Microsoft Outlook down: Thousands hit by email outage as users unable to send, receive or open messages

Microsoft Outlook users across the US are reporting widespread problems Monday morning, with thousands unable to access emails as Microsoft investigates an authentication issue affecting Exchange Online.

The outage began around 8 a.m. PT on August 31, with users reporting that Outlook was not working properly across both the website and app.

At around 8:17 a.m. PT, Downdetector recorded more than 6,000 reports of problems with Outlook, signaling a major spike in disruptions.


The reports were spread across the US, with users describing problems ranging from missing incoming emails to difficulties opening Outlook and accessing their accounts.

Microsoft confirms Outlook outage

Microsoft acknowledged the disruption through its official Microsoft 365 Status account on X, saying it had identified an issue with an authentication component.

“We’ve identified an issue with an authentication component which is contributing to impact,” Microsoft said.

The company said engineers had already developed a remediation strategy and were testing it on a portion of its infrastructure.

Microsoft said the fix would be rolled out more broadly after engineers confirmed that it was resolving the problem.


The incident is being tracked as EX1464935 in Microsoft's systems.

Why is Outlook not working?

The problem appears to be connected to Exchange Online, Microsoft's cloud-based email platform that handles mailbox access and email delivery for Outlook and Microsoft 365 users.

That means the disruption can affect users even when the Outlook application itself is installed and functioning normally.

An authentication problem can prevent users from successfully connecting to Microsoft's services, potentially leaving them unable to open their mailbox, retrieve new messages or perform other actions.

Outlook users report different problems

Downdetector's reports showed that users were experiencing several different issues.

Among the reported problems were:

• Receiving emails
• Using the Outlook app
• Accessing the Outlook website
• Sending messages
• Searching emails
• Opening Outlook

The range of problems suggests that the outage was affecting more than one part of the Outlook experience.

Thousands report Outlook problems

The number of Downdetector reports climbed rapidly during the morning.

More than 6,000 reports were recorded at 8:17 a.m. PT, according to reports tracking the outage.

Reports appeared across multiple parts of the country, suggesting that the problem was not limited to a particular region or a small number of users.

Microsoft's confirmation of an Exchange Online authentication problem provided an explanation for the widespread reports.

Is Outlook down right now?

Microsoft was still working on the problem as of the latest update available Monday morning.

The company said it was first applying its remediation to a portion of its infrastructure. If the test successfully restores service, Microsoft planned to extend the fix more broadly.

That means Outlook users may see the service gradually return rather than having all affected accounts restored at exactly the same time.

Users who continue to experience problems can check Microsoft's Microsoft 365 service status and monitor Downdetector for changes in user reports.

Outlook outage: What users need to know

The key issue is that this appears to be a Microsoft-side service disruption, rather than an isolated problem with individual Outlook accounts.

Microsoft has identified an authentication component as contributing to the impact and is testing a fix under incident EX1464935.

For users waiting on important emails, the safest approach is to wait for Microsoft's service restoration while checking the official status information rather than repeatedly changing account settings.

The outage also highlights how closely Outlook is tied to Microsoft's wider cloud infrastructure: when Exchange Online experiences problems, the effects can quickly reach users trying to send, receive or access email.

As Microsoft continues deploying its remediation, the situation could change quickly, with more users potentially regaining access as the fix is rolled out.