route.cfg

hi, i have a route.cfg specified routing all messages for a specific domain off to the ip address of an exchange server. usually works well but problems with the exchange server means some messages are not being delivered, but instead of the message being queued for delivery they are going out via the 'standard' route to the external smart host which fires back an undeliverable as it obviously doesn't recognise the internal domain thats specified.

i assume this means the route.cfg file is an order of preference as opposed to a fixed route, if thats the case is there a way of forcing it to only take the path specified ?

thanks