Email CSS Animation Guide https://www.emailonacid.com/blog/article/email-development/css-animations-part-1
Three steps to mastering the email GIF https://www.mailjet.com/blog/mastering-the-email-gif-frame-by-frame/
25 Wonderful Examples of Animated GIFs in Email Marketing Templates https://mailbakery.com/blog/25-wonderful-examples-of-animated-gifs-in-email-marketing-templates/
Animation in email – does it serve a purpose? http://www.pure360.com/blog/blog-entries/Animation-in-email-does-it-serve-a-purpose