[exim] Help with router

I am trying to configure a router for the following situation, but I
am not sure how to do it:

We have a rocketseed server (rs.sun.ac.za), exchange servers using
stbhub01.sun.ac.za as a gateway between Exchange and the rest of the
campus. Then we have mail.sun.ac.za (an exim gateway).

Some of the management of the university wants to use rocketseed (let
us call them rocketseedusers) which means the following should happen
to the email:

rocketseeduser --> Exchange
stbhub01.sun.ac.za --> mail.sun.ac.za
mail.sun.ac.za --> rs.sun.ac.za
rs.sun.ac.za --> mail.sun.ac.za
mail.sun.ac.za --> whereever the mail should go.

We use a postgresql database which contains inter alia the fields

user, emailaddress, rocketseed (boolean).

I have to tell exim that when it receives email from
stbhub01.sun.ac.za and the sender is a rocketseeduser the email should
be delivered at rs.sun.ac.za.

I have tried the following router, but Exim does not like "hosts" in
there.

I am not sure how to do it without being able to use "hosts"

 rocketseed:
       driver = redirect
       hosts  = stbhub01.stb.sun.ac.za
       senders = ${lookup pgsql (select emailaddress from emailuser where rocketseed=true}
       allow defer
       transport = remote_smtp
       route_list = rs.sun.ac.za

Can somebody show me the direction please?

Regards
Johann
-- 
Johann Spies          Telefoon: 021-808 4599
Informasietegnologie, Universiteit van Stellenbosch

     "Every good gift and every perfect gift is from above, 
      and cometh down from the Father of lights, with whom 
      is no variableness, neither shadow of turning."       
                                   James 1:17