Email more than one customer

Is it possible to have a second email address set up for a particular customer so that both people will get all emails when there is any communication or orders placed.

I haven’t tested with ALL mail functions, but if you put a comma (,) and space between 2 emails it will send to both,

it works within admin pages, don’t know whether it would work from the customer side.

Under the customer profile, I tried to put a comma between two email addresses and it told me that the email address was invalid.