mail-us.atlassian.net has no NS records.
NS records for this zone are defined at atlassian.net.
NS records for this zone are defined at atlassian.net.
Question and response
Question
dig atlassian.mail.e.sparkpost.com. NS
Answer
The response has no answer records.
Authority
mail.e.sparkpost.com. 900 SOA ns-1031.awsdns-00.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0