mx.faster.cz has no CNAME records.
Question and response
Question
dig mx.faster.cz. NS
Answer
The response has no answer records.
Authority
faster.cz. 844 SOA inet.faster.cz. hostmaster.faster.cz. 2026022015 16384 2048 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0