[Exim] Fowarding email to/from a particular user

Hi all,

I am trying to find a simple way in Exim where we can send a copy of emails
coming to/from a user to another email address. This has to be without the
user's knowledge, so they continue to send and receive emails as normal but
any mail activity to/from their address is CC'd to another email address
for monitoring.

I'm not trying to do anything dodgy here - just assist the police in investing
one of our users who is involved in dubious practices! Can I do this using
Exim rules?

Cheers,
Ray