...

// ----------------------------------
// PLUGINS
// ----------------------------------
// List of active plugins (in plugins/ directory)

// For composer.json
$config['plugins'] = array(
    'advanced_search',
    'contextmenu',
    'dovecot_ident',
    'google_addressbook',
    'image_paster',
    'keyboard_shortcuts',
    'persistent_login',
    'rc_smime'
);

// For released plugins
array_push($config['plugins'],
    'acl',
    'additional_message_headers',
    'archive',
    'emoticons',
    'hide_blockquote',
    'jqueryui',
    'managesieve',
    'markasjunk',
    'new_user_dialog',
    'newmail_notifier',
    'subscriptions_option',
    'vcard_attachments',
    'zipdownload'
);

// For other way installed plugins
array_push($config['plugins'],
    'serverinfo',
    'google_analytics'
);

...