Blab Tech
Microsoft Outlook and 365 Services Down for Hundreds of Users Amid Authentication Outage
On Monday, August 31 2026, Microsoft confirmed a widespread outage that left Outlook and several other Microsoft 365 services unusable for thousands of users. Logged as EX1464935 in the Microsoft 365 admin center, the incident began in the late afternoon and has caused email delivery failures, login problems, and disruptions to Teams, the Microsoft Store, Azure, and even OpenAI’s ChatGPT.
The first signs of trouble surfaced on Downdetector, where by 3:00 p.m. ET users had filed tens of thousands of complaints. Of those, 38 % cited issues receiving messages in Outlook, 24 % reported general app problems, and 21 % struggled to sign in. While the volume of new reports has been slowly declining, each page refresh continues to reveal fresh complaints.
Microsoft’s official response appears on its status page and X account. The company said it had pinpointed an authentication component that is contributing to the impact. A remediation strategy has been drafted and is currently being applied to a portion of the infrastructure for testing. Once the test confirms that the fix resolves the impact, the solution will be rolled out more broadly. For more details, Microsoft directs users to the admin center, referencing incident number EX1464935.
The authentication component in question belongs to the Exchange Online service that underpins Outlook’s email delivery and login processes. When the component fails, users can experience delayed or missing emails and errors when attempting to sign in. The problem has also affected other services that rely on the same authentication infrastructure, including Microsoft Teams, the Microsoft Store, and Azure services.
Historically, Microsoft has resolved similar outages within a few hours, though some incidents have stretched into the following day. At present, the duration of this outage remains uncertain; the company is still testing the fix on a limited set of infrastructure before a wider deployment.
The impact of the outage extends beyond individual users. Many businesses rely on Outlook for daily communication, and the interruption of email and calendar functions can disrupt meetings, project coordination, and customer service. Teams, used for collaboration and video conferencing, is also affected, potentially delaying meetings and file sharing.
While Microsoft has not released detailed technical diagnostics, its public statements indicate that the root cause is an authentication failure. The company is analyzing telemetry to confirm the cause and validate the remediation strategy.
Other Microsoft 365 services have reported issues during the same period. Users have noted problems with the Microsoft Store, Azure, and even OpenAI’s ChatGPT, suggesting that the authentication component’s failure may have broader implications across Microsoft’s cloud ecosystem.
At this time, Microsoft has not announced a definitive timeline for full resolution. The company is continuing to monitor the situation and will update users through its status page and X account.
In summary, Microsoft has confirmed a significant outage affecting Outlook and related Microsoft 365 services, traced to an authentication component failure. The company is testing a fix on a limited infrastructure before wider deployment. Users experiencing email, login, or app issues are advised to monitor the Microsoft 365 status page for updates.
The first signs of trouble surfaced on Downdetector, where by 3:00 p.m. ET users had filed tens of thousands of complaints. Of those, 38 % cited issues receiving messages in Outlook, 24 % reported general app problems, and 21 % struggled to sign in. While the volume of new reports has been slowly declining, each page refresh continues to reveal fresh complaints.
Microsoft’s official response appears on its status page and X account. The company said it had pinpointed an authentication component that is contributing to the impact. A remediation strategy has been drafted and is currently being applied to a portion of the infrastructure for testing. Once the test confirms that the fix resolves the impact, the solution will be rolled out more broadly. For more details, Microsoft directs users to the admin center, referencing incident number EX1464935.
The authentication component in question belongs to the Exchange Online service that underpins Outlook’s email delivery and login processes. When the component fails, users can experience delayed or missing emails and errors when attempting to sign in. The problem has also affected other services that rely on the same authentication infrastructure, including Microsoft Teams, the Microsoft Store, and Azure services.
Historically, Microsoft has resolved similar outages within a few hours, though some incidents have stretched into the following day. At present, the duration of this outage remains uncertain; the company is still testing the fix on a limited set of infrastructure before a wider deployment.
The impact of the outage extends beyond individual users. Many businesses rely on Outlook for daily communication, and the interruption of email and calendar functions can disrupt meetings, project coordination, and customer service. Teams, used for collaboration and video conferencing, is also affected, potentially delaying meetings and file sharing.
While Microsoft has not released detailed technical diagnostics, its public statements indicate that the root cause is an authentication failure. The company is analyzing telemetry to confirm the cause and validate the remediation strategy.
Other Microsoft 365 services have reported issues during the same period. Users have noted problems with the Microsoft Store, Azure, and even OpenAI’s ChatGPT, suggesting that the authentication component’s failure may have broader implications across Microsoft’s cloud ecosystem.
At this time, Microsoft has not announced a definitive timeline for full resolution. The company is continuing to monitor the situation and will update users through its status page and X account.
In summary, Microsoft has confirmed a significant outage affecting Outlook and related Microsoft 365 services, traced to an authentication component failure. The company is testing a fix on a limited infrastructure before wider deployment. Users experiencing email, login, or app issues are advised to monitor the Microsoft 365 status page for updates.
