prdmailhostl01.netnames.net has no SRV records.
Question and response
Question
dig prdmailhostl01.netnames.net. SRV
Answer
The response has no answer records.
Authority
netnames.net. 172800 SOA udns1.cscdns.net. hostmaster.cscdns.net. 2017101448 3600 1800 3600000 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0