Answer:
You type the content if your email in "Subject"
Explanation:
The subject is where the person opening the email see's what the email is about, therefore the content of the email. Putting what the email is about in subject allows the receiver to see what the email is about before clicking on it to verify the importance.
This question wasn't very clear therefore it is either right below the subject where you write the actual email or it is the subject. Where you put the "contents" of your email, if it is not subject I apologize and it is the space below subject, but my best educated guess would be "Subject".
