ip-51-81-30.us has no MX records.
Question and response
Question
dig ip-51-81-30.us. MX
Answer
The response has no answer records.
Authority
ip-51-81-30.us. 60 SOA dns100.ovh.us. tech.ovh.us. 2025052901 86400 3600 3600000 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0