By Sergiu Gatlan
Publication Date: 2026-02-09 10:47:00
Microsoft is investigating an ongoing Exchange Online issue that mistakenly flags legitimate emails as phishing and quarantines them.
The incident began on February 5 and continues to affect Exchange Online customers, preventing them from sending or receiving emails.
“Some users’ legitimate email messages are being marked as phish and quarantined in Exchange Online,” Microsoft said in a service alert when it acknowledged the bug on Thursday.
“We’ve determined that the URLs associated with these email messages are incorrectly marked as phish and quarantined in Exchange Online due to ever-evolving criteria aimed at identifying suspicious email messages, as spam and phishing techniques have become more sophisticated in avoiding detection.”
Over the weekend, Microsoft confirmed that the issue is caused by a new URL rule that incorrectly flags some URLs as malicious and the emails as phishing attempts.
“An updated URL rule intending to identify more…
