A global Microsoft outage that began late on Thursday has cut millions of people off from Outlook email, disrupting businesses, governments, public services and the media for more than half a day. Downdetector recorded more than 130,000 reports of Outlook problems in the US at its peak, and users in 74 countries reported issues with Microsoft services within an hour, with Outlook reports peaking at more than 2,000 times their normal level. Teams, Microsoft's Copilot AI assistant and other Microsoft 365 services were also disrupted, as were AI chat services such as OpenAI's ChatGPT and Anthropic's Claude.
Microsoft said the outage was caused by an elevated load on its infrastructure rather than by malicious activity. The company said servers were unexpectedly becoming available and then failing automated health checks, which strained the remaining infrastructure, and that the underlying trigger was traced to a specific component responsible for processing server health. Microsoft said it validated an alternative health check method that returned a subset of affected servers to service, and prepared automated recovery systems to detect and restart unresponsive servers. Executive vice-president Charles Lamanna said the outages did not appear to be the result of a cyber attack, and the company said it had no evidence of malicious activity.S1S2
By Friday, Microsoft said traffic was being gradually restored and that it was seeing improvements in mailbox access and delayed email processing, though some users may continue to experience intermittent issues. The company said reducing email queues and backlogs remained a priority and that an extended 48-hour email timeout window remained in place to protect delayed messages. Microsoft said it would share a full post-incident report with root cause and defence-in-depth actions after recovery is complete.S1S2
The disruption reached public services and businesses far beyond the tech sector. In the UK, police forces said they could not receive crime reports online and urged people to call 101 or 999 for urgent matters, while NHS England said staff were using long-standing paper-based measures and asked patients to keep contacting services such as 999 and 111. The National Pharmacy Association warned of possible prescription delays, and councils reported impacts. Rail operators in Germany, Canada and the UK advised passengers unable to retrieve train tickets sent by email to use the website or app they bought them through. In France, the town hall of Aulnay-sous-Bois reported its email system was down, and the European stock market operator Euronext advised listed companies to communicate corporate information by telephone.S2S3
The Federation of Small Businesses said its national chair, Tina McKenzie, expected small firms to be left floundering, and urged clients to be patient, noting the outage fell on Friday the 13th and warning that fraudsters may exploit the situation with fake offers of help. Christophe Aulnette, a former president of Microsoft France, told Franceinfo that the outage highlighted the fragility of an interconnected world in which central points of vulnerability can affect the entire planet.S2S3
