- Problems with Microsoft's cloud infrastructure disrupted Outlook and other Microsoft 365 services from November 12
- A patch has shown early signs of improving server stability, but full restoration remains a work in progress
- Businesses have turned to alternative communication channels as the outage exposes their dependence on Microsoft's workplace ecosystem
The disruption began on Thursday, November 12, initially affecting users trying to access Exchange Online mailboxes in the Americas. It subsequently spread across regions, with reports coming from 74 countries and territories.
At its peak, Downdetector recorded more than 130,000 reports of problems with Outlook in the US. Users reported being unable to open inboxes, send or receive emails, access calendars and connect to workplace applications. Problems were also reported in India, Australia and Japan.
The disruption extended beyond Microsoft's own applications. OpenAI and Anthropic reported problems with their Microsoft 365 connectors, affecting the ability of some users to connect their AI tools to workplace data. The incident therefore exposed how services that appear independent can rely on the same underlying cloud infrastructure.
What went wrong with Microsoft's services?
Microsoft initially pointed to elevated infrastructure load as a possible reason for the connectivity problems. Its subsequent investigation found that a number of servers had unexpectedly become unavailable, leaving the remaining infrastructure struggling to handle requests.
The company also identified a problem with a core process responsible for establishing secure connections. This process became overwhelmed on affected servers, causing them to stop processing requests. Microsoft began restarting servers, redirecting traffic and reviewing network configurations to restore capacity.
However, the first recovery measures did not deliver the expected results. Some servers became unresponsive again when traffic returned, forcing engineers to explore alternative ways of stabilising the infrastructure. Microsoft also paused deployments while it worked on the problem.
The company has said it is not aware of any malicious activity causing the incident and has not identified evidence of a cyberattack. It has promised a post-incident report explaining the root cause and the measures it intends to take to prevent a recurrence.
Microsoft also clarified that the disruption was not affecting every feature in its product ecosystem equally. Services dependent on Exchange Online and email connectivity experienced problems, while some functions that did not rely on those systems continued to operate.
What is working now, and how are businesses coping?
Microsoft's latest update on Friday offered some encouragement, although it did not confirm a complete restoration.
The company said it was seeing positive results for server stability after applying a patch to an upstream authentication and routing configuration component on part of its infrastructure. It was monitoring the results and working to extend the patch to servers supporting affected regions.
The services listed as impacted included Outlook.com, OneDrive, OneNote, Microsoft To Do, Teams and Microsoft 365 for the web. Users could continue experiencing problems with other Microsoft 365 applications as well. The company had not provided a confirmed timeline for full recovery.
In India, the disruption was recorded across several cities, including Chennai, Ahmedabad, Indore and Bengaluru, according to network intelligence company ThousandEyes.
Air India said its flight operations remained unaffected and that there was no disruption to its communication channels. The airline temporarily rerouted its emails to ensure that customer messages continued to reach the company, while maintaining its usual 24-hour response timeline.
Some businesses also found ways to keep essential work moving. A large financial global capability centre (GCC) in Chennai routed employee correspondence through Microsoft Teams, using the platform to share files and obtain approvals. An employee said screenshots were being preserved as records of sign-offs.
At a consulting firm, employees were asked to prioritise critical work through Teams, with less urgent tasks being moved to the following Monday.
But such workarounds can create their own risks. Ben Mudie, field chief technology officer for Asia-Pacific at cybersecurity company Tenable, warned that employees might turn to personal email accounts or unapproved file-sharing services when official systems become unavailable.
"When essential tools become unavailable, employees naturally look for ways to keep working. The security risk is that temporary workarounds, such as personal email accounts or unapproved file-sharing services, can move sensitive business information beyond an organisation's visibility and control," he said.
He also warned that disruption could create opportunities for impersonation, with employees needing to scrutinise urgent requests arriving through unfamiliar channels or messages claiming to offer help restoring access.
Tarun Pathak, research director at Counterpoint, in a news report quoted as saying, the incident highlighted how deeply businesses had integrated Microsoft's products into their operations.
"Microsoft's outage is a reminder that for most enterprises, Outlook and Teams are no longer just productivity apps but core operational infrastructure," he reportedly said.
He further added that India's exposure was particularly significant because of the large number of IT services companies, business process outsourcing firms and GCCs that depend on Microsoft infrastructure for client delivery.
The financial impact is difficult to quantify, as the cost extends beyond the period when services are unavailable. Delayed approvals, interrupted communication and lost working hours can affect productivity even after systems return.
Pathak expects businesses to review their continuity plans and establish backup communication channels for future disruptions.
The incident also raises a wider question for companies investing in cloud-based operations and AI tools: whether having several applications from the same technology ecosystem provides genuine resilience. For businesses that depend on Microsoft across email, collaboration, file storage and AI, the outage has shown how quickly a disruption in one part of the infrastructure can spread across everyday operations.
