Washington: Microsoft has confirmed that its Microsoft 365 services are back online following a widespread technical outage that disrupted email, workplace communication and productivity tools across the world for more than a day.

In its final status update, the technology giant announced that the underlying issue had been resolved and services restored.

“We have completed our efforts to address the underlying issue of the incident and restored service,” Microsoft said.

The disruption began on November 12, when users in the Americas reported difficulties accessing their Exchange Online mailboxes. Microsoft first acknowledged the problem at 5:54 pm GMT before warning, just 13 minutes later, that users in other regions could also be affected.

The outage spread across at least 74 countries, affecting businesses, government institutions, hospitals and airlines. Several organisations were forced to rely on telephone calls, paper records and even fax machines to maintain essential operations.

Microsoft apologised for the disruption, clarifying that the incident was not linked to a cyberattack or artificial intelligence.

According to a company spokesperson, the outage resulted from an issue introduced during an earlier network capacity upgrade, which surfaced following a recent network change.

Initial investigations suggested increased traffic was overwhelming servers. However, Microsoft later clarified that several servers had unexpectedly become unavailable after failing automated health checks, placing additional pressure on the remaining infrastructure.

Engineers eventually identified a problem involving a core server process responsible for handling secure connections, which became overloaded and stopped processing requests.

Restoration efforts proved challenging as some servers became unresponsive again after being brought back online.

To resolve the issue, Microsoft restricted certain types of network traffic, restored earlier server configurations, patched authentication and routing components, and deployed additional virtual machines to increase capacity.

Email recovery also faced delays as undelivered messages accumulated during the outage. Microsoft extended its email timeout window to 48 hours to prevent messages sent during the disruption from being lost.

“Given the scale of demand, we restored services gradually, validating stability at each stage. While this took longer, it helped ensure a stable restoration,” the company said.

The Asia-Pacific region was among the first to stabilise on November 13, followed by Europe and North America. By the afternoon, Microsoft reported that email backlogs had significantly reduced and were approaching normal levels.

While Teams chats and meetings recovered earlier, calendar functions dependent on Exchange Online experienced longer disruptions. Personal services, including Outlook.com, OneDrive, OneNote and Microsoft To Do, were also affected.

Microsoft has promised to release a detailed post-incident report explaining the cause of the outage and the measures being taken to prevent similar disruptions in the future.