I have a client who is running cpanel/whm (RHEL5)and hosting various domains. They have been having various email issues to some of these hosts, and other dns related issues and there is no "standardized" set of DNS settings that they are using. Some of the hosted domains use the hosting server's (the one running cpanel/whm) dns servers, and some of the hosted domains are using "other" DNS servers, one running AD for the client's network, others off-site. I have repeated to the client over-and-over that ALL domains hosted on the server running cpanel/whm MUST/SHOULD be using the hosting server's name servers as the top-level, authoritative name servers and if they wish to use other name servers, these can be used as tertiary name servers. However, the client continues to use their own AD name servers or name servers off site and NOT the ones for the actual hosting name server. Can anyone suggest any ICAAN or general/standard regulations/guidelines which clearly support how the client should be setting up their name servers? Or, can anyone respond with suggestions/support for the use of the hosting server's name servers FIRST as authoritative and then others as tertiary, assuming this is the accepted/best approach?