Port 25 (SMTP) through PFSense + HAProxy to specific email server

[billsecond]

Hello, I have multiple email domains, and multiple email servers.
I want to scale down to a single IP Address, but if I do, is there a way to direct inbound email traffic (port 25 SMTP) to the proper destination server?

I do this for Web traffic, but this works well because the header contains the information that HAProxy needs to perform the proper redirect.

Here is where I think the answer is no! When the server sends the Email to my server, it performs an NSLookup to find out what the domain is. I would assume that in most cases, the mail servers next step is to resolve the domain to get the IP address. When this happens, it connects to the destination server (in this case mine), then says this IP address is connecting to This IP address and here is the email... Done...

So I don't think this is possible because I don't have the same host header information.

Have you had any experience with this?