Guest checkout and email address

-- url of the page with the problem -- : atv-utv-accessories.com
-- HikaShop version -- : 2.3.2
-- Joomla version -- : 1.7
-- PHP version -- : 5.3
-- Browser(s) name and version -- : all

I have no registration enabled for checkout, (we do not want users to register) If I do not put login in the checkout configuration, then the address fields do not show up. So I have to put login, if someone who has already bought something comes to the page and enters their email address, the cart will not allow them to checkout. I am confused as to optimum settings and checkout layout for a cart with no user registration needed.
This is what I have right now
cart,login_address,shipping_payment,confirm_cart_status_fields,end

Hi,

if someone who has already bought something comes to the page and enters their email address, the cart will not allow them to checkout

Do you have any error message display when the checkout refuse the email address ?

HikaShop guest checkout does not allow to use emails which already have an Joomla user account.
It means that if you just use the email for guest checkout, you should be able to re-use afterwards.
But if you create a Joomla account with the email, HikaShop won't allow you to use this email because you can "login" with.

Regards,