What is Microsoft Exchange? The cloud tool behind Microsoft Outlook issues.

November 12, 2026

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Microsoft's popular suite of enterprise products, known as Microsoft 365, which includes Outlook, Teams, and Copilot, suffered from a massive outage on Thursday.

Or did it?

While more than 100,000 users reported problems accessing Microsoft Outlook and Microsoft 365 on the platform DownDetector, Microsoft is saying it's actually a cloud tool called Microsoft Exchange that's causing problems.

So, what is Microsoft Exchange? And why does it being down affect your ability to access your email or message your coworkers?

Microsoft Exchange is the backend cloud tool that sends data updates to Outlook. It's essentially the server that stores the actual data, handles the mail flow, syncs the data to services like Outlook, and controls account security policies. Put simply, Outlook is the front end; Exchange is the back end.

For most users, though, this is a distinction without a difference. The end result is that users can't access their email, calendar, or messages.

The company has been providing updates on the situation on X:

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Mashable reached out to Microsoft with questions about the outage, but the company has not responded, as of this writing.

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