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

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

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

Your Outlook emails might be moved to the Junk folder. Check this. If you find your emails there, move them to the Inbox. Right-click on the email and select Move to > Inbox. You might have ...