At the moment Gmail doesn't offer IMAP, but it does allow you to access your mail from Mac OS X Mail using POP. This means all your mail will be downloaded to Mail.app, but will leave a copy on the Gmail server, even if you delete or move message in mail. This means that its only really feasible to use your Gmail account from one computer, as messages marked read in mail, will still be marked unread in Gmail.

First you must enable POP access in hte Gmail settings. Go to your Gmail inbox and click Settings at the top. Go to the Forwarding and POP tab, and Enable POP from all mail (or just mail from now on if you wish).

Now switch to Mail and open up the preferences (Mail -> Preferences) then navigate to the Accounts tab, creating a new account with the following details:


Account Type: POP
Description: Gmail (or something similar)
Full Name: Your Name
Email Address: example123@gmail.com (your gmail address)
Incoming Mail Server: pop.gmail.com
User Name: example123@gmail.com (your gmail address)
Password: Your Gmail Password

Make sure Use Secure Sockets Layer (SSL) is checked.

Authentication: Password
Outgoing Mail server: smtp.gmail.com

Make sure Use Authentication is checked.

User Name: example123@gmail.com (your gmail address)
Password: Your Gmail Password

Make sure Use Secure Sockets Layer (SSL) is checked.

Authentication: Password

Click continue then Done. With the new Gmail account highlighted, click server settings, under outgoing mail server. In server port, type 465.
Close and save the account preferences.

An alternative to setting up Gmail with Mail is to use this stripped down web browser, intended solely for Gmail.