Setting up an email proxy server?

Raymond Holguin asked:

So i have 4 application servers and each one directly connects to an SMTP server to send out the emails. What I want is to have something in the middle that my servers connect through instead, and that middle-ware (?) will be what pushes my emails through to the SMTP server. So this SMTP server will only see emails coming from one source instead of 4.

I am unfamiliar with how this sort of thing works, but It sounds like I need to create my own SMTP server which would accept the incoming requests and send them off to the main SMTP?

I just need something very lightweight and basic as its just going to be these servers accessing it and it will be only have the function of relaying these emails. Any help to get me going in the right direction would be appreciated.

UPDATE

Thanks for the corrections in that what I am looking for is an email relay. There is a reason though I used the work “proxy” and I mistakenly did not explain that clearly.

What I want is the new relay to assume the role of the sender of the email. With a web proxy the user IP is hidden and the traffic appears as though its from the proxy IP. That’s what I want for this email relay. My relay IP should appear to be the sender, not the application servers as those should be hidden.

So no matter which application server sends the email, the sender IP should always appear to be the relay I setup. Is that possible?

My answer:


This is called an email relay, and any mail server can do it easily.

A setup with Postfix, the usual default mail server, is as simple as installing it from packages and then setting mynetworks in main.cf to the IP addresses of the machines allowed to send mail through that host.


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