roundcube.net
Roundcube is free and open source webmail software written in PHP. It is a browser-based multilingual IMAP client with a desktop-like interface offering drag-and-drop message management, MIME and HTML support, address book with groups and LDAP connectors, threaded message listing, spell checking, shared IMAP folders and a plugin API. It supports PGP encryption and is released under the GNU General Public License version 3 or later.
