pp3166.ppsmtp.net has no CNAME records.
Question and response
Question
dig pp3166.ppsmtp.net. NS
Answer
The response has no answer records.
Authority
ppsmtp.net. 1399 SOA ns1.p68.dns.oraclecloud.net. hostmaster.ppsmtp.net. 490 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0