A breakdown in Microsoft's server infrastructure has left users across Europe and beyond unable to access Outlook, Teams and other everyday office tools for more than a day. The disruption, which began on Thursday afternoon Central European Time, was still not fully resolved by Friday morning, with problems reported in 74 countries and territories. Microsoft has ruled out a cyber attack but has yet to identify a definitive root cause.
What happened and who was affected?
The outage first hit Outlook, Teams and the AI assistant Copilot on Thursday evening, according to Euronews. Since then, the situation has worsened. Microsoft's initial fixes failed to hold, with servers that were brought back online crashing again once traffic resumed. The company admitted its changes were “not taking as expected” and reported only “marginal success” by Friday morning.
Downdetector, which tracks outages based on user reports, logged nearly 140,000 issues for Outlook alone. The list of affected services has expanded to include SharePoint Online, the security tool Defender XDR, and the task-management apps Planner and To Do. Microsoft says more than 430 million people use its 365 apps, though the true number of affected users remains unknown.
The knock-on effects reached far beyond missed emails. In the UK, several GP practices advised patients to phone with urgent queries instead of using email or online forms. The Singaporean government and Australia's intelligence agency confirmed they were affected. Even rival AI firms OpenAI and Anthropic reported problems with the tools that link their services to Microsoft 365. US electric vehicle maker Workhorse postponed its earnings call to Monday. Paul Spain of New Zealand-based advisory firm Gorilla Technology said many companies had effectively “lost a business day”.
What went wrong?
Microsoft has not yet named a root cause, and its explanation has shifted during the outage. It first blamed “elevated load”, meaning servers were under unusual strain. It later clarified that this was not due to a surge in users, but rather a large number of servers becoming “unexpectedly unavailable”, pushing their workload onto the remaining machines.
Attention has turned to Microsoft's automated “health checks”, which determine whether a server is fit to handle traffic. The company said it was testing a configuration change to fix a problem that was causing servers to fail these checks and drop out of service. Mahmoud Elkhodr, a senior lecturer in ICT at CQUniversity in Australia, offered an explanation in The Conversation: health checks are meant to pull faulty servers out of action, but if the checking system itself malfunctions, it can switch off healthy servers and overload the rest. He stressed this was only an inference from Microsoft's public updates.
Was it a cyber attack, and is your data at risk?
There is no evidence of a hack. Microsoft said it was not aware of any “malicious activity”, and executive vice-president Charles Lamanna said the outage did not appear to be a cyber attack. No group has claimed responsibility. Elkhodr noted that the most common attack used to knock services offline, a distributed denial of service (DDoS), works by flooding a system with external traffic—which does not match Microsoft's statement that traffic had not increased.
Despite this, speculation spread on social media. Smitarani Tripathy, a social media analyst at data firm GlobalData, said rumours of hacking circulated on X because Microsoft offered no confirmed cause or timeline for a fix.
On the evidence so far, this is a problem of access, not theft. An outage stops people reaching their emails and files; it does not in itself mean anyone else has seen them. Microsoft has said nothing to suggest customer data has been exposed or lost. However, there are indirect risks: Defender XDR, used by organisations to spot threats, was among the affected services, which could weaken security monitoring while it is down. Fraudsters often exploit major outages to send fake “support” messages, so users should be wary of any request to log in or reset a password, and check Microsoft's official status page instead. Some emails may arrive late, so users should verify that important messages sent during the outage were received.
What does this mean for Europe?
This is not a one-off. In January, Outlook, Teams and other Microsoft 365 services went down for hours. In August, a faulty code update disrupted Outlook and Exchange Online for several days. The latest outage coincides with growing debate across European governments and businesses about how far they should depend on a handful of US cloud providers. When one of them fails, thousands of services built on top of it can fail too, including those run by other companies.
Elkhodr argued that organisations should plan for digital outages the way they prepare for natural disasters—having backup systems and testing them regularly, not just writing plans that are never used. For individuals, he suggested keeping essentials such as contacts available offline.
Microsoft has promised continued updates through its service status page. Until it publishes a full review, the key questions of why so many servers failed at once, and how to prevent a recurrence, remain unanswered. For those looking for practical alternatives, our guide on keeping work going during an Outlook outage offers useful tips. The incident also echoes earlier concerns about protests at Microsoft data centres in Amsterdam, and comes as Europe grapples with glitches in border systems that highlight broader digital vulnerabilities.
