(Just FYI, IMAP is not part of the Apple propaganda... in other words: Its an acronym, not something that is supposed to sound cool by having a lowercase letter "i"...)
Anyways, it sounds like you are using either POP3 or you didnt set up IMAP right.
IMAP means: Internet Message Access Protocol
Go into Gmail on the web, and click Settings at the top right of your screen.
Then go to the tab that says: "Forwarding and POP/IMAP"
Make sure IMAP is enabled.
Then go to Configuration Instructions (
or click here to see it)
Configuration instructions for Apple Mail version 3.0 Leopard, located here:
http://mail.google.com/support/bin/answer.py?answer=81379Run through the setup