smtp.appazur.com has no CNAME records.
Question and response
Question
dig smtp.appazur.com. NS
Answer
The response has no answer records.
Authority
appazur.com. 1800 SOA andy.ns.cloudflare.com. dns.cloudflare.com. 2397398974 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0