aa.net.do has no MX records.
Question and response
Question
dig aa.net.do. MX
Answer
The response has no answer records.
Authority
aa.net.do. 86400 SOA dns1.cscdns.net. hostmaster.cscdns.net. 2013121403 21600 3600 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0