I think this email also makes quite a brilliant use of responsive design. The colors are bright, and it's not too hard to scroll and click -- notice the CTAs are large enough for me to hit with my thumbs. Also, the mobile email actually has features that make sense for recipients who are on their mobile device. Check out the CTA at the bottom of the email, for example: The "Open Stitcher Radio" button prompts the app to open on your phone.
Emails triggered by milestones, like anniversaries and birthdays, are fun to get -- who doesn't like to celebrate a special occasion? The beauty of anniversary emails, in particular, is that they don't require subscribers to input any extra data, and they can work for a variety of senders. Plus, the timeframe can be modified based on the business model.
If links and looks are set, begin interacting with the page. Abandon it, adjust the window size, convert. Are error messages appearing when they’re supposed to (if, for example, you don’t input all the form’s required info)? Is your CTA button working? If you abandon the page, are you retargeted with ads? When you resize the window, does your landing page respond accordingly?