Hi Nicolas,
I am using HikaShop Business 2.6.4 and Joomla 3.6.4.
I created a custom field named address_email.
The following code was added at the end of the email in system -> emails, order creation notification, order creation, notification, order notification:
<?php $data->customer->user_email = array($data->customer->user_email,$data->cart->billing_address->address_email); ?>
And I added the following code in template isis (set as default), back end, mailform just before <table class="table">.
<?php
$class = hikashop_get('class.order');
$order = $class->loadFullOrder($this->element->order_id,false,false);
$this->element->mail->dst_email.=$order->billing_address->address_email;
?>
The only emails disabled are 'wait list administrator notification; and 'subscription expired' notification.
Kind regards
Lene