Configure Postfix to send/relay emails Gmail (smtp.gmail.com) via port 587
I have multiple drupal websites running on an Ubuntu slicehost vps. Naturally, that means that I have a fair number of domains pointing to my one slice. For some of those domains, we use the non-profit version of google apps for email.
I Followed Google's instructions for configuring DNS, so sending and receiving email from within our google apps accounts works just fine. The problem comes when we try to send email from our drupal sites. Generally, email simply doesn't get through. I think that I have trained my personal gmail inbox (which is NOT using google apps) to accept email coming from the vps, but no one else ever gets any of the emails.
What can I do to fix the problem?