Microsoft 365, Outlook, Teams and other apps were disrupted for thousands of users for more than five hours on Thursday, with Microsoft saying it was still working to return affected servers to service, but had observed limited recovery.
A Microsoft spokesperson said the company “had no indication of a cyber attack”.
Outage website Down Detector showed a spike in Microsoft 365 problems around 1pm ET, with nearly 130,000 reports of issues affecting access to Word, Excel, PowerPoint, Outlook and Teams as well as enterprise services such as SharePoint and OneDrive. AI assistant Copilot was also affected.
New reports fell from that peak, to around 13,000 five hours later, but many said they couldn’t send and receive emails, or had trouble loading their inboxes altogether.
Earlier, Microsoft said that a portion of its infrastructure was “experiencing elevated load” – which it said was “likely contributing to the connectivity errors”. The company determined a number of servers were “unexpectedly unavailable” due to a problem that caused them to fail during automated checks.
Posting on X, Microsoft said it was “investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods”.
The company said the servers it had restored had remained stable so far and that it was shifting traffic to alternate routes wherever possible while streamlining the process to bring the remaining affected servers back online.
“As capacity is restored, users may experience a gradual recovery as their clients reconnect,” the company said in a statement.
The Microsoft outage also hit connectors used by OpenAI’s and Anthropic’s AI services.
OpenAI said it was investigating an issue with Microsoft connectors in which new connections may be broken and tools were not working as expected. Anthropic said it had identified an issue with an upstream provider affecting its Microsoft 365 connector.
Microsoft last month reported an outage of its Azure cloud platform that affected suite of productivity software, and a range of industries worldwide.
As the company worked to restart and validate affected servers, it said it was in parallel “assessing whether reverting the small number of recent configuration updates we identified could help accelerate recovery”.
‘A cascading problem’
Mark Gregory, associate professor in the School of Engineering at RMIT University, said the outage appears to be affecting the network layer in Microsoft’s systems, and was potentially similar to the configuration issue which brought down Optus’s network in 2023.
He said when some of the servers have configuration issues, it means customers are forced to share a smaller pool of servers to access the cloud services.
“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 said it showed companies should invest more in testing environments for configuration changes before deployment in the live network, and said businesses reliant on cloud services such as Microsoft 365 should have backup options.
“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 said.
“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.”
Earlier, the company said it had “successfully restored” problems related to Microsoft Teams in North America, although some users continued to report connectivity issues.
– with Associated Press and Reuters
