JFoxMail is a opensource J2EE webmail application. Access to read from IMAP account, Compose using SMTP, and Address Book management using LDAP is supported.
RetrieveUserData is a plugin for the webmailer Squirrelmail. It retrieves a user's name and e-mail address from a configurable source like LDAP or MySQL. Your users don't need to configure Squirrelmail before writing their first mail.