internal.akamaistream.net has no MX records.
Question and response
Question
dig internal.akamaistream.net. MX
Answer
The response has no answer records.
Authority
akamaistream.net. 180 SOA internal.akamaistream.net. hostmaster.akamai.com. 1552675992 90000 90000 90000 180
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0