How to setup srv1.domain.com, srv2.domain.com with mutliple domains per VPS
I want to setup this:
VPS 1: hostname srv1.mydomain.com
VPS 2: hostname srv2.mydomain.com
On both VPS-es I want to host like maximum 5 websites.
For all the websites I want mailserver per site. Like mailserver hostname is: mail.website1.com and for the second website on VPS 1 it would be mail.website2.com.
I know how to setup a VPS with mutliple domains (done this using VirtualMin), but how to set up multiple VPS-es where the hostname is a subdomain / hostname of my purchased domain (srv1. or srv2, etc.). How would I setup mail correctly per server?
I now was thinking about this as DNS for mydomain.com:
srv1.mydomain.com points to Droplet 1 (A record)
srv2.mydomain.com points to Droplet 2 (A record)
In DOs DNS manager I have set-up a add a new website for every website on srvX. The A records of this website redirects to either VPS1 or VPS2 depending on what srvX the website is on.
This seems to work, but now: how to setup mail? (just the DNS settings, I already set up mailservers with postfix and dovecot)
Should I just add mail.websiteX.com per website, which points to a specific VPS?
Because I have read that the VPS name has to be the mailserver name for the PTR record to setup correctly. That would make it impossible to add multiple mail.websiteX records?