backupmx.exwire.com has no NS records.
NS records for this zone are defined at exwire.com.
NS records for this zone are defined at exwire.com.
Question and response
Question
dig backupmx.exwire.com. NS
Answer
The response has no answer records.
Authority
exwire.com. 900 SOA ns-1416.awsdns-49.org. postmaster.exwire.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0