Welcome to the Community page, thank you for your question about the email header on sent emails, currently is no way to remove it from the header. We do appreciate that is not ideal in this case. You have the option of downloading the invoice to your computer and then adding as an attachment to your own email and sending that way as an alternative.
You have clicked a link to a site outside of the QuickBooks or ProFile Communities. By clicking "Continue", you will leave the community and be taken to that site instead.