Duplicate of #12937

Hello, since a few weeks I have the problem that Ingo filters, which 
move mails to a subfolder with german Umlauts don't work anymore.
In my backends.local.php file I defined the following:

$backends['sieve'] = array(
     // Disabled by default
     'disabled' => false,
     'transport' => array(
         Ingo::RULE_ALL => array(
             'driver' => 'timsieved',
             'params' => array(
                 // Hostname of the timsieved server
                 'hostspec' => 'localhost',
                 // Login type of the server
                 'logintype' => 'PLAIN',
                 // Enable/disable TLS encryption
                 'usetls' => true,
                 // Port number of the timsieved server
                 'port' => 4190,
                 // Name of the sieve script
                 'scriptname' => 'ingo',
                 // Enable debugging. The sieve protocol communication 
is logged
                 // with the DEBUG level.
                 'debug' => false,
             ),
         ),
     ),
     'script' => array(
         Ingo::RULE_ALL => array(
             'driver' => 'sieve',
             'params' => array(
                 // If using Dovecot or any other Sieve implementation that
                 // requires folder names to be UTF-8 encoded, set this
                 // parameter to true.
                 'utf8' => true,
              ),
         ),
     ),
     'shares' => false
);

The script is generated like this regardless of setting the "utf8" 
parameter to "true" or "false"

if header :comparator "i;ascii-casemap" :contains "Subject" "Neue 
Nachricht"  {
  fileinto "INBOX.Ank&APw-ndigungen";
  stop;
}

If I manually comment the line

$this->_vars['folder'] = 
Horde_String::convertCharset($this->_vars['folder'], 'UTF-8', 
'UTF7-IMAP');

in ingo/lib/Script/Sieve/Action/Fileinto.php it works as it should:

if header :comparator "i;ascii-casemap" :contains "Subject" "Neue 
Nachricht"  {
  fileinto "INBOX.Ankündigungen";
  stop;
}

Could you please tell me what I'm doing wrong?

Thanks in advance,
Christian