SanFrancisco1.Level3.net has no MX records.
Question and response
Question
dig SanFrancisco1.Level3.net. MX
Answer
The response has no answer records.
Authority
SanFrancisco1.Level3.net. 3600 SOA ns2.Level3.net. dns.level3.net. 2026022501 7200 600 2592000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0