mail.sockettelecom.com has no CNAME records.
Question and response
Question
dig mail.sockettelecom.com. NS
Answer
The response has no answer records.
Authority
sockettelecom.com. 8240 SOA ns1.socket.net. dns.socket.net. 2026021102 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0