frontieronline.com has no MX records.
Question and response
Question
dig frontieronline.com. MX
Answer
The response has no answer records.
Authority
frontieronline.com. 21600 SOA auth.roch.ny.frontiernet.net. hostmaster.frontiernet.net. 2505060001 10800 3600 604800 21600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0