I just created our support desk today. I created two branded support portals using the Multi Product feature and configured it's email and domain name.
In testing the support email for the Product support the confirmation email includes all the details of the primary support desk rather than the Product support desk, which poses a significant problem.
I have looked for support documentation on how to properly configure the settings so that the confirmation email will include the Product support details but I have been unable to find any documentation.
I found the solution in Admin > Email Notifications > Requestor Template and then replacing the Insert Placeholders with the Product versions.
You should definitely provide this instruction as a notice when someone sets up a Multiple Product instance as it was not easy for me to find documentation on making this change. I simply kept searching until I found it. Having a notification would have save me a couple hours of searching.