mail.4net.tv has no CNAME records.
Question and response
Question
dig mail.4net.tv. NS
Answer
The response has no answer records.
Authority
4net.tv. 204 SOA ns0.4net.tv. hostmaster.4net.tv. 2026021912 14400 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0