Sending an email to 'x' contacts, and cc'ing one contact results in the cc receiving x number of emails

Users have been complaining that contacts have been getting multiple emails. I tracked this down to a problem with 'cc'. If selecting a number of contacts to send an email to (where that number is 'x') and cc-ing a contact, the cc contact will receive 'x' emails. e.g. my user selected 14 contacts, and cc'd her boss in - who got 14 emails! I tested this on a 4.5.8 system with 2 addressees and the cc got 2 emails; then on a different 4.5.8 system with 3 addressees and the cc got 3 emails.

I guess the 'cc' logic is incorrectly included in the same loop as the addressees. This problem is of course not present in bulk emails.