Slackware is one of the oldest and most mature Gnu/Linux distributions.
Samba
Samba is a file and printer sharing protocol that can easily interoperate with
Microsoft-based workstations and servers.
Apache
Apache is the world's most popular web server.
MySQL
MySQL is the world's most popular open source database server.
Asterix PBX
An open source Voice-over-IP PBX (private branch exchange) that can
also bridge between the IP network to the PSTN (public switched
telephone network)
phone system.
Qmail
Qmail is an open source mail transfer agent, highly secure, fast, powerful and user-friendly when coupled with vpopmail and qmailadmin.
Symantec
Symantec is the maker of high quality mail filtering and antiviral protection
for Windows-based systems.
Vexira
Vexira Mail Armor is a snap-in email virus filtering package that works with
Qmail.
DSPAM
DSPAM is a self-learning spam filter with Bayesian Noise Reduction capability. It is known to reach accuracy of 99.991%.
