Hi Azure, in a few words, real HTML5 video on email is not well supported. Only Outlook.com and Apple mail will show real HTML5 video. It does not work in Android either, and it stopped working in iOS since version 8. From the email marketing point of view, video in email is a flawed idea. If you are looking to WOW your users, a well designed and well executed animated .gif might do the trick. I created a mobile FAKE VIDEO PLAYER using an animated gif with a play and pause button. The only clever use for something like this could be in a SHOW PREVIEW, where y client can tease a brief "video" of an upcoming show. HBOGO does somethign similar in their weekly email newsletter. You can check it out here in my github repo https://github.com/micposso/fake-email-video-player.
Thank you Justin. I'm curious to hear how that function works. If the app is retrieving images to render the "peek" version, does that mean that a user could potentially see an incomplete rendering of the email? or are the images downloaded first so they are ready when the users "peeks" the email?