d358.server4u.cz has no CNAME records.
Question and response
Question
dig d358.server4u.cz. NS
Answer
The response has no answer records.
Authority
server4u.cz. 600 SOA ns.web4u.cz. admin.web4u.cz. 2026030200 14400 3600 1209600 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0