One of my observations, both with this client (who I’ve been working with for more than two years) and with other clients, is the focus on subject line testing. My personal goal, with this project and in general, is to get email marketers to go beyond just testing subject lines and look at other elements that might improve response. There are a lot of "100+ things to test in email" lists out there. But these leave me a bit flat. Many of the items they list are specific to an industry or type of email, and many aren’t things that will normally drive large increases in response. So here’s my much-less-impressive sounding list of 15 types of email tests you can do, along with some narration on my personal favorites and least favorites. The list is roughly organized from what generally provides the most to least value in terms of increased performance for the long term.