Email marketing is changing.

Today, more and more people are viewing emails from their mobile devices. People are getting more email than ever. And products like Priority Inbox show users the most important emails first.

So, how can your marketing email stand out in an already crowded inbox? The first step is with the subject line. Because if you can’t get them to open it, then the actual email message doesn’t matter. After that, there is seemingly an endless list of elements to test.

And this is what’s great about email – there are so many things you can test.

The sender, the subject line, the preview snippet, the layout of the email, and the CTAs make email one of the most testable assets for a marketing team.

So, where do you start? If you’re lost, today’s infographic should provide some guidance. Even if you are already an email marketing pro, you may still be able to pick up some ideas.

About the Author: Zach Bulygo (Twitter) is the Blog Manager for Kissmetrics.