AJAX Web mail client - RoundCube

For those who want to go for robust classical mail solutions based on Postfix, Doveport and MailDB technologies and still want to offer users a rich web interface to access mails, Roundcube is the answer. 

RoundCube Webmail is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality you expect from an e-mail client, including MIME support, address book, folder manipulation, message searching and spell checking. RoundCube Webmail is written in PHP and requires a MySQL or Postgres database. The user interface is fully skinnable using XHTML and CSS 2.