Ok, guys I might be wanting to do the unthinkable but here goes.

I know how to run a physical ZCS FOSS on a dynamic IP behind a firewall (IPCop).
Basically, I forward ports 25, 443, 7071, and 22 to the physical server.
I know how to do this configuration with SplitDNS and all that.
In my configuration, I use zimbra to receive a copy of emails from my real email server.
Also, I have my users use zimbra itself to email back and forth.
Under the hood, I use SMTP Auth technique to relay emails from zimbra to my real email server.
I don't use the desktop client, just to be clear. All web

Now why couldnt I setup a 2nd physical box and forward ports as shown:
225 -> 25
4443 -> 443
7701 -> 7071
2222 -> 22
It seems the real question is this.
To pull this off wouldn't I need to get into the 2nd physical server configuration and tell it not to use port 25 but rather port 225 ?
If that's he case then I wouldn't need to port forward 225 to 25 right ?
So, where and how do I tell zimbra not to use the standard port 25 for it's business but the port I say ?

Any other problems with what I want to do ?