arfbefore_admin_send_mail_body

add_filter('arfbefore_admin_send_mail_body', 'your_function', 10, 3);

function your_function($mail_body, $entry_id, $form_id){

    //Customize email body content.

    $mail_body = str_replace('[SHORTCODE]', 'CUSTOM VALUES', $mail_body);

    return $mail_body;

}