cpanel

This PHP webmail front-end is designed for existing mail servers and offers IMAP/SMTP/SSL, LDAP, mobile compatibility, CalDAV/CardDAV sync, folders, calendar, rich-text editor, address book, and a web admin panel. The software supports skins, UTF-8, MySQL and is compatible with cPanel and Plesk.

This software is an open source PHP webmail front-end with a fast AJAX interface and supports IMAP/SMTP/SSL, LDAP, folders, rich-text editor, address book, web admin panel, UTF-8, non-English languages, MySQL, cPanel, and Plesk for your existing mail server.