The problem happens for users who encrypt the email using the settings under the email File dialog (File > Encrypt), Microsoft further explained. To prevent the issue, there are two possible ...

If your hard drive is nearing full capacity, you can delete your Windows temporary files to gain space back again.

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

Some Windows users are seeing an error in Device Manager or DXDiag of Windows 11/10 that says: Windows cannot verify the digital signature for the drivers required ...