What we have is:

Public IP. xxx.xxx.101.21  --> MX1 Inbound gateway

Public IP xxx/xxx.198.30 --> TheReal Eamil Server

 

Both the TheRealEmail server and the MX1  have access to common internal network:  192.168.50.X

The RealEmail server is on 192.168.50.5,   and the MX1 server is on 192.168.50.55

 

What it looks like is that the MX1 server takes the email (as one of the gateways... ) but rather then sending via the intranet 192.168.50.x  route, it sends back out to the public I/P to the RealEmailServer.

 

So we changed it the routing for outbound to:
  Routing--> Outgoing Gateway --> 192.168.50.5  (the RealEmailserver)

We want to keep the traffic internal, once the emails are "accepted" by the MX1 server, and send via 192.168.50.X to realEmailserver.

 

Is it just a matter of making the RealEmailServer as the outbound gateway for the MX1 server??
As I test this, the RealEmailServer tags this from MX1 ( unknown host 192.168.50.X).
There are zero settings that have been made on the RealEmailServer, acknowledging anything about MX1(at all.) 

 The MX1 has designated:

    routing-->IncomingGateway: DomainForward: I/P Address 192.168.50.5

 

Am testing this as write, but hearing the best practice approach, is desired.