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Microsoft Exchange Online IMAP4 outage

Service Disruption
First reported
Last updated
Happening score
H score 25
1 unique sources, 1 articles

Summary

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Microsoft Exchange Online is facing an IMAP4 outage that intermittently blocks mailbox access for some users, disrupting email availability. The incident is tracked as EX1215307 and was first acknowledged at 23:35 UTC on Wednesday. Microsoft says the outage was triggered by a code conflict in a recent IMAP deployment that introduced an authentication misconfiguration. Other connection methods are unaffected, and Microsoft says a fix is being deployed.

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Timeline

  1. 08.01.2026 14:45 1 articles · 4mo ago

    Exchange Online IMAP4 outage acknowledged

    Initial Disclosure

    Microsoft acknowledged EX1215307 after an Exchange Online service issue began intermittently blocking mailbox access through IMAP4. Microsoft said other connection methods were unaffected, advised affected users to retry access, and classified the problem as an incident in the Microsoft 365 admin center.

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  2. 08.01.2026 14:45 2 articles · 4mo ago

    Microsoft deploys Exchange Online IMAP4 fix

    Mitigation Patch Update

    Microsoft said it already deployed a fix for the Exchange Online IMAP4 mailbox access issue and was continuing to roll out the configuration change. The disruption was attributed to a code conflict in a recent IMAP deployment that introduced an authentication misconfiguration, with completion expected by the next scheduled update.

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