Unable to log in to Roundcube after an upgrade to Plesk Onyx 17.8 or Plesk Obsidian: Failed to load plugin file sieverules.php

Symptoms

• It is not possible to log in to Roundcube webmail after an upgrade to Plesk Onyx 17.8 or Plesk Obsidian. The login operation hangs and then fails with "504 Gateway Time-out" or "500 Internal Server Error".

• The following error message appears in the Roundcube logfile /var/log/plesk-roundcube/errors:

  CONFIG_TEXT: PHP Error: Failed to load plugin file /usr/share/psa-roundcube/plugins/sieverules/sieverules.php in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_plugin_api.php on line 173 (GET /)

• The SieveRules plugin is enabled in Roundcube configuration file /usr/share/psa-roundcube/config/config.inc.php:

  # grep sieverules /usr/share/psa-roundcube/config/config.inc.php
  /usr/share/psa-roundcube/config/config.inc.php:$config['plugins'] = array('password', 'markasjunk2', 'sieverules')

Cause

The SieveRules plugin has been replaced with Managesieve plugin in Roundcube shipped with Plesk starting from Plesk Onyx 17.8.

This is as a Plesk bug with ID PPPM-8397, which will be fixed in future product updates.

Resolution

1. Connect to the Plesk server via SSH.

2. Open the file /usr/share/psa-roundcube/config/config.inc.php in any text editor. In this example, we are using the vi editor:

   # vi /usr/share/psa-roundcube/config/config.inc.php

3. Remove or comment out the below lines with "//":

   • Before:

     CONFIG_TEXT: $config['default_host'] = 'localhost';
     $config['temp_dir'] = '/var/tmp/plesk-roundcube';
     $config['plugins'] = array('password', 'markasjunk2', 'sieverules');

   • After:

     CONFIG_TEXT: // $config['default_host'] = 'localhost';
     // $config['temp_dir'] = '/var/tmp/plesk-roundcube';
     // $config['plugins'] = array('password', 'markasjunk2', 'sieverules');

4. Save the changes and close the file.