Access mail from Windows® Mobile

To take advantage of this feature, you must first enable Google Sync for your domain.

Once Google Sync is enabled for your domain, have each user follow these instructions on their Windows® Mobile device.

1. Important: Back up all contacts and calendars currently on your phone to your computer.
2. Open the Microsoft Exchange ActiveSync application on your device's home screen.
3. Click set up your device to sync with it.
   
   
   
4. Enter m.google.com as the server address.
5. Ensure that the SSL option is selected.
   
   
   
6. Click Next.
7. Enter your full Google Apps email address as the User name, and then enter your password. (Leave the Domain field empty. If your device requires a domain name, enter google.)
   
   
   
8. Click Next.
9. Check Contacts, Calendar, or Email, depending on which you'd like to sync. (Tasks is not supported and will lead to an error if checked.)
10. Click Finish.
    
    
    
11. Press the Sync softkey on the left to synchronize.
    
    
    

That's it! You can now access Gmail from Windows Mobile.

Source: [Google]