aztestsmtp.brassring.com has no NS records.
NS records for this zone are defined at brassring.com.
NS records for this zone are defined at brassring.com.
Question and response
Question
dig aztestsmtp.brassring.com. NS
Answer
The response has no answer records.
Authority
brassring.com. 3600 SOA a1-160.akam.net. hostmaster.hiresystems.com. 2015092183 10800 600 86400 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0