mail2.oneliner.be has no CNAME records.
Question and response
Question
dig mail2.oneliner.be. NS
Answer
The response has no answer records.
Authority
oneliner.be. 3102 SOA dns1.iwantmyname.com. dnsadmin.iwantmyname.com. 2026021604 43200 900 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0