A major Microsoft outage disrupted Outlook, Teams, Copilot and other Microsoft 365 services for more than eight hours, affecting users across dozens of countries.
The company attributed the disruption to overloaded infrastructure after some servers unexpectedly went offline, forcing the remaining systems to handle more work than they could manage.
According to outage monitoring platform Downdetector, reports of problems with Outlook peaked at nearly 140,000 worldwide. Within approximately an hour, disruptions had been reported in 74 countries.
Microsoft said its recovery efforts were beginning to show positive results, although some services could remain unstable.
The disruption affected users in countries including the United States, Japan, Singapore, the United Kingdom and Australia.
Outlook reports peaked at nearly 140,000
The first reports of technical problems appeared on Thursday shortly after 6.15pm Greek time, according to Downdetector.
By approximately 8pm, reports of Outlook problems had climbed to almost 140,000 worldwide, more than 2,000 times the usual level.
In a later update, the number of reports had fallen to more than 28,000, suggesting that the disruption was easing. However, services had not yet been fully restored.
Which Microsoft services were affected?
The Microsoft outage affected several Microsoft 365 applications, with significant problems reported in Exchange Online, which includes the Outlook email service.
Users reported difficulties signing in and accessing application features. Microsoft also confirmed that some customers might be unable to view certain files or information in their calendars.
Connectivity problems were also reported with Teams and Copilot, Microsoft’s artificial intelligence platform.
However, Microsoft said messaging and online meeting functions in Teams remained largely available despite the wider disruption.
Microsoft identifies server overload as cause
Microsoft said it had detected increased pressure on its technology infrastructure across several geographical regions, which was likely responsible for the connectivity problems.
The company clarified that the overload was not caused by an unusual increase in traffic.
Instead, some servers had unexpectedly gone offline, forcing the remaining infrastructure to handle a higher workload than it could support.
Microsoft later found that a critical part of the affected server infrastructure was under excessive pressure, making the disruption worse.
In a subsequent update on X, the company said attempts to restart the affected systems were producing positive results.
“We are seeing positive results,” Microsoft said, adding that its technical teams were actively monitoring infrastructure performance.
However, it warned that some services could become unresponsive again as demand increased, while investigations into the cause continued.
At the time of the update, the company had not provided a clear timetable for full recovery.
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