mx3.sanwell.biz has no MX records.
Question and response
Question
dig mx3.sanwell.biz. MX
Answer
The response has no answer records.
Authority
sanwell.biz. 38400 SOA NS1.101DOMAIN.COM. ADMIN.sanwell.biz. 2015062751 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0