Because this site did not build a domain name server, so the use of the interface itself to resolve the function.
Third-party parsing interfaces are also provided, provided you fill in the third party DNS API parameters.
Once set, you can manage the resolution record of a domain name through a third-party resolution API.
In "My Domain" there are relevant Settings buttons:
How do I know the default server for each interface?
Open the Domain Name Details page, click "Domain Name Server", and select the Default DNS if it is supported:
Once you know this, you can batch set up the DNS server and batch resolution in My Domains.