Postfix

Limit incoming Mail Rate against Spam Scripts

edit main.cf and set:

smtpd_error_sleep_time = 1s
smtpd_soft_error_limit = 5
smtpd_hard_error_limit = 10
smtpd_client_connection_count_limit = 10
smtpd_client_connection_rate_limit = 10

Testing Mail Loop (send a Mail every Second):

 
while true; do `date | mail -s "Test Postfix" postbox@yourdomain.com`;sleep 1; done

Result: after 10Mails the sending IP should by blocked! Add "fail2ban" Log Monitor as second wall protection to kick out bad IP's forever!

Automatic Firewall Update

edit a Script firewall.sh set:

#!/bin/bash
# GET BAD IP'S
cat /var/log/mail.log | grep rejected | cut -d"[" -f3 | cut -d"]" -f1 > /tmp/firewall.txt
# insert to Firewall
while read line; do sudo ufw insert 1 deny from $line to any; done < /tmp/firewall.txt
service ufw restart
exit 0

run by cron hourly..