Nic.it makes some preliminary tests on authoritative nameservers for any domain, and the nameservers must pass successfully the test before being approved.
Tests are as follow:

1. there must be at least 2 (two) authoritative nameservers for the domain name
2. the IP addresses of the nameserver specified in the form must correspond to those actually associated with them in the DNS;
3. a CNAME record cannot be associated with the domain name;
4. the name of the nameserver specified in the SOA record cannot be a CNAME;
5. the names of the authoritative nameservers for the domain name cannot be CNAME;
6. a CNAME cannot be associated with the MX record, if present;
7. if, during the verification procedure, at least one nameserver gives one of the following responses:
   •Not responding
   •Not reachable
   •Not running
   •Non-existent domain
   •Host not found
   •Server failure
   •Query failed
   the procedure fails.