I was searching the Forum with the very same question, and found this topic.
Xavier, I have two questions for you:
1) Could you elaborate a bit more on your response? By that I mean, could you give us a better example of what you mean by "check the products in the cart"? I am quite proficient in PHP, but without the in-depth knowledge of the internals of HikaShop, it is quite difficult to understand what you mean by the specifically.
2) Wouldn't it be much simpler (and easier) to add this functionality as an enhancement to the configuration? This could be a simple as adding a "Order Notification Email Address" column to Brand, Category, and Product, which would allow such configuration to be as granular as is necessary, and during the course of the email generation to load an array of email recipients, and then eliminate the duplicates before finally addressing the email.
Question 2 is really more of an enhancement request. What Mat and I are suggesting is really quite a common occurrence, and adding the functionality I described would make for a great enhancement to your product.
Thanks and Regards,
David