Email Migration Tools Added to Google Apps
Google Apps added the option to migrate the messages from your existing email accounts if you use the business or the educational edition. "Administrators use a self-service wizard to easily and securely transfer existing email data from an IMAP server over to users' Gmail accounts on Google Apps. Gmail will put messages into conversation threads, display the original sender, recipient, and date of messages, and convert existing mail folders into labels. (...) This tool currently supports email servers with an IMAP interface."
When composing messages, you should be able to access Gmail's new address book by clicking on "choose from contacts" link. Unlike the old way of adding contacts to a new email, you can now browse through your entire address book, choose your frequently mailed contacts, or use the search feature to add more people at a time. The address book includes all the users from your domain. The feature has already been available for a while in Google Video and Google Docs.