stage.certifiedmail.com has no NS records.
NS records for this zone are defined at certifiedmail.com.
NS records for this zone are defined at certifiedmail.com.
Question and response
Question
dig stage.certifiedmail.com. NS
Answer
The response has no answer records.
Authority
certifiedmail.com. 3600 SOA ns1-01.azure-dns.com. azuredns-hostmaster.microsoft.com.certifiedmail.com. 30 3600 60 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0