dns4.hostwindsdns.com has no MX records.
Question and response
Question
dig dns4.hostwindsdns.com. MX
Answer
The response has no answer records.
Authority
hostwindsdns.com. 3600 SOA dns1.hostwindsdns.com. abuse.hostwinds.com. 2017051200 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0