ns4.g.aaplimg.com has no MX records.
Question and response
Question
dig ns4.g.aaplimg.com. MX
Answer
The response has no answer records.
Authority
g.aaplimg.com. 300 SOA a.gslb.aaplimg.com. hostmaster.apple.com. 1715790868 1800 300 60480 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0