Postfix: Relay Through a Smarthost, Stamp Origin, Alias Root

MediumNetworking15-25 min

The brief

This host should hand all outbound and system mail to the site smarthost instead of delivering it directly, stamp its mail with the org's origin domain, and forward root's mail to a real admin. Your assignment is in /root/case/assignment.env (RELAY_HOST, ADMIN_USER, ORIGIN_DOMAIN).

Edit /etc/postfix/main.cf and /etc/aliases:

1. Relay — relayhost = [RELAY_HOST] (brackets skip the MX lookup; a :port is fine).

2. Origin — myorigin = ORIGIN_DOMAIN (or mydomain = ORIGIN_DOMAIN + myorigin = $mydomain).

3. Alias — add root: ADMIN_USER to /etc/aliases (then newaliases).

Grading reads the config files (Postfix need not be running). See /root/case/brief.txt.

What you'll do

Relay outbound mail through the assigned smarthost
Set the outbound origin domain
Forward root's mail to a real administrator
Know the main.cf vs /etc/aliases split

Hands-on lab: you work on a real Linux box in your browser, graded on the machine's actual state.