If you signed up before Aug 9, 2021, please click Previous plans to view your applicable plans.
For each portal on your account, you would have one dedicated primary email address associated with it. The main portal will have a similar primary support email and the product portal will have it's own distinct primary email address.
Existing emails cannot be used while creating a new product. You would have to add a new/unique email address and associated it with the New Product which is being created.