MacRumors published a story that a vulnerability in the mail app of macOS exists that leave encrypted emails readable

Apple to Fix macOS Mail Vulnerability That Leaves Text of Some Encrypted Emails Readable

There's a vulnerability in the macOS version of the Apple Mail app that leaves some of the text of encrypted emails unencrypted, according to a report from IT specialist Bob Gendler

Apple to Fix macOS Mail Vulnerability That Leaves Text of Some Encrypted Emails Readable