[Exim] Moving exim server to another machine

I want to move my mail server to another machine - my plan is to
shutdown the old server, and bring up the new machine - using the same
IP address etc.

However, there will probably be messages waiting to be delivered on the
old server, therefore I would like to restart exim on the old server to
send all waiting mail to the new server with no local delivery - is
there an easy way of doing this. I guess I would have to set up
something base on a "route_list", but would appreciated some help ...

Thanks

James Pearson