E-Mail and LDAP

Mozilla, Pine, Evolution and MANY other E-mail clients may be configured to utilize an LDAP server as a contacts data source
In many cases, just typing the LDAP server name and "dc=yourdomain,dc=com" gets it working
E-mail MTAs such as Sendmail, Exim, Postfix, and Qmail may be configured to use LDAP for e-mail address, mail groups, routing, and alias information
IMAP and POP servers can use LDAP for e-mail, account, and password information

Mozilla, Pine, Evolution and MANY other E-mail clients may be configured to utilize an LDAP server as a contacts data source