Hi, integrator. The main recipients can be seen directly at the Email column in the Sales transactions page. For the carbon copies, you'll have to click the View/Edit link of the specific invoice, then click the Cc/Bcc link just below the customer's main email address.

If you're unable to see the Email column, click on the small gear icon and check the box next to the Email option to display it.

To save time, you can add those addresses directly to the Customer's Profile. This sets them as the default, so they’ll auto-populate every time you create an invoice.
Leave a reply below if you have any other questions.