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Microsoft Exchange Online outage blocks mailbox and calendar access

Service Disruption
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Last updated
Happening score
H score 1
1 unique sources, 1 articles

Summary

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Microsoft is still dealing with an ongoing Exchange Online outage that is blocking access to mailboxes and calendars. The disruption affects Outlook on the web, Outlook desktop, and Exchange ActiveSync, so users cannot reliably reach email through standard connection paths. The issue matters because it interrupts core collaboration and communication services for customers. Microsoft acknowledged the outage at 06:42 AM UTC on 2026-03-16 and said it was monitoring service health for sustained recovery.

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About this happening: **Microsoft** issued immediate mitigation guidance for **CVE-2026-42897**, reducing risk for **Exchange Server 2016, 2019, and Subscription Edition (SE)** on-premises servers that...

Latest development: 15.05.2026 15:35

Microsoft issued temporary mitigation guidance for CVE-2026-42897 while a patch is still in development, recommending the Exchange Emergency Mitigation (EM) Service, which is enabled by default and can be checked with the Exchange Health Checker script, or the Exchange On-premises Mitigation Tool (EOMT) for disconnected or air-gapped environments. Microsoft noted that the mitigations can disrupt features such as OWA Print Calendar and Inline images, and that servers older than March 2023 cannot receive new mitigations through EM Service.

Open Happening

Timeline

  1. 16.03.2026 08:42 2 articles · 3mo ago

    Microsoft acknowledges Exchange Online mailbox-access outage

    Initial Disclosure

    Microsoft acknowledged an ongoing Exchange Online outage at 06:42 AM UTC on 2026-03-16 after users reported trouble accessing their Exchange Online mailbox through one or more connection methods. The disruption affected Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols, and Microsoft said telemetry indicated the issue was no longer occurring for affected users while engineers monitored service health for sustained recovery.

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