debug email template for forms

How do I create a debug file (or output) to check errors in my email template I have created for a form response?

I have set debug to true in config.php

 define('PERCH_DEBUG', true);

Also I tried to output something in the email itself, by adding this in the email_template.html

<?php PerchUtil::output_debug(); ?>

How can I debug my forms email template?