ntp.netlinkify.com has no MX records.
Question and response
Question
dig ntp.netlinkify.com. MX
Answer
The response has no answer records.
Authority
netlinkify.com. 1800 SOA melody.ns.cloudflare.com. dns.cloudflare.com. 2397256807 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0