Record of all communication sent with invoices (etc.)

I would like to suggest there be a way to view any comments send with an invoice (etc.) when emailed to the client. I needed to refer back to to comment sent with invoice recently and found you can only view the invoice and no way to recover info in email/comment sent and I forgot to CC myself which I normally do. I feel it’s important to have record of ALL communication between designer and client. -Hope this made sense..lol