Webmin>Servers Index "No Route to Host"

Debian 10
Webmin 1.96

Hi guys,
I am running a backup server for my email. I got a notification from client today saying that incoming email isnt working.

In looking at a copy of the bounced email that was sent to their hotmail account, the error in the bounced email says the following…

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

host server2.hostdomain.com.au []
SMTP error from remote mail server after RCPT TO:<contact@clientdomain.com>:
554 5.7.1 <contact@clientdomain.com>: Relay access denied

i note the “relay access denied” error above

On both of my servers i went to Webmin>Servers Index

Server1 had the following issue when i attempted to click on server2

*Failed to connect to server2.hostdomain.com : Failed to lookup IP address for server2.hostdomain.com*

I was positive that its a dns resolution problem on one of the servers…and no surprise its server 1 causing the problem (which is the primary mail server). I have setup server 2 so that it only uses googles dns servers, but server1 is losing those ipaddresses and reverting back to the server1 itself (ie

3 Questions

  1. How do i force Webmin>Network Configuration>dns servers to not change whenever system is rebooted or upgraded?

  2. will my having a backup mail server network link (ie Webmin>webmin servers index) between two systems still keep working if i disable bind and disable dhcp on server1?
    EDIT…throws an error if i attempt to disable bind
    " Failed to save enabled features : The feature BIND DNS domain cannot be disabled, as it is used by the following virtual servers : hostdomain.com"

  3. my hostdomain.com is not being used by any client domains for dns resolution, however, as per question 2, is it required for the webmin servers index link?