_spfremote.dragon.cz has no MX records.
Question and response
Question
dig _spfremote.dragon.cz. MX
Answer
The response has no answer records.
Authority
dragon.cz. 14400 SOA ns.dragon.cz. hostmaster.dragon.cz. 2026021900 7200 3600 1209600 14400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0