I currently have an edge transport role on IP address 192.168.14.10, and a hub transport role on IP address 192.168.12.10.
Rules are setup to both publish a listener on the external IP no:1, as well as to allow sending of SMTP traffic via "external".
All MX records are setup correctly, and all SMTP traffic works fine incoming and outgoing, with external email server being able to confirm that the sending IP matching my External IP for the Edge role.
My question is this: How do I publish and configure a second SMTP role, ie. a second Edge transport server? I can set it all up fine, but of course all traffic from it appears to come from the primary external IP, so external mail servers reject messages from it with it's IP not matching it's name.
This is what Microsoft says on the matter:
"If you have multiple SMTP servers behind the ISA Server computer, only one SMTP server can be published with the primary IP address of the external network adapter. In this case, you install an SMTP gateway that will handle all SMTP traffic for all of your SMTP servers. You need to configure the following"
That's all well and good, but sounds like a single point of failure to me! Plus it doesn't allow for spreading the load from the Edge servers. Does anyone have any idea how I could make this work?