A global Microsoft 365 outage disrupted Outlook email and calendars, Teams features and Microsoft's Copilot.
ChatGPT and Claude users also faced problems with Microsoft 365 connectors used to access workplace emails, calendars and other information.
Microsoft began restoring affected servers, but service availability remained inconsistent as the company investigated the cause.
A global Microsoft 365 outage disrupted Outlook email and calendar functions in Teams, while also affecting connections used by AI assistants ChatGPT and Claude to access workplace information, as the company struggled to restore services on Friday morning in India.
The disruption left some users unable to access their inboxes, delayed email delivery and affected Microsoft's Copilot. Downdetector recorded 138,058 reports of Outlook problems at the peak of the outage in the US. The disruption lasted more than five hours for some users, while Microsoft began restoring server capacity but had yet to confirm a full recovery.
Open reported that the problems also affected third-party services relying on Microsoft 365 connectors to access users' workplace information. Although some Microsoft services continued functioning, the failure of Exchange Online, the company's email and calendar platform, disrupted several applications that rely on it.
Microsoft Begins Restoring Outlook Services As Users Continue Reporting Problems
Microsoft had begun restoring affected infrastructure by Friday morning in India, although service availability remained inconsistent. In an update at around 7:15 am IST, the company reported positive results after restarting affected servers and said it was monitoring their stability before expanding its recovery measures.
At around 7:39 am IST, Microsoft said it was applying infrastructure capacity improvements to support traffic in regions where services were coming back online. However, an update at around 8:24 am IST indicated that the measures to improve service availability were not working as expected. The company said it was identifying alternative ways to increase capacity.
Earlier, Microsoft had also been testing a configuration change on a small group of servers and reversing a recent network configuration change that coincided with the start of the disruption. Some customers had regained access to their mailboxes, while others continued experiencing difficulties connecting to the service. Full restoration had not been confirmed.
The scale of the disruption was reflected in Downdetector's figures. Reports of Outlook problems reached 138,058 at around 1 pm US Eastern time on Thursday, corresponding to 11:30 pm IST, before declining to approximately 34,490 by Thursday evening in the US.
These figures reflect user-submitted reports to Downdetector and do not represent a verified count of affected customers.
Microsoft initially identified mailbox problems in the Americas before warning that users in any region could be affected. The disruption extended to Australia, where Service NSW asked customers to delay visits to its centres because some government services and transactions were unavailable.
Exchange Online Failure Behind Outlook And Calendar Disruptions
Microsoft 365 is Microsoft's subscription-based productivity suite, which includes applications and services such as Outlook, Teams and SharePoint. The principal service affected during Thursday's incident was Exchange Online, the platform responsible for storing and delivering work emails and managing calendars for Microsoft 365 customers.
Outlook provides the interface for accessing mailboxes, while Exchange Online manages the underlying email service. If Exchange Online stops responding, Outlook may still open, but users can be unable to load their inboxes or receive messages on time.
Microsoft recorded mailbox-related problems from 9:47 pm IST on Thursday. It logged the wider Microsoft 365 disruption separately, beginning at 11:56 pm IST.
The disruption affected Exchange Online and several Microsoft 365 features that rely on it, rather than necessarily making every Microsoft application inaccessible. Microsoft's incident updates also listed problems with specific functions in SharePoint, Planner, To Do, Intune and Power BI. These did not necessarily affect every feature of those applications. For instance, direct access to files stored in SharePoint remained functional.
This distinction was particularly evident in Teams, where some functions continued to operate even as calendar-related features became unavailable.
Microsoft Traces Outage To Overloaded Server Process
Microsoft traced the disruption to a process on affected servers responsible for establishing secure connections, which became overwhelmed and caused the servers to stop processing requests.
As individual servers dropped out, fewer machines remained available to handle incoming traffic, reducing the overall capacity of the infrastructure and increasing the strain on the remaining servers.
According to Open, Microsoft was also investigating whether a recent change to its network settings, which coincided with the beginning of the incident, had contributed to the failure. The company had begun reversing the change as part of its recovery efforts, but had not established it as the confirmed cause.
A Microsoft spokesperson told The Guardian that the company had found no indication of a cyberattack.
Microsoft's investigation is still examining what initially triggered the server problems and whether reversing the network settings change will help prevent a recurrence.
Why Teams Calendar And Meeting Functions Were Affected Differently
Teams' core messaging and online meeting functions remained largely operational during the outage, according to Microsoft. However, users could encounter problems when attempting to schedule new meetings or access calendars because these features rely on Exchange Online.
This meant users could potentially join an existing Teams meeting while being unable to access the calendar needed to arrange another one.
Microsoft had also resolved a separate Teams messaging disruption earlier on Thursday. The subsequent Microsoft 365 outage caused another set of problems, with Outlook inboxes and Teams calendar functions affected through their dependence on Exchange Online.
Some organisations using Information Barriers in Teams could also encounter problems creating chats.
ChatGPT, Claude And Copilot Also Face Connectivity Problems
The outage also affected third-party AI services that use Microsoft 365 connectors to access users' workplace information with their permission.
OpenAI reported problems with its Microsoft 365 connector, warning that new connections and certain functions might fail. The disruption affected ChatGPT's ability to connect with users' workplace information.
Anthropic also reported failures involving Claude's Microsoft 365 integration. According to Anthropic, most requests involving email, calendars and search through its connector were failing at the time of its update. Open also reported that Anthropic had flagged problems with Claude operating within Outlook.
Microsoft 365 Copilot was affected as well, with users potentially unable to access work emails, calendars and files through the assistant.
Previous Microsoft Outages And Unclear Impact In India
This is not the first time disruptions to Microsoft's infrastructure have affected Outlook and Teams simultaneously.
On January 25, 2023, Microsoft 365 services, including Outlook and Teams, were disrupted by a global networking failure. Microsoft's investigation traced the incident to a change in its Wide Area Network (WAN), which affected connectivity to Azure and other Microsoft services. Users in India also reported difficulties accessing services during that outage.
Another disruption occurred in October 2025, when a failure involving Azure Front Door affected Microsoft 365 services. Azure Front Door directs internet requests to the appropriate servers, and problems with the service can prevent users from reaching applications that depend on it.
In both instances, customers experienced failures in the applications they were trying to use, while the underlying problems originated in the infrastructure supporting those services.
For the November 12 incident, Microsoft warned that users across regions could be affected. However, no India-specific figures or confirmed list of affected organisations were available in the updates reviewed.
India has previously experienced the consequences of widespread dependence on shared technology infrastructure. In July 2024, airlines operating from Terminal 3 of Delhi airport resorted to issuing handwritten boarding passes after a faulty CrowdStrike software update caused widespread disruptions to Windows computers.
The two incidents involved different technical failures. The July 2024 disruption affected computers running Windows, while the November 2026 incident involved Microsoft's servers and the services hosted on them. The latest outage did not necessarily require users' devices or the Outlook application itself to malfunction. Problems with the infrastructure delivering email and calendar services were enough to disrupt access.
Microsoft Continues Recovery Efforts As Root Cause Remains Unclear
Microsoft's recovery efforts depend on whether restarted servers remain stable as normal traffic is gradually restored. The company has been monitoring server performance and applying capacity improvements to support the return of services in affected regions.
For Microsoft 365 administrators, the wider incident can be tracked under reference number MO1550821, while the mailbox-related disruption is listed under EX1550543.
Microsoft has not yet confirmed the root cause of the outage or established whether reversing the recent network configuration change will resolve the problem. Its recovery efforts remain focused on restoring server capacity and ensuring that affected infrastructure can handle normal traffic.
Recovery will depend on whether the restored servers remain stable as normal traffic resumes.
