I have a domain registered with GoDaddy called nimblework.com and we have pointed the NS server to the Cloudflare NS servers. DNS resolution is working fine for all the A, CNAME, TXT, and MX records. But I am getting issue for the subdomains those are delegated to external Name server.
You have successfully delegated email.nimblework.com to the four name servers listed, so there is nothing wrong on that part.
However, all those four name servers are returning REFUSED for any queries you make to them, for the email.nimblework.com.
Name servers generally return REFUSED, when they are being queried for a domain that they are not confgured to provide responses for.
As such, you will therefore need to contact ExactTarget for further assistance, as the DNS zone email.nimblework.com hasn’t (yet) been set up on their name servers, that they asked you to delegate the zone to.
Thanks for your reply, let me check about this with ExactTarget. But I have still a doubt if that is the case then why it is getting resolved in some of the country as you can see in the attached screenshot.
In a perfect set up, you do technically have two points of “NS” records for DNS zones.
Within the nimblework.com zone (on Cloudflare), you have set up some NS records to delegate the name servers for sub-zones of that domain to some other servers.
You also have the NS records from the child’s authoritative zone (e.g. email.nimblework.com), which is the actual zone file stored on the child’s authoritative DNS servers (e.g. ns1.exacttarget.com, ns2.exacttarget.com, ns3.exacttarget.com, ns4.exacttarget.com).
Even though it is best / wise to keep those consistent (e.g. the same) across the whole line, both within the parent zone’s delegation point (in the nimblework.com zone at Cloudflare) and the the child zone (e.g. email.nimblework.com zone set on ns1.exacttarget.com, ns2.exacttarget.com, ns3.exacttarget.com, ns4.exacttarget.com), they can technically be completely different.
The locations on dnschecker.org that actually show the name servers, are likely showing the parent zone’s delegation’s NS records, because they are unable to reach any further than that.
The locations that fail, are likely be depending on seeing authoritative responses from the child zone’s name servers, however, they are never getting that far due to the failed set up at ExactTarget.
Those kind of inconsistencies between the different locations as you see, could very well be because the different locations are using different software (or different versions of the software), to resolve the DNS queries, causing things to behave slightly different.