Registro.it, the registrar for all .it-DOMAINs only accepts name servers that meet certain criterias;
The test must be passed successfully, otherwise the name servers can not be not entered successfully.
You can use the DNS configuration validation tool to perform a name server check. The name servers of your zone (DOMAIN) are subjected to various tests to ensure that they are correctly configured and that the DOMAIN can be delegated safely and easily. This guarantees a high quality DOMAIN.
Please test the desired name servers in the web interface provided by Registro.it. Please enter your domain name in the form. This is, of course, only possible with already registered domains.