spf.tricorn.net has no MX records.
Question and response
Question
dig spf.tricorn.net. MX
Answer
The response has no answer records.
Authority
tricorn.net. 3600 SOA ns000.d-53.net. infra-general.tricorn.co.jp. 2025101001 3600 900 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0