Install & Configure Popasswd in Debian (for Horde)

  $ apt-get install poppassd   # installs server-side mechanism for changing the password
    $ cd /var/www-ssl/horde/passwd/config
    $ cp -p backends.php.dist backends.php
    $ vi backends.php:
      - delete all but 'poppassd'

   ###########################################
   # note:
   # My poppassd service didnt start, because the deb-package put the startup command in 
   # the /etc/inetd.conf superserver file, which my system does not use.
   # If you want to run poppassd on the xinetd superserver, create a poppassd startup file:

   $ vi /etc/xinetd.d/poppassd
   ###########################################

service poppassd
{
disable = no
socket_type = stream
wait = no
user = root
server = /usr/sbin/poppassd
only_from = localhost
log_on_success += USERID
log_on_failure += USERID
}
###########################################

check the poppassd service:
$ /etc/init.d/xinetd restart
$ nmap localhost | grep pop3pw
$ telnet localhost 106

-> finish the horde-configuration of passwd using the Web-GUI.