capacity and were being rolled out across affected regions in pursuit of "persistent recovery." The BBC reported "early signs of stabilisation" and noted Microsoft's warning that intermittent issues could continue. The National reported that Microsoft said service recovery had been completed in parts of Asia-Pacific. That is regional progress, not a global all-clear.
UPI also reported a useful detail for administrators: Microsoft extended to 48 hours the time Outlook will wait for a delayed email to arrive before timing out. Microsoft's stated aim was to preserve mail held up during the incident. Delayed messages may still arrive, so a late flood of mail should be expected rather than treated as a new fault.
Reports conflict on consumer services. UPI cited Microsoft's status page at 5:30 a.m. as showing Outlook.com, OneDrive, the free version of Teams, To-Do and the consumer web version of Office as operational. An explainer from System Design Academy said the consumer status page that morning listed Outlook.com, OneDrive, OneNote, To Do, Teams and Microsoft 365 for the web were affected for personal accounts too. The two snapshots were probably taken at different times in a fast-moving incident. Treat consumer impact as variable rather than settled.
How it was felt around the world
The BBC's survey of the global impact reads like a list of the places where email is still essential:
- United States: House of Representatives staff told Politico their work had stopped. Courts from Los Angeles to Texas warned of delays. The City of Austin said employees could not send or receive email, while phone lines and 911 services kept working. Electric truck maker Workhorse Group moved its third-quarter results from November 12 to November 16.
- Canada: CBC reported that Unity Health Toronto declared a code grey, its alert for an infrastructure failure. Its teams struggled with email, but patient care was not affected.
- Japan: The government said its shared IT platform was disrupted. The Japan Times quoted one X user whose company had switched its regular PDF updates to fax.
- Singapore and the Philippines: Some Singapore government systems were hit, though emergency services stayed fully operational. Singapore's courts asked people to phone about urgent matters. The Philippines' Supreme Court warned of delayed email responses.
- India: Emails were not arriving and Teams calls were unreliable. Equity-market workers told the BBC they panicked when they could not open the morning research reports they need before their daily decision meetings.
- Australia: ASIO chief Mike Burgess said the impact on his agency was largely limited to email.
- Europe and the UK: Reuters reported that Euronext told listed companies to communicate corporate information by phone. UPI reported that the National Pharmacy Association warned of prescription delays. The GMB union said emergency dispatchers could not access patient details in the normal way. Parliament's "alternative communication arrangements" allowed the House of Commons to sit on Friday.
The outage also reached AI tools. The BBC reported that OpenAI and Anthropic both had problems with their connections to Microsoft's services. This was a dependency failure, not an outage of either company's own service.
How big was it? Be careful with the numbers
Estimates of the scale vary widely, so they need careful attribution:
| Figure | Source | What it actually measures |
|---|---|---|
| 430 million | Microsoft, via the BBC and UPI | Total Microsoft 365 users, not the number affected |
| 140,000 | Downdetector, via the BBC | Outlook problem reports from 74 countries on Thursday evening |
| 74 countries in about an hour | Downdetector, via The National | Spread of user reports |
| "Tens of millions" | UPI | Media estimate; Microsoft has not confirmed it |
The National added that Outlook reports peaked at more than 2,000 times their normal level. Downdetector relies on users choosing to report problems. The BBC argued the real number of affected people is probably higher. The BBC also noted that apparent quiet in some countries may reflect censorship of Downdetector itself.
Former Skype and Uber engineer Gergely Orosz told the BBC this may be the "most disruptive" business email outage ever. That is an informed opinion, not a measurement. Australian Home Affairs Minister Tony Burke's reported comparison with the 2024 CrowdStrike incident describes the scale of disruption, not a shared technical cause.
What admins should do now
The following advice is based on general incident-management practice, applied to the facts Microsoft has published:
- Follow the incident IDs. Check EX1550543 and MO1550821 under Service health in the Microsoft 365 admin center. Outlook India reported that Microsoft pointed admins to these records and gave a separate status link for anyone who could not reach the admin center.
- Do not troubleshoot the client. The fault is on Microsoft's servers. Rebuilding Outlook profiles, resetting passwords or reimaging PCs will not fix it and will create more help-desk tickets.
- Expect delayed mail. With the 48-hour timeout extension, late messages may keep arriving after service returns. Tell users so they do not assume mail has been duplicated or lost.
- Check compliance and security gaps. If Purview DLP, auto-labeling or Defender for Office 365 Safe Links were affected in your tenant, review what passed through while protections were degraded.
- Review your fallbacks. The organizations that coped best already had another way to communicate, such as phone lines, rerouted support channels or, apparently, a fax machine. If your plan for an email outage depends on email, now is a good time to rewrite it.
The bigger picture
Concentration risk sounds abstract until a whole parliament has to fall back on paper. The shift to Microsoft 365 put mail, calendars, compliance, AI assistants and some virtual desktops on one shared dependency. Most of the time that is efficient. When servers start failing their health checks at scale, that dependency becomes a single point of failure.
Microsoft has a fair defense. The company reports no malicious activity, Teams' core messaging stayed largely available, and recovery is moving region by region. It has also committed to a Post-Incident Report. Whether that report explains why so many servers failed at once, and what will stop it from happening again, will matter more than any status update this week.
Until that report appears, keep the phone numbers handy.
Update: Additional details (November 13, 2026)
According to Trending Topics, Microsoft rolled back a recent configuration change. The outlet did not establish that the change caused the outage.
The outlet also reported that Microsoft Graph requests for mail, calendars and contacts were timing out. In SharePoint, files remained accessible, but external sharing and email-related features were affected.