Before we get started let me start by saying that this software is provided as
is and should only be used in the understanding that I accept no liability 
in regards to any damages that might result from its use (or misuse). 

Setting up RADIUS before SMTP:
1. Figure out where to put your database file and the Perl scripts and edit
   the Perl scripts to match your choice. by default its assumed the database
   is in /var/mail/radius-smtp.db and the scripts are in /usr/local/bin

2. set up your RADIUS server to execute the Perl scripts for Start and Stop 
   accounting packets. First you need a radius server that can execute 
   commands in response to accounting events such as FreeRADIUS.  a sample 
   radius.conf and acct-user file are provided. You will need at minimum:

   1) The Livingston radius compatible files module loaded in the modules
      section of the radius.conf file like so:

      files {
                usersfile = ${confdir}/users    
                acctusersfile = ${confdir}/acct_users
                preproxy_usersfile = ${confdir}/preproxy_users
                compat = no
        }

    2) A preacct section  that passes off to the files module.

       preacct {
		files
       }

    3) an acct-user file that calls start and stop with the framed IP address 
       of the user for both Start and Stop accounting packets
       (this adds the user's IP to the database on login and removes it
	on logout to control who is allowed in by the MTA or whatever else 
	you want to control access to).

       DEFAULT Acct-Status-Type == Start
	  Exec-Program = "/usr/local/bin/start %{Framed-IP-Address}"

       DEFAULT Acct-Status-Type == Stop
          Exec-Program = "/usr/local/bin/stop %{Framed-IP-Address}"
   
3. Finally you need to setup your own MTA to use the Berkeley database hash 
   file to control access to your mail server. I recommend you let the database
   populate for at least a day or more before doing this so that just about
   everyone that is really logged in will be in the database. 

   You just need to setup your dialup pools to be denied access to your mail
   server and accept any IP address that is in the database file. 

   Since the scripts just simply put in (or remove) their arguments in the 
   database file you can easily test your ACL by running the start and stop 
   scripts by hand. another good command to monitor the database is the db 
   command that comes as part of most Berkley db distributions. just type db 
   hash and the full path to the database file to see its contents.  for 
   example "db hash /var/mail/radius-smtp.db" will spit out the contents of 
   the database file /var/mail/radius-smtp.db.