Windows Mobile : Microsoft Global Contact Access

With Microsoft Global Contact Access, you can use Pocket Outlook on your Windows Mobile-based Smartphone or Pocket PC Phone Edition to look up contacts in the Global Address List (GAL) on your corporate Exchange server.
You can also check your co-workers’ schedules to see if they’re free or busy, and add multiple recipients to a meeting request. Even if you’re away from your office you’ll have all the information you need to connect with any co-worker in your organization, and send them e-mail or request a meeting.