AfterLogic WebMail Lite PHP is a Webmail script with a modern AJAX interface. It supports IMAP accounts, SMTP, and SSL (including Gmail). Users can check and send mail and use an address book. It provides a slick skin, a three-pane view, non-English language support, UTF-8 support, IMAP folders, and viewing and composing HTML mail. A MySQL backend is supported, with Web-based administration and installation and cPanel/Plesk/DirectAdmin integration.
Dolda Webmail (or d-mail for short) is a Webmail system written in PHP and interfacing with a back-end IMAP server. Advantages over most other projects of a similar sort are that it uses a persistant connection to the IMAP server (which increases performance on the Web server, reduces load on the network and on the IMAP server, and doesn't force the Web server to store the user's password in-core), and that it makes full use of XHTML 1.1 and CSS 2.
GroupOffice is a groupware suite that takes your office online, implementing online collaboration and CRM. It allows you to share projects, calendars, files and email online with co-workers and clients. It is easy to use and fully customizable. It also features synchronization with PDAs and Outlook.
Horde Groupware Webmail Edition is an enterprise ready browser-based communication suite. Users can read, send, and organize email messages and manage and share calendars, contacts, tasks, and notes with the standards compliant components from the Horde Project. It bundles the separately available applications IMP, Ingo, Kronolith, Turba, Nag, and Mnemo. It can be extended with any of the released Horde applications or the Horde modules that are still in development, like a file manager, a bookmark manager, a forum, or a wiki.
Insight Server is a Linux-based email server utilizing open source components to provide a highly reliable, scalable, and cost effective email solution for customers of all sizes. It's designed to facilitate complete messaging and collaboration capabilities within a company. It supports all standard protocols, and provides backup and recovery tools, server redundancy, migration tools, and resource management.
Inverse Lightning enhancer plugin enhances the functionalities of the Lightning calendar plugin for Thunderbird. It is meant to add better integration with CalDAV compatible servers such as SOGo. It provides support for CalDAV freebusy information in the scheduling interface and in the addressbook. It manages the iCalendar organizers by taking into account the identities configured in Thunderbird. And it fixes bugs found from time to time in Lightning which are not yet fixed upstream.