rb-e-tech-mgmt.rb.slc.efscloud.net has no MX records.
Question and response
Question
dig rb-e-tech-mgmt.rb.slc.efscloud.net. MX
Answer
The response has no answer records.
Authority
rb.slc.efscloud.net. 600 SOA ns1.efscloud.net. root.efscloud.net. 1652275552 7200 900 3600000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0