Below is the template we use for our Approval Email - which your customer receives when you approve their return request.
You can modify both the Heading "Your return was Approved" and the body in the settings.
To do so, go to the app settings, select the Returns Dashboard tab, and you will find the relevant card in the "Notifications" section.
Can't find the Returns Dashboard tab? You need to activate your Returns Manager first.
Scroll to the bottom of your Exchange It settings and check the last option: "Show returns manager".