ns1.systemdns.com has no MX records.
Question and response
Question
dig ns1.systemdns.com. MX
Answer
The response has no answer records.
Authority
systemdns.com. 300 SOA ns1.tucows.com. hostmaster.systemdns.com. 1771791517 10800 3600 2592000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0