1. Seamless Integration with Outlook
Google Apps Sync for Microsoft Outlook® lets you use Microsoft Outlook® as a client for Google Apps email, calendar, and contacts. Email, calendar events, and contacts are all synchronized between Google Apps and Outlook. Outlook Notes are synced with Google Drive. And your organization's Global Address List is synchronized, as well.
Download Google Apps Sync | System requirements | User help
2. Alternate Outlook Integration Options
Alternately, you can access your Google Apps email from Outlook using the IMAP protocol. For more information and step-by-step instructions see the supported IMAP client list.
To configure calendar synchronization between Microsoft Outlook and Google Calendar, use the Google Calendar Sync tool.
3. Connecting Calendaring on your Exchange Server to Google Apps
The Google Calendar Connectors are a set of services, typically deployed by our Google Enterprise Partners, that allow Google Calendar to interoperate with Exchange 2003 servers through the bi-directional sharing of Calendar Free / Busy information. Each of the tools is installed in the local Exchange environment and must be maintained and configured by an Exchange Administrator.
4. Dual Delivery options for Exchange and Google Apps
Dual delivery allows incoming mail to be delivered to your current email infrastructure as well as Google Apps Email. This lets your organization test Google Apps Email without interrupting current systems, making it a nearly risk-free pilot. It also allows users to test Google Apps without having to abandon their current setup.
5. Migrating Email to Google Apps
If you're interested in migrating mail from Exchange Server, an Outlook Client or another email system to Google Apps, review the list of migration options.
6. Single Sign-On and Directory Sync
You can use Google Apps tools to leverage your existing data with Google Apps. Google Apps provides single sign-on (SSO) support for SAML based systems, to centralize authorization. Also, you can use Google Apps Directory Sync to provision and synchronize users and groups based on the user data in your LDAP server, such as Microsoft Active Directory or Lotus Domino.