yes manualroute seems to pop up in my researches.
i have had this working in the past using allow_localhost, so i'm perplexed why exim is still balking on it. maybe i didnt use dnsroute driver
(in case i wasnt clear, another mta is on 25, exim on 26, trying to cause exim to route an address whose domain is the box, to the other mta)
whose 1st mx of the domain is the box*
the reason is that internal requests, eg the mail command, php code, etc will generally target exim on port 26, and not the primary mta on 25