Hi there, BretyboyOO.

We understand the pain in entering the email addresses again for customers when sending different forms. It has been sent as feedback and I'll send another one. It'll be reviewed and reevaluated by our product engineers. We would not know when is the turn around time to add it is a new feature. But, rest assured we are doing the best in upgrading the software. You can see the changes and updates in QuickBooks in our blog website. 

On another note, you may use the Recurring Transactions feature. You can enter different email addresses for a customer when creating any sales forms (invoice, estimates, etc.). Please see this reference for the steps: Create templates for recurring transactions

We are here if you have any other questions. Please post them here.