mail.bestname.com.ua has no MX records.
Question and response
Question
dig mail.bestname.com.ua. MX
Answer
The response has no answer records.
Authority
bestname.com.ua. 600 SOA ns1.bestname.com.ua. domainmaster.bestname.com.ua. 2025123000 600 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0