A bug in the web version of Exchange causes emails to be mistakenly blocked as phishing. Microsoft is seeking a solution.
Exchange Online has been unintentionally blocking email traffic for several days. Microsoft acknowledges that this is due to an error in the mail server’s anti-phishing protection. Both incoming and outgoing emails can be mistakenly labeled as phishing and placed in ‘quarantine’.
The bug can prevent you from sending and/or receiving emails. Microsoft has informed Exchange Online users via the admin center that it is working on a solution.
More Difficult Detection
Many email services, such as Exchange Online, have built-in spam and phishing filters. These are trained to recognize traces of potential phishing and eliminate phishing emails before they can reach your inbox. This way, Exchange performs the initial cleanup for you, reducing the risk of you clicking on a phishing email in a moment of inattention. However, Exchange’s filters are now doing their job too well and are also labeling legitimate traffic as phishing, preventing users from sending and receiving emails.
The cause of the bug appears to be an update to the URL rules, which incorrectly identifies certain URLs as phishing. Microsoft states that it must regularly implement adjustments “due to the constantly changing criteria for identifying suspicious email messages, as spam and phishing techniques are becoming increasingly sophisticated to avoid detection.”
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Until a solution for the bug is found, Microsoft has no choice but to release the blocked emails from quarantine. Affected users should see the emails trickle back into their inboxes, the company assures. Earlier, Microsoft announced that Exchange Online will no longer work on older devices starting in March.