[Dovecot] CCing outbound IMAP mail?

For some users on my site I'd like to be able to CC a particular user
on all outgoing IMAP mails. Incoming I can do but don't see how to do
outgoing. Ideas?

Dave

-- It is told that such are the aerodynamics and wing loading of the
bumblebee that, in principle, it cannot fly...if all this be
true...life among bumblebees must bear a remarkable resemblance to
life in the United States.

-- John Kenneth Galbraith, in American Capitalism: The Concept of
Countervailing Power