external-proxy.cpanel.net has no MX records.
Question and response
Question
dig external-proxy.cpanel.net. MX
Answer
The response has no answer records.
Authority
cpanel.net. 300 SOA c.cpanel.net. dns.cpanel.net. 2026030901 1200 7200 1600000 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0