t.ertelecom.ru has no MX records.
Question and response
Question
dig t.ertelecom.ru. MX
Answer
The response has no answer records.
Authority
t.ertelecom.ru. 3600 SOA ns6.ertelecom.ru. noc.ertelecom.ru. 2017083001 86400 1800 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0