mail.tvintel.org has no NS records.
NS records for this zone are defined at tvintel.org.
NS records for this zone are defined at tvintel.org.
Question and response
Question
dig mail.tvintel.org. NS
Answer
The response has no answer records.
Authority
tvintel.org. 38400 SOA ns1.tvintel.org. root.tvintel.org. 1197 38400 10800 259200 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0