Microsoft said on Saturday that is has finished restoring service to the remaining customers and regions affected by a global outage that began on Thursday, Nov 12 and ran for more than 24 hours.
The disruption hit Outlook, Microsoft Teams, Microsoft 365, Microsoft Copilot and Exchange Online, the cloud system behind email and calendars. Users reported problems opening inboxes, sending and receiving email, managing calendars and joining meetings.
What caused it
Microsoft said the outage was not linked to a cyberattack or to AI agents. It said a problem introduced during an earlier network capacity upgrade surfaced after a later network change. Some servers became unavailable and others came under heavy load, which affected connectivity and processing for Exchange Online.
The company said recovery was slowed by technical challenges and failure modes that made the process harder than normal. It restored services gradually, monitored stability, cleared queued messages and rebalanced traffic. Some regions recovered faster than others, and some users had intermittent access rather than a complete traffic.
Scale
Downdetector, a site where users report problems, logged more than 7.4 million reports from 74 countries and territories, peaking at nearly 20,000 a minute.
Who was affected
United Kingdom: The National Health Service had disruption to digital operations and some pharmacies warned of prescription delays. Police ha trouble receiving some online crime reports, and a court trial in Manchester was briefly interrupted.
India: IndiGo, Akasa Air and Air India reported problems with email-based customer support.
Singapore: Some government systems were affected, DBS, UOB and OCBC reported email connectivity problems and SIngapore Airlines warned of delays in replying to customers.
Australia: Government agencies, including the Australian Federal Police and the Australian Security Intelligence Organisation were reported to be affected.
Japan: Sagawa Express had trouble accepting some online reservations at airports and railway stations, and drugmaker Taisho handled some orders by telephone.
Hong Kong and Taiwan: Some firms had disruptions to communications and financial operations. A Taiwanese financial firm reportedly used fax to confirm trades.
United States and Europe: The US House of Representatives reported Microsoft service problems. Euronext reported email disruption, Aviva activated contingency plans for earnings calls, Maersk warned customers of delayed updates, and some companies delayed financial announcements.
Cost
Morningstar DBRS estimates insured losses at US$300 million to US$500 million.
