ns.v6.PTL.RU has no MX records.
Question and response
Question
dig ns.v6.PTL.RU. MX
Answer
The response has no answer records.
Authority
v6.PTL.RU. 86400 SOA ns.quantum.RU. admin.PTL.RU. 2013100905 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0