Microsoft outage also disrupts Teams and Copilot amid infrastructure overload.
Microsoft Outlook suffered a major global outage on Thursday, leaving tens of thousands of users unable to access their email as the company said it was working “aggressively” to minimise the disruption.
Microsoft attributed the issue to “elevated load” on its infrastructure. The outage continued for much of the US working day and affected other products, including Teams and its AI assistant Copilot.
The disruption spread worldwide within an hour, affecting Microsoft services in 74 countries and territories, according to outage tracker Downdetector.
A map shared by Downdetector on X showed users reporting problems across the Americas, as well as parts of Europe, Asia and Africa.
Microsoft initially said it was investigating outage reports in the Americas. It later confirmed that the issue appeared to be affecting “Microsoft 365 service connectivity for users in any region”.
Microsoft 365 is the company’s cloud-based subscription service, which includes popular applications such as Outlook and Teams.
“We’ve determined a portion of infrastructure is experiencing elevated load across multiple regions, which is likely contributing to the connectivity errors,” Microsoft said on X.
“We’re aggressively pursuing all pathways to reduce impact,” it added.
The company said it had paused all deployments, redirected additional traffic away from the affected infrastructure and restarted impacted servers in an effort to restore services.
In the US, around 130,000 users reported problems with Outlook shortly after 1pm Eastern Time (1800 GMT), according to Downdetector.
The number of reports later declined, with around 37,000 users still reporting Outlook issues by 6pm Eastern Time (2300 GMT).
Thousands of users also reported problems accessing Teams and Copilot, Downdetector data showed.
As the outage continued for several hours, Microsoft posted a series of updates on X, outlining its ongoing efforts to restore services.
In an update shortly after 6pm Eastern Time, the company said it was “observing limited recovery” as it worked to redirect user traffic away from affected servers.
“As capacity is restored, users may experience a gradual recovery as their clients reconnect,” Microsoft said.
