mail.rg.net has no CNAME records.
Question and response
Question
dig mail.rg.net. NS
Answer
The response has no answer records.
Authority
rg.net. 10482 SOA rip.psg.com. hostmaster.psg.com. 1772400543 86400 3600 2592000 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0