Quark Ecommerce - customers don't get email with invoice

Hi,
I marked that some of the customers don't get the email with invoice (controlled only with Pay by Invoice option).
The customers who don't get the invoice have @hotmail.com and @yahoo.com emails (may be some other too, I don't know).
I controlled also that the invoices come to @gmail.com, @mail.ru and some local mail services.

Our online shop: http://www.dalanre.com/shop
You can do the trial purchase if you need, just mark "Quark" so we will know that's not the real order.

Hi,
sorry but e-commerce extenstion used in Quickstart is not our production as you may know, so if you're using VM3 you have to ask on their forum. I guess you are not first or last with this issue.