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Microsoft Exchange Online mailbox quarantine disruption after infrastructure change

Service Disruption
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Happening score
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1 unique sources, 1 articles

Summary

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A Microsoft Exchange Online service disruption is mistakenly quarantining customer mailboxes, blocking email delivery and calendar access for affected users. The issue is tracked as EX1436407 and began on July 19. Microsoft tied the problem to a recent infrastructure change that caused excessive memory consumption and an out-of-memory condition. Remediation is underway, with mailboxes being removed from quarantine as cleanup progresses.

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Timeline

  1. 23.07.2026 12:20 2 articles · 13d ago

    Microsoft Exchange Online mailbox quarantine disruption after infrastructure change

    Initial Disclosure

    An Exchange Online mailbox quarantine problem surfaced on July 19 and quickly affected users’ ability to send and receive email and access calendars. Microsoft identified a recent infrastructure change as the trigger and began cleanup to restore quarantined mailboxes.

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