OPEN-SYSTEM.bear2.Houston1.Level3.net has no MX records.
Question and response
Question
dig OPEN-SYSTEM.bear2.Houston1.Level3.net. MX
Answer
The response has no answer records.
Authority
Houston1.Level3.net. 3600 SOA ns2.Level3.net. dns.level3.net. 2026030604 7200 600 2592000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0