mx1.forwardemail.net has no CNAME records.
Question and response
Question
dig mx1.forwardemail.net. NS
Answer
The response has no answer records.
Authority
forwardemail.net. 1436 SOA greg.ns.cloudflare.com. dns.cloudflare.com. 2397169529 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0