smtp4.wntpr.com has no CNAME records.
Question and response
Question
dig smtp4.wntpr.com. NS
Answer
The response has no answer records.
Authority
wntpr.com. 462 SOA lennox.ns.cloudflare.com. dns.cloudflare.com. 2395610770 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0