Hi kamstudio, welcome to WebmasterWorld!
It looks to me like everything in the <settings> node are merely formatting options for the HTML form.
So, step one will be to parse the XML and render it into an HTML page. You can do that with an XSLT stylesheet, or you can write a PHP script that does it using some of PHP's built-in XML parsing tools.
sending mail via PHP is easily accomplished with the mail() command.
So what you'll do is set the "action" attribute of the <form> do it posts to a PHP script. Then in that PHP script, get the data from the $_POST array, format it the way you like, then use mail() to send it.
There are lots of tutorials explaining this on the www, and many in the PHP forum who can help if you get stuck.