The outage, which began on Thursday, impacted Microsoft 365 services including Outlook, Teams, and Copilot, disrupting essential functions such as sending emails, managing calendars, and hosting virtual meetings. In the UK, NHS England staff were forced to use paper records, and ambulance services were affected. In Australia, councils, schools, and courts reported email outages, while the federal police and Asio were also impacted. In the U.S., school districts had to communicate with parents via phone or apps, and a Colorado detention facility was unable to process online bond payments. In Japan, government staff used text messaging instead of email, and in France, a municipality instructed citizens to use the phone for communication.

Microsoft attributed the outage to a technical issue during a recent network capacity upgrade and said it was not related to cyberattacks or AI agents. The company stated it was not aware of any malicious activity behind the disruption. Steven Murdoch, a professor of security engineering at University College London, told the Guardian an outage of this size was usually “the result of some surprising interaction between systems. Each of the systems is normally quite well understood but interactions between them are complex and frequently the cause of large outages like this.”

Downdetector, an online outage tracker, logged over 7.4 million reports worldwide, peaking at nearly 20,000 reports per minute. The service received reports from more than 70 countries and territories. Microsoft said approximately 430 million people use Microsoft 365 apps.

The incident has raised concerns about the overreliance on a small number of Big Tech companies for critical communications and infrastructure. Josh Gilbert of eToro said if reliability becomes a recurring problem, it could give IT departments reason to think twice before placing more of their business in one provider’s hands.

Analysts estimated global insured losses from the outage at between $300 million and $500 million. Microsoft shares closed flat on Friday.