Click on the Desktop.
Click on the Go menu at the top and select
Applications.
Double-click on the Address Book application.
Once Address Book is open, click on the Address
Book menu at the top and select Preferences....
Click on the LDAP icon located in the tool bar. Then click
on the Add button located in the bottom-left corner of the
window 
.
A sheet will come down. Type a name in the Name: field to
describe the Directory server you will be connecting to.
Type directory.umd.edu in the Server: field.
Type dc=umd,dc=edu in the Search Base: field.
Leave the rest of the settings like in the image below and click on the
Save button.
The Directory server you just added will show on the LDAP.
You are done! You can now use Mac OS X Mail to auto-complete E-mail addresses
when you are going to send mail.
