Microsoft Exchange Online Quarantines Legit Mail

Microsoft Exchange Online quarantines have disrupted business communications after the platform mistakenly flagged legitimate emails as phishing. The issue, tracked as incident EX1227432, began on Feb. 5, 2026, and remains unresolved. Microsoft identified a flawed URL policy as the root cause, which incorrectly classifies safe links as malicious, sending authentic messages to quarantine.

Affected users face delays in both sending and receiving emails, with administrators reporting the need for manual approvals to release trusted content. Microsoft is reviewing the policy, gradually restoring quarantined messages and removing false phishing flags. The company has not disclosed how many customers or regions are impacted.

This incident follows several other filtering errors in 2025, including URL blocks in Teams and a Gmail misclassification. System administrators say image-heavy messages and missing DMARC records often trigger false positives.

Microsoft Exchange Online quarantines raise ongoing concerns about detection overreach. Users can monitor updates through the Microsoft 365 admin center.

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Microsoft Exchange Online Flags Customers Legitimate Email as Phishing