Follow the instructions below to configure IMAP for Mozilla Thunderbird.

How to do it

Note: if you're using an older version of Thunderbird, we highly recommend upgrading to version 2.0.

To set up your Thunderbird client to work with Google Apps mail:

1. Enable IMAP in Gmail. Make sure you click Save Changes when you're done.
2. Open Thunderbird, and select Tools > Account Settings.
3. Click Add Account.
4. Select the Email account radio button and click Next. The Identity screen appears.
5. Enter your full name in the Your Name field. 
6. Enter your email address (username@eckerd.edu)
7. Select IMAP as the type of incoming server you are using. Enter imap.gmail.com in the Incoming Server field.
8. Set the Outgoing Server to smtp.gmail.com and click Next.
   
9. Enter your full email address (username@eckerd.edu) in the Incoming User Name and Outgoing User Name fields, and click Next.
   
10. Enter a name for your email account in the Account Name field, and click Next.
11. Verify your account information in the dialog box, and click Finish.
12. Select Server Settings from the folder list below your new account.
13. Update the Port value to 993.
14. In the Security Settings section, select SSL from the Use secure connection options.
15. Select the 'Check for messages at startup' checkbox and the 'Check for new messages every 10 minutes' checkbox.
16. Click Outgoing Server (SMTP) in the folder list.
17. Select the smtp.gmail.com (Default) entry from the list and click Edit. The SMTP Server page appears.
18. Enter smtp.gmail.com as the Server Name and set the Port to 587.
19. Select User name and password and enter your full email address (username@eckerd.edu) in the User Name field.
20. Select TLS from the Use secure connection radio buttons and click OK.
21. Click OK to save your changes and exit the Account Settings dialog.
    

For more information, see Google: Configure IMAP access in Mozilla Thunderbird