mx0.aspentechlabs.com has no NS records.
NS records for this zone are defined at aspentechlabs.com.
NS records for this zone are defined at aspentechlabs.com.
Question and response
Question
dig mx0.aspentechlabs.com. NS
Answer
The response has no answer records.
Authority
aspentechlabs.com. 900 SOA ns-1309.awsdns-35.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0