mail.taiwancloud.com.tw has no MX records.
Question and response
Question
dig mail.taiwancloud.com.tw. MX
Answer
The response has no answer records.
Authority
taiwancloud.com.tw. 86400 SOA dns1.tfn.net.tw. dns_admin.tfn.net.tw. 2025032501 10800 3600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0