mail8.hspheredns.com has no MX records.
Question and response
Question
dig mail8.hspheredns.com. MX
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