Key Highlights
- Microsoft is investigating an ongoing Exchange Online issue that mistakenly flags legitimate emails as phishing and quarantines them.
- The incident began on February 5, 2026, affecting Exchange Online customers, preventing them from sending or receiving emails.
- Misclassified URLs are incorrectly marked as malicious due to ever-evolving criteria aimed at identifying suspicious email messages.
- An updated URL rule intended to identify more sophisticated spam and phishing emails is incorrectly quarantining legitimate messages.
Microsoft’s Exchange Online Struggles with Phishing Misfires
Microsoft, the behemoth of tech, finds itself grappling with a persistent issue in its Exchange Online service. The problem, which began on February 5, 2026, is causing legitimate emails to be flagged as phishing attempts and quarantined by the system. This has left users unable to send or receive important messages, creating significant disruptions for both personal and business communications.
Evolution of Email Security
The issue stems from a new URL rule designed to combat increasingly sophisticated spam and phishing techniques. However, this update has backfired, leading to the misclassification of harmless URLs as malicious. This not only hampers user productivity but also underlines the ever-evolving nature of cybersecurity challenges.
Impact on Users
Microsoft acknowledged the bug in a service alert on Thursday, February 9, 2026. “Some users’ legitimate email messages are being marked as phish and quarantined in Exchange Online,” they stated. The company is working to resolve the issue by reviewing the release of quarantined emails for affected users. Yet, many remain unsure when or if their messages will see the light of day again.
Microsoft has faced similar challenges before, with previous incidents involving the misquarantine of legitimate emails as spam.
In March 2026, anti-spam systems mistakenly quarantined some user emails, and another bug in May caused a machine learning model to incorrectly flag emails from Gmail accounts as spam. The September incident blocked users from opening URLs and quarantined their emails.
These repeated issues highlight the complexities of maintaining effective email security while minimizing false positives. As technology advances, so do the techniques used by spammers and phishers, making it a constant battle to keep up with evolving threats.
Customer Frustration
The ongoing issue has caused significant frustration among users who rely on Exchange Online for their daily communications. “You might think this is new,” one user lamented, “but Microsoft has had similar issues before.” The repeated nature of these problems raises questions about the company’s ability to fully address and prevent such glitches in the future.
While Microsoft continues to work on resolving the issue, the incident serves as a reminder of the ongoing challenges in email security. As the landscape evolves, companies like Microsoft must remain vigilant and adaptive to protect their users from both real and perceived threats.