smtp.srt.cnr.it has no NS records.
NS records for this zone are defined at srt.cnr.it.
NS records for this zone are defined at srt.cnr.it.
Question and response
Question
dig smtp.srt.cnr.it. NS
Answer
The response has no answer records.
Authority
srt.cnr.it. 3600 SOA nameserver.rm.cnr.it. root.nameserver.rm.cnr.it. 2021100701 43200 1800 2592000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0