I am interested in making sure my customers are never emailed via quickbooks. I use a different customer management system and use quickbooks only for accounting
You can leave the email address field in the customer's profile blank and set the delivery method to None in the Payment and billing information. Every time you create a transaction for that customer, the email address won't auto-fill.
You also have the option to view and check them by batch by adding an email column. From the Sales menu, select Customers. Click the Gear icon above the ACTION column. Then, mark a check on the Email box.
I'll be around to help you with your concerns. Have a good one!