a2.domain.by has no MX records.
Question and response
Question
dig a2.domain.by. MX
Answer
The response has no answer records.
Authority
domain.by. 600 SOA dns1.domain.by. root.ok.by. 2026021002 21600 7200 1296000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0