I have a private network with an email server, basically for an intranet service. I also have a server I want to use as a relay to send and receive mail for the intranet mail server. I've seen many guides using Postfix's
relayhost config option to have mail sent out of a server.
I want my relay configured to get mail for my domain and forward it over an SSH tunnel to the mail server on the private network. I also want the private server to send email outbound to the internet. To get started I have a VPS running Debian 9, I just need to know how to configure postfix to do these two things.
The answer to this question would be how to modify the default Postfix configuration to achieve this two-way relay solution.