mx2.csof.net has no CNAME records.
Question and response
Question
dig mx2.csof.net. NS
Answer
The response has no answer records.
Authority
csof.net. 5518 SOA ns1.gandi.net. hostmaster.gandi.net. 1771459200 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0