oa.emailr.com has no CNAME records.
Question and response
Question
dig oa.emailr.com. NS
Answer
The response has no answer records.
Authority
emailr.com. 10800 SOA ns1.gandi.net. hostmaster.gandi.net. 1772064000 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0