In the sending screen for your invoices and quotes, there is a checkbox next to each contact to Cc the contact to the email.
If the checkbox is ticked, it means this contact will be Cced to the email you will send to the other contacts mentioned.
If this checkbox isn’t ticked, it means the contacts will receive the email separately (one separate email for each contact).
Under People > Clients, there is also a checkbox for each contact to indicate that you would like this contact to be Cced by default to all the emails your will send with LSP.expert to this client.
If you tick this checkbox, the Cc checkbox in the sending screen will automatically be ticked for this contact, for all your emails to this client.