Access one of your business partners and select the Contacts tab. To add a contact, click on + and fill in the fields. To delete one, use the trash.
Within a quotation, booking, credit note o invoice, choosing this business partner, you can select one of his contacts from the same field.
In this way, when a document is sent by email, the e-mail address of the contact is inserted into the corresponding row, not the business partner’s.