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

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

You may see this error because the Microsoft 365 encryption service cannot verify your identity or check if you have permission to view the message. This is not ...

Microsoft is investigating a known issue that triggers Outlook errors when opening encrypted emails sent from other organizations. According to a recently published support document, this issue ...