mail4.mobiltel.bg has no MX records.
Question and response
Question
dig mail4.mobiltel.bg. MX
Answer
The response has no answer records.
Authority
mobiltel.bg. 300 SOA ns.mobiltel.bg. sysadmin.mtel.net. 2025092301 3600 900 1209600 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0