Microsoft has recognized a significant issue affecting Exchange Online users, where legitimate emails are being incorrectly flagged as phishing and sent to quarantine. This situation arises from a new URL-detection rule that is resulting in an overabundance of false positives, preventing users from sending and receiving important emails. Although the company is working on a solution, responses have varied among users with quarantined emails being gradually restored.
The problem stems from Microsoft’s latest service alert, which detailed how a newly implemented URL rule misclassifies trustworthy links as potentially malicious. This misclassification inadvertently increases the risk score of certain emails, rerouting them to quarantine even if both the sender and content are verified. Microsoft has reported that a fix is in progress, with some previously quarantined emails re-emerging in users’ inboxes as the update rolls out.
Such false positives frequently occur when anti-abuse measures become overly aggressive. Cyber attackers continuously adapt their techniques, including link shortening and using deceptive domains, prompting companies like Microsoft to tighten their filtering criteria. As part of its response, Microsoft is adjusting its rules to strike a balance between effective protection and minimizing impact on legitimate communications.
To recover missing emails while maintaining security, users should access the Quarantine page within the Microsoft Defender portal linked to their work or school accounts. It is advisable to inspect quarantined messages carefully, such as filtering by categories like Phish, and confirming their authenticity through email headers and authentication results like SPF, DKIM, and DMARC. Users are told to release only the messages they can verify as genuine. For administrators, enabling or tightening end-user notifications can alert employees about pending messages, allowing for more efficient recovery of important correspondence.
Administrators can implement temporary allow rules for trusted senders, helping to streamline the process without exposing the organization to broader threats. Adjusting settings to ensure greater visibility into quarantined emails and keeping an eye on patterns can also mitigate disruptions. Email authentication measures must remain intact to bolster the credibility of outbound messages, ultimately reducing the chances of being wrongly flagged.
While incidents of mislabeling legitimate emails can arise, the overarching importance of email security cannot be underestimated. Reports have consistently identified human factors—such as phishing and social engineering—as prevalent threats, making vigilance necessary. Microsoft’s aggressive filtering is a reaction to an environment rife with cyber threats, yet there remains a risk of inadvertently diminishing trust in this essential communication tool.
As Microsoft works on solutions, organizations are encouraged to stay informed through the Microsoft 365 Service Health dashboard, monitor their own respective environments for fluctuations in quarantined messages, and continue to report any false positives. Businesses must find a balance between ensuring continuity in communication and upholding security measures, as cyber threats continue to evolve. The situation underlines the necessity for adaptive responses in both email security and corporate communication strategies.