Hi,
HikaShop sends two emails to the customer, one when the order is created at the end of the checkout before going to the payment gateway, and one when the order status changes to confirmed when HikaShop receives the IPN from PayPal.
It seems that you're saying that your customers don't receive the second one.
In that case, you might have a problem with IPN:
www.hikashop.com/support/documentation/i...or.html#notification
And if you don't want your customers to receive the first email, you can go in the menu System>Emails and disable the "order creation notification" email. Note that this menu is only available in the Business edition with HikaShop 2.x versions while HikaShop 3.x offers it for all the editions.