[exim] exim4 seperate internal mail server??

Could someone please explain OR point me in the right direction for a
howto...

Our company is on a DSL connection, for which we have a debian woody box
as our mail server, running a backport of exim4 (on 192.168.1.1).

We have it configed to accept mail for domain-a.com and domain-b.com for
local users, but now would like it to accept mail for domain-c.com, but
not to the local users... i need the mail for domain-c.com to be
forwarded to another internal server (192.168.1.250). This runs exim4 on
sarge.

I have only done this on postfix and cannot seem to locate the correct
info to do it on exim4... Any help is very appeciated.

Thanks muchly:

Simon