Fail2ban is installed automatically and bans IP addresses for 3 hours after 3 failed attempts in 10 minutes by default. If you want to change this, you can easily edit [config/fail2ban-jail.cf](https://github.com/tomav/docker-mailserver/blob/master/config/fail2ban-jail.cf). You can do the same with the values from fail2ban.conf, e.g dbpurgeage. In that case you need to edit [config/fail2ban-fail2ban.cf](https://github.com/tomav/docker-mailserver/blob/master/config/fail2ban-fail2ban.cf) __Important__: The mail container must be launched with the NET_ADMIN capability in order to be able to install the iptable rules that actually ban IP addresses. Thus either include `--cap-add=NET_ADMIN` in the docker run commandline or the equivalent docker-compose.yml: ``` cap_add: - NET_ADMIN ``` If you don't you will see errors of the form ``` iptables -w -X f2b-postfix -- stderr: "getsockopt failed strangely: Operation not permitted\niptables v1.4.21: can't initialize iptabl es table `filter': Permission denied (you must be root)\nPerhaps iptables or your kernel needs to be upgraded.\niptables v1.4.21: can' t initialize iptables table `filter': Permission denied (you must be root)\nPerhaps iptables or your kernel needs to be upgraded.\n" 2016-06-01 00:53:51,284 fail2ban.action [678]: ERROR iptables -w -D INPUT -p tcp -m multiport --dports smtp,465,submission - j f2b-postfix ``` You can also manage and list the banned IPs with the [setup.sh](https://github.com/tomav/docker-mailserver/wiki/Setup-docker-mailserver-using-the-script-setup.sh) script.