EXSMTP3.enbridgegas.com has no MX records.
Question and response
Question
dig EXSMTP3.enbridgegas.com. MX
Answer
The response has no answer records.
Authority
enbridgegas.com. 1800 SOA blue.foundationdns.com. webpresence.enbridge.com. 2396776306 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0