Emailing invoice as attachment - Courtesy Copy Address

Hi,

I'm struggling with using the Courtesy Copy Address in the email invoice as attachment. While emailing works fine, when I try to have a 2nd or 3rd email address in the Courtesy Copy Address it does not work.

Can you please let me know what setup/update should I do? Invoice is coming from Contract (CA/BI interface, BI interface and then invoices approved in Update Billing Worksheet). After approving, I'm retrieving the invoice in Standard Billing and trying to update in the Courtesy Copy Address but whatever I select there is overriding prior default. Most likely I'm doing something wrong. Any help would be much appreciated.