Exchange Outage Today (March 16th 2026)

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Microsoft experienced a major Exchange Online outage that prevented many users from accessing:

  • Their mailboxes
  • Calendars
  • Outlook on the web
  • Outlook desktop
  • Mobile clients (Exchange ActiveSync)

The issue was acknowledged by Microsoft at 06:42 AM UTC and tracked under EX1253275 in the Microsoft 365 admin center.

Scope of the Outage

According to multiple reports:

  • All major Exchange Online connection protocols were affected.
  • Users saw errors accessing Office.com, which temporarily displayed “Something went wrong.”
  • A separate outage also impacted Microsoft 365 Copilot web sign‑in and Copilot web clients (e.g., office.com/chat).

Cause of the Problem

Microsoft reported:

  • A section of service infrastructure was not processing traffic efficiently.
  • The root cause involved supporting network infrastructure, leading to service degradation across Exchange Online.

Engineers implemented configuration changes to mitigate the impact.

Is It Fixed?

partially.

Microsoft stated the outage has been mitigated, and telemetry shows the issue is no longer occurring for most users.
However:

  • Many users continued to report access issues even after Microsoft declared recovery.
  • The Copilot web sign‑in issue (MO1253428) remains under investigation.

Who Was Affected?

  • Users across the U.S. and other regions were unable to connect via Outlook (web, desktop, ActiveSync).

  • Some admins in North America were unable to access the Microsoft 365 admin center.

Background: Recent Similar Outages

Microsoft has had several Exchange‑related incidents in the past year:

  • January 2026: IMAP4 outage caused by a code conflict.
  • November 2025: Classic Outlook clients blocked from connecting.

Workarounds and Microsoft's Guidance

  • Use Outlook on the Web or desktop clients if still operational.
  • For Copilot access issues, use desktop apps, Teams integration, or Copilot in Office apps.

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