smtpmmus.grpitsrv.com has no NS records.
NS records for this zone are defined at grpitsrv.com.
NS records for this zone are defined at grpitsrv.com.
Question and response
Question
dig smtpmmus.grpitsrv.com. NS
Answer
The response has no answer records.
Authority
grpitsrv.com. 1800 SOA ns1-05.azure-dns.com. azuredns-hostmaster.microsoft.com. 2019022593 900 600 86400 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0