The problem happens for users who encrypt the email using the settings under the email File dialog (File > Encrypt), ...

Classic Outlook tells you to open the email to "read its contents and verify your credentials," but that doesn't work.

Microsoft has confirmed a known issue that prevents recipients from opening encrypted emails in classic Outlook.

A new Outlook (Classic) update is preventing Windows users from opening encrypted emails. Microsoft confirms the bug and ...

Microsoft is looking into a newly identified issue in classic Outlook that prevents users from opening certain encrypted ...