172206.usersglobalnet.com has no MX records.
Question and response
Question
dig 172206.usersglobalnet.com. MX
Answer
The response has no answer records.
Authority
usersglobalnet.com. 3600 SOA usersglobalnet.com. root.usersglobalnet.com. 69 604800 86400 2419200 604800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0