Message rejected - Delivery failed using google apps

Hello,

I'm using smtp in conjunction with rules to send the node author an email when their content is approved.

No matter what I do, it seems that the email message is automatically rejected by gmail's server before even being sent. The emails don't even reach the recipients spam inbox.

Google cites this as the explanation: Technical details of permanent failure:
Message rejected. See http://support.google.com/mail/bin/answer.py?answer=69585 for more information.

I've tried google searching for an answer, but I can't seem to find anything relevant. I'm assuming it may have to do with my server setup but I am not sure exactly what to do. Any help is appreciated, thanks!!