mx2.sk.eserver.net has no CNAME records.
Question and response
Question
dig mx2.sk.eserver.net. NS
Answer
The response has no answer records.
Authority
sk.eserver.net. 1754 SOA ns1.eserver.net. hostmaster.eserver.sk. 2025102801 7200 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0