Multiple e-mail addresses for customer invoice output settings

Hi together, how is it possible to enter more than one E-Mail address when I use the output setting E-Mail for customer invoices? I can add them manually, when I create the invoice in the Output Settings, but is there away to add the addresses directly in account master data under addresses or in the collaboration tab? When I try to enter them and separate them by semicolon or comma the E-Mail address is shown as invalid. Thanks for your reply and best regards Jens Halter