Free rhsd software for linux

The Email Server is designed to provide services offered by its commercial email products, such as IMAP/POP services, Web-Based Email Interface and Administration, Mail Filtering, Spam Blocking and Directory-Based Authentication and Addressbooks.
RH Email Server is fine for businesses and organizations of all sizes. Multiple commercial and educational installations are already using this project. The largest current user load that has been reported is 7,000 + users.
Interoperability between RHSD projects such as the RHSD Email Server and the RHSD Domain Controller will allow for use of Single-Sign On. RHSD also utilizes IETF Standardized projects and therefore will be compatible with any Directory system compatible with LDAP v.3.
Main features:
- Web-Based Email Client for Users
- LDAP Directory / Authentication
- Mail Filtering
- Addressbooks
- Web-Based Administration Tools
- Role-Based Tool Delegation
- Spam Blocking