Question : How to configure postfix users to get authentication from ldap

Dear Sir:

I am having rhel5 working as a mail server and ftp server  but as of now /etc/passwd is used for the authentication but i want to configure such that postfix should use the LDAP for the authentication

1. please give me step by step docs to configure LDAP server
2. please give me step by step docs to  switch postfix users from /etc/passwd to LDAP  authentication.

Answer : How to configure postfix users to get authentication from ldap

OpenLDAP Setup Howto for RHEL/CentOS 5
http://www.linuxmail.info/openldap-setup-howto/

Postfix -- Active Directory/LDAP Virtual Users for RHEL/CentOS 5
http://www.linuxmail.info/postfix-dovecot-ldap-centos-5/