Gmail has finally rolled out its long-awaited IMAP (Internet Message Access Protocol) compatibility enabling users of such email clients as Outlook, Lotus Notes, Thunderbird, a host of others, and even Apple's iPhone to now take advantage of IMAP instead of the more limited POP connection.
Google is rolling it out, and it needs to migrate to many accounts, so it may not be available on your account yet. To enable IMAP, click on the Settings link on any Gmail page, and look for the "Forwarding and POP/IMAP" tab. Click that, and follow the instructions in the IMAP Access section. For some general Gmail help information on IMAP, click here. This help section contains configuration information, FAQ's, and troubleshooting links--very useful. You can also find a list of supported IMAP client applications here. Also, here is a link to Google's official blog announcing and explaining IMAP.
This really raises the bar for Gmail by opening up more and more of its functionality to client apps. POP has served many well for Gmail, but this opens the door to many more uses, especially for some mobile devices.