Fail2ban

• http://ittipsoftheday.blogspot.com.br/2016/01/how-to-remove-ip-from-iredmail.html
• http://www.the-art-of-web.com/system/fail2ban-log/
• https://github.com/fail2ban/fail2ban/issues/132
• https://www.raspberrypi.org/forums/viewtopic.php?t=67934&p=496490
• http://serverfault.com/questions/285256/how-to-unban-an-ip-properly-with-fail2ban

iptables -D fail2ban-NAME -s IP -j DROP