Plesk 12 + Postfix und Dovecot - Mailempfang und Versand funktioniert nur sporadisch

# Fail2Ban filter Dovecot authentication and pop3/imap server
# 
# based on filter dovecot.conf from fail2ban-0.8.13

[INCLUDES]

before = common.conf

[Definition]

_daemon = (auth|dovecot(-auth)?|auth-worker)

failregex = ^%(__prefix_line)s(pam_unix(\(dovecot:auth\))?:)?\s+authentication failure; logname=\S* uid=\S* euid=\S* tty=dovecot ruser=\S* rhost=<HOST>(\s+user=\S*)?\s*$
            ^%(__prefix_line)s(pop3|imap|managesieve)-login: (Info: )?(Aborted login|Disconnected)(: Inactivity|: Too many invalid commands\.)? \(((auth failed, \d+ attempts)( in \d+ secs)?|tried to use (disabled|disallowed) \S+ auth)\):( user=<\S*>,)?( method=\S+,)? rip=<HOST>(, lip=(\d{1,3}\.){3}\d{1,3})?(, TLS( handshaking(: SSL_accept\(\) failed: error:[\dA-F]+:SSL routines:[TLS\d]+_GET_CLIENT_HELLO:unknown protocol)?)?(: Disconnected)?)?(, session=<\S+>)?\s*$
            ^%(__prefix_line)s(Info|dovecot: auth\(default\)): pam\(\S+,<HOST>\): pam_authenticate\(\) failed: (User not known to the underlying authentication module: \d+ Time\(s\)|Authentication failure \(password mismatch\?\))\s*$

ignoreregex = 

# DEV Notes:
# * the first regex is essentially a copy of pam-generic.conf
# * Probably doesn't do dovecot sql/ldap backends properly  
# * Removed the 'no auth attempts' log lines from the matches because produces  
#    lots of false positives on misconfigured MTAs making regexp unuseable
#
# Author: Martin Waschbuesch
#         Daniel Black (rewrote with begin and end anchors)

[plesk-dovecot]
enabled = true
filter = plesk-dovecot
action = iptables-multiport[name="plesk-dovecot", port="imap,imap3,imaps,pop3,pop3s,4190"]  
logpath = /var/log/maillog
maxretry = 5

Jul 26 12:31:13 Xxxxxxx dovecot: imap-login: Aborted login (auth failed, 1 attempts in 2 secs): user=<>, method=DIGEST-MD5, rip=87.xxx.xxx.xxx, lip=85.xxx.xxx.xxx, TLS, session=<YhpZvMQbqABXnQQT>

Jul 26 15:45:49 Xxxxxxx dovecot: service=imap, user=user@domain.tld, ip=[87.xxx.xxx.xxx]. Disconnected for inactivity rcvd=505, sent=1184

...dovecot: imap-login: Aborted login (no auth attempts in 0 secs): user=<>...

[INCLUDES]
before = common.conf

[Definition]
_daemon = (auth|dovecot(-auth)?|auth-worker)
failregex =     user=<>, rip=<HOST>, lip=xx.xxx.xxx.xxx, TLS, session=
                @domain.tld ip=\[<HOST>]
ignoreregex =