mail.vtrenz.com has no NS records.
NS records for this zone are defined at vtrenz.com.
NS records for this zone are defined at vtrenz.com.
Question and response
Question
dig mail.vtrenz.com. NS
Answer
The response has no answer records.
Authority
vtrenz.com. 900 SOA ns1.acoustic-adm.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0