In Adagio, if you enter multiple email addresses separated by semi-colons into any email address field, emails will be sent to all listed emails. This would allow you to sent the same email and attached invoice/statement to multiple people.

This may not perfectly solve the CC: request from your original post, but you could include your tracking email address along with the customer address. Or use the MAPI method of sending emails, meaning you can keep track of Sent emails.