mx-relay.iristel.net has no MX records.
Question and response
Question
dig mx-relay.iristel.net. MX
Answer
The response has no answer records.
Authority
iristel.net. 86400 SOA pdns104.ultradns.com. tldadmin.iristel.com. 2020112466 86400 86400 86400 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0