[exim] Forward all outgoing mail to one email address

I'm setting a dev server to test some email delivery and would like
to just have all of the outgoing mail go to specific address so I can
check that everything is working properly with the content.

I setup a system like this several years ago, but I can't for the
life of me remember how to do it now. It may have been with Exim3.

Can someone point in the right direction?

Since this is just a dev box, I'd like to just have one simple filter
that just traps all outgoing mail and forwards it to another email
address.

Thanks,
Keith