ns4.indosatooredoo.com has no MX records.
Question and response
Question
dig ns4.indosatooredoo.com. MX
Answer
The response has no answer records.
Authority
indosatooredoo.com. 900 SOA external.auth-dns001-udc1. domain\.admin.indosatooredoo.com. 20152894 3600 3600 1728000 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0