smtp.cablelink.at has no CNAME records.
Question and response
Question
dig smtp.cablelink.at. NS
Answer
The response has no answer records.
Authority
cablelink.at. 9322 SOA adns001.dc1.conova.com. domainadmin.conova.com. 2026022704 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0