diff --git a/CHANGELOG b/CHANGELOG
index b125dbebb..354d3e0c9 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Display Tiff as Jpeg in browsers without Tiff support (#1488452)
 - Don't display Pdf/Tiff/Flash attachments inline without browser support (#1488452, #1487929)
 - Fix html2text conversion of strong|b|a|th|h tags when used in upper case
 - Add listcontrols template container in Larry skin (#1488498)
diff --git a/program/include/rcube_image.php b/program/include/rcube_image.php
index 21cb5f136..80e8bd4f3 100644
--- a/program/include/rcube_image.php
+++ b/program/include/rcube_image.php
@@ -13,7 +13,7 @@
  | See the README file for a full license statement.                     |
  |                                                                       |
  | PURPOSE:                                                              |
- |   Image resizer                                                       |
+ |   Image resizer and converter                                         |
  |                                                                       |
  +-----------------------------------------------------------------------+
  | Author: Thomas Bruederli <roundcube@gmail.com>                        |
@@ -25,6 +25,19 @@ class rcube_image
 {
     private $image_file;
 
+    const TYPE_GIF = 1;
+    const TYPE_JPG = 2;
+    const TYPE_PNG = 3;
+    const TYPE_TIF = 4;
+
+    public static $extensions = array(
+        self::TYPE_GIF => 'gif',
+        self::TYPE_JPG => 'jpg',
+        self::TYPE_PNG => 'png',
+        self::TYPE_TIF => 'tif',
+    );
+
+
     function __construct($filename)
     {
         $this->image_file = $filename;
@@ -66,7 +79,7 @@ class rcube_image
      * @param int    $size      Max width/height size
      * @param string $filename  Output filename
      *
-     * @return Success of convert as true/false
+     * @return bool True on success, False on failure
      */
     public function resize($size, $filename = null)
     {
@@ -95,10 +108,10 @@ class rcube_image
             $p['-opts'] = array('-resize' => $size.'>');
 
             if (in_array($type, explode(',', $p['types']))) { // Valid type?
-                $result = rcube::exec($convert . ' 2>&1 -flatten -auto-orient -colorspace RGB -quality {quality} {-opts} {in} {type}:{out}', $p) === '';
+                $result = rcube::exec($convert . ' 2>&1 -flatten -auto-orient -colorspace RGB -quality {quality} {-opts} {in} {type}:{out}', $p);
             }
 
-            if ($result) {
+            if ($result === '') {
                 return true;
             }
         }
@@ -148,6 +161,71 @@ class rcube_image
             }
         }
 
+        // @TODO: print error to the log?
+        return false;
+    }
+
+    /**
+     * Convert image to a given type
+     *
+     * @param int    $type      Destination file type (see class constants)
+     * @param string $filename  Output filename (if empty, original file will be used
+     *                          and filename extension will be modified)
+     *
+     * @return bool True on success, False on failure
+     */
+    public function convert($type, $filename = null)
+    {
+        $rcube   = rcube::get_instance();
+        $convert = $rcube->config->get('im_convert_path', false);
+
+        if (!$filename) {
+            $filename = $this->image_file;
+
+            // modify extension
+            if ($extension = self::$extensions[$type]) {
+                $filename = preg_replace('/\.[^.]+$/', '', $filename) . '.' . $extension;
+            }
+        }
+
+        // use ImageMagick
+        if ($convert) {
+            $p['in']   = $this->image_file;
+            $p['out']  = $filename;
+            $p['type'] = self::$extensions[$type];
+
+            $result = rcube::exec($convert . ' 2>&1 -colorspace RGB -quality 75 {in} {type}:{out}', $p);
+
+            if ($result === '') {
+                return true;
+            }
+        }
+
+        // use GD extension (TIFF isn't supported)
+        $props    = $this->props();
+        $gd_types = array(IMAGETYPE_JPEG, IMAGETYPE_GIF, IMAGETYPE_PNG);
+
+        if ($props['gd_type'] && in_array($props['gd_type'], $gd_types)) {
+            if ($props['gd_type'] == IMAGETYPE_JPEG) {
+                $image = imagecreatefromjpeg($this->image_file);
+            }
+            else if ($props['gd_type'] == IMAGETYPE_GIF) {
+                $image = imagecreatefromgif($this->image_file);
+            }
+            else if ($props['gd_type'] == IMAGETYPE_PNG) {
+                $image = imagecreatefrompng($this->image_file);
+            }
+
+            if ($type == self::TYPE_JPG) {
+                $result = imagejpeg($image, $filename, 75);
+            }
+            else if ($type == self::TYPE_GIF) {
+                $result = imagegif($image, $filename);
+            }
+            else if ($type == self::TYPE_PNG) {
+                $result = imagepng($image, $filename, 6, PNG_ALL_FILTERS);
+            }
+        }
 
         // @TODO: print error to the log?
         return false;
@@ -169,4 +247,5 @@ class rcube_image
             }
         }
     }
+
 }
diff --git a/program/steps/mail/func.inc b/program/steps/mail/func.inc
index 829f159f4..33041d43d 100644
--- a/program/steps/mail/func.inc
+++ b/program/steps/mail/func.inc
@@ -1097,12 +1097,6 @@ function rcmail_message_body($attrib)
     }
   }
 
-  // Skip TIFF images if browser doesn't support this format
-  // @TODO: we could convert TIFF to JPEG and display it
-  $tiff_support = !empty($_SESSION['browser_caps']) && !empty($_SESSION['browser_caps']['tif']);
-  $mime_regex   = $tiff_support ? '/^image\//i' : '/^image\/(?!tif)/i';
-  $ext_regex    = '/\.(jpg|jpeg|png|gif|bmp' . ($tiff_support ? '|tif|tiff' : '') .')$/i';
-
   // list images after mail body
   if ($CONFIG['inline_images'] && !empty($MESSAGE->attachments)) {
     foreach ($MESSAGE->attachments as $attach_prop) {
@@ -1112,12 +1106,7 @@ function rcmail_message_body($attrib)
       }
 
       // Content-Type: image/*...
-      if (preg_match($mime_regex, $attach_prop->mimetype) ||
-        // ...or known file extension: many clients are using application/octet-stream
-        ($attach_prop->filename &&
-          preg_match('/^application\/octet-stream$/i', $attach_prop->mimetype) &&
-          preg_match($ext_regex, $attach_prop->filename))
-      ) {
+      if (rcmail_part_image_type($attach_prop)) {
         $out .= html::tag('hr') . html::p(array('align' => "center"),
           html::img(array(
             'src' => $MESSAGE->get_part_url($attach_prop->mime_id, true),
@@ -1135,6 +1124,48 @@ function rcmail_message_body($attrib)
   return html::div($attrib, $out);
 }
 
+function rcmail_part_image_type($part)
+{
+  $rcmail = rcmail::get_instance();
+
+  // Skip TIFF images if browser doesn't support this format...
+  $tiff_support = !empty($_SESSION['browser_caps']) && !empty($_SESSION['browser_caps']['tif']);
+  // until we can convert them to JPEG
+  $tiff_support = $tiff_support || $rcmail->config->get('im_convert_path');
+
+  // Content-type regexp
+  $mime_regex = $tiff_support ? '/^image\//i' : '/^image\/(?!tif)/i';
+
+  // Content-Type: image/*...
+  if (preg_match($mime_regex, $part->mimetype)) {
+    return $part->mimetype;
+  }
+
+  // Many clients use application/octet-stream, we'll detect mimetype
+  // by checking filename extension
+
+  // Supported image filename extensions to image type map
+  $types = array(
+    'jpg'  => 'image/jpeg',
+    'jpeg' => 'image/jpeg',
+    'png'  => 'image/png',
+    'gif'  => 'image/gif',
+    'bmp'  => 'image/bmp',
+  );
+  if ($tiff_support) {
+    $types['tif']  = 'image/tiff';
+    $types['tiff'] = 'image/tiff';
+  }
+
+  if ($part->filename
+    && preg_match('/^application\/octet-stream$/i', $part->mimetype)
+    && preg_match('/\.([^.])$/i', $part->filename, $m)
+    && ($extension = strtolower($m[1]))
+    && isset($types[$extension])
+  ) {
+    return $types[$extension];
+  }
+}
 
 /**
  * Convert all relative URLs according to a <base> in HTML
diff --git a/program/steps/mail/get.inc b/program/steps/mail/get.inc
index 750011f74..658538a20 100644
--- a/program/steps/mail/get.inc
+++ b/program/steps/mail/get.inc
@@ -22,7 +22,7 @@
 
 // show loading page
 if (!empty($_GET['_preload'])) {
-  $url = preg_replace('/[&?]+_preload=1/', '', $_SERVER['REQUEST_URI']);
+  $url = preg_replace('/([&?]+)_preload=/', '\\1_embed=', $_SERVER['REQUEST_URI']);
   $message = rcube_label('loadingdata');
 
   header('Content-Type: text/html; charset=' . RCMAIL_CHARSET);
@@ -76,6 +76,17 @@ else if (strlen($pid = get_input_value('_part', RCUBE_INPUT_GET))) {
 
     // overwrite modified vars from plugin
     $mimetype = $plugin['mimetype'];
+
+    // TIFF to JPEG conversion, if needed
+    $tiff_support = !empty($_SESSION['browser_caps']) && !empty($_SESSION['browser_caps']['tif']);
+    if (!empty($_REQUEST['_embed']) && !$tiff_support
+      && $RCMAIL->config->get('im_convert_path')
+      && rcmail_part_image_type($part) == 'image/tiff'
+    ) {
+      $tiff2jpeg = true;
+      $mimetype = 'image/jpeg';
+    }
+
     list($ctype_primary, $ctype_secondary) = explode('/', $mimetype);
     if ($plugin['body'])
       $part->body = $plugin['body'];
@@ -150,8 +161,33 @@ else if (strlen($pid = get_input_value('_part', RCUBE_INPUT_GET))) {
 
       header("Content-Disposition: $disposition; filename=\"$filename\"");
 
+      // handle tiff to jpeg conversion
+      if (!empty($tiff2jpeg)) {
+        $temp_dir  = unslashify($RCMAIL->config->get('temp_dir'));
+        $file_path = tempnam($temp_dir, 'rcmAttmnt');
+
+        // write content to temp file
+        if ($part->body) {
+          $saved = file_put_contents($file_path, $part->body);
+        }
+        else if ($part->size) {
+          $fd = fopen($file_path, 'w');
+          $saved = $RCMAIL->storage->get_message_part($MESSAGE->uid, $part->mime_id, $part, false, $fd);
+          fclose($fd);
+        }
+
+        // convert image to jpeg and send it to the browser
+        if ($saved) {
+          $image = new rcube_image($file_path);
+          if ($image->convert(rcube_image::TYPE_JPG, $file_path)) {
+            header("Content-Length: " . filesize($file_path));
+            readfile($file_path);
+          }
+          unlink($file_path);
+        }
+      }
       // do content filtering to avoid XSS through fake images
-      if (!empty($_REQUEST['_embed']) && $browser->ie && $browser->ver <= 8) {
+      else if (!empty($_REQUEST['_embed']) && $browser->ie && $browser->ver <= 8) {
         if ($part->body) {
           echo preg_match('/<(script|iframe|object)/i', $part->body) ? '' : $part->body;
           $sent = true;
diff --git a/program/steps/mail/show.inc b/program/steps/mail/show.inc
index 7fcfafcaa..158ba31c8 100644
--- a/program/steps/mail/show.inc
+++ b/program/steps/mail/show.inc
@@ -61,7 +61,7 @@ if ($uid = get_input_value('_uid', RCUBE_INPUT_GET)) {
   $OUTPUT->set_env('mailbox', $mbox_name);
 
   // mimetypes supported by the browser (default settings)
-  $mimetypes = $RCMAIL->config->get('client_mimetypes', 'text/plain,text/html,text/xml,image/jpeg,image/gif,image/png,image/tiff,application/x-javascript,application/pdf,application/x-shockwave-flash');
+  $mimetypes = $RCMAIL->config->get('client_mimetypes', 'text/plain,text/html,text/xml,image/jpeg,image/gif,image/png,image/bmp,image/tiff,application/x-javascript,application/pdf,application/x-shockwave-flash');
   $mimetypes = is_string($mimetypes) ? explode(',', $mimetypes) : (array)$mimetypes;
 
   // Remove unsupported types, which makes that attachment which cannot be
@@ -72,9 +72,11 @@ if ($uid = get_input_value('_uid', RCUBE_INPUT_GET)) {
   if (empty($_SESSION['browser_caps']['flash']) && ($key = array_search('application/x-shockwave-flash', $mimetypes)) !== false) {
     unset($mimetypes[$key]);
   }
-  // @TODO: we could convert TIFF to JPEG and display it
   if (empty($_SESSION['browser_caps']['tif']) && ($key = array_search('image/tiff', $mimetypes)) !== false) {
-    unset($mimetypes[$key]);
+    // we can convert tiff to jpeg
+    if (!$RCMAIL->config->get('im_convert_path')) {
+      unset($mimetypes[$key]);
+    }
   }
 
   $OUTPUT->set_env('mimetypes', $mimetypes);