mailhost.discoursehosting.com has no CNAME records.
Question and response
Question
dig mailhost.discoursehosting.com. NS
Answer
The response has no answer records.
Authority
discoursehosting.com. 866 SOA anuj.ns.cloudflare.com. dns.cloudflare.com. 2396729677 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0