mailserv1.dobsontelco.net has no SRV records.
Question and response
Question
dig mailserv1.dobsontelco.net. SRV
Answer
The response has no answer records.
Authority
dobsontelco.net. 180 SOA ns11.constellix.com. dns.constellix.com. 2015010102 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0