smtp.ispworks.net has no MX records.
Question and response
Question
dig smtp.ispworks.net. MX
Answer
The response has no answer records.
Authority
ispworks.net. 1800 SOA liz.ns.cloudflare.com. dns.cloudflare.com. 2397134119 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0