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Microsoft 365 Outage Knocks Out Outlook and Teams for Hours

A Microsoft 365 disruption on August 31, 2026 broke Outlook email, Teams, and SharePoint for several hours, and Microsoft still hasn't confirmed what caused it.

Meridians Money Desk

Published 1 September 2026 · Updated 1 September 2026 · 3 min read

Microsoft 365 Outage Knocks Out Outlook and Teams for HoursSoftware
Photo: Photo by Tima Miroshnichenko / Pexels (Pexels License — free to use, no attribution legally required (credited above as good practice).)

The short answer

  • Microsoft 365 suffered a widespread outage on August 31, 2026, disrupting Outlook email, Exchange Online, Microsoft Teams, OneDrive, and SharePoint.
  • Microsoft tracked the problem internally as incident EX1464935 and linked it to a failure pattern involving authentication and protocol connectivity in Exchange Online.
  • Downdetector complaint counts climbed into the thousands within roughly an hour, and the disruption lasted more than four hours.
  • Microsoft had not confirmed an official root cause as of the latest public updates, though some outlets reported error logs pointing to an expired security certificate.

Microsoft 365 users lost reliable access to Outlook email, Microsoft Teams, and SharePoint for several hours on August 31, 2026. Microsoft tracked the disruption internally as incident EX1464935 and said it centered on Exchange Online, the backend service that handles Outlook mail delivery.

Key facts

  • Reports of Outlook problems began around 8:30 to 9 a.m. Pacific on August 31, according to Tom's Guide's live outage tracker.
  • Microsoft opened incident EX1464935 in its admin center and posted on its Microsoft 365 Status account that Exchange Online functionality was degraded.
  • Downdetector complaint counts rose quickly: GV Wire reported more than 13,000 reports by around 9:32 a.m. Pacific, while Tom's Guide separately logged a peak near 6,000 reports, with roughly 4,500 still active by late morning.
  • The disruption stretched past four hours, affecting Exchange Online, Outlook (desktop and web), Teams calendar and search, OneDrive, SharePoint Online, Microsoft Purview, and Microsoft Defender XDR to varying degrees, according to BleepingComputer.

What Microsoft said

“We've confirmed that users may experience degraded functionality with various Exchange Online functionalities. We're reviewing service telemetry and diagnostic data to isolate the source.”

Microsoft 365 Status, via X

Microsoft later described finding "a common failure pattern across affected Exchange Online requests that is associated with authentication and protocol connectivity" and said it was "continuing to assess the scope of impact," according to BleepingComputer's reporting on the admin center incident notes.

Who felt it

  • Anyone relying on Outlook, desktop or web, for sending or receiving mail saw delays or outright failures.
  • Teams users reported calendar and search problems on top of the email issues.
  • Admin Center and Partner Center consoles were reportedly inaccessible for some affected tenants, per BornCity's reporting.

Sources

Every factual claim above is traceable to these documents. Check them — that is why they are here.

About this byline

Meridians Money Desk is an editorial desk at Meridians, not an individual. A desk byline means the article was produced and fact-checked to that desk's published standards. Read our editorial standards and corrections policy.

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