Hi James,
MX-records must point to A-records and not to IP adresses. A "dig -t AXFR obrien-pifer.com @ns1.obrien-pifer.com | grep MX" returns: mail.obrien-pifer.com. 38400 IN MX 1 70.62.90.185.obrien-pifer.com.
Whereas you list "mail.obrien-pifer.com. IN MX 1 70.62.90.185" in your config.
So your setup is invalid because: - you're pointing your one and only MX record directly to an IP - since it is interpreted as host and missing a "." at the end it's expanded to "70.62.90.185.obrien-pifer.com." which doesnt exist - it's a MX record for mail.obrien-pifer.com and not obrien-pifer.com
Your whole definition of the MX record looks goofy to me, dont want to sound like an a.. but you better (re)read some tutorials on setting up DNS. I really wonder if you receive the reply at all.
Regards, Thomas