mail.keyweb.org has no CNAME records.
Question and response
Question
dig mail.keyweb.org. NS
Answer
The response has no answer records.
Authority
keyweb.org. 1800 SOA nitin.ns.cloudflare.com. dns.cloudflare.com. 2396877342 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0