In email marketing, one thing you learn pretty quickly is that sending your email is only the half of it. The next part (and arguably the most important) is what happens after the reader receives the email. You track opens and clickthroughs, as well as other metrics, but even this doesn’t provide the whole story.
You should put yourself in your subscribers’ shoes, and ask what you would do if you received your own email. Whether the campaign worked or not depends on the many things your readers do when they get your mail.