mt.hexaoperator.com has no MX records.
Question and response
Question
dig mt.hexaoperator.com. MX
Answer
The response has no answer records.
Authority
hexaoperator.com. 3600 SOA dns.home.pl. admin.home.pl. 1583999709 14400 7200 2419200 3600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0