mail.openhouse.org has no MX records.
Question and response
Question
dig mail.openhouse.org. MX
Answer
The response has no answer records.
Authority
mail.openhouse.org. 1800 SOA ns1.parkingcrew.net. hostmaster.mail.openhouse.org. 1770900966 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0