mail-back.profik.cz has no CNAME records.
Question and response
Question
dig mail-back.profik.cz. NS
Answer
The response has no answer records.
Authority
profik.cz. 3600 SOA ns.profik.cz. hostmaster.profik.cz. 2011100920 3600 900 2073600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0