Can anybody explain me how to setup a backup/secondary mail server please?

add entry to your dns zone file like:
mail2 14400 IN a <ip of backup server>
<domain> 14000 IN MX 2 mail2

and setup normal email on the 2nd server with this domain, when 1st goes down all mail should be on the second.

Miha.

Do I need to add accounts on 2nd server like on 1st server (eg. user@mailserver1.org and user@mailserver2.org)? or just add those records on dns of my 1st domain?

Depends if you want a secondary MX or a slow/manual failover.

Secondary MX will hang on to the mail for queuelifetime or until the primary comes back. Much easier to manage.

Creating mailboxes means keeping them in sync, changing the primary MX to the secondary box (or rebinding ip's) and waiting for propagation. Tedious.

All I want is creating a failover mail.
I just add additional MX record on my DNS.


TIA.

Surely there must be additional configuration for the secondary MX's MTA.... no? Shouldn't you have to configure it as a relay for the first or something?