1. Roundcube
Roundcube Webmail is a browser-based IMAP client that offers a rich range of features including MIME, Address Book, folder manipulation, mail search and spell checking. Roundcube Webmail is written in PHP and requires support from MySQL or Postgres database. Its UI is fully compliant with XHTML and CSS 2.
2. Zimbra
Zimbra provides an open source mail and calendar system, and is also based on Ajax technology, a very powerful client, he can integrate the third party application "Mash-ups" through the Web service, so you can enjoy CRM, map or other more functions.
3. Xuheki
Xuheki is a fast IMAP client developed using AJAX technology. You can think of a feature that basically has it, and it uses the GNU general public License.
4. SquirrelMail
SquirrelMail This is a good webmail,php language written, and does not use AJAX technology, so it is not very flashy, but it is using the pure built-in PHP features support IMAP and SMTP. All pages are plain HTML 4.0 (without any JavaScript), which is intended primarily to maximize compatibility with different browsers.
5. Atmail
AtMail, a free lightweight Ajax Webmail client, written by PHP, supports Web and WAP.
6. Afterlogic
Afterlogic WebMail Lite PHP is a very easy to use WebMail but its interface is also very cool, it supports AJAX and skins. Supports POP3 and SMTP. Support to send and receive mail, multi-attachments, multi-account, multi-domain, mail preview, site management. The installation is very easy and requires PHP 4.1+, fully open source and completely free.
7. Hastymail
Hastymail is a full-featured IMAP/SMTP client, written in PHP. Compatible with PDAs, mobile phones, text browsers, and all major browsers. Hastymail has a powerful plug -in system, because PHP programmers can arbitrarily change or add the plugins they want.
8. MAILR
MAILR is an open source webmail written by Ruby, which uses the Ruby on Rails Web application framework.
9. Claros InTouch
Claros InTouch is an Ajax messaging suite that contains the main features of webmail, Address Book, Notepad, calendar (still in development), Network hard drive (still in development), built-in instant chat, and RSS reader. This is the first open source webmail project that contains built-in spam protection and instant chat features. But the main use of the Java language, the use of jsp/servlets and EE technology and MySQL database.
Ten. Postaci
Postaci is a PHP-based pop3/imap mail client that supports SMTP authentication. It uses MySQL, MSQL, Microsoft SQL, Sybase, or PostgreSQL databases.