Scheint also ob es ein generelles Problem ist weil iptables (Debian Stretch) mit dem Standart Eintrag imap3 in der jail.local ( auch original jail.conf) nicht zurechtkommt.
Nachdem ich den in imap geändert habe klappt es
iptables -w -A f2b-courier-auth -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports smtp,465,submission,imap3,imaps,pop3,pop3s -j f2b-courier-auth -- stdout: b''
2019-02-15 20:39:47,435 fail2ban.action [21923]: ERROR iptables -w -N f2b-courier-auth
iptables -w -A f2b-courier-auth -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports smtp,465,submission,imap3,imaps,pop3,pop3s -j f2b-courier-auth -- stderr: b"iptables v1.6.0: invalid port/service `imap3' specified\nTry `iptables -h' or 'iptables --help' for more information.\n"
2019-02-15 20:39:47,435 fail2ban.action [21923]: ERROR iptables -w -N f2b-courier-auth
iptables -w -A f2b-courier-auth -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports smtp,465,submission,imap3,imaps,pop3,pop3s -j f2b-courier-auth -- returned 2
2019-02-15 20:39:47,436 fail2ban.actions [21923]: ERROR Failed to execute unban jail 'courier-auth' action 'iptables-multiport' info '{'time': 1550258986.3629622, 'ip': '51.15.201.86', 'failures': 55, 'matches': 'Feb 15 20:19:46 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:19:51 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:19:56 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:01 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:06 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:11 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:16 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:21 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:26 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:31 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:36 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:41 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:46 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:52 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:20:57 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:02 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:07 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:12 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:17 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:22 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:27 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:32 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:37 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:42 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:47 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:52 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:21:57 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:02 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:08 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:13 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:23 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:28 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:33 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:38 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:43 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:48 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:53 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:22:58 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:03 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:08 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:14 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:19 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:24 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:29 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:34 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:39 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:44 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:49 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:54 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:23:59 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:24:04 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:24:09 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:24:14 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:24:19 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]Feb 15 20:24:25 mail pop3d: LOGIN FAILED, user=test@website_to_be_blocked.org, ip=[::ffff:51.15.201.86]'}': Error starting action
