(Part 2) This video shows a free website called Litmus and https://www.litmus.com that allows you to send emails using your specialty HTML files that are meant only for use in email clients. The Litmus web site allows you to test your fancy emails that are developed using HTML code and CSS. PutsMail and Litmus are great for HTML Email Template Testing.
This is an interesting article about Litmus and modularizing your emails.
https://www.litmus.com/blog/email-mod...