Microsoft 365 Outage Ends After 24 Hours; Outlook and Teams Services Restored
In Short
Microsoft has restored Outlook, Teams and other Microsoft 365 services after a global outage disrupted businesses, airlines, hospitals and government offices across 74 countries.
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Microsoft 365 Outage Ends After 24 Hours; Outlook and Teams Services Restored
Microsoft has confirmed that its Microsoft 365 outage, which affected Outlook, Teams and Copilot for more than 24 hours, has finally been resolved. The disruption, which began on November 12, caused widespread problems for businesses, government departments, hospitals and airlines, forcing many organisations to temporarily return to traditional ways of working.
In its final update on the incident, Microsoft said, “We have completed our efforts to address the underlying issue of the incident and restored service.”
The company also apologised for the disruption, describing the incident as a technical failure rather than a cyberattack or an issue involving artificial intelligence.
Network upgrade triggered Microsoft 365 disruption
According to Microsoft, the problem was linked to an earlier network capacity upgrade. A company spokesperson explained that the incident “was introduced by an issue during an earlier network capacity upgrade that surfaced following a recent network change.”
Microsoft further clarified that it was “a technical issue not related to cyber or AI/agents.”
The first reports emerged on November 12, when users in the Americas began experiencing difficulties accessing their Exchange Online mailboxes. Microsoft acknowledged the issue at 5:54 pm GMT (11:24 pm IST). Within minutes the company warned that customers in regions could also face disruptions.
At first Microsoft said the issue was due to " load”, in multiple regions. As they looked deeper, they found that traffic levels had not gone up. The real problem was that several servers had unexpectedly gone down after failing automated health checks. This caused stress on the servers that were still working.
Engineers later identified an issue involving a core process responsible for handling secure server connections, which prevented affected systems from processing requests properly.
Why restoring Outlook and Teams took so long
Getting the servers operational again was more complicated than I had expected. When normal traffic was redirected to the servers some systems stopped responding.
Microsoft engineers worked hard to limit traffic bring back server settings fix login problems and routing parts and put in more virtual machines to boost capacity. The engineers kept the system running.
Another challenge involved delayed emails. Messages that could not be delivered during the outage continued to accumulate in external mail servers. To prevent emails from being lost, Microsoft extended its email timeout window to 48 hours.
Explaining the gradual recovery, the company said, “Given the scale of demand, we restored services gradually, validating stability at each stage. While this took longer, it helped ensure a stable restoration,”
Asia Pacific services stabilised first on November 13, followed by Europe and North America. Teams chats and meetings recovered relatively early, although calendar functions dependent on Exchange Online continued experiencing problems.
Businesses and essential services affected worldwide
The disruption highlighted how heavily organisations depend on Microsoft's services. In January, the company said it had more than 450 million paid commercial subscriptions to Microsoft 365.
In India, IndiGo and Akasa Air experienced email support disruptions, while Air India rerouted its emails to continue receiving customer messages. Its flight operations remained unaffected.
The impact was equally significant overseas. NHS staff in the UK resorted to paper records, pharmacies warned about prescription delays, and a Manchester judge sent jurors home. In Japan, some businesses returned to fax machines.
OpenAI and Anthropic both ran into problems, with their Microsoft 365 connectors. At the time electric truck maker Workhorse Group pushed back its quarterly results announcement until November 16.
Although the services are working again the event has brought back worries, about how regular business activities rely on a few big cloud companies.
