When I use an email template, the subject is filled in but the email body is empty

Before using Simple CRM email templates, it is important to configure the email software you use in Simple CRM.

For that:

1) Go to the Admin module (top menu -> Admin)
2) Click on the "User List" tab
3) If you are a Simple CRM Administrator, click on the user concerned, otherwise, go directly to step 4
4) In the "Email software" field, select the email software you are using
5) Enter your password twice (or that of the user concerned)
6) Click Save