<?php
/*
 * Plugin Name: pjw-wp-phpmailer-nosender
 * Version: 0.1
 * Plugin URI: http://blog.ftwr.co.uk/wordpress/
 * Description: Unset the sender on PHPMailer
 * Author: Peter Westwood
 * Author URI: http://blog.ftwr.co.uk/
 * */

add_action('phpmailer_init','pjw_phpmailer_init');

function pjw_phpmailer_init($php_mailer)
{
    $php_mailer->Sender = '';
}
?>