mail.profinetworks.cz has no CNAME records.
Question and response
Question
dig mail.profinetworks.cz. NS
Answer
The response has no answer records.
Authority
profinetworks.cz. 889 SOA ns.web4u.cz. admin.web4u.cz. 2026021901 14400 3600 1209600 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0