Think as well about the kinds of metrics you're evaluating. You probably know that interaction with email campaigns is measured through open and click-through rates. While it's meaningful to review email response in this way, if this is all you measure, you're missing the bigger picture of the value of email to your company and its customers. These rich metrics in the email are great. However, there is a distinction must be made between:

When you’re working with marketing emails, always think about recipients on an individual level. Consider where each recipient is on their journey with you. Notice opens, click-throughs – any engagements or behaviours, and pin down behavioural patterns which often point to purchase. Every time you send out an email campaign, you'll be collecting behavioural data, use it to inform your email strategy.
This article is by far one of the most interesting and fun articles that I have read in a long time. I say fun because the points mentioned here are simple and easy to read. They are not long passages that speak a lot and tends to lose focus. On the contrary the points mentioned here were in short crisp sentences that did not bore me but made my read a pleasurable one. Thanks!