[Dovecot] How to log login errors?

[Sven Schmidt]

Hi!
I used "auth_debug=yes" and "auth_debug_passwords=yes". But I only see 
connects and disconnects:
Apr 11 09:17:43 dovecot: POP3(info at xxxx.xx): Disconnected: Logged out 
top=0/0, retr=0/0, del=0/0, size=0
Apr 11 09:17:43 dovecot: POP3(info at xxxx.xx): Disconnected: Logged out 
top=0/0, retr=0/0, del=0/0, size=0
Apr 11 09:18:11 dovecot: pop3-login: Login: user=<pop-test at xxxx.xx>, 
method=PLAIN, rip=80.146.3.204, lip=87.106.66.95