Nine-Hour Microsoft Outage Disrupts Outlook, Teams, and 365 Services

Microsoft 365, Outlook, Teams, and other applications experienced significant disruption for thousands of users over a period exceeding nine hours spanning Thursday and Friday. Engineers worked urgently to resolve the issue after initial remediation attempts failed to restore service availability.

A Microsoft spokesperson confirmed the company “had no indication of a cyber-attack”.

Outage tracking platform Down Detector recorded a surge in Microsoft 365 incidents beginning around 1pm ET, logging approximately 130,000 user reports across 74 nations. Affected products included Word, Excel, PowerPoint, Outlook, and Teams, alongside enterprise tools like SharePoint and OneDrive. Microsoft’s Copilot AI assistant also faced interruptions.

Microsoft indicated the disruption likely stemmed from configuration errors applied to servers maintaining Microsoft 365 operations. During the roughly nine-hour duration at the time of reporting, the firm attempted multiple recovery methods, including update rollbacks and traffic throttling to impacted servers.

Upon deploying corrections, Microsoft observed that those servers returned to an unavailable state once user traffic resumed.

By 3.30am GMT on Friday, Microsoft identified Exchange services—the backend infrastructure supporting Outlook email—as the primary point of failure, creating ripple effects for dependent products. Teams messaging and meeting functionality remained comparatively stable.

Charles Lamanna, Executive Vice President of Copilot, stated on X that further details would follow. “We regret that today’s outages caused disruptions for our customers, and we are working to address the issue,” he wrote.

“We will continue to share more information as soon as we have it, and for now I can confirm that there is no indication this is the result of malicious or cyber activity.”

Earlier, the company attributed the issue to an infrastructure segment experiencing elevated load, which it said likely drove the connectivity errors. It noted several servers were unexpectedly unreachable because they failed automated health checks due to a specific problem.

On X, Microsoft stated it was examining reports regarding users unable to access Exchange Online mailboxes via various connection methods.

Previously, the firm reported that restored servers remained stable thus far, and it was redirecting traffic to alternate pathways where feasible while optimizing the restoration process for remaining affected servers.

“As capacity is restored, users may experience a gradual recovery as their clients reconnect,” the company explained.

The Microsoft service failure also impacted connectors utilized by AI providers OpenAI and Anthropic.

OpenAI reported investigating a Microsoft connector issue where new connections were failing and tools were underperforming. Anthropic confirmed an upstream provider issue affecting its Microsoft 365 connector.

This follows an Azure cloud platform outage last month that disrupted a broad suite of productivity software and impacted industries globally.

While restarting and validating affected servers, Microsoft stated it was simultaneously evaluating whether reverting a small number of recent configuration updates could expedite recovery.

‘A cascading problem’

Mark Gregory, an associate professor in the School of Engineering at RMIT University, noted the outage appeared to strike the network layer of Microsoft’s systems, potentially mirroring the configuration fault that disabled Optus’s network in 2023.

He explained that configuration errors on specific servers force customers to rely on a reduced pool of resources for cloud access.

“If you lose part of that pool, then all of the users are trying to access the remaining servers, and that overloads them. And then they go down.”

“And so you end up with a cascading problem. Then it takes time to find the underlying problem, in this case, a misconfiguration in the network layer.”

Gregory advised that organizations should prioritize testing configuration changes in isolated environments prior to live deployment, and that businesses dependent on cloud services like Microsoft 365 should maintain backup alternatives.

“From a global perspective, there is someone somewhere that’s that’s been badly affected by this and you end up with lost productivity,” he noted.

“They’re being left high and dry now … it then becomes important to have an alternative.”

“Many people would keep a Gmail account, if their Microsoft goes down, they use Gmail. If Gmail goes down, they use Microsoft.”

Prior to this, the company stated it had successfully resolved Teams-related problems in North America, though some users still reported connectivity difficulties.

– with Associated Press and Reuters

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