smtp.cue.telconet.net has no CNAME records.
Question and response
Question
dig smtp.cue.telconet.net. NS
Answer
The response has no answer records.
Authority
cue.telconet.net. 900 SOA ns1.telconet.net. abuse.telconet.net. 9 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0