I can confirm this for S/MIME encryption: when I select Require Encryption from the Options menu and S/MIME from the Encryption Technology submenu under Options and immediately choose Message Security Info from the View menu, Digitally Signed and Encrypted is still shown as No, although the status of the certificates of the recipients is already shown correctly. For OpenPGP messages, onl the status of the keys of the recipients is shown, to the security info for such messages is shown correctly.
Bug 1683701 Comment 3 Edit History
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I can confirm this for S/MIME encryption: when I select Require Encryption from the Options menu and S/MIME from the Encryption Technology submenu under Options and immediately choose Message Security Info from the View menu, Digitally Signed and Encrypted is still shown as No, although the status of the certificates of the recipients is already shown correctly. For OpenPGP messages, only the status of the keys of the recipients is shown, to the security info for such messages is shown correctly.