[Exim] transport smart_route: cannot find transport driver "…

Hi all,

I'm trying to set up exim so that one of the local domains can relay
outgoing mail via a specific host. I got the above error when I tried adding
the following lines to the transport section of the config file:

(I've substituted the values assigned to driver & route_list to 'protect the
innocent')

smart_route:
driver = local.domain
transport = remote_smtp
route_list = "* specific.domain" bydns_a

I've also tried using send_to_gateway and had very similar results. My
initial reaction is that a transport driver needs to be defined somewhere
somehow (aliasfile?), but I can't find much about it on exim.org FAQ or in
the archives of the mailing list. Can anyone point me to the right place or
offer some guidance?

Thanks in advance,

Joe Atkinson
2nd Line Hosted Systems Support Engineer
Energis Squared