mail.tgtact.com has no NS records.
NS records for this zone are defined at tgtact.com.
NS records for this zone are defined at tgtact.com.
Question and response
Question
dig mail.tgtact.com. NS
Answer
The response has no answer records.
Authority
tgtact.com. 7200 SOA n1.xundns.com. nsadmin.xundns.com. 437896 3600 600 86400 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0