gate.lasvegas.net has no MX records.
Question and response
Question
dig gate.lasvegas.net. MX
Answer
The response has no answer records.
Authority
lasvegas.net. 3600 SOA gate.lasvegas.net. postmaster.lasvegas.net. 2002020684 7200 3600 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0