I would also like to point you to this app, which seems to be a full-featured open source mail server (based on postfix) that works out-of-the-box. I played around with it and was fairly impressed. There is a VMWare Player virtual machine image you can download to play around with.
http://www.artica.fr/ Artica for Postfix allows you to install a full solution by one single command line: * Postfix: Main MTA * Kaspersky Anti-spam: powerful Anti-spam provided by Kaspersky Inc * Kaspersky Anti-Virus * Bogofilter: Bayesian anti-spam * SPFMilter: SPF Checking application * Milter-greylist: Powerfull greylisting daemon * SpamAssassin: Open Source Perl Anti-Spam * MIMEDefang: Powerfull SMTP toolit * Clam Antivirus: Open Source antivirus * Amavis: Open Source scanner dispatcher * OpenLDAP: Database for main configuration and user management * SQLite library: zeroconf sql database engine with high perfomances. * Cyrus-imap: powerfull MDA System * Procmail: MDA Filter * Fetchmail: Email retreival * DnsMasq:DNS forwarder and DHCP server * Mailman:Mailing List manager * Sieve: End-user mail filters * Yorel script: Statistics of yorel * QueueGraph: Statistics for postfix * MailGraph: Statistics for postfix * AWSTats and geoip plugin: Statistics set for postfix * renattach: attachments filter * NTP: Network Time Protocol * pure-ftpd : FTP server using LDAP. * Squid : The main proxy server. * DansGuardian : URL filtering... * Kaspersky For SQUID : antivirus ICAP designed for squid * Samba : File server
