mail2.edu.sk has no CNAME records.
Question and response
Question
dig mail2.edu.sk. NS
Answer
The response has no answer records.
Authority
edu.sk. 3375 SOA ns.telecom.sk. hostmaster.telecom.sk. 2025100209 28800 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0