A major technical outage affecting Microsoft cloud applications has stretched past 20 hours into nearly a full day, disrupting operations for schools, healthcare systems, businesses, courts, and government bodies across the globe before services began demonstrating broad recovery.
Microsoft confirmed that the global disruption was caused by an internal technical issue rather than a cyber-security incident, expressing apologies as engineers worked to restore access to key tools including Outlook, Microsoft Teams, and AI software Copilot.
By Friday afternoon, the technology giant reported encouraging recovery progress across Europe alongside marked improvements in North America. In subsequent updates, Microsoft stated that it was addressing remaining areas of disruption, noting that email queues had been significantly reduced and were approaching normal operational levels.
However, the company cautioned that some users might continue to experience intermittent access issues, inbox loading struggles, and delayed email delivery while systems catch up.
To prevent delayed messages from being lost while delivery queues normalize, Microsoft announced it is extending Outlook's email timeout window—the duration the application waits to receive incoming messages—to 48 hours. The company clarified that when delayed messages finally arrive in inboxes, their displayed timestamps will reflect the precise time of delivery rather than the moment they were originally sent, meaning users should not assume all outbound communications have reached recipients immediately.
Microsoft attributed the ongoing outage to elevated load on its infrastructure resulting from an issue encountered during an earlier network capacity upgrade. Explaining how the disruption escalated, Prof James Ferryman from the University of Reading's department of computer science noted that secure connection infrastructure became overwhelmed.
"What Microsoft has told us is that the part of its servers that sets up secure connections is getting swamped, and once that happens the server just stops answering," Ferryman said.
"The trouble is that this kind of failure snowballs. One server falls over, its work gets passed to the next one, and meanwhile huge numbers of phones and laptops keep trying to get back in. You can't just turn it all back on at once. You have to bring it back bit by bit."
Industry experts highlighted the unprecedented nature and wide scope of the incident. Gergely Orosz, a former leading software engineer at tech firms including Skype and Uber, observed that the event could be the "most disruptive" business email outage "of all time," adding that he "cannot recall" an outage over business email taking this long to return to normal. Australian cyber-security expert Troy Hunt emphasized Microsoft's central role in everyday digital operations.
"Microsoft is a massive part of the internet backbone and reminds us how critical email still is. Not only does this outage affect many people's ability to work but also things like the ability to communicate about appointments, purchase things that need verification, create or access accounts and services," Hunt said. According to Microsoft's website, more than 430 million people use Microsoft 365 applications, though the full scale of the disruption has not been officially confirmed.
The technical troubles extended beyond Microsoft's direct user base, causing knock-on effects for third-party artificial intelligence developers including OpenAI and Anthropic. ChatGPT-maker OpenAI reported investigating an issue affecting its connections to Microsoft services, which caused several of its tools not to work as expected.
Globally, disruption was widespread, impacting US city governments as well as Australian spy agencies. Courts stretching from Los Angeles to Texas issued warnings that communications might be delayed.
In Canada, public broadcaster CBC reported that a healthcare network running several hospitals in Toronto experienced email issues, though patient care remained unaffected. Japan's government confirmed that its shared IT platform was disrupted. Across the United Kingdom, GP surgeries, pharmacies, police forces, and schools were affected.
Some GP surgeries urged patients not to submit online messages via their website while issues persisted, while several large police forces requested that members of the public call if they needed to make a report.
Initial reports of connectivity problems surfaced late Thursday, with users experiencing varying levels of service access. While many customers were unable to send or receive emails, view calendar details, or access specific files, others were able to use Teams messaging and online meeting functions without disruption. Addressing the event, Microsoft said in a statement that it was "deeply sorry for the disruption this incident has caused our customers and partners.
We know the trust they place in our services and take that responsibility extremely seriously. We are seeing broad recovery and stability across our services."
Although email service Outlook appears to be resuming, the outage has so far lasted for more than 20 hours – in outage terms that is considered a long time.
