US software giant Microsoft announced on Thursday that it was working to fix a global outage affecting its Microsoft 365 apps, including Outlook and Teams.

The company said its efforts to repair the major Outlook outage were not going as expected, so it sought alternative solutions. 

Microsoft said that it was "not aware" of malicious activity that could have caused the outage.

Outage tracker Downdetector received reports from 74 countries and territories within about an hour.

The outage, which blocked users from accessing their e-mail and other services, also impacted Microsoft 365 connectors used by the companies OpenAI and Anthropic, which said tools were not working as expected.

Downdetector logged nearly 130,000 US reports of Outlook problems shortly after 1 p.m. EST (1800 GMT). Some customers reported having trouble sending and receiving e-mail; others said the program was entirely inaccessible.

The outtage is the second disruption to Microsoft's 365 services this year.

Teams messaging app also affected

Microsoft 365 is a cloud-based subscription service that also includes popular applications such as the Teams workplace messaging app.

Outages of Teams were also reported, as well as other Microsoft 365 services such as the AI assistant Copilot.

Microsoft initially said on X that it was aware that users were "experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas," noting that part of its infrastructure was "experiencing elevated load" that was "likely contributing to connectivity errors."

"We are aggressively pursuing all pathways to reduce impact," it added.

Microsoft said some restarted servers stopped responding again once traffic returned. In an update at 0254 GMT Friday, the company said its latest changes had not worked as expected and that it was looking for other ways to restore service.