posta.edera.cz has no CNAME records.
Question and response
Question
dig posta.edera.cz. NS
Answer
The response has no answer records.
Authority
edera.cz. 1895 SOA ns.edera.cz. admin.netforms.cz. 2026030602 14400 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0