To enable IMAP, log in to your Gmail account, click on the Settings link at the top, click on the Forwarding And POP/IMAP link, select Enable IMAP, and click on Save Changes. You can then click on the Configuration Instructions link to learn how to set up your favorite e-mail client to access Gmail via IMAP. (To learn more about the ins and outs of using Gmail via IMAP with Mail, see “Achieving E-mail Bliss with IMAP, Gmail, and Apple Mail”.)