The Cc: header is one of a few that specify the list of primary recipients. The sendmail program treats the Cc: header no differently from the way it treats the To: header. From the user's point of view, the Cc: header implies that there are recipients to whom an informational copy of the message was supplied.

The Cc: header should never be declared in the configuration file.

The field for the Cc: header must contain one or more properly formed addresses, where multiple addresses must be separated by commas.