My customer's order status remains at "new order placed" at my user order page and admin orders maintenance even after successful transaction at worldpay

Have you enabled Callback response? option and entered the Callback url as http://www.yoursite.com/payments/worldpay_confirm.php
in the Configuration Options of the Worldpay admin?
 
Successful transactions should then appear as validated.
 
I just need to figure out how to get the emails responses working properly - any suggestions appreciated?