Users in as many as 74 countries and territories are unable to access their emails and other programmes, including Microsoft 365, Outlook, Teams and other cloud-based products.

Users woke up on Friday morning to a major email blackout, finding themselves locked out of their emails or unable to receive them, following the disruption that hit the US, Asia and Australia overnight.

The US tech giant blamed the issue on “elevated load” on its infrastructure as the problem dragged on for more than 14 hours. Schools, police services and the NHS were also among those affected.

Microsoft said on X that it was “aggressively” working to reduce the effects, adding: “We’ve determined a portion of infrastructure is experiencing elevated load across multiple regions, which is likely contributing to the connectivity errors.

“We’re aggressively pursuing all pathways to reduce impact. We’ve paused all deployments, we’re moving additional traffic off the affected infrastructure, and we’re restarting affected servers to return them to service.”

Minister for Defence Procurement Luke Pollard told BBC Radio 4’s Today programme that the government was engaging with Microsoft to assess the economic impact and look at getting systems back online.

Mr Pollard continued: “For me, this reinforces the need for greater resilience… We need to make sure there are backup systems in place to provide that resilience.

“My appetite for disruption when it comes to using my phone is virtually zero, and I imagine that’s the case for every one of your listeners.

“People want it to work all the time, every time, and we’re seeing more disruption from those tech companies. That’s partly because we’ve become more dependent on technology.”

Microsoft’s mass email blackout could be the biggest for the tech giant

Programming commentator Gergely Orosz claimed on X that the outage appeared to be Microsoft’s worst email failure since 1997, when it was out for two days nearly 30 years ago.

On 14 October 1997, an employee hit “reply all” to an email list called “Bedlam”, which contained 25,000 employee addresses. This knocked 15m emails out of Microsoft’s internal email systems.

However, the current outage is expected to be far more extensive, appearing to affect millions of email and AI users across the globe.

A Government spokesman said: “We are aware of the ongoing global technical issues affecting Microsoft services.

“We are working closely with Microsoft to assess any impact on government services, with robust contingency plans in place to minimise disruption.”