smtp.fullsave.net has no MX records.
Question and response
Question
dig smtp.fullsave.net. MX
Answer
The response has no answer records.
Authority
fullsave.net. 10800 SOA ns1.gandi.net. hostmaster.gandi.net. 1771459200 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0