backup.mx.spoje.net has no CNAME records.
Question and response
Question
dig backup.mx.spoje.net. NS
Answer
The response has no answer records.
Authority
mx.spoje.net. 1800 SOA ns.spoje.net. tech.spoje.net. 1772215363 1800 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0