bk188.mta.pdmailservice.com has no MX records.
Question and response
Question
dig bk188.mta.pdmailservice.com. MX
Answer
The response has no answer records.
Authority
pdmailservice.com. 3600 SOA ns1.exacttarget.com. hostmaster.exacttarget.com. 2024022800 7200 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0