iristelsecurity.com has no MX records.
Question and response
Question
dig iristelsecurity.com. MX
Answer
The response has no answer records.
Authority
iristelsecurity.com. 86400 SOA pdns104.ultradns.com. tldadmin.iristel.com. 2018121705 86400 86400 86400 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0