The BCC action sends a Bcc (blind carbon copy) to a recipient or recipients configured in the rule. It is one of the "monitor" class of actions. You can only configure a notification to be sent to an address in your own domain.
From the Monitor section of the Action page, select BCC.
Type the email address of the recipient in the field. If you have more than one email address, enter them in the field separated by commas or semicolons.