ns2.force9.net has no MX records.
Question and response
Question
dig ns2.force9.net. MX
Answer
The response has no answer records.
Authority
force9.net. 10200 SOA ns1.force9.net. hostmaster.force9.net. 2026020201 3600 1800 3600000 10200
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0