Apex domains cannot have CNAME records.
Question and response
Question
dig mail.lviv.ua. NS
Answer
mail.lviv.ua. 2 NS zeta.uar.net.
mail.lviv.ua. 2 NS eta.uar.net.
mail.lviv.ua. 2 NS iota.uar.net.
mail.lviv.ua. 2 NS theta.uar.net.
mail.lviv.ua. 2 NS kappa.uar.net.
Authority
The response has no authority records.
Additional
eta.uar.net. 2 A 194.44.245.234
iota.uar.net. 2 A 95.216.126.26
zeta.uar.net. 2 A 194.44.147.51
kappa.uar.net. 2 A 194.44.10.3
theta.UAR.Net. 2 A 194.44.214.213
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0