Add Customer Email to Billing Address

Please can you tell me how to add a customers email address to the billing details.
I understand which file to edit and I have tried this but it does not work:

<?php
/**
* @package HikaShop for Joomla!
* @version 2.0.0
* @author hikashop.com
* @copyright (C) 2010-2012 HIKARI SOFTWARE. All rights reserved.
* @license GNU/GPLv3 www.gnu.org/licenses/gpl-3.0.html
*/
defined('_JEXEC') or die('Restricted access');
?>{address_company}
{address_title} {address_firstname} {address_lastname}
{address_street}
{address_street2}
{address_city}
{address_state}
{address_post_code}
{address_country}

<p>Contact Details:
<?php echo JText::sprintf('TELEPHONE_IN_ADDRESS','{address_telephone}');?>
{customer_Email}
</p>

I just need to know what tag to use for the email address.

Thanks,
Sean R.

This file only handle shipping/billing address fields display.
The customer email is not an address field and there is no tag available for it on that view.

It's actually not that view that you should edit but the view files which call that address_template view file.
For example, for the invoice, it's the "invoice" file of the view "order" for your backend template where you can add: after:

How/where can I add this to the Shipping Invoice? The above adds it to the regular Invoice under the billing address but not to the shipping invoice. I'm not sure which file needs to be modified for it.

Thanks!
-Matt

It is the same file actually with the same modification as the file is used for both the invoice and the shipping invoice.