How to raise the second mail server without touching the first one?

Question

FreeBSD

Hello.
We have: a "tail" comes from the provider, which is stuck into the mail server. Everything works and therefore touch no way. It is known that there is some kind of BSD-based combiner and, in fact, that's it.
It is necessary: ​​to raise the second server
Thoughts are as follows:
1. Some kind of piece of iron that will mirror the traffic passing between the wire and the mailer to one more port.
2. Not exactly what you need, because you will need to get into this server - for sure, because BSD has the ability to independently mirror incoming traffic to another interface.
Maybe what else?
Alas, there is no money now. That is, if there is exactly what you need, we will find it, but for experiments - no.

Answer 1

Given that "there's some kind of BSD-based combiner" - shouldn't you learn first? Courses there, or books ... Google for example?
I must say right away that your network has already been built incorrectly and it takes experience to redo it. And you don't have it.
Well, to the answer .. Are you aware that you can raise many domains on one mail server?
And if you need a backup mail server, then it would not hurt to have a backup provider