Microsoft is investigating an issue with its Microsoft 365 service and its Teams app, with some users reporting to DownDetector that they are having problems using services such as Exchange and Outlook.

Microsoft said Monday that it has identified the cause of a major Outlook and Teams outage, and is deploying a fix to the problem.

Several Microsoft programs, including Outlook, Microsoft 365, and Teams, are experiencing outages, according to reports on Downdetector.

A global glitch shut down Microsoft 365 applications like email, calendars, and Powerpoint. The tech giant said it was working on a fix.

In September, another Microsoft outage impacted thousands of people using Outlook, Teams, cloud services, Skype, SharePoint, and more. In that outage, Microsoft blamed a third-party ISP’s managed environment for the issues.

Reports of issues began around 8 a.m. ET and spiked around 12:30 p.m. ET, according to DownDetector (which shares a parent company with Mashable). Reported outages have since tapered off, suggesting the issue might be resolved soon.

Thousands of Microsoft 365 customers worldwide reported issues with Outlook, Teams and other services on Monday.

Microsoft 365 users are experiencing issues on Monday with the free email service Outlook. Users began reporting that outage just before 8 a.m. ET, according to Downdetector. It appears most people are reporting problems when trying to use the website version.

On social media service X, Microsoft posted a message early Monday that it is assessing "an issue impacting users attempting to access Exchange Online or functionality within Microsoft Teams calendar.