Mailto snippet with subject and body text and styled link:
<a href="mailto:((Email))?subject=A Subject&body=A Body" target="_blank" style="color:#000001;text-decoration: none;"> <span style="color:#000001"> ((Email)) </span> </a>
How to choose Outlook 2016 to open when mailto: is clicked:
How Outlook 2016 open when email link is clicked: