mta-iq.expertsender.com has no MX records.
Question and response
Question
dig mta-iq.expertsender.com. MX
Answer
The response has no answer records.
Authority
expertsender.com. 3600 SOA pdns07.domaincontrol.com. dns.jomax.net. 2026020200 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0