mail.rdsor.ro has no CNAME records.
Question and response
Question
dig mail.rdsor.ro. NS
Answer
The response has no answer records.
Authority
rdsor.ro. 7653 SOA ns.rdsnet.ro. dns-adm.rdsnet.ro. 2026021904 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0