71.27.in-addr.arpa has no MX records.
Question and response
Question
dig 71.27.in-addr.arpa. MX
Answer
The response has no answer records.
Authority
71.27.in-addr.arpa. 10800 SOA dns1.vietel.com.vn. tuananh.viettel.com.vn. 2010101701 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0