net-a1.smtp2go.com has no CNAME records.
Question and response
Question
dig net-a1.smtp2go.com. NS
Answer
The response has no answer records.
Authority
smtp2go.com. 600 SOA ns2.smtpcorp.com. hostmaster.smtp2go.com. 2015074667 14400 3600 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0