mx1.a1.net has no CNAME records.
Question and response
Question
dig mx1.a1.net. NS
Answer
The response has no answer records.
Authority
a1.net. 1398 SOA dns1.a1.net. domainadmin.a1.net. 2026021800 10800 3600 1814400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0