Hi there,
First of all, thanks for the awesome service that Netlify provides! It’s great, for both companies and also new learners eg. our bootcamp students at upleveled.io 
We’re using Netlify DNS (because we want to use Netlify for the apex domain upleveled.io) and it’s worked out well so far.
However, MXToolBox has detected a few problems with the DNS configuration (which I assume that is not a fault of how we have configured it, but more Netlify’s global DNS config):
- An “Primary Name Server Not Listed At Parent” error on a Domain Health Report: upleveled.io Domain Health
This is described by MXToolBox as follows:
Your Primary Name Server was not in the list of name servers given to us by the root.
If your name server is not listed at the root this could cause impaired/incorrect lookups for your domain.
The Primary Name Server is the name server declared in your SOA file and is usually the name server that reads your records from zone files and is responsible for distributing that data to your secondary name servers. This problem is present when this primary name server is not included in the parent referrals and is almost always accompanied by a Local Parent Mismatch problem.
RFC 1035: Here a primary name server acquires information about one or more
zones by reading master files from its local file system, and
answers queries about those zones that arrive from foreign
resolvers.If your Primary Name Server is not listed at your Parent or is not responding, then our DNS Propagation test tool will not operate properly. You will most likely also be experiencing other real world problems with DNS queries for your domain. Users with Basic or Pro accounts can contact our Support Team for assistance with understanding any DNS warnings or errors with specific information about your domain. If you are still a free user, upgrading your account will give you access to support as well as many other benefits.
- An “There is a problem. We were not able to find a Start of Authority (SOA) record which may indicate a DNS problem.” error when using the SuperTool: Network Tools: DNS,IP,Email
I must admit, my knowledge on DNS and various problems is still fledgling, so I’m not entirely sure what I should be checking for. But I did try running a dig command, where I was unable to see any issues:
$ dig SOA upleveled.io
; <<>> DiG 9.10.6 <<>> SOA upleveled.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42668
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;upleveled.io. IN SOA
;; ANSWER SECTION:
upleveled.io. 3600 IN SOA dns1.p01.nsone.net. domains+netlify.netlify.com. 1638894161 43200 7200 1209600 3600
;; Query time: 65 msec
;; SERVER: 2a02:8383:d:c::1000#53(2a02:8383:d:c::1000)
;; WHEN: Wed Dec 08 17:06:32 CET 2021
;; MSG SIZE rcvd: 122
I did read https://answers.netlify.com/t/modification-to-soa-record/32899 about a potential issue caused by the domains+netlify.netlify.com part above, but I’m unsure if this is really a problem.