By default 'managesieve' plugin is enabled in CentOS Webpanel (CWP) Rouncube's Plugins array . And we need to ensure that the 'managesieve plugin is enable by do the following (Go to Line number 79) , If not then add the plugin manually # vi /usr/local/cwpsrv/var/services/roundcube/config/config.inc.php $config['plugins'] = array( 'archive', 'zipdownload', 'managesieve', 'password', ); So it would look like the following (From Line number 79) : Configuring the 'managesieve' plugin # cd /usr/local/cwpsrv/var/services/roundcube/plugins/ # cp -p managesieve/config.inc.php.dist managesieve/config.inc.php # vi managesieve/config.inc.php // Enables separate management interface for vacation responses (out-of-office) // 0 - no separate section (default), // 1 - add Vacation section, // 2 - add Vacation section, but hide Filters section $config['managesieve_vacation'] = 1; Her