Is Outlook Down? Users Report Possible Microsoft Outlook Problems, Weeks After Multi-Day Exchange Outage

REDMOND, Wash. — Users reported possible problems with Microsoft Outlook on Monday, according to the outage-tracking service Downdetector, though the sources reviewed for this article did not show a confirmed Microsoft statement about an incident today. The reports come weeks after one of the most disruptive email outages of the year for Microsoft 365 customers.

Downdetector flagged a rise in user reports about Outlook, Microsoft's email and calendar application, which is offered on the web, PC, Mac and mobile as part of Microsoft 365 and provides messaging, scheduling, contact management and task organization. The alert provided did not include the number of reports, the regions affected or the specific symptoms. Downdetector's figures reflect user-submitted complaints rather than a verified count of affected customers, and a spike can have causes that are local to a network, an organization or a device. Microsoft had not, in the coverage reviewed, acknowledged a new problem or offered an explanation.

Users who suspect an outage can check Microsoft's own status channels. Administrators should look first at the Service Health section of the Microsoft 365 admin center, and the public service status page and the Microsoft 365 Status account on X provide a broader view, according to a guide from the security firm Hornetsecurity. "Third-party tools, such as Downdetector, can help you determine if other users are already experiencing similar issues," the firm wrote. "However, they should not replace checking your organization's service status." Basic steps that outlets have suggested during past disruptions include refreshing Outlook, restarting the app, checking the internet connection and trying Outlook on the web.

The recent history explains why users are sensitive to any sign of trouble. On August 31, Microsoft began investigating an Exchange Online incident tracked as EX1464935, which produced delays and failures in sending and receiving email, authentication errors and problems with mailbox search, according to Microsoft's advisory as reported by Hornetsecurity. "We've confirmed that users may experience degraded functionality with various Exchange Online functionalities," Microsoft's status account wrote on X. "We're reviewing service telemetry and diagnostic data to isolate the source of the issue."

Microsoft later attributed the problem to authentication. A preliminary root cause published in the incident updates described "an issue within a core authentication configuration used by multiple Microsoft 365 services," according to Tom's Guide's live coverage. BleepingComputer reported that Microsoft began tracking a broader incident, MO1465074, which also affected Teams, Microsoft Graph, Purview, OneDrive for Business, SharePoint Online, the Microsoft 365 admin center, Copilot, Universal Print and Defender XDR. In an update reproduced by TechCrunch, Microsoft said it had identified an issue with an "authentication component" and was testing a remediation on part of its infrastructure.

The disruption lasted more than a day. TechCrunch reported on September 1 that Microsoft's effort to fix what had become a multi-day outage was entering its second day, and that as of Tuesday the issues were not fully resolved. In a status update that day, Microsoft said, "Indications from telemetry remain positive, and we've confirmed service availability is improving," adding that it was entering a period of extended monitoring. By September 2, Microsoft reported considerable recovery even though some users still faced problems, according to a report by The Sunday Guardian. GV Wire reported that more than 6,000 users reported problems on Downdetector on Wednesday, September 2, and that Monday's outage had drawn reports from more than 50,000 users. The Sunday Guardian cited more than 130,000 Downdetector reports for the incident, a figure it said should not be read as an exact count of affected customers.

The August incident followed other disruptions this year. On January 22, a Microsoft 365 outage lasting nearly 10 hours affected services including Outlook, Defender and Purview, The Register reported, with Microsoft blaming "a portion of service infrastructure in North America that is not processing traffic as expected." Downdetector reports peaked at about 15,000 or more that day, and Microsoft confirmed early on January 23 that the impact had been resolved, according to reporting syndicated on Yahoo. Cybersecurity News noted earlier this year that Microsoft traced an Exchange Online incident, EX1454755, to a DNS-related fault at a third-party email provider, and that in June a mail-flow pipeline issue caused delivery delays across North America, Europe and Asia-Pacific, with some messages undelivered for more than an hour.

Outlook problems can also be easy to misattribute. Many Microsoft 365 subscribers connect through Exchange Online, Microsoft's cloud email platform, which means a fault in that service can look like an Outlook problem even if the application itself is unchanged, The Sunday Guardian explained. That distinction matters for administrators, who use different incident numbers for Exchange-specific and broader Microsoft 365 issues.

Whether Monday's reports reflect a genuine platform incident is not yet clear from the information available. Outage trackers can register spikes when a single company's network fails or when a popular service has a brief glitch, and Downdetector's own description of the current alert uses the phrase "possible problems." Microsoft's status channels are the authoritative place to look for confirmation. If a service incident is declared, the company typically posts an incident number in the admin center and updates through X.

For readers affected now, the practical advice is to check the Microsoft 365 Status account and the admin center before troubleshooting further, to try Outlook on the web if the desktop or mobile app will not sync, and to expect that any backlog of delayed messages may take time to clear if a broader outage is confirmed. This article will be updated if Microsoft acknowledges an incident.