Most people receive their email on their mobile device. Some of these devices would mark the email as open even if the contact didn't look at it.
Also, just because someone opened an email doesn't mean they read it.
Engagement with your email list needs to be measured by using click-through rates.
Keep the information short within the email and include a learn more button.
Now the people who click the link are interested in what you're sending.
Concentrate on sending engaging emails more than just building the number of contacts.