I though about trying this; /opt/zextras/libexec/zmsetservername -n mailhost.mydomain.com if that's the correct command ..........or could it make...

Firstly, thank you so much for your attention and I appreciate your insistance 😉 however both statements 1 and 2 are true, my hosts file has the line;...

Thanks, but that is exactly as it is. single space between ip, fqdn and hostname. which is why I can tell the script or process that is editing the am...

OK I now realise I should not have upgraded Ubuntu, thanks