relay.corehr.com has no MX records.
Question and response
Question
dig relay.corehr.com. MX
Answer
The response has no answer records.
Authority
corehr.com. 1800 SOA leonidas.ns.cloudflare.com. dns.cloudflare.com. 2395607305 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0