I have a server machine. If an incoming connection comes on https://abc.com:443, it's redirected to internal port :81 and if https://xyz.com:443, it's redirected to :82. This works fine.

Now I have 2 SMTP mail servers running on this same machine. Of course both cannot listen on port :25. I want to do the similar thing. e.g. abc.com:25 should be redirected to internal port :26. With IIS somehow I am not able to do it.

Is that possible and which tools can be used?

[Note: ChatGPT gives a detailed answer with tools like Nginx (with Stream Module), HAProxy, Postfix with Transport Maps.]

  • You seem to be asking about a reverse proxy. Sorry, protocols above the transport layer, host configurations, resource or product recommendations are all explicitly off topic here, see the help center. You could try on Software Recommendations probably.
    – Zac67
    Commented May 28 at 6:26
  • 1
    IIS can't do it because it's a WEB server, not SMTP. Yes, there are various software projects out there to do this, but in general, one just lets SMTP do what it's designed to do... "relay".
    – Ricky
    Commented May 28 at 13:51
  • 2
    Yes it sounds like you are trying to do both things the 'wrong' way. Generally you do not need to run different websites on different ports, you simply let the web server serve different content for different hostnames. Same for mail, the server uses one port and handles mail for different domains as it is configured to do. No need for multiple servers/server installations etc. Commented May 28 at 14:14