Free openwebmail software for linux

AqMail fetches mails from remote mailboxes (POP3), applies admin-defined filters, and stores the email in local mailboxes for POP3 daemons to serve them.
AqMail project supports virtual mail domains and users. It has been tested with QMail as the MTA and with Spamassassin and ClamAV as filters.
Main features:
- supports virtual users and domains
- supports multiple remote boxes per user (mails can be gathered from remote boxes into local boxes)
- individual fetch intervals for every remote box of every user
- system-wide, domain-wide or per-user filtering of mail
- ordering of mail filters
- simple interface to filter scripts (basically "FILTER INFILE OUTFILE")
- POP3 client plugin with APOP or USER/PASS authentification
- maildir plugin (reads and writes maildir folders)
- tested with QMail, SpamAssassin and ClamAV
You can use AqMail to gather mails from multiple email accounts into a single account which can then be accessed via a webmail interface (e.g. OpenWebMail) or via a POP3 server (e.g. QMail).
AqMail can be used as a daemon which continuously fetches, filters and distributes mails. It can also be used in command mode (e.g. to fetch mails and store them directly to a maildir in order to just replace the tool fetchmail).
AqMail is running on my own system in combination with QMail. However, any mail transfer agent which is able to serve from maildir folders can be used.
Enhancements:
- The daemon mode has been improved since 0.9.0beta.

vHost is a one-step solution for all virtual hosting needs. It enables a Linux/BSD server with single or multiple IP addresses to function as unlimited virtual hosts with HTTP, FTP, SMTP, POP3, IMAP, and other virtual services extendible via modules.
vHost comes with both a command-line interface and a web-based GUI ("control panel"), offering maximum control to a domains owner while relieving the system administrator of most routine administration tasks. Other major features include four levels of login, comprehensive quota control, and built-in clustering capability.
Main features:
- Supports all major Linux distros, and FreeBSD, NetBSD.
- Integrated install/upgrade module provides effortless one-step install and upgrade from any old version.
- Retains all previous system configurations while upgrading in order to ensure zero downtime.
- Clean virtual host file system follows *nix conventions.
- Virtual user home/web space.
- Integrated web-based FTP client for virtual users as well as host owners.
- All operations available in both command-line and web-based GUI ("control panel").
- Modularized architecture allows for arbitrary features and virtual services extended by modules.
- Four levels of login and security: root, vroot ("reseller"), host owner, and virtual user.
- Comprehensive quota control: disk space limit, inbox size limit, per-owner host limit, per-host user limit.
- Built-in clustering capability supports DNS round-robin clustering and distributed host/DNS.
- Automatic local and remote DNS setup.
- Automatic IP address aliasing and management for multiple-IP systems.
- Supports host alias and user alias.
- Built-in log rotation, easy exclusion of logs from rotation.
- Optional email "catch-all".
- Built-in "POP before SMTP" relay support.
- True virtual webmail per virtual host.
- Virtual host webstats.
- Command logging.
- Optional per-host and per-owner profiles for fine-grained system configuration.
- Easy system migration with command --cphost.
- No database backend required.
Enhancements:
- This is a major release with a minor version number increment (version 4.0 is planned for a new Web GUI).
- Changes include an integrated Web-based FTP client, a virtualization module for OpenWebmail, the new commands --addmydb/--delmydb, virtual user ".forward" support, improved SELinux support, improvements for clustering/distributed systems, numerous other fixes and enhancements, and documentation.