mail.simplesimple.com has no CNAME records.
Question and response
Question
dig mail.simplesimple.com. NS
Answer
The response has no answer records.
Authority
simplesimple.com. 2295 SOA simplesimple.com. hostmaster.logixcom.net. 2021041211 1800 300 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0