mail.dnmailer.net has no MX records.
Question and response
Question
dig mail.dnmailer.net. MX
Answer
The response has no answer records.
Authority
dnmailer.net. 3600 SOA ns1.viidakko.fi. admin.dnsimple.com. 1727956589 86400 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0