137stb30.codetel.net.do has no MX records.
Question and response
Question
dig 137stb30.codetel.net.do. MX
Answer
The response has no answer records.
Authority
codetel.net.do. 153 SOA ns1.claro.net.do. hostmaster.claro.net.do. 2017041241 21600 900 604800 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0