I cant receive email on my cpanel linux vps domains

Alright so I had some issues with my domain on my cpanel linux vps..
and I finally get the domains pointing to the right name servers... but now
I can send email from the domain but when i send email to the domain...
I dont get the messages... I get bounce backs

Also this problem... was happening..before the name server issues...

any idea what this could be......

This is the error message...

** The error that the other server returned was: 550 550-ey-out-1920.google.com [xx.22.321.877] is currently not permitted to relay
550-through this server. Perhaps you have not logged into the pop/imap server
550-in the last 30 minutes or do not have SMTP Authentication turned on in your
550 email client. (state 14).

http://forums.cpanel.net/f34/user-server-mail-550-relay-not-permitted-121597.html

Anyone ?

DNS or RDNS issues?
I have a few things in mind. PM me.