I've just built from the ground up a replacement server. The old server was centos 7 based, new one Ubuntu Server 18.04. So all software is current as per the distribution / Virtualmin install.
The server is behaving correctly, I can serve up web sites to the outside world, receive emails to Postfix, and internal network is talking correctly to outside world. (However, if I take the nameserver section out of the yaml file, it no longer works).
This note added later) If I go into Servers >> Read User Mail ... no problem, but if I try and use Usermin, all I get are the menus on the left and a blank screen where emails should be displayed. Happens on machine on local network and the server.
I cannot connect to the Samba server or get emails using Thunderbird from my local machine. The config files seem to match what I had on Centos 7, for Postfix, Dovecot and Samba. Searched the internet and getting nowhere. Never had an issue like this is the past and believe it might be related to the networking.
I'm using shorewall / iptables as the firewall, no other firewall is active. Here is the YAML file for the internal network.
Any help / pointers would be gratefully received.