ns21.domaincontrol.com has no MX records.
Question and response
Question
dig ns21.domaincontrol.com. MX
Answer
The response has no answer records.
Authority
domaincontrol.com. 3600 SOA ans01.domaincontrol.com. dns.jomax.net. 2026021679 3600 7200 604800 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0