Using add_action
I am able to add a function to the plugin.
// add action to after_record_action
add_action('after_record_action', 'marian_rick_custom_action', 10, 3);
// add function
function marian_rick_custom_action ($result, $data, $format){
// get data from $data[] array
$email = $data['email'];
$key = $data['key'];
// use $data to create a personalized mail
$to = $email;
$subject = "Wordpress Test";
$content = "Hi, this us your key:" . $key . "Enjoy using it!";
// send mail using wp_mail
$status = wp_mail($to, $subject, $content);
}