Nameserver configuration

Hi everyone
Recently I just installed Centos Web Panel its nice and I like it,
But before I want to go with pro version I need to learn somethings!
To prevent handling email delivery troubles I just using nameservers which my datacenter gave me and they have 3 nameservers for each server instead of two!
But in nameserver settings I just be able to add only two
Thi jist make problems and my emails does not delivered to some providers like gmail!
So my question is how can i add third nameserver? Manually or via gui?

Thanks a lot and have a lovely day

If you hosted your domain to another provider you dont need insert NameServer in CWP.
Name Server in CWP mean your domain DNS will be hosted in your CWP.

Or you can add your own nameserver by adding child/private nameserver in your domain manager and pointing to CWP.
For example, you add child record ns1.domain.com -> your IP, ns2.domain.com -> your IP

Just make sure you already add DNS for MX record, SPF, and DKIM to domain manager.
Mail provider like gmail need SPF record.