Outlook rules don't offer a BCC action.

The sample code at http://www.slipstick.com/dev/code/autobcc.txt shows how
to add a Bcc recipient using the Application.ItemSend event in Outlook VBA

Another approach, which would avoid security prompts without the need to use
Redemption, would be to create a custom form with the desired address in the
Bcc field, publish it to the Personal Forms library, and then modify the
registry to substitute the published custom form for the default. (See
http://www.slipstick.com/dev/newdefaultform.htm#sub)