pa.frontiernet.net has no MX records.
Question and response
Question
dig pa.frontiernet.net. MX
Answer
The response has no answer records.
Authority
pa.frontiernet.net. 21600 SOA auth.roch.ny.frontiernet.net. hostmaster.frontiernet.net. 2602200016 10800 3600 604800 21600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0