This post explains how to set up GMail IMAP on a BlackBerry. The instructions on the Google site will never help you get it set up correctly. If you don't want to preamble and background, skip down to the "Instructions" section.
Although a BlackBerry may be the best mobile device for e-mail, this assessment should probably be made only if you're running it off of a BES, BlackBerry Enterprise Server. With BES you'll get full two way sync with you desktop e-mail. Without BES, your stuck with BIS, BlackBerry Internet Service, the consumer version of BlackBerry e-mail. Although it uses the same application on the device, the interaction with mail servers is not as seamless as with BES. The touted advantage of a BlackBerry is that mail is "pushed" to you. Your device doesn't have to "reach" out to the mail server and pull the mail down. The result is that mail reaches you more quickly and without as much work on the part of the mobile device. If you delete an item on your desktop machine, it will still show up on your BlackBerry. In recent years, other mobile systems have launched push e-mail as well. Google recently announced two-way sync with push e-mail service between GMail and the iPhone and Windows Mobile devices. But it left off any special push e-mail with GMail for BlackBerry. With BES, you can get push e-mail for most any e-mail service, but it's not a two way sync.
If you want two way sync between GMail and BlackBerry and you're only running BES, you are left with two choices. First, you can use a special GMail application that you can download to from your BlackBerry browser using the address m.google.com/go. It works extremely well but doesn't allow you to change the frequency with which it gets your e-mail. Best I can figure is it's more than every five minutes but less than every minute. You can manually force it to grab your mail. It's a really good application. The only other drawback is that it does not render HTML e-mail. You'll probably want to have it set up on your device regardless because it allows you to see threaded conversations and search and find every one of the many GMail messages you undoubtedly have stored in your GMail archive.
The second choice is to set up GMail IMAP. IMAP is a mail protocol that allows two-way sync between a mail server and a device, whether a desktop or a mobile device. This way, if you delete an item on your desktop, it will also be deleted on the server and therefore also on your mobile device. However, it doesn't actually work as well as you'd think.
Google's instructions (LINK) are incomplete. They say the following:
To integrate Gmail with the BlackBerry's email client, just follow these steps:
-- On your BlackBerry device, navigate to your home screen
-- Select the icon that lets you set up email (this can be called BlackBerry Set-up, E-mail settings, or Personal Email Set-up)
-- Follow the setup instructions provided on your device
Unfortunately, that won't work! The key is to put in your e-mail address and NOT put in your password. Here are instructions that work: