The company says it has fixed the underlying fault and restored service to all remaining customers and regions. The outage began on Thursday evening and affected millions of users, including public services across the UK.
Microsoft has confirmed that all services are fully restored after a global outage that disrupted the NHS, police forces, schools and courts in the UK. A technical fault began to affect email, messaging and other Microsoft 365 services from 6pm UK time on Thursday, and the remaining problems were cleared by Saturday morning. A notice on the company’s Microsoft 365 status page said it had “completed our efforts to address the underlying issue of the incident and restored service to the remaining impacted customers and regions”. Microsoft said on Friday that the outage was triggered by a “technical issue not related to cyber or AI agents”.
What went wrong
Microsoft’s latest technical statement says a problem introduced during an earlier network-capacity upgrade was exposed by a more recent network change. It has not yet published a full root-cause analysis. Failures in automated server-health checks left servers unavailable, which cut infrastructure capacity, Associated Press reported. The servers still working then had to handle additional demand, contributing to widespread connection problems.
Engineers deployed an upstream authentication and routing configuration patch, then monitored server stability and extended it to more regions during peak business hours, according to Microsoft incident updates reproduced by the University of Pennsylvania. Service was restored gradually, with Microsoft checking that servers stayed stable before increasing traffic. The company said this lengthened recovery but reduced the risk of further disruption. It has promised a formal post-incident report setting out its findings and the measures meant to prevent a recurrence.
Microsoft has marked the incident, MO1550821, as restored. Other advisories, including an unrelated issue with Microsoft Purview audit-log data first recorded in October, remain active.
A backlog of emails
Restored access did not mean every message had been delivered. Microsoft’s service-health notices said customers could regain access to Outlook while delayed messages continued moving through its systems, and that engineers were checking whether the backlog had cleared. A Japanese university’s status record lists restoration at 1.10pm Japan time on Saturday, or 4.10am GMT. That is one institution’s recovery time and not a universal figure.
The Scottish Courts and Tribunals Service warned that messages might continue to arrive late and asked people with urgent enquiries to telephone courts or tribunals directly.
Impact in the UK
Millions of customers were unable to send or receive Outlook emails, and Teams, Copilot and other Microsoft 365 services were also affected. More than 130,000 people in the US reported Outlook problems on Downdetector at the peak on Thursday night. Downdetector recorded reports from 74 countries and territories within an hour, Associated Press said, which measures geographical spread and not the number of users who lost access. Microsoft had more than 450 million paid commercial Microsoft 365 subscriptions as of January 2026, according to AP, which is not a count of those affected.
Government cyber minister Baroness Lloyd of Effra said contingency measures had been put in place. She confirmed there had been “limited reports of impact on frontline service delivery”, which she described as “inconvenient and disruptive”. She spoke to Darren Hardman, chief executive of Microsoft UK.
Police: Some forces in England and Wales said they could not receive crime reports online on Friday.
NHS: NHS England said some staff were using paper records. The Guardian reported that some operations and appointments were cancelled, though no figure has been published, and that some staff could not send urgent cancer referrals. No patient-harm figures have been released. More than a million NHS employees rely on NHS.net Connect, a Microsoft-powered system for email, calendars, meetings and documents, which explains how one failure could hit many organisations at once. The National Pharmacy Association warned of prescription delays caused by difficulties sending prescriptions electronically, AP reported, without giving a total.
Courts: The Guardian reported that a trial at Manchester’s Minshull Street Crown Court, involving nine defendants, was halted for the day. Judge Maurice Greene sent the jurors home because the court could not manage the usual exchange of information, and staff reportedly tried to find a fax machine as an alternative to email. The allegations in the case remain subject to criminal proceedings. The UK Supreme Court temporarily lost incoming email, though its online portal and contact forms kept working. Some civil and family judgments could not be delivered as scheduled. In Scotland, the Crown Office and Procurator Fiscal Service lost email and some online contact forms while its case-management systems kept working, and the Scottish Courts and Tribunals Service said all courts stayed open but some hearings were delayed.
Rail: National Rail told passengers who could not retrieve tickets from their email to use the relevant train operator’s website or app where possible.
Beyond Britain
According to Associated Press, the Arapahoe County Sheriff’s Office in Colorado reported problems accepting online bond payments, and government bodies in Singapore, Greece and Norway had communication problems. Banks in Hong Kong reported disruption, and a director at a Hong Kong aluminium company said it could not receive updates from American customers.
