The hostname is the name you give your server. It needs to be a fully qualified domain name, meaning it needs to resolve, and should resolve to your server IP.
The value of your hostname should be in the form similar to:
where you run/manage domain.com (usually something like your webhost domain). The value "server" or something like that needs to be in front of it. (ns1 or www are both valid). You cannot use just "domain.com" as the hostname, as this will conflict with the email in your actual domain.com hosting account (with regards to how system accounts get their emails).
Domain Name: server.domain.com
IP Address: 18.104.22.168 (your server IP)
where server.domain.com is your new hostname, the server IP address will usually be your license/main IP, and the ns1/ns2 values can be whatever your domain.com uses. Leave the "Create Reverse IP Lookup" checkbox disabled/unchecked.
The reason we add a new zone for the hostname is to ensure that
- it resolves
- it has it's own MX record, so email from the hostname are valid. Without the MX records, many of your emails (eg: from the php/apache "mail()" function) may be rejected.