static.tfn.net.tw has no MX records.
Question and response
Question
dig static.tfn.net.tw. MX
Answer
The response has no answer records.
Authority
static.tfn.net.tw. 86400 SOA dns1.tfn.net.tw. dns_admin.tfn.net.tw. 2018052405 86400 3600 1209600 604800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0