pp0021.ppsmtp.net has no CNAME records.
Question and response
Question
dig pp0021.ppsmtp.net. NS
Answer
The response has no answer records.
Authority
ppsmtp.net. 1269 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