dyndns6.inwx.com has no MX records.
Question and response
Question
dig dyndns6.inwx.com. MX
Answer
The response has no answer records.
Authority
inwx.com. 1800 SOA damon.ns.cloudflare.com. dns.cloudflare.com. 2398108380 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0