mx.towersgross.com has no NS records.
NS records for this zone are defined at towersgross.com.
NS records for this zone are defined at towersgross.com.
Question and response
Question
dig mx.towersgross.com. NS
Answer
The response has no answer records.
Authority
towersgross.com. 3600 SOA dns.towersgross.com. hostmaster.towersgross.com. 1696792832 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0