mail.hspheredns.com has no NS records.
NS records for this zone are defined at hspheredns.com.
NS records for this zone are defined at hspheredns.com.
Question and response
Question
dig mail.hspheredns.com. NS
Answer
The response has no answer records.
Authority
hspheredns.com. 86400 SOA ns1.hspheredns.com. admin.hspheredns.com. 2018040877 10800 3600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0