mail8.viatel.com has no CNAME records.
Question and response
Question
dig mail8.viatel.com. NS
Answer
The response has no answer records.
Authority
viatel.com. 4732 SOA dns1-auth.viatel.net. hostmaster.viatel.net. 2023092500 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0