Email marketing is a smart way to continually drive engagement from people who already know (and hopefully) trust you. So understanding effectiveness is looking at – how many people opened the email, how many clicked through, how many unsubscribed, how many new people signed up, how many people shared the newsletter.
Often email marketing platforms will help by providing benchmarks. Which is a useful starting point, are people opening my newsletter as much as my peers.
Then, of course, looking at downstream marketing analytics. Do email subscribers subsequently go and make a purchase, or visit a store, or speak with our sales team.