Question and response
Question
dig smtpin3.smtp.com. NS
Answer
smtpin3.smtp.com. 5 CNAME s0-in.smtp.com.
Authority
smtp.com. 900 SOA ns-1304.awsdns-35.org. awsdns-hostmaster.amazon.com. 2 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0