fl.frontiernet.net has no MX records.
Question and response
Question
dig fl.frontiernet.net. MX
Answer
The response has no answer records.
Authority
fl.frontiernet.net. 86400 SOA auth.roch.ny.frontiernet.net. hostmaster.frontier.com. 2603030002 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0