[Exim] mixing local and non-local users of the same domain

Hi all,

Is it possible to have local and non-local user of the same daomian
in a exim 3.x configuration?

the idea ist to migrate users of the same domain from one machine to
another within a few weeks.
if i set the mx to the new machine (exim) beginning to setup the
useraccounts there and some other users are still on the old machine,
exim should forward nonexistend user to the old machine.

can i do this within a director and pass the mail to a domainlist
router if it fails?


thank you for advices...

Robert