We've built custom email templates in Marketo and have been optimizing the mobile view for a few months. We are finding that the text size is significantly smaller on mobile devices when we include an image above the body copy. The size of the copy in the email is perfect when no image is included. The template also works great on desktop. The two factors we are looking at include images and mobile.
Hoping to hear if anyone else has had this issue and how they have solved it.