I am sorry there is no short way,
Specifically you can backup a system running with Exchange on box and restore the
backup information onto a clean install of the same version of Unity that's connected to
Exchange 2000/2003 server off box. Any combination of 55/2K/2K3 and on/off box should work
fine.
The disaster recovery tools will make the changes in the database and registry to make
this transition work. You cannot, however, migrate between Exchange back ends and Domino
back ends or vice versa.