_spf.vas-hosting.cz has no CNAME records.
Question and response
Question
dig _spf.vas-hosting.cz. NS
Answer
The response has no answer records.
Authority
vas-hosting.cz. 1869 SOA ns.vas-hosting.cz. info.vas-hosting.cz. 2601071669 28800 600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0