sea1.dsl.speakeasy.net has no MX records.
Question and response
Question
dig sea1.dsl.speakeasy.net. MX
Answer
The response has no answer records.
Authority
sea1.dsl.speakeasy.net. 300 SOA ns1.megapath.net. support.megapath.net. 1369196189 14400 3600 2718281828 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0