Starting to do some testing to see how engaged people are when they go to articles from the email. However, is it possible to understand how long someone spent reading your email?

Testing out long text vs short CTA focused emails. Obviously more people click on the short CTA emails, but I am curious to understand if I can see if someone spends a specific amount of time in the email, then spends more time on the page after they click.

However, I know for examples on Apple Mail, whatever the top email is is technically open (I Think).

Thoughts/help are appreciated.