ip-217-18-184-230.static.reverse.dsi.net has no MX records.
Question and response
Question
dig ip-217-18-184-230.static.reverse.dsi.net. MX
Answer
The response has no answer records.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0