The ultimate guide to email design (Cameron Chapman)

While a lot of online communication has moved to social media, email is still a very important part of any online marketing campaign. And when we think of marketing emails, what generally comes to mind is HTML email, rather than plain text. 

Designing for email is much like designing a simple webpage, but there are some key differences you need to take into consideration. You also need to keep in mind that email is a push, rather than pull, communication.(webdesignerdepot.com)