SocketMail Pro  

SocketMail is a powerful, scalable and fully customisable e-mail solution. Based on the PHP language, backed with a blisteringly fast MySQL back-end database, SocketMail is the ideal messaging solution for all small-to-large web sites and enterprises.

Hosting Requirements: Unix/Linux
Price: $219

   Hail  

Hail is a web based Hotmail client written in PHP. This client will give users some advanced abilities over their hotmail account.

Price: Free (GPL)

   Super Web-mail  

With Super Pop, you can read all of your email through a password protected portion of a web site. All you need is a net connection and a web browser.

Hosting Requirements: Unix, Windows
Price: $199

   POPMail  

POPMail is a POP3 client to send and check your mail. Features: Checking and sending mail - Sending and receiving attachments - Encrypted addressbook - Support for multiple users - Multiple languages.

Hosting Requirements: Unix, Windows
Price: Free

   SquirrelMail  

SquirrelMail is a standards-based webmail package written in PHP4. It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages render in pure HTML 4.0 (with no JavaScript required) for maximum compatibility across browsers. It has very few requirements and is very easy to configure and install. SquirrelMail has all the functionality you would want from an email client, including strong MIME support, address books, and folder manipulation.

Hosting Requirements: Unix/Linux, Windows; PHP 4.1.2+
Price: Free (GPL)

   NuralStorm Webmail  

NuralStorm Webmail does exacly what it says, it is an online php based webmail client. The client can connect to all POP3 and IMAP servers, so it is very versatile. It is all template based so you can easily add you own look to the client.

Price: Free (GPL)

   Virtual Mail ManaGer Interface  

vmmi (Virtual Mail ManaGer Interface) is a web-based interface to VMailMgr. It is written in PHP and distributed under the GPL license. I also rewrote the PHP-interface to VMailMgr which is itself LGPL'd. VMailMgr is a very popular software package, as it allows you to manage multiple independent mailboxes on a domain (each with their own passwords, quota rules, expiry dates etc.)

Hosting Requirements: Unix
Price: Free (GPL)

   VAMP  

VAMP is a web-mail client written entirely in the PHP scripting language which can access POP3 mailboxes. It features an interface not entirely dissimilar to other web-mail clients like Microsoft's Hotmail or IMP. The main goal of this project is to deliver a solid web-based E-Mail reading and composing platform that is fast, simple and easy to set up. VAMP also has some features rarely found in other web-mail packages.

Hosting Requirements: PHP 3/4
Database: MySQl, PostgreSQL
Price: Free

   eCorrei  

Webmail system which uses PHP and IMAP. It is easy, fast and small.

Hosting Requirements: Unix/Linux, Windows; PHP 4.0.3+; IMAP
Price: Free (GPL)

   NOCC Webmail  

NOCC is a webmail client written in PHP. It provides webmail access to IMAP and POP3 accounts. Features: Connection to IMAP and POP3 server with c-client library - Sending mail with Sendmail or SMTP server - Support MIME attachment messages - Multi-language support (22 languages so far) - Themable - Renders pages in XHTML 1.0 for maximum compatibility with any browser, works with text browsers - No frames, cookies not required (can use URL-based sessions) - No need of a database.

Hosting Requirements: PHP 4+
Price: Free (GPL)