relay906.mysmtp4.com has no MX records.
Question and response
Question
dig relay906.mysmtp4.com. MX
Answer
The response has no answer records.
Authority
mysmtp4.com. 600 SOA pdns07.domaincontrol.com. dns.jomax.net. 2026011903 28800 7200 604800 600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0