ns.oxismtp.com has no MX records.
Question and response
Question
dig ns.oxismtp.com. MX
Answer
The response has no answer records.
Authority
oxismtp.com. 38400 SOA ns.oxismtp.com. postmaster.oxismtp.com. 2025040402 10800 3600 1209600 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0