tccmr5.taiwanmobile.com has no MX records.
Question and response
Question
dig tccmr5.taiwanmobile.com. MX
Answer
The response has no answer records.
Authority
taiwanmobile.com. 600 SOA dns1.taiwanmobile.com. postmaster.taiwanmobile.com. 2026030502 1800 600 620000 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0