I run Google Apps email and have traditionally hosted my own DNS records through my Plesk setup. It has been recommended to us that we'd more reliably serve emails during downtime if we kept the MX and CNAME listings required by Google Apps hosted at Enom instead of handling it internally.
I have essentially copied the settings from Plesk over to Enom. The domain itself forwards with no problem, but the MX records, while they seem to be input into Enom without error, never seem to reroute my mail. If I try to send to the email address I'm trying to route, I get the following error bounced back:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 553 553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1) (state 14).
This sort of error gets referenced a lot with regard to propogation, but It's been two days and Enom updates everything else almost instantly.