Roundcube Webmail is a free and open source PHP webmail solution with a desktop-like user interface which is easy to install/configure and that runs on a standard LAMPP server. It is a browser-based multilingual PHP IMAP client with an application-like user interface providing full functionality like MIME support, address book, folder manipulation, searching and spell checking.

Roundcube is written in PHP and JavaScript and it includes other sophisitcated open-source libraries such as PEAR, an IMAP library derrived from IlohaMail the TinyMCE rich text editor, Googiespell library for spell checking or the WasHTML sanitizer by Frederic Motte.

Features of Roundcube Webmail:
- Multilingual capabilities
- Full support for HTML messages
- Multiple sender identities
- Find-as-you-type address book
- Richtext/HTML message composing
- Searching messages and contacts
- Threaded message listing
- Int. domain names (IDNA) New!
- Shared folders New!
- Extensible using the Plug-in API
- Built-in caching for fast mailbox access
- Unlimited users and messages
- Template system for custom skins
- Plug-in API for flexible extensions

Requirements:
- Apache or Lighttpd webserver
- PHP Version 5.2.1 or greater
- MySQL, PostgreSQL, SQLite or MSSQL database
- An IMAP server which supports IMAP4 rev1
- An SMTP server (recommended) or PHP configured for mail delivery