1e100.net has no MX records.
Question and response
Question
dig 1e100.net. MX
Answer
The response has no answer records.
Authority
1e100.net. 60 SOA ns1.google.com. dns-admin.google.com. 873285235 900 900 1800 60
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0