smtp.private.onappcdn.com has no CNAME records.
Question and response
Question
dig smtp.private.onappcdn.com. NS
Answer
The response has no answer records.
Authority
onappcdn.com. 2345 SOA dns41.cloudns.net. noc.virtuozzo.com. 2026030102 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0