Add a directory service (LDAP) account
Internet directory services, also known as LDAP services, are used to find e-mail addresses that are not in your local Outlook contacts. Directory services search directories on other servers to look up names and other information that can then be viewed in Outlook. You can locate an LDAP server on the Internet, on your organization's intranet, or through another company that hosts an LDAP server.
On the Tools menu, click Accounts.
In the lower-left corner of the Accounts dialog box, click Add , and then click Directory Service.
Enter the information for your directory service, and then click Add Account.