If you are using Active Directory, importing these contacts into the Global Address Book would require importing them as Contacts in Active Directory, and that can get pretty hairy. I would suggest instead using an Exchange public contact list thatis available to all users in your Exchange system. You can create a public address book from a workstation running Outlook. In Outlook, using the folder list, you would go to Public Folders/All Public Folders, right click on the All Public Foldersitems and click New Folder. Then, you name the folder, manage the permissions and import the contact information just like you would any other folder in Outlook.
For a public folder, the easiest way to make it accessible to all users is to set the Default permissions to Publishing Editor - this means everyone can add/delete contacts, etc., in that folder. You can also restrict permissions more than that if desirable. In order to make sure that the folder is searched automatically when users type a name into the "to" field in an email, you have to make sure they have it configured as an email address book (in the properties of the folder, Outlook Address Book tab).
Hope this helps!
