mail.webx.cz has no CNAME records.
Question and response
Question
dig mail.webx.cz. NS
Answer
The response has no answer records.
Authority
webx.cz. 900 SOA ns.webx.cz. hostmaster.webx.cz. 2026012805 10800 1800 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0