message.twig

<h1>Congratulations to {{name}}</h1>
<p>You're really great so we're giving you a prize of {{prize}}</p>

my_mail_file.php

my_ajax_mail_function(){
	$data['name'] = 'My User Name';
	$data['prize'] = 'Vacation to Paris';
	$message = Timber::render('message.twig, $data, false);
	wp_mail("user@gmail.com", "You win a Prize!", $message);
}