Use Google Apps on Windows Phone
Using Native Windows Phone apps
Set up your Windows Phone or Windows Mobile device with Google Sync to access your Google Apps mail, contacts and calendars using your phone's native applications (requires that your Google Apps administrator enables Google Sync for your domain).
Using your phone's mobile browser
You can access many other Google products from a mobile browser. In most cases, you can just go to m.google.com in your phone's browser, touch the product you want to use, and sign in to your Google Apps account. For details, see Using any smartphone's mobile browser.