Free and open source webmail software
SquirrelMail is a PHP-based Web email client. It includes built-in pure PHP support for IMAP and SMTP, and renders all pages in pure HTML 4.0 for maximum compatibility across browsers. It has strong MIME support and a flexible plugin system.
SaltOS, ERP, CRM, Business Management Suite, Josep Sanz Campderrós
SaltOS is a Business Management solution 100% Cloud Computing. It integrates features like CRM (Customer Relation Management) and ERP (Enterprise Resource Planning). Moreover is it licensed as 100% free software GPL-3.0.
NOCC is a simple and fast Webmail client which can handle POP3, SMTP, and IMAP servers. It is written with PHP5 (uses sessions), has low requirements (no database, frames). Features multi-language support, MIME attachments, displays HTML messages.
Hastymail is a fast, secure, rfc-compliant, cross-platform IMAP/SMTP client application written in PHP providing a clean web interface for sending and reading E-mail. This version of Hastymail is no longer being developed. We are now working on a new version, Hastymail 3, AKA, "Cypht". http://cypht.org
Allow to redirect (a.k.a. "remail") mail messages to other recipients
The Mailredirect extension for Mozilla Thunderbird and Mozilla SeaMonkey adds the ability to redirect one or more email messages to one or more recipients. The feature of email redirecting is also known as remailing or resending. The extension is an answer for https://bugzil.la/12916
Special Folders Plugin is a plugin for the popular webmail Roundcube. This plugin lets the admin define new special folders, which will be displayed at top of folders lists. Admin can directly choose the real mail folder, a name for it and the icon.
The OpenP2M is a software that lets you store and share files on your email account.
BlogMail software is a CMS and a Webmail application integrated in one. It's based on WordPress MultiUser and has all the functionality of this, like RSS and comments, plus support for LDAP, smarty templates, automatic subdomains and antispam filtering.
GMailSite es un script que permite que uses tu cuenta de correo de GMail para crear una página en la cuál se publicarán todos los archivos adjuntos de tus mensajes que esten guardados bajo algún label en tu cuenta de correo.
This plugin adds to RoundCube the ability to easily give different permissions to users by creating a roles table and assigning users to it. This and other plugins may use its public function to register permissions and admin them with this plugin.