Use the LDAP search engine to find users emails, address and phone numbers. LDAP is a public database of user's details from around the globe. To begin a search you must specify the full name of the user to search for, and optional email address.
When viewing the results of the search you can select to add the user to your address book, compose an email or click for additional information on the user.
If enabled on your e-mail service you can search your domain or site for users by setting 'Search Type' to 'Search System Database'.