"Lost Working Day": What is known about the global Microsoft outage

According to outage tracking website Downdetector, reports of issues with the Outlook email service peaked on Thursday evening at 20:00 Minsk time, with around 140,000 complaints recorded worldwide.

Microsoft stated that the outage was not caused by a cybersecurity incident, but attempts to resolve the issues have not yet yielded significant results.

Here is what is known so far about which services were affected and what exactly went wrong.

What is not working?

"Connection issues" affected Microsoft 365 services, including Teams, Outlook, and the AI-powered software Microsoft Copilot.

Users complained that they were unable to send or receive emails, view certain files, or access data in their calendar applications.

At the same time, some users were still able to work normally in Teams, exchange messages, and hold online meetings as usual.

How many users are affected?

The exact scale of the disruptions has not yet been confirmed, but according to Downdetector, around 140,000 people from 74 countries reported issues on Thursday evening. The following morning (around 07:00 GMT), there were 43,000 reports of problems with Microsoft Outlook.

According to Microsoft's website, more than 430 million people use Microsoft 365 suite applications.

This software is used by companies worldwide, so the outage is expected to potentially impact other services as well.

Tech companies OpenAI and Anthropic also reported issues caused by the outage.

OpenAI, the creator of ChatGPT, stated that it was investigating issues affecting connectivity to Microsoft services, which caused some tools to malfunction.

Government agencies also faced difficulties—specifically, the Singapore government and an Australian intelligence agency. In Japan, disruptions affected government bodies and numerous large companies. Deputy Chief Cabinet Secretary Masanao Ozaki warned that the government's shared IT infrastructure, which relies on Microsoft solutions, experienced interruptions. Local media reported that some banks and financial institutions were forced to use fax machines to confirm transactions.

British clinics and GP surgeries warned of possible disruptions, with some asking patients to call by phone for urgent matters rather than using email or web forms. British police also urged the public to call rather than use the online form.

As the Financial Times reported, Swiss luxury group Richemont, owner of brands Cartier and Chloé, was forced to postpone the publication of its half-year financial results on Friday, while US electric truck maker Workhorse Group postponed its quarterly earnings presentation scheduled for Thursday.

What went wrong?

Microsoft ruled out a cyberattack and attributed the outage to "excessive load" on its infrastructure.

This term means that servers are operating under significantly higher load than usual.

According to the company's statement, during the outage a large number of servers "unexpectedly became unavailable," causing an increased flow of requests to the remaining servers, which led to their overload.

In its latest update, the company said there were "early signs" of system stabilization, but their status was not yet fully stable. Service throughput "has not yet returned to normal levels."

"As part of these measures, we are increasing the email delivery timeout window to 48 hours. This will allow messages delayed by the outage to be preserved while service recovery continues," the statement said.

In this context, the "email delivery timeout window" refers to the period during which an email client—such as Outlook—will wait to receive an incoming message.

Microsoft is taking this step to prevent a situation in which emails sent from other systems (for example, from Gmail or other services unaffected by the outage) could be lost if they entered the system before it was fully restored.

Earlier, the corporation stated that attempts to remediate the situation "did not produce the expected result."

What do experts say?

Australian cybersecurity expert Troy Hunt told the BBC that this outage could have far-reaching consequences.

"Microsoft is a critical part of the internet's infrastructure. What happened reminds us of how critically important email remains. The outage not only prevents people from working, but also interferes with other tasks: scheduling meetings, making purchases that require verification, creating accounts, or gaining access to them," he noted.

Paul Spain from the New Zealand consulting firm Gorilla Technology added that due to the unavailability of email and other services, companies effectively "lost a working day," leaving users "frustrated."

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