ns02.btsaas.net has no MX records.
Question and response
Question
dig ns02.btsaas.net. MX
Answer
The response has no answer records.
Authority
btsaas.net. 3600 SOA ns01.btsaas.net. hostmaster.nsone.net. 1618492601 43200 7200 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0