Looks like you figured this one out. Great job.
You should be able to create forms using almost any email provider with your custom HTML form code but it may require some adjustments to your CSS and/or HTML to make it look the way you want it to.
Adding the following classes to your HTML form code should take care of most the work but may require some other minor adjustments to format everything correctly and ensure proper functioning. Below are the important classes:
Form class: thesis_email_form
Name input class: thesis_email_form_name
Email input class: thesis_email_form_email
Submit input class: thesis_email_form_submit
Additionally, for adding a text title & description before the form, use the following classes:
Heading class: email_form_title
Description class: email_form_intro
Hope this information helps.