gateway3.wavify.com has no MX records.
Question and response
Question
dig gateway3.wavify.com. MX
Answer
The response has no answer records.
Authority
wavify.com. 1800 SOA aria.ns.cloudflare.com. dns.cloudflare.com. 2397690439 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0