oppay.tw has no MX records.
Question and response
Question
dig oppay.tw. MX
Answer
The response has no answer records.
Authority
oppay.tw. 28800 SOA dns1.taiwanmobile.com. hostmaster.dns1.taiwanmobile.com. 2025112403 10800 3600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0