I think that I am looking for a mail gatway also.
Would this work ?
From the Spec:
http://www.exim.org/exim-html-3.30/doc/html/spec_28.html#IDX1646
#for internal mail
through_firewall:
driver = domainlist
transport = remote_smtp
route_file = /internal/host/routes
search_type = lsearch
#for all other mail
# transport
local_delivery_internet:
driver = pipe
group = mail
return_output
log_output
suffix = ! washcoll.edu
# director
local_user_outgoing:
driver = localuser
suffix = ! washcoll.edu
transport = local_delivery_internet
host_auth_accept_relay = *
host_accept_relay = 0.0.0.0/0
/internal/host/routes
#all wash mail would be directed to the internal server
washcoll.edu: blitz.washcoll.edu:mail.washcoll.edu byname
> All incoming mail is forwarded from the hub to a blitz-mail server for final deliver to
> the client.
>
> All outgoing mail is passed out indirectly through the client to the
> SMTP machine or from Blitz-mail.
