Hey your making progress! Now, onward: When Postfix receives an incoming message, it must decide its disposition. The choice is governed by a couple of factors, but boils down to this:
1 - is the message for one of my recipient domains. If so, receive the message and process it via the chosen delivery message. If not, then
2 - Is the message being sent from either: mynetworks or from an SASL authenticated user? If the answer is yes at this point, the message will be sent out or relayed via your relay host. If the answer is no, the message will be rejected with relay-access denied.

In your case, the messages are inbound from gmail and hence should be delivered, via your courier POP/IMAP.

There are two things I can think of that govern the control of this process: the mydestination and your recipient restrictions, which should include things like mydestination. Have a look at the following documentation to see if that helps: http://www.postfix.org/BASIC_CONFIGU...#mydestination. The situation can also be a little more difficult if you have virtual addressing for your recipients. If necessary, bypass that and specify either mailbox or maildir format.

I would also suggest that you will want to look in your mail log (/var/log/mail.log) and you can even "tail -f" it to watch what it thinks the recipient information is. With what you are facing, this will probably have the key information you need.

Once you get to this step, you will then need to focus on your courier delivery. A good test method at this point would be to telnet into your system, which you can do via localhost, or via a system that you can remotely work from via SSH. If you can telnet in from a remote host, you can also debug the delivery to local mail, like your current task.