mail10.cdkcrm.com has no MX records.
Question and response
Question
dig mail10.cdkcrm.com. MX
Answer
The response has no answer records.
Authority
cdkcrm.com. 300 SOA ns.las.us.cdk.com. named.cdk.com. 2019092904 16384 2048 604800 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0