dns.gtsi.sk has no MX records.
Question and response
Question
dig dns.gtsi.sk. MX
Answer
The response has no answer records.
Authority
gtsi.sk. 900 SOA ns.nextra.sk. hostmaster.nextra.sk. 2022110901 21600 7200 1209600 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0