vm.mail.rcn.net has no MX records.
Question and response
Question
dig vm.mail.rcn.net. MX
Answer
The response has no answer records.
Authority
mail.rcn.net. 7200 SOA lists.lnh.mail.rcn.net. root.rcn.com. 2025121205 7200 1800 604800 21600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0