The option under Gear > Company > Contact Info (shown below) is misleading. It suggests that the email address that customers will see when receiving emails will be the address added in this field... but it's NOT! Invoices are sent using a generic sending address of QuickBooks @notification.intuit.com. I sincerely hope that someone from Intuit replies saying I've completely got it wrong otherwise this is one million percent unacceptable on so many levels.