fives.mandevilletrailhead.com has no MX records.
Question and response
Question
dig fives.mandevilletrailhead.com. MX
Answer
The response has no answer records.
Authority
mandevilletrailhead.com. 300 SOA ns1.dyna-ns.net. hostmaster.mandevilletrailhead.com. 2026030901 16384 2048 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0