Email marketing is a tough race to win. A race which, by design, is rigged against you -- the sender. First, you need permission from the recipients. In most cases you have to trick or bribe them into giving you that permission. Even then, there's no guarantee that they will ever bother checking out what you're sending them. 80% of your list members won't open your next email. They won't even look at the envelope. Out of those who do open it, only a small percentage will actually look and read through its content. From a marketer's point of view, this situation is quite depressing. For a user's point of view, that's a blessing. Imagine what your inbox would look like if every yahoo in the world was able to reach your inbox freely.
Enters email design: a craft that will help decide what those (few) users who open and scan the message will do with it. Will they remember your brand? Will they understand your message? Will they be tempted to do something. At this point in the race, you can see the finish line. It's up to you to sculpt a message that will put you on pace with the leaders of the pack and eventually get you there.
Here's a checklist of the design touch points that you need to keep track of, every single time you send an email. If you're going to stand a chance, we can only recommend not to send anything until all the boxes are checked. Don't worry: this list will remember your choices. Just make sure the X's are in all the boxes before you ship 'em.