At least 74 countries have been affected by the Microsoft outage since it was detected after midday US Eastern Time (17:00 GMT) on Thursday.
Microsoft 365 Services, including Teams, Outlook and artificial intelligence software Copilot, are experiencing "connectivity problems", the company said.
From city governments in the US to Australian spy agencies, disruption has been widespread. Here's what's been happening around the world.
US tech giants OpenAI and Anthropic have both reported problems.
OpenAI, which makes ChatGPT, said it was investigating an issue affecting its connections to Microsoft's services, which caused some tools not to work as expected.
Electric truck maker Workhorse Group, which was expected to report third-quarter results on 12 November, rescheduled to 16 November, citing business disruptions caused by the outage.
Meanwhile, officials in some US cities encouraged citizens to call local offices and agencies where needed instead of using email.
The City of Austin in Texas posted on X early on Friday: "Due to an ongoing Microsoft Outlook outage, City of Austin employees cannot receive or send emails at this time.
"City phone lines remain operational, and 911 Emergency services are not impacted."
Courts from Los Angeles to Texas also warned that communications might be delayed.
In Canada , the public broadcaster CBC reported that a healthcare network running several hospitals in Toronto had declared a code grey, indicating an infrastructure failure.
The company, Unity Health Toronto, said its teams were having trouble sending or receiving email but that patient care was not affected.
The government of Japan said its shared IT platform had been disrupted.
"We understand that Microsoft is working to restore services, and we will continue to monitor the company's response," Deputy Chief Cabinet Secretary Masanao Ozaki told reporters.
In India , the outage was disrupting work for many on Friday, with emails not landing and Teams calls not going through smoothly.
People working in the equity markets told BBC News they had panicked when they realised they could not access daily research reports before their morning meeting where they make their big decisions of the day.
"Outlook wasn't working. We fortunately have an alternative so it was not a problem. But we conduct most of our calls, especially with big clients, on Teams - that has been a challenge," a senior executive with a big Indian brokerage said on condition of anonymity.
Singapore confirmed the outage had affected some government systems, but said "emergency services remain fully operational".
Singapore's Government Technology Agency urged people to check official social media channels or websites.
Singapore's courts also said they were "experiencing issues with incoming and outgoing emails", urging people to contact them by telephone for urgent matters.
In the Philippines , the Supreme Court warned that "responses to emails and other transactions may be delayed".
Firms in China use software that has been made locally - WPS Office is a favourite - but the Microsoft outage caused frustration there too.
Outlook is one of the few reliable channels for many offices and businesses in the country who work with colleagues across the world.
China operates one of the world's most sophisticated systems of internet censorship, known as the Great Firewall, which restricts access to many Western websites including Google, Facebook and Instagram along with many international news organisations including the BBC.
Australia's spy and federal police agencies have been affected by the outage, though officials have suggested the impact is minimal.
"The impact that they are dealing with is very much on email system", the head of the Australian Security Intelligence Organisation, Mike Burgess, told reporters.
Other Australian public service providers also confirmed they had been affected by the outage, but similarly said this was mostly limited to emails, and the BBC understands there were no major impacts across New South Wales' primary services in health, education, transport, and emergency services.
European stock market operator Euronext advised listed companies on Friday morning to use the phone to communicate corporate information because of the Outlook email disruption, Reuters reports.
In the UK , GPs, police and pharmacies are among services affected.
Some GP surgeries have urged patients not to submit messages via their website while the problem remains, while several large police forces are urging members of the public to call if they want to make a report.
Politicians are also affected. At Westminster, MPs were reporting their access via parliamentary accounts to Microsoft products was down.
A parliamentary spokesperson said: "We are aware of the global issue affecting Microsoft email services, which is impacting users of the parliamentary network. We are working with Microsoft to resolve the matter as quickly as possible.
"Alternative communication arrangements are in place, allowing today's business to continue."
Some parts of Asia, Europe and Africa remain unaffected, according to Downdetector. These include Russia, where the use of Microsoft applications is heavily restricted, or phased out in favour of domestic alternatives.
However, this could also be a case of under-reporting in some countries, where Downdetector is among the websites blocked due to censorship.
