What Do Scalable, Fluid, Responsive and Hybrid Email Design Mean?

http://blog.chamaileon.io/what-do-scalable-fluid-responsive-and-hybrid-email-design-mean/

The growing appeal of responsive-aware email design

http://marketingland.com/growing-appeal-responsive-aware-email-design-186727

Understanding Retina Images in HTML Email

https://litmus.com/blog/understanding-retina-images-in-html-email

Email CSS Animation Guide

https://www.emailonacid.com/blog/article/email-development/css-animations-part-1

Adding Interactivity to Email Design

http://www.emailmonks.com/interactive-email-advancement.html

How to Design Emails for Smartwatches

http://www.benchmarkemail.com/blogs/detail/how-to-design-emails-for-smartwatches