The subject line of your email is the most important part of your emails. I guess we all know that by now. It’s what makes people open your emails (together with other elements such as what recipients see in the preview pane of their email client).
Earlier, I explained why it is important that you test your subject lines and even why you should do it in real-time.
What is sometimes forgotten is that there also has to be a clear link between the subject line and the email copy. Things should be consistent. Just like the messaging, content, style and many other aspects of the landing page should be consistent with the email.