pp3017.ppsmtp.net has no MX records.
Question and response
Question
dig pp3017.ppsmtp.net. MX
Answer
The response has no answer records.
Authority
ppsmtp.net. 1800 SOA ns1.p68.dns.oraclecloud.net. hostmaster.ppsmtp.net. 490 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0