Mail Routing (NRPC) to Single Server

I have searched the forum with no luck in trying to get this working - if there is a previous post on this, let me know -

I have a Domino server (BES server) that I wish to route all messages (Notes NRPC mail) to a specific server within the same domain. The BES server is currently in the NNN with all servers and there is a message routing connection document to the HUB server. The BES server is in a DMZ-like environment that does not have access to DNS, so for mail to route properly (hub-spoke style), I need a connection document to every mail server.

What I would like is to have all message routing go to a single server (Hub) which is within the internal network, and let that server handle routing to individual mail servers.

I have tried removing the BES server from the NNN, but then I get errors trying to route any mail - I have also tried using smart-host, but that has no effect on NRPC routing (or at least none that I could see). SMTP is not enabled and cannot be.