You can use {{hasOpened}} and {{hasClicked}} within the email. The value will be true or false depending on if that prospect has opened a previous email or has clicked a link in a previous email.

This means you can do something like this to send custom or different messages to propspects whether they've opened a previous email or not:

{% if hasOpened == true %}
✅ You Opened one of our previous emails!
{% else %}
❌ You did not open one of our previous emails!
{% endif %}