Outlook Outage: Microsoft Investigates Email Problems Affecting Thousands of Users

A widespread Outlook outage disrupted Microsoft 365 users on August 31, 2026, with users reporting problems sending and receiving email, accessing mailboxes and signing into Exchange Online. Microsoft confirmed the incident and identified an authentication-related problem within Exchange Online.  

The disruption led to thousands of user reports on Downdetector, although the exact number of affected customers was not immediately clear. Microsoft continued investigating and testing a fix as the incident developed.  

Is Outlook down right now?

The answer depends on the user’s Microsoft 365 environment and location.

The August 31 incident primarily affected Exchange Online, the cloud infrastructure that powers Microsoft-hosted business email and related services. Microsoft said users could experience degraded functionality, including authentication errors and failures or delays when sending and receiving messages.  

At one point, Microsoft’s public status page indicated that its products were operational even while users were reporting problems and Microsoft was investigating Exchange Online. That difference is important: a general status page may not immediately reflect every active service incident.  

What caused the Microsoft Outlook outage?

Microsoft initially said it was investigating a common failure pattern associated with authentication and protocol connectivity.

Later updates identified an issue involving a core authentication configuration used by multiple Microsoft 365 services. Microsoft began testing corrective actions on individual servers while continuing to analyze service telemetry.  

The incident was tracked as EX1464935 in Microsoft’s service-management system.

It is important not to confuse confirmed information with speculation. Reports circulated about a potentially expired internal certificate, but Microsoft’s documented preliminary root cause pointed to an authentication-configuration issue.  

What Outlook problems were users seeing?

The outage did not affect everyone in exactly the same way.

Reported symptoms included:

• Delays sending or receiving email
• Failed email delivery
• Problems connecting to Exchange Online
• Authentication errors
• Mailbox search problems
• Intermittent mailbox-operation failures
• Difficulties accessing Exchange administration tools  

For someone simply trying to open Outlook, this could appear as if Outlook was completely down, even though the underlying problem was within Microsoft’s cloud-based Exchange Online infrastructure.

How many people were affected?

Downdetector showed a sharp increase in reports during the outage.

GV Wire reported more than 3,000 reports at 9:06 a.m. Pacific Time, rising above 7,000 reports shortly afterward. Other reporting showed Outlook complaints reaching more than 6,000 at the peak of the disruption.  

Downdetector figures represent user-submitted reports rather than a direct count of affected Microsoft customers. They are therefore useful for identifying an outage and its apparent scale, but they should not be interpreted as an official number of affected users.

Was this only an Outlook outage?

No.

Although Outlook and Exchange Online were the most visible parts of the disruption, Microsoft said the authentication problem also affected other Microsoft 365 services.

The broader incident was tracked under MO1465074 and included potential effects on services such as:

• OneDrive for Business
• SharePoint Online
• Microsoft Teams
• Microsoft Purview
• Microsoft Defender XDR  

That explains why some organizations experiencing the Microsoft outage may have noticed problems beyond email.

What should you do if Outlook is still down?

If Outlook isn’t working, first determine whether the problem is local or affecting Microsoft’s servers.

1. Check Microsoft’s service status

Microsoft’s official service-status information is the best place to look for confirmed incidents.

2. Check Downdetector

Downdetector can show whether reports are suddenly increasing from other users. A large spike is a useful indication that the problem may not be limited to your device. However, it is not an official Microsoft diagnostic tool.

3. Don’t immediately delete your Outlook profile

If the problem is a Microsoft server-side outage, repeatedly changing account settings, resetting passwords or reinstalling Outlook is unlikely to solve it.

4. Try another Microsoft 365 service

If Outlook, Teams, OneDrive or SharePoint are all behaving unusually, that points more strongly toward a broader Microsoft 365 issue rather than a problem with your individual account.

5. Wait for Microsoft’s recovery update

During a server-side incident, email may be delayed rather than permanently lost. Businesses should avoid making unnecessary configuration changes while Microsoft works through the incident.

What does EX1464935 mean?

EX1464935 is the incident identifier Microsoft assigned to the Exchange Online disruption.

Searching for that identifier can be useful for administrators because it distinguishes this incident from other Microsoft Outlook issues and provides a reference for Microsoft’s technical updates.

The incident was classified as a service degradation affecting Exchange Online, with Microsoft continuing to investigate the scope and remediation.  

Outlook outages have broader consequences

For consumers, an Outlook outage can mean delayed personal messages.

For businesses, the consequences can be more serious. Exchange Online is used for corporate communication, calendars, contacts and other workflows. A disruption can therefore affect customer communication, internal operations and time-sensitive transactions.

The August 31 incident also illustrates why cloud-service outages can feel larger than a problem with a single application. Outlook is the interface many people see, but the underlying infrastructure is shared across Microsoft’s broader cloud ecosystem.

The bottom line

The August 31, 2026 Outlook outage was a confirmed Microsoft Exchange Online incident rather than simply a problem with individual Outlook apps. Microsoft linked the disruption to an authentication configuration issue and was testing remediation while monitoring its services.  

If you’re searching “is Outlook down,” “is Microsoft Outlook down,” or “Outlook outage today,” checking Microsoft’s official status information alongside Downdetector is the quickest way to distinguish a widespread service problem from an issue affecting only your account or device.