If you have a list of contacts, you need to track their engagement! But don't do this based on email opens; do this based on link clicks. These are the people who are interested in finding out more information.
Run a report that tells you who hasn't clicked a link in the last 90 days.
Send them an email asking them if they are ok and that you just wanted to make sure they still enjoy being on your list and receiving your messages.
Create a button to click to tell you they are ok and connect it to a landing page that thanks them for their response.
Anyone who doesn't click the link within a week needs to go.
You want people on your list that are engaged and reliable to take action on your information you send.