Create two textareas, one for create a form template and other for a mail template.
The first one can be included on any page(s)/post(s)/sidebar. The advantage of this methos is have all control on your form. PHP tags will be scaped.
The second textarea determines a template mail that the form. On the template you can use [names] to put your content anywhere.
Sample:
This email was send by [name]
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[message]