b.ns.keyweb.org has no MX records.
Question and response
Question
dig b.ns.keyweb.org. MX
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