Free and open source webmail software
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.
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.
The OpenP2M is a software that lets you store and share files on your email account.