Webmail is a email client based on web and implemented as a web application running on a web server. There are several free webmail client scripts are available.
Roundcube is a free and open source browser based webmail client for LAMPP server. It is a multilingual IMAP client with over more than 70 languages.It is available under the GNU General Public License version 3. It comes with Modern user interface and Drag-&-drop message management. It supports IDNA, IMAP and the external SMTP server. It run on webservers like Apache, Nginx, Lighttpd, Hiawatha or Cherokee with MySQL, PostgreSQL and SQLite databases. It also provide strong privacy protection.
Some other features are Canned response templates,Multiple sender identitiesm, Spell checking, Built-in caching for fast mailbox access and Import/export functions.
Rainloop is a free web browser based webmail client for Apache, nginx, lighttpd, MS IIS servers. It offers rich Modern user interface and Drag’n’drop for mails and attachments and comes with IMAP and SMTP protocols including SSL and STARTTLS support. RainLoop Webmail Community edition is available under GNU AFFERO GENERAL PUBLIC LICENSE Version 3 (AGPLv3). It was designed with efficient memory use in mind. It also comes with built-in caching system for improving performance of the system. And some other fuctions are simultaneous access of different accounts in different browser tabs.
Mailpile is also a 100% Free & Open Source email client with built-in PGP encryption and other nice features. It is available under GNU AFFERO GENERAL PUBLIC LICENSE Version 3 (AGPLv3). It supports Powerful search & tagging and search index is encrypted to avaoid any leaks.
Afterlogic is also a 100% Free & Open Source email client with More than 30 languages, right-to-left interface support (for Hebrew and Arabic), date and time formats.It is available in dual licensing, GNU AFFERO GENERAL PUBLIC LICENSE Version 3 (AGPLv3) and commercial license .It Can run on a secure HTTPS server. The user inter face is clean and Minimalistic. It is built on the latest HTML5 and CSS3 technology. Other some important features are 2-Step Verification, Authentication via Google, Facebook, Twitter and Mail threading and Attachment preview thumbnails.