mta124.3.donweb.com has no CNAME records.
Question and response
Question
dig mta124.3.donweb.com. NS
Answer
The response has no answer records.
Authority
donweb.com. 189 SOA carol.ns.cloudflare.com. dns.cloudflare.com. 2397336165 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0