relay.rostel.ru has no MX records.
Question and response
Question
dig relay.rostel.ru. MX
Answer
The response has no answer records.
Authority
rostel.ru. 3600 SOA ns0.donpac.ru. noc.rostel.ru. 2025081100 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0