[Exim] default address

I am trying to set up a default address to which all mail that is not
delivered to a valid user on a particular system is sent to. I thought
under exim 3 that you used smartuser for this but I cannot find
smartuser in the online manual for exim 4 (I am using 4 on the new
system). Could anybody point me at the bit of the documentation I should
be reading. I would just like any email that is addressed to that domain
but does not have a valid local user to be dropped into default mailbox.

Cheers

Ron
--
Ron McKeating
Senior IT Services Specialist
Internet Services and Software Solutions
Loughborough University
01509 222329