mail43.dptagent.net has no CNAME records.
Question and response
Question
dig mail43.dptagent.net. NS
Answer
The response has no answer records.
Authority
dptagent.net. 2911 SOA pdns01.domaincontrol.com. dns.jomax.net. 2025050904 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0