zrelay02.impulse.net has no MX records.
Question and response
Question
dig zrelay02.impulse.net. MX
Answer
The response has no answer records.
Authority
impulse.net. 1800 SOA jasmine.ns.cloudflare.com. dns.cloudflare.com. 2397332497 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0