smtp1.arin.net has no CNAME records.
Question and response
Question
dig smtp1.arin.net. NS
Answer
The response has no answer records.
Authority
arin.net. 1453 SOA ns1.arin.net. bind.arin.net. 2021113325 10800 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0