mailob2.concordfax.com has no MX records.
Question and response
Question
dig mailob2.concordfax.com. MX
Answer
The response has no answer records.
Authority
concordfax.com. 600 SOA a1.uberns.com. postmaster.concordfax.com. 2602240013 3600 600 691200 600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0