ns.library.kr.ua has no MX records.
Question and response
Question
dig ns.library.kr.ua. MX
Answer
The response has no answer records.
Authority
library.kr.ua. 3600 SOA ns.library.kr.ua. hostmaster.library.kr.ua. 2017111630 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0