There are several ways to create your own RBL: This is a simple script which converts a text file with a list of IP addresses into a bind zone http://j-chkmail.ensmp.fr/tools/mk_dnsbl rbldnsd is a small and fast DNS daemon which is
Spammers learn that you use GreyList
Some spammers learn that you use graylisting – which is great because they try to send less spam to your server. This is at least what I learnt since I have implemented graylisting on one of my mailservers. Besides the
Fail2ban
Fail2ban scans log files like /var/log/pwdfail or /var/log/apache/error_log and bans IP that makes too many password failures. It updates firewall rules to reject the IP address. Resources http://www.fail2ban.org/wiki/index.php/Main_Page
SpamAssasin Alternatives
If your tests show that you really can’t use SA, then other choices are dspam and bogofilter. but these are “pure” statistical filters. so you need to train them to get anything. Another choice is FUSSP – Final Ultimate Solution
iptables Video Tutorial Link
Mastering IPTables, Part I. http://www.linuxjournal.com/video/mastering-iptables-part-i