Postfix + Courier_IMAP + LDAP - A bit outdated but some concepts are there. There are errors in his walkthrough and there is little explanation as to WHY he's setting certain options.
A better ldap, postfix and courier-imap howto - This page does a better job explaining the particular settings that need to be changed to effect using LDAP with your postfix MTA and Courier-IMAP MS.
Postfix + LDAP + DOVECOT + JAMM - replace courier with dovecot and tequila with JAMM. NOTE: It might be desirable to substitute dovecot for courier-imap but leave tequila in place. Tequila seems to handle vacation responses and such.
the JAva Mail Manager - is a web application to manage virtual email account information stored in an LDAP directory. It does not manage the mailserver specific configuration files so manual intervention might be required at times (such as cleaning up Maildirs of deleted accounts.)
Gnarwl E-Mail Autoresponder - An LDAP based auto-responder (unlike the 'vacation' command). Would require a custom html form for the user to input their own vacation response to the LDAP database. A how-to of sorts located here. NOTE: A basic HTML form COULD be implemented into EGW to alleviate the need for the user to have to type in ANOTHER web address just to set their vacation response. Alternatively, edit the main EGW header to include a link to a standalone custom form. It could be spruced up like the EGW interface, but wouldn't be necessary.
Postfix SMTP AUTH (and TLS) HOWTO - This HOWTO will help you deploy SMTP AUTH for Postfix. It will explain installation, configuration and use of the softwares needed (Cyrus-SASL, TLS and Postfix) for this solution. This link provides a pretty good insight on when you would want to use SMTP AUTH (SASL)