diff --git a/CHANGELOG b/CHANGELOG
index 6b5fd6f86..6d9b02b7e 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -37,6 +37,7 @@ CHANGELOG Roundcube Webmail
 - Managesieve: Support filter action with custom IMAP flags (#6011)
 - Managesieve: Support 'mime' extension tests - RFC5703 (#5832)
 - Managesieve: Support GSSAPI authentication with krb_authentication plugin (#5779)
+- Managesieve: Support enabling the plugin for specified hosts only (#6292)
 - Password: Support host variables in password_db_dsn option (#5955)
 - Password: Automatic virtualmin domain setting, removed password_virtualmin_format option (#5759)
 - Password: Added password_username_format option (#5766)
diff --git a/plugins/enigma/lib/enigma_ui.php b/plugins/enigma/lib/enigma_ui.php
index c0b1f2eca..b3bd41bc6 100644
--- a/plugins/enigma/lib/enigma_ui.php
+++ b/plugins/enigma/lib/enigma_ui.php
@@ -87,7 +87,6 @@ class enigma_ui
 
             $this->rc->output->add_handlers(array(
                     'keyslist'     => array($this, 'tpl_keys_list'),
-                    'keyframe'     => array($this, 'tpl_key_frame'),
                     'countdisplay' => array($this, 'tpl_keys_rowcount'),
                     'searchform'   => array($this->rc->output, 'search_form'),
             ));
@@ -191,18 +190,6 @@ class enigma_ui
         $this->add_js();
     }
 
-    /**
-     * Template object for key info/edit frame.
-     *
-     * @param array Object attributes
-     *
-     * @return string HTML output
-     */
-    function tpl_key_frame($attrib)
-    {
-        return $this->rc->output->frame($attrib, true);
-    }
-
     /**
      * Template object for list of keys.
      *
diff --git a/plugins/enigma/skins/classic/templates/keys.html b/plugins/enigma/skins/classic/templates/keys.html
index 09692fa2b..366bdccb7 100644
--- a/plugins/enigma/skins/classic/templates/keys.html
+++ b/plugins/enigma/skins/classic/templates/keys.html
@@ -60,7 +60,7 @@
 </script>
 
 <div id="enigmacontent-box">
-    <roundcube:object name="keyframe" id="keyframe" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+    <roundcube:object name="contentframe" id="keyframe" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/plugins/enigma/skins/elastic/templates/keys.html b/plugins/enigma/skins/elastic/templates/keys.html
index fcef199b1..c4ec76313 100644
--- a/plugins/enigma/skins/elastic/templates/keys.html
+++ b/plugins/enigma/skins/elastic/templates/keys.html
@@ -69,7 +69,7 @@
 		</div>
 	</div>
 	<div class="iframe-wrapper">
-		<roundcube:object name="keyframe" id="keyframe" src="/watermark.html" />
+		<roundcube:object name="contentframe" id="keyframe" src="env:blankpage" />
 	</div>
 </div>
 
diff --git a/plugins/enigma/skins/larry/templates/keys.html b/plugins/enigma/skins/larry/templates/keys.html
index e60608054..a280627fc 100644
--- a/plugins/enigma/skins/larry/templates/keys.html
+++ b/plugins/enigma/skins/larry/templates/keys.html
@@ -63,7 +63,7 @@
 
         <div id="enigmacontent-box" class="uibox">
             <div class="iframebox">
-                <roundcube:object name="keyframe" id="keyframe" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+                <roundcube:object name="contentframe" id="keyframe" width="100%" height="100%" frameborder="0" src="env:blankpage" />
             </div>
         </div>
     </div>
diff --git a/plugins/help/help.php b/plugins/help/help.php
index c00c69ba7..352c764df 100644
--- a/plugins/help/help.php
+++ b/plugins/help/help.php
@@ -74,11 +74,11 @@ class help extends rcube_plugin
 
         // register UI objects
         $rcmail->output->add_handlers(array(
-            'contentframe' => array($this, 'content_frame'),
             'helpcontent'  => array($this, 'help_content'),
             'tablink'      => array($this, 'tablink'),
         ));
 
+        $rcmail->output->set_env('help_links', $this->help_metadata());
         $rcmail->output->send(!empty($_GET['_content']) ? 'help.content' : 'help.help');
     }
 
@@ -114,17 +114,6 @@ class help extends rcube_plugin
         return $rcmail->output->button($attrib);
     }
 
-    function content_frame($attrib)
-    {
-        $rcmail  = rcmail::get_instance();
-        $content = $this->help_metadata();
-        $src     = $content[$rcmail->action] ?: $content['index'];
-
-        $rcmail->output->set_env('help_links', $content);
-
-        return $rcmail->output->frame($attrib, true);
-    }
-
     function help_metadata()
     {
         $rcmail  = rcmail::get_instance();
diff --git a/plugins/help/skins/classic/templates/help.html b/plugins/help/skins/classic/templates/help.html
index 538a2c6da..00179d5e5 100644
--- a/plugins/help/skins/classic/templates/help.html
+++ b/plugins/help/skins/classic/templates/help.html
@@ -41,7 +41,7 @@ function help_init_settings_tabs()
 </div>
 
 <div id="mainscreen" class="box help-box">
-<roundcube:object name="contentframe" id="helpcontentframe" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+<roundcube:object name="contentframe" id="helpcontentframe" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </body>
diff --git a/plugins/help/skins/elastic/templates/help.html b/plugins/help/skins/elastic/templates/help.html
index 30dd86185..b45f1a628 100644
--- a/plugins/help/skins/elastic/templates/help.html
+++ b/plugins/help/skins/elastic/templates/help.html
@@ -24,7 +24,7 @@
 		<span class="header-title"><roundcube:label name="help.help" /></span>
 	</div>
 	<div class="iframe-wrapper">
-		<roundcube:object name="contentframe" id="helpcontentframe" src="/watermark.html" title="arialabelhelpcontent" />
+		<roundcube:object name="contentframe" id="helpcontentframe" src="env:blankpage" title="arialabelhelpcontent" />
 	</div>
 </div>
 
diff --git a/plugins/help/skins/larry/templates/help.html b/plugins/help/skins/larry/templates/help.html
index 2085cf5f2..960579462 100644
--- a/plugins/help/skins/larry/templates/help.html
+++ b/plugins/help/skins/larry/templates/help.html
@@ -19,7 +19,7 @@
 
 <div id="pluginbody" class="uibox offset">
 	<div class="iframebox help_<roundcube:var name='env:action' />">
-		<roundcube:object name="contentframe" id="helpcontentframe" style="width:100%; height:100%" frameborder="0" src="/watermark.html" />
+		<roundcube:object name="contentframe" id="helpcontentframe" style="width:100%; height:100%" frameborder="0" src="env:blankpage" />
 	</div>
 </div>
 
diff --git a/plugins/managesieve/Changelog b/plugins/managesieve/Changelog
index 6e1f78c63..f109a09ea 100644
--- a/plugins/managesieve/Changelog
+++ b/plugins/managesieve/Changelog
@@ -1,8 +1,11 @@
+* version 9.1 [2018-05-19]
+-----------------------------------------------------------
 - Added GSSAPI support (#5779)
 - Added option managesieve_default_headers
 - Added option managesieve_forward to enable settings dialog for simple forwarding (#6021)
 - Support filter action with custom IMAP flags (#6011)
 - Support 'mime' extension tests - RFC5703 (#5832)
+- Support enabling the plugin for specified hosts only (#6292)
 - Support Elastic skin
 - Fix bug where text: syntax was forced for strings longer than 1024 characters (#6143)
 - Fix missing Save button in Edit Filter Set page of Classic skin (#6154)
diff --git a/plugins/managesieve/config.inc.php.dist b/plugins/managesieve/config.inc.php.dist
index 9efb82713..2d10ddbf2 100644
--- a/plugins/managesieve/config.inc.php.dist
+++ b/plugins/managesieve/config.inc.php.dist
@@ -119,5 +119,11 @@ $config['managesieve_raw_editor'] = true;
 // Disabled actions
 // Prevent user from performing specific actions:
 // list_sets, enable_disable_set, delete_set, new_set, download_set, new_rule, delete_rule
-// Note: disabling list_sets removes the Filter sets widget from the UI and means the set defined in managesieve_script_name will always be used (and activated)
+// Note: disabling list_sets removes the Filter sets widget from the UI and means
+//       the set defined in managesieve_script_name will always be used (and activated)
 $config['managesieve_disabled_actions'] = array();
+
+// List of hosts that support managesieve.
+// Activate managesieve for selected hosts only. If this is not set all hosts are allowed.
+// Example: $config['managesieve_allowed_hosts'] = array('host1.mydomain.com','host2.mydomain.com');
+$config['managesieve_allowed_hosts'] = null;
diff --git a/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php b/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php
index 12e8a0074..a1850704b 100644
--- a/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php
+++ b/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php
@@ -60,7 +60,7 @@ class rcube_sieve_engine
     );
     private $disabled_actions;
 
-    const VERSION  = '9.0';
+    const VERSION  = '9.1';
     const PROGNAME = 'Roundcube (Managesieve)';
     const PORT     = 4190;
 
@@ -84,7 +84,6 @@ class rcube_sieve_engine
         $this->rc->output->add_handlers(array(
             'filterslist'      => array($this, 'filters_list'),
             'filtersetslist'   => array($this, 'filtersets_list'),
-            'filterframe'      => array($this, 'filter_frame'),
             'filterform'       => array($this, 'filter_form'),
             'filtersetform'    => array($this, 'filterset_form'),
             'filterseteditraw' => array($this, 'filterset_editraw'),
@@ -1320,11 +1319,6 @@ class rcube_sieve_engine
         return $out;
     }
 
-    function filter_frame($attrib)
-    {
-        return $this->rc->output->frame($attrib, true);
-    }
-
     function filterset_editraw($attrib)
     {
         $script_name = isset($_GET['_set']) ? $_GET['_set'] : $_POST['_set'];
diff --git a/plugins/managesieve/managesieve.php b/plugins/managesieve/managesieve.php
index 0012d0ba6..876c8a4cc 100644
--- a/plugins/managesieve/managesieve.php
+++ b/plugins/managesieve/managesieve.php
@@ -38,6 +38,13 @@ class managesieve extends rcube_plugin
     {
         $this->rc = rcube::get_instance();
 
+        $this->load_config();
+
+        $allowed_hosts = $this->rc->config->get('managesieve_allowed_hosts');
+        if (!empty($allowed_hosts) && !in_array($_SESSION['storage_host'], (array) $allowed_hosts)) {
+            return;
+        }
+
         // register actions
         $this->register_action('plugin.managesieve', array($this, 'managesieve_actions'));
         $this->register_action('plugin.managesieve-action', array($this, 'managesieve_actions'));
@@ -100,10 +107,8 @@ class managesieve extends rcube_plugin
      */
     function settings_actions($args)
     {
-        $this->load_config();
-
         $vacation_mode = (int) $this->rc->config->get('managesieve_vacation');
-        $forward_mode = (int) $this->rc->config->get('managesieve_forward');
+        $forward_mode  = (int) $this->rc->config->get('managesieve_forward');
 
         // register Filters action
         if ($vacation_mode != 2 && $forward_mode != 2) {
@@ -264,14 +269,12 @@ class managesieve extends rcube_plugin
     public function get_engine($type = null)
     {
         if (!$this->engine) {
-            $this->load_config();
-
             // Add include path for internal classes
             $include_path = $this->home . '/lib' . PATH_SEPARATOR;
             $include_path .= ini_get('include_path');
             set_include_path($include_path);
 
-            $class_name = 'rcube_sieve_' . ($type ?: 'engine');
+            $class_name   = 'rcube_sieve_' . ($type ?: 'engine');
             $this->engine = new $class_name($this);
         }
 
diff --git a/plugins/managesieve/skins/classic/templates/managesieve.html b/plugins/managesieve/skins/classic/templates/managesieve.html
index 6cec376c8..d676c93c6 100644
--- a/plugins/managesieve/skins/classic/templates/managesieve.html
+++ b/plugins/managesieve/skins/classic/templates/managesieve.html
@@ -61,7 +61,7 @@
 </script>
 
 <div id="filter-box">
-  <roundcube:object name="filterframe" id="filter-frame" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+  <roundcube:object name="contentframe" id="filter-frame" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/plugins/managesieve/skins/elastic/templates/managesieve.html b/plugins/managesieve/skins/elastic/templates/managesieve.html
index fd2ca8734..f29baacac 100644
--- a/plugins/managesieve/skins/elastic/templates/managesieve.html
+++ b/plugins/managesieve/skins/elastic/templates/managesieve.html
@@ -53,7 +53,7 @@
 	</div>
 	<h2 id="aria-label-filterframe" class="voice"><roundcube:label name="managesieve.arialabelfilterform" /></h2>
 	<div class="iframe-wrapper">
-		<roundcube:object name="filterframe" id="filter-box" src="/watermark.html" title="managesieve.arialabelfilterform"
+		<roundcube:object name="contentframe" id="filter-box" src="env:blankpage" title="managesieve.arialabelfilterform"
 			aria-labelledby="aria-label-filterform" />
 	</div>
 </div>
diff --git a/plugins/managesieve/skins/larry/templates/managesieve.html b/plugins/managesieve/skins/larry/templates/managesieve.html
index 56ee88d0b..08327d7e5 100644
--- a/plugins/managesieve/skins/larry/templates/managesieve.html
+++ b/plugins/managesieve/skins/larry/templates/managesieve.html
@@ -42,7 +42,7 @@
 <div id="filter-box" class="uibox contentbox">
   <div class="iframebox" role="complementary" aria-labelledby="aria-label-filterform">
     <h2 id="aria-label-filterframe" class="voice"><roundcube:label name="managesieve.arialabelfilterform" /></h2>
-    <roundcube:object name="filterframe" id="filter-frame" style="width:100%; height:100%" frameborder="0" src="/watermark.html" title="managesieve.arialabelfilterform" />
+    <roundcube:object name="contentframe" id="filter-frame" style="width:100%; height:100%" frameborder="0" src="env:blankpage" title="managesieve.arialabelfilterform" />
   </div>
 </div>
 
diff --git a/program/include/rcmail_output_html.php b/program/include/rcmail_output_html.php
index 2dee78232..0ff45fe39 100644
--- a/program/include/rcmail_output_html.php
+++ b/program/include/rcmail_output_html.php
@@ -58,6 +58,18 @@ class rcmail_output_html extends rcmail_output
         'messageprint' => 'printmessage',
     );
 
+    // deprecated names of template objects used before 1.4
+    protected $deprecated_template_objects = array(
+        'addressframe'        => 'contentframe',
+        'messagecontentframe' => 'contentframe',
+        'prefsframe'          => 'contentframe',
+        'folderframe'         => 'contentframe',
+        'identityframe'       => 'contentframe',
+        'responseframe'       => 'contentframe',
+        'keyframe'            => 'contentframe',
+        'filterframe'         => 'contentframe',
+    );
+
     /**
      * Constructor
      */
@@ -139,6 +151,11 @@ EOF;
             'charsetselector' => array($this, 'charset_selector'),
             'aboutcontent'    => array($this, 'about_content'),
         ));
+
+        // set blankpage (watermark) url
+        $blankpage = $this->config->get('blankpage_url', '/watermark.html');
+        $blankpage = $this->abs_url($blankpage);
+        $this->set_env('blankpage', $blankpage);
     }
 
     /**
@@ -1036,6 +1053,45 @@ EOF;
         return eval("return ($expression);");
     }
 
+    /**
+     * Parse variable strings
+     *
+     * @param string $type Variable type (env, config etc)
+     * @param string $name Variable name
+     *
+     * @return mixed Variable value
+     */
+    protected function parse_variable($type, $name)
+    {
+        $value = '';
+
+        switch ($type) {
+            case 'env':
+                $value = $this->env[$name];
+                break;
+            case 'config':
+                $value = $this->config->get($name);
+                if (is_array($value) && $value[$_SESSION['storage_host']]) {
+                    $value = $value[$_SESSION['storage_host']];
+                }
+                break;
+            case 'request':
+                $value = rcube_utils::get_input_value($name, rcube_utils::INPUT_GPC);
+                break;
+            case 'session':
+                $value = $_SESSION[$name];
+                break;
+            case 'cookie':
+                $value = htmlspecialchars($_COOKIE[$name], ENT_COMPAT | ENT_HTML401, RCUBE_CHARSET);
+                break;
+            case 'browser':
+                $value = $this->browser->{$name};
+                break;
+        }
+
+        return $value;
+    }
+
     /**
      * Search for special tags in input and replace them
      * with the appropriate content
@@ -1183,6 +1239,11 @@ EOF;
                 $object  = strtolower($attrib['name']);
                 $content = '';
 
+                // correct deprecated object names
+                if ($this->deprecated_template_objects[$object]) {
+                    $object = $this->deprecated_template_objects[$object];
+                }
+
                 // we are calling a class/method
                 if (($handler = $this->object_handlers[$object]) && is_array($handler)) {
                     if (is_callable($handler)) {
@@ -1254,6 +1315,18 @@ EOF;
                     $title .= $this->get_pagetitle();
                     $content = html::quote($title);
                 }
+                else if ($object == 'contentframe') {
+                    if (empty($attrib['id'])) {
+                        $attrib['id'] = 'rcm' . $this->env['task'] . 'frame';
+                    }
+
+                    // parse variables
+                    if (preg_match('/^(config|env):([a-z0-9_]+)$/i', $attrib['src'], $matches)) {
+                        $attrib['src'] = $this->parse_variable($matches[1], $matches[2]);
+                    }
+
+                    $content = $this->frame($attrib, true);
+                }
 
                 // exec plugin hooks for this template object
                 $hook = $this->app->plugins->exec_hook("template_object_$object", $attrib + array('content' => $content));
@@ -1284,32 +1357,7 @@ EOF;
             // return variable
             case 'var':
                 $var = explode(':', $attrib['name']);
-                $name = $var[1];
-                $value = '';
-
-                switch ($var[0]) {
-                    case 'env':
-                        $value = $this->env[$name];
-                        break;
-                    case 'config':
-                        $value = $this->config->get($name);
-                        if (is_array($value) && $value[$_SESSION['storage_host']]) {
-                            $value = $value[$_SESSION['storage_host']];
-                        }
-                        break;
-                    case 'request':
-                        $value = rcube_utils::get_input_value($name, rcube_utils::INPUT_GPC);
-                        break;
-                    case 'session':
-                        $value = $_SESSION[$name];
-                        break;
-                    case 'cookie':
-                        $value = htmlspecialchars($_COOKIE[$name], ENT_COMPAT | ENT_HTML401, RCUBE_CHARSET);
-                        break;
-                    case 'browser':
-                        $value = $this->browser->{$name};
-                        break;
-                }
+                $value = $this->parse_variable($var[0], $var[1]);
 
                 if (is_array($value)) {
                     $value = implode(', ', $value);
@@ -1825,7 +1873,6 @@ EOF;
         // register as 'contentframe' object
         if ($is_contentframe || $attrib['contentframe']) {
             $this->set_env('contentframe', $attrib['contentframe'] ? $attrib['contentframe'] : $attrib['name']);
-            $this->set_env('blankpage', $this->asset_url($attrib['src']));
         }
 
         return html::iframe($attrib);
diff --git a/program/lib/Roundcube/rcube_message.php b/program/lib/Roundcube/rcube_message.php
index b378c4cde..67396ca83 100644
--- a/program/lib/Roundcube/rcube_message.php
+++ b/program/lib/Roundcube/rcube_message.php
@@ -854,17 +854,16 @@ class rcube_message
                     ) {
                         $this->add_part($mail_part, 'inline');
                     }
-                    // regular attachment with valid content type
-                    // (content-type name regexp according to RFC4288.4.2)
-                    else if (preg_match('/^[a-z0-9!#$&.+^_-]+\/[a-z0-9!#$&.+^_-]+$/i', $part_mimetype)) {
-                        $this->add_part($mail_part, 'attachment');
-                    }
-                    // attachment with invalid content type
-                    // replace malformed content type with application/octet-stream (#1487767)
-                    else if ($mail_part->filename) {
-                        $mail_part->ctype_primary   = 'application';
-                        $mail_part->ctype_secondary = 'octet-stream';
-                        $mail_part->mimetype        = 'application/octet-stream';
+
+                    // Any non-inline attachment
+                    if (!preg_match('/^inline/i', $mail_part->disposition)) {
+                        // Content-Type name regexp according to RFC4288.4.2
+                        if (!preg_match('/^[a-z0-9!#$&.+^_-]+\/[a-z0-9!#$&.+^_-]+$/i', $part_mimetype)) {
+                            // replace malformed content type with application/octet-stream (#1487767)
+                            $mail_part->ctype_primary   = 'application';
+                            $mail_part->ctype_secondary = 'octet-stream';
+                            $mail_part->mimetype        = 'application/octet-stream';
+                        }
 
                         $this->add_part($mail_part, 'attachment');
                     }
diff --git a/program/steps/addressbook/func.inc b/program/steps/addressbook/func.inc
index 77f237b47..924b8efbb 100644
--- a/program/steps/addressbook/func.inc
+++ b/program/steps/addressbook/func.inc
@@ -117,7 +117,6 @@ $OUTPUT->add_handlers(array(
     'savedsearchlist'     => 'rcmail_savedsearch_list',
     'addresslist'         => 'rcmail_contacts_list',
     'addresslisttitle'    => 'rcmail_contacts_list_title',
-    'addressframe'        => 'rcmail_contact_frame',
     'recordscountdisplay' => 'rcmail_rowcount_display',
     'searchform'          => array($OUTPUT, 'search_form')
 ));
@@ -455,18 +454,6 @@ function rcmail_contacts_list_title($attrib)
 }
 
 
-// similar function as /steps/settings/identities.inc::rcmail_identity_frame()
-function rcmail_contact_frame($attrib)
-{
-    global $OUTPUT;
-
-    if (!$attrib['id'])
-        $attrib['id'] = 'rcmcontactframe';
-
-    return $OUTPUT->frame($attrib, true);
-}
-
-
 function rcmail_rowcount_display($attrib)
 {
     global $RCMAIL;
diff --git a/program/steps/mail/func.inc b/program/steps/mail/func.inc
index 301b8c0e9..36b3ec218 100644
--- a/program/steps/mail/func.inc
+++ b/program/steps/mail/func.inc
@@ -125,7 +125,6 @@ $OUTPUT->add_handlers(array(
     'messagecountdisplay' => 'rcmail_messagecount_display',
     'listmenulink'        => 'rcmail_options_menu_link',
     'mailboxname'         => 'rcmail_mailbox_name_display',
-    'messagecontentframe' => 'rcmail_messagecontent_frame',
     'messageimportform'   => 'rcmail_message_import_form',
     'searchfilter'        => 'rcmail_search_filter',
     'searchinterval'      => 'rcmail_search_interval',
@@ -683,20 +682,6 @@ function rcmail_options_menu_link($attrib = array())
     ), $inner);
 }
 
-/**
- * Return an HTML iframe for loading mail content
- */
-function rcmail_messagecontent_frame($attrib)
-{
-    global $OUTPUT;
-
-    if (empty($attrib['id'])) {
-        $attrib['id'] = 'rcmailcontentwindow';
-    }
-
-    return $OUTPUT->frame($attrib, true);
-}
-
 function rcmail_messagecount_display($attrib)
 {
     global $RCMAIL;
diff --git a/program/steps/settings/folders.inc b/program/steps/settings/folders.inc
index 0fee502f5..5b0d1fe7e 100644
--- a/program/steps/settings/folders.inc
+++ b/program/steps/settings/folders.inc
@@ -189,7 +189,6 @@ $OUTPUT->add_label('deletefolderconfirm', 'purgefolderconfirm', 'movefolderconfi
 // register UI objects
 $OUTPUT->add_handlers(array(
     'foldersubscription' => 'rcmail_folder_subscriptions',
-    'folderframe'        => 'rcmail_folder_frame',
     'folderfilter'       => 'rcmail_folder_filter',
     'quotadisplay'       => array($RCMAIL, 'quota_display'),
     'searchform'         => array($OUTPUT, 'search_form'),
@@ -419,17 +418,6 @@ function rcmail_folder_tree_element($folders, &$key, &$js_folders)
     return html::tag('li', $attribs, $content);
 }
 
-function rcmail_folder_frame($attrib)
-{
-    global $OUTPUT;
-
-    if (!$attrib['id']) {
-        $attrib['id'] = 'rcmfolderframe';
-    }
-
-    return $OUTPUT->frame($attrib, true);
-}
-
 function rcmail_folder_filter($attrib)
 {
     global $RCMAIL;
diff --git a/program/steps/settings/func.inc b/program/steps/settings/func.inc
index d4ec2f989..1b28d1a7a 100644
--- a/program/steps/settings/func.inc
+++ b/program/steps/settings/func.inc
@@ -26,7 +26,6 @@ if (!$OUTPUT->ajax_call) {
 // register UI objects
 $OUTPUT->add_handlers(array(
     'settingstabs'   => 'rcmail_settings_tabs',
-    'prefsframe'     => 'rcmail_preferences_frame',
     'sectionslist'   => 'rcmail_sections_list',
     'identitieslist' => 'rcmail_identities_list',
 ));
@@ -50,19 +49,6 @@ $RCMAIL->register_action_map(array(
 ));
 
 
-// similar function as /steps/settings/identities.inc::rcmail_identity_frame()
-function rcmail_preferences_frame($attrib)
-{
-    global $OUTPUT;
-
-    if (!$attrib['id']) {
-        $attrib['id'] = 'rcmprefsframe';
-    }
-
-    return $OUTPUT->frame($attrib, true);
-}
-
-
 function rcmail_sections_list($attrib)
 {
     global $RCMAIL;
diff --git a/program/steps/settings/identities.inc b/program/steps/settings/identities.inc
index 288c161ab..f33c8dda8 100644
--- a/program/steps/settings/identities.inc
+++ b/program/steps/settings/identities.inc
@@ -46,21 +46,7 @@ define('IDENTITIES_LEVEL', intval($RCMAIL->config->get('identities_level', 0)));
 $OUTPUT->set_pagetitle($RCMAIL->gettext('identities'));
 $OUTPUT->include_script('list.js');
 
-$OUTPUT->add_handler('identityframe', 'rcmail_identity_frame');
 $OUTPUT->set_env('identities_level', IDENTITIES_LEVEL);
 $OUTPUT->add_label('deleteidentityconfirm');
 
 $OUTPUT->send('identities');
-
-
-// similar function as /steps/addressbook/func.inc::rcmail_contact_frame()
-function rcmail_identity_frame($attrib)
-{
-    global $OUTPUT;
-
-    if (!$attrib['id']) {
-        $attrib['id'] = 'rcmIdentityFrame';
-    }
-
-    return $OUTPUT->frame($attrib, true);
-}
diff --git a/program/steps/settings/responses.inc b/program/steps/settings/responses.inc
index 1b88640c3..41335f73c 100644
--- a/program/steps/settings/responses.inc
+++ b/program/steps/settings/responses.inc
@@ -78,7 +78,6 @@ $OUTPUT->set_pagetitle($RCMAIL->gettext('responses'));
 $OUTPUT->include_script('list.js');
 
 $OUTPUT->add_handlers(array(
-    'responseframe' => 'rcmail_response_frame',
     'responseslist' => 'rcmail_responses_list',
 ));
 $OUTPUT->add_label('deleteresponseconfirm');
@@ -115,17 +114,3 @@ function rcmail_responses_list($attrib)
 
     return $out;
 }
-
-// similar function as /steps/addressbook/func.inc::rcmail_contact_frame()
-function rcmail_response_frame($attrib)
-{
-    global $OUTPUT;
-
-    if (!$attrib['id']) {
-        $attrib['id'] = 'rcmResponseFrame';
-    }
-
-    $OUTPUT->set_env('contentframe', $attrib['id']);
-
-    return $OUTPUT->frame($attrib, true);
-}
diff --git a/skins/classic/templates/addressbook.html b/skins/classic/templates/addressbook.html
index c102ae441..a70fd7221 100644
--- a/skins/classic/templates/addressbook.html
+++ b/skins/classic/templates/addressbook.html
@@ -115,7 +115,7 @@
 </script>
 
 <div id="contacts-box">
-<roundcube:object name="addressframe" id="contact-frame" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+<roundcube:object name="contentframe" id="contact-frame" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/skins/classic/templates/folders.html b/skins/classic/templates/folders.html
index eb41da3d5..b4774bdae 100644
--- a/skins/classic/templates/folders.html
+++ b/skins/classic/templates/folders.html
@@ -54,7 +54,7 @@
 </script>
 
 <div id="folder-box">
-    <roundcube:object name="folderframe" id="folder-frame" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+    <roundcube:object name="contentframe" id="folder-frame" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/skins/classic/templates/identities.html b/skins/classic/templates/identities.html
index 89937ad51..60c2dcd55 100644
--- a/skins/classic/templates/identities.html
+++ b/skins/classic/templates/identities.html
@@ -35,7 +35,7 @@
 </script>
 
 <div id="identity-box">
-  <roundcube:object name="identityframe" id="identity-frame" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+  <roundcube:object name="contentframe" id="identity-frame" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/skins/classic/templates/mail.html b/skins/classic/templates/mail.html
index 07558b588..b51df40fb 100644
--- a/skins/classic/templates/mail.html
+++ b/skins/classic/templates/mail.html
@@ -84,7 +84,7 @@
 </div>
 
 <div id="mailpreviewframe">
-<roundcube:object name="messagecontentframe" id="messagecontframe" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+<roundcube:object name="contentframe" id="messagecontframe" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/skins/classic/templates/responses.html b/skins/classic/templates/responses.html
index 4a52f4c82..3b362b4a9 100644
--- a/skins/classic/templates/responses.html
+++ b/skins/classic/templates/responses.html
@@ -35,7 +35,7 @@
 </script>
 
 <div id="response-box">
-  <roundcube:object name="responseframe" id="response-frame" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+  <roundcube:object name="contentframe" id="response-frame" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/skins/classic/templates/settings.html b/skins/classic/templates/settings.html
index 0055722ba..3099d2cf6 100644
--- a/skins/classic/templates/settings.html
+++ b/skins/classic/templates/settings.html
@@ -30,7 +30,7 @@
 </script>
 
 <div id="prefs-box">
-<roundcube:object name="prefsframe" id="prefs-frame" width="100%" height="100%" frameborder="0" src="/watermark.html" />
+<roundcube:object name="contentframe" id="prefs-frame" width="100%" height="100%" frameborder="0" src="env:blankpage" />
 </div>
 
 </div>
diff --git a/skins/elastic/templates/addressbook.html b/skins/elastic/templates/addressbook.html
index b14aa51e1..4e1bf5b2a 100644
--- a/skins/elastic/templates/addressbook.html
+++ b/skins/elastic/templates/addressbook.html
@@ -92,7 +92,7 @@
 	</div>
 	<h2 id="aria-label-contact-frame" class="voice"><roundcube:label name="contactproperties" /></h2>
 	<div class="iframe-wrapper">
-		<roundcube:object name="addressframe" id="contact-frame" src="/watermark.html" title="contactproperties"
+		<roundcube:object name="contentframe" id="contact-frame" src="env:blankpage" title="contactproperties"
 			aria-labelledby="aria-label-contact-frame" />
 	</div>
 </div>
diff --git a/skins/elastic/templates/folders.html b/skins/elastic/templates/folders.html
index 8a72402a9..8b61e5919 100644
--- a/skins/elastic/templates/folders.html
+++ b/skins/elastic/templates/folders.html
@@ -57,7 +57,7 @@
 		</div>
 	</div>
 	<div class="iframe-wrapper">
-		<roundcube:object name="folderframe" id="preferences-frame" src="/watermark.html" />
+		<roundcube:object name="contentframe" id="preferences-frame" src="env:blankpage" />
 	</div>
 </div>
 
diff --git a/skins/elastic/templates/identities.html b/skins/elastic/templates/identities.html
index 22134bf5e..b1ff97e35 100644
--- a/skins/elastic/templates/identities.html
+++ b/skins/elastic/templates/identities.html
@@ -38,7 +38,7 @@
 		</div>
 	</div>
 	<div class="iframe-wrapper">
-		<roundcube:object name="identityframe" id="preferences-frame" src="/watermark.html" title="arialabelidentityeditfrom" />
+		<roundcube:object name="contentframe" id="preferences-frame" src="env:blankpage" title="arialabelidentityeditfrom" />
 	</div>
 </div>
 
diff --git a/skins/elastic/templates/mail.html b/skins/elastic/templates/mail.html
index 5991578c6..b88acbcf1 100644
--- a/skins/elastic/templates/mail.html
+++ b/skins/elastic/templates/mail.html
@@ -105,10 +105,10 @@
 	</div>
 	<h2 id="aria-label-mailpreviewframe" class="voice"><roundcube:label name="arialabelmailpreviewframe" /></h2>
 	<div class="iframe-wrapper">
-		<roundcube:object name="messagecontentframe"
+		<roundcube:object name="contentframe"
 			id="messagecontframe"
 			aria-labelledby="aria-label-mailpreviewframe"
-			src="/watermark.html"
+			src="env:blankpage"
 			title="arialabelmailpreviewframe"
 		/>
 	</div>
diff --git a/skins/elastic/templates/responses.html b/skins/elastic/templates/responses.html
index e463d55ed..cc15160cb 100644
--- a/skins/elastic/templates/responses.html
+++ b/skins/elastic/templates/responses.html
@@ -36,7 +36,7 @@
 		</div>
 	</div>
 	<div class="iframe-wrapper">
-		<roundcube:object name="responseframe" id="preferences-frame" src="/watermark.html" title="arialabelresonseeditfrom" />
+		<roundcube:object name="contentframe" id="preferences-frame" src="env:blankpage" title="arialabelresonseeditfrom" />
 	</div>
 </div>
 
diff --git a/skins/elastic/templates/settings.html b/skins/elastic/templates/settings.html
index 387d5c227..8b80f8581 100644
--- a/skins/elastic/templates/settings.html
+++ b/skins/elastic/templates/settings.html
@@ -22,7 +22,7 @@
 		<span class="header-title"></span>
 	</div>
 	<div class="iframe-wrapper">
-		<roundcube:object name="prefsframe" id="preferences-frame" src="/watermark.html" title="arialabelpreferencesform" />
+		<roundcube:object name="contentframe" id="preferences-frame" src="env:blankpage" title="arialabelpreferencesform" />
 	</div>
 </div>
 
diff --git a/skins/larry/templates/addressbook.html b/skins/larry/templates/addressbook.html
index e11fdebc2..a8d4a8cef 100644
--- a/skins/larry/templates/addressbook.html
+++ b/skins/larry/templates/addressbook.html
@@ -122,7 +122,7 @@
 
 <div id="contacts-box" class="uibox">
 	<div class="iframebox">
-		<roundcube:object name="addressframe" id="contact-frame" style="width:100%; height:100%" frameborder="0" src="/watermark.html" title="contactproperties" />
+		<roundcube:object name="contentframe" id="contact-frame" style="width:100%; height:100%" frameborder="0" src="env:blankpage" title="contactproperties" />
 	</div>
 </div>
 
diff --git a/skins/larry/templates/folders.html b/skins/larry/templates/folders.html
index 6b7978387..d7bf2a6e9 100644
--- a/skins/larry/templates/folders.html
+++ b/skins/larry/templates/folders.html
@@ -55,7 +55,7 @@
 
 <div id="folder-details" class="uibox contentbox">
 	<div class="iframebox">
-		<roundcube:object name="folderframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="/watermark.html" />
+		<roundcube:object name="contentframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="env:blankpage" />
 	</div>
 </div>
 
diff --git a/skins/larry/templates/identities.html b/skins/larry/templates/identities.html
index 163469d16..436fc4c6c 100644
--- a/skins/larry/templates/identities.html
+++ b/skins/larry/templates/identities.html
@@ -27,7 +27,7 @@
 
 <div id="identity-details" class="uibox contentbox">
 	<div class="iframebox">
-		<roundcube:object name="identityframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="/watermark.html" title="arialabelidentityeditfrom" />
+		<roundcube:object name="contentframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="env:blankpage" title="arialabelidentityeditfrom" />
 	</div>
 </div>
 
diff --git a/skins/larry/templates/mail.html b/skins/larry/templates/mail.html
index e42d85099..1c853fe88 100644
--- a/skins/larry/templates/mail.html
+++ b/skins/larry/templates/mail.html
@@ -147,7 +147,7 @@
 
 <div id="mailpreviewframe" class="iframebox" role="complementary" aria-labelledby="aria-label-mailpreviewframe">
 <h2 id="aria-label-mailpreviewframe" class="voice"><roundcube:label name="arialabelmailpreviewframe" /></h2>
-<roundcube:object name="messagecontentframe" id="messagecontframe" style="width:100%; height:100%" frameborder="0" src="/watermark.html" title="arialabelmailpreviewframe" />
+<roundcube:object name="contentframe" id="messagecontframe" style="width:100%; height:100%" frameborder="0" src="env:blankpage" title="arialabelmailpreviewframe" />
 </div>
 
 </div><!-- end mailview-bottom -->
diff --git a/skins/larry/templates/responses.html b/skins/larry/templates/responses.html
index 69e050bc6..4c3c1ba17 100644
--- a/skins/larry/templates/responses.html
+++ b/skins/larry/templates/responses.html
@@ -28,7 +28,7 @@
 
 <div id="response-details" class="uibox contentbox">
 	<div class="iframebox">
-		<roundcube:object name="responseframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="/watermark.html" title="arialabelresonseeditfrom" />
+		<roundcube:object name="contentframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="env:blankpage" title="arialabelresonseeditfrom" />
 	</div>
 </div>
 
diff --git a/skins/larry/templates/settings.html b/skins/larry/templates/settings.html
index 34c3440cc..a0da74fbd 100644
--- a/skins/larry/templates/settings.html
+++ b/skins/larry/templates/settings.html
@@ -25,7 +25,7 @@
 
 <div id="preferences-box" class="uibox contentbox" role="main">
 	<div class="iframebox">
-		<roundcube:object name="prefsframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="/watermark.html" title="arialabelpreferencesform" />
+		<roundcube:object name="contentframe" id="preferences-frame" style="width:100%; height:100%" frameborder="0" src="env:blankpage" title="arialabelpreferencesform" />
 	</div>
 </div>