I realize I am late to this thread, but after a week of pulling my hair out with this, and having none of the above options work, nor any others online, I randomly stumbled across a resolution today and successfully created mailto: links with Divi & ACF. I created a tutorial in hopes that someone else won’t spend a week trying to figure it out.
Hope this helps: http://keilassociates.com/divi-advanced-custom-fields-email-link-not-sending.html
