mailserver.myorderbox.com has no CNAME records.
Question and response
Question
dig mailserver.myorderbox.com. NS
Answer
The response has no answer records.
Authority
myorderbox.com. 1350 SOA andy.ns.cloudflare.com. dns.cloudflare.com. 2397959821 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0