mx.avasin.plus.net has no CNAME records.
Question and response
Question
dig mx.avasin.plus.net. NS
Answer
The response has no answer records.
Authority
plus.net. 5111 SOA ns1.force9.net. hostmaster.plus.net.uk. 2026021301 43200 1800 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0