Hi Chris, On 24/05/2020 21:46, Christian Baer wrote:
I want to move the full fledged server
That server is known as the 'primary mail exchanger' (primary MX).
to the machine in my basement
You'll need a static IP address from your home ISP, and be able to set the reverse DNS to match the forward DNS hostname. Can your home ISP provide static IP addresses and reverse DNS hostname management? If not, don't proceed with this project.
and want to use mx1, mx2 and mx3 as smart hosts that accept mail for my domains and forward it to the server in my basement.
Mail smart hosts are sending hosts on a LAN that are smart enough to know which hosts on the LAN to relay outbound mail for.
I think you mean you want your remote rented servers to all be backup MX machines, as mx2 & mx3 are now. Simple:- configure mx1 as another backup and have your home machine as mx0 (i.e;- the primary MX server).
They also should relay mail sent from this server. Perfect would be a setup where they'll be used round robin.
DNS is your friend: configure relay.mail.your.domain with the IP address of all 3 remote mail servers. Use this DNS hostname as your outbound relay. Set your authoritative DNS daemon (NSD, BIND, etc.) to serve records in round-robin fashion. Done!
But if you have a static IP address & rDNS at home, you don't need to relay via your remote servers. Your primary MX can send to the world.