Backends

Radius Servers

• FreeRadius: http://freeradius.org
• Radiator: http://www.radiator.com/

Mail Servers

• Qmail: http://qmail.org
• Sendmail: http://sendmail.org
• JES: Jave Enterprise System http://www.sun.com/software/javaenterprisesystem 
• or any other server with openldap or mysql backends

FTP

• Proftpd: http://www.proftpd.org
• JES: Jave Enterprise System
• or any other server with openldap or mysql backends

SMS

• Any SMS gateway provider with a well defined API

AntiVirus

• Drweb AV-Desk: http://av-desk.com