mx.kyivstar.net has no MX records.
Question and response
Question
dig mx.kyivstar.net. MX
Answer
The response has no answer records.
Authority
kyivstar.net. 600 SOA ns.kyivstar.net. hostmaster.kyivstar.net. 2026021902 3600 3600 3542400 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0