ze.akamaitech.net has no MX records.
Question and response
Question
dig ze.akamaitech.net. MX
Answer
The response has no answer records.
Authority
akamaitech.net. 180 SOA internal.akamaitech.net. hostmaster.akamai.com. 1698937200 90000 90000 90000 180
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0