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