wordpress - 格式化电子邮件礼品券

I'm using an older gift certificate plugin (6 years at least) on my wordpress site and I want to be able to format the way the gift certificate looks. I've emailed the developer with my questions but never received a response so I'm reaching out to anyone that may be able to help me crack this nut.

My questions that I had are:

1. Where and how is the email sent from? Does it originate with my site or with Paypal?
2. If it originates from my site, is there a way to format it to make it look the way I want it to?

The following link is to the downloaded source files: https://drive.google.com/folderview?id=0B0yqpr4p6kePSGtudWJHYWdVQXc&usp=sharing

I've gone through every file trying to track where the email is being sent but I cannot find it.