smtp.cluster.ncport.ru has no MX records.
Question and response
Question
dig smtp.cluster.ncport.ru. MX
Answer
The response has no answer records.
Authority
cluster.ncport.ru. 1800 SOA ns1.ncport.ru. postmaster.ncport.ru. 2013013109 1800 900 691200 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0