Reading Digitally Signed Email
Digitally Signed Email proves the identity of the sender and the integrity of the message content. Recipient may verify the authenticity of an email using supported email clients.
In general, email clients use icon in message header to represent digital signature. Clicking on the icon reveals signing information.
Signed Email in Outlook 2016
Not all email clients understand digital signature. For unsupported clients, digital signature appears as an attachment to the email.