One of the benefits of your content going nice and viral is that places like Twitter, Facebook, Stumbleapon, Digg and Delicious where people share your content are great for giving SEO juice.
Emails on the other hand are not. Traffic from an email is not seen by Google or Bing in the same way and subsequently cannot help get your site up the search rankings.
This is why email does not own social and why SEO tends to run social.
There are more SEO benefits from social than direct revenue.
Q: So what do you do?
A: Use video in email the same way as you use everything else. To get the click through!
Like TV documentaries are a window on the world, emails are a window on the web;
They have a frame and glass to only show you what it can and wants to.
Use the video to increase engagement and get more clicks.
If you make the video too good, people will have no reason to visit your site unless they absolutely want to buy something or they think there are more videos that are that good.
Of course people will still forward popular emails to each other and with a video they are more likely.
But where you give the opportunity to share the email on a social network consider making the share button share the url of the landing page instead of the browser view of the email.
Of course you could also host a version of the browser view on your own site and link to that and still get the SEO juice but you are asking someone to take and extra step to achieve your goals for them.
A full web page / dedicated landing page will also be more attractive than an email, it can do more. For email there is only really novelty value to go with.
More money is still going to SEO and Social than email, so why not share links back to your site rather than the actual email, and have something to show the purse strings about how email can beat SEO at its own social game?