smtp.is.hvfree.net has no MX records.
Question and response
Question
dig smtp.is.hvfree.net. MX
Answer
The response has no answer records.
Authority
hvfree.net. 1800 SOA ns1.hvfree.cz. info.hvfree.net. 2026030600 3600 3600 4000 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0