ns4.afternic.com has no MX records.
Question and response
Question
dig ns4.afternic.com. MX
Answer
The response has no answer records.
Authority
afternic.com. 600 SOA cns1.secureserver.net. dns.jomax.net. 2026011500 3600 7200 1209600 600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0