diff --git a/INSTALL b/INSTALL
index 623f478cf..2664e7f89 100644
--- a/INSTALL
+++ b/INSTALL
@@ -17,7 +17,7 @@ REQUIREMENTS
    - mbstring, fileinfo, mcrypt (optional)
 * PEAR packages distributed with Roundcube or external:
    - MDB2 2.5.0 or newer
-   - Mail_Mime 1.6.1 or newer
+   - Mail_Mime 1.7.0 or newer
    - Net_SMTP 1.4.2 or newer
 * php.ini options (see .htaccess file):
    - error_reporting E_ALL & ~E_NOTICE (or lower)
diff --git a/program/lib/Mail/mime.php b/program/lib/Mail/mime.php
index c08c7cfcb..ca54a8a6c 100644
--- a/program/lib/Mail/mime.php
+++ b/program/lib/Mail/mime.php
@@ -1028,6 +1028,7 @@ class Mail_mime
      * $array['header-name'] = 'header-value';
      *
      * @param array $xtra_headers Assoc array with any extra headers (optional)
+     *                            (Don't set Content-Type for multipart messages here!)
      * @param bool  $overwrite    Overwrite already existing headers.
      * @param bool  $skip_content Don't return content headers: Content-Type,
      *                            Content-Disposition and Content-Transfer-Encoding
@@ -1064,6 +1065,8 @@ class Mail_mime
             unset($headers['Content-Type']);
             unset($headers['Content-Transfer-Encoding']);
             unset($headers['Content-Disposition']);
+        } else if (!empty($this->_build_params['ctype'])) {
+            $headers['Content-Type'] = $this->_build_params['ctype'];
         }
 
         $encodedHeaders = $this->_encodeHeaders($headers);
@@ -1075,6 +1078,7 @@ class Mail_mime
      * (usefull if you want to use the PHP mail() function)
      *
      * @param array $xtra_headers Assoc array with any extra headers (optional)
+     *                            (Don't set Content-Type for multipart messages here!)
      * @param bool  $overwrite    Overwrite the existing headers with new.
      * @param bool  $skip_content Don't return content headers: Content-Type,
      *                            Content-Disposition and Content-Transfer-Encoding
@@ -1110,6 +1114,54 @@ class Mail_mime
         return $ret;
     }
 
+    /**
+     * Sets message Content-Type header.
+     * Use it to build messages with various content-types e.g. miltipart/raport
+     * not supported by _contentHeaders() function.
+     *
+     * @param string $type   Type name
+     * @param array  $params Hash array of header parameters
+     *
+     * @return void
+     * @access public
+     * @since 1.7.0
+     */
+    function setContentType($type, $params = array())
+    {
+        $header = $type;
+
+        $eol = !empty($this->_build_params['eol'])
+            ? $this->_build_params['eol'] : "\r\n";
+
+        // add parameters
+        $token_regexp = '#([^\x21,\x23-\x27,\x2A,\x2B,\x2D'
+            . ',\x2E,\x30-\x39,\x41-\x5A,\x5E-\x7E])#';
+        if (is_array($params)) {
+            foreach ($params as $name => $value) {
+                if ($name == 'boundary') {
+                    $this->_build_params['boundary'] = $value;
+                }
+                if (!preg_match($token_regexp, $value)) {
+                    $header .= ";$eol $name=$value";
+                } else {
+                    $value = addcslashes($value, '\\"');
+                    $header .= ";$eol $name=\"$value\"";
+                }
+            }
+        }
+
+        // add required boundary parameter if not defined
+        if (preg_match('/^multipart\//i', $type)) {
+            if (empty($this->_build_params['boundary'])) {
+                $this->_build_params['boundary'] = '=_' . md5(rand() . microtime());              
+            }
+
+            $header .= ";$eol boundary=\"".$this->_build_params['boundary']."\"";
+        }
+
+        $this->_build_params['ctype'] = $header;
+    }
+
     /**
      * Sets the Subject header
      *
diff --git a/program/steps/mail/func.inc b/program/steps/mail/func.inc
index 7f67b2974..1cac61566 100644
--- a/program/steps/mail/func.inc
+++ b/program/steps/mail/func.inc
@@ -1437,7 +1437,6 @@ function rcmail_send_mdn($uid, &$smtp_error)
       'Subject' => rcube_label('receiptread') . ': ' . $message->subject,
       'Message-ID' => sprintf('<%s@%s>', md5(uniqid('rcmail'.mt_rand(),true)), $RCMAIL->config->mail_domain($_SESSION['imap_host'])),
       'X-Sender' => $identity['email'],
-      'Content-Type' => 'multipart/report; report-type=disposition-notification',
     );
     
     if ($agent = $RCMAIL->config->get('useragent'))
@@ -1460,6 +1459,7 @@ function rcmail_send_mdn($uid, &$smtp_error)
                "Disposition: manual-action/MDN-sent-manually; displayed\r\n";
     
     $compose->headers($headers);
+    $compose->setContentType('multipart/report', array('report-type'=> 'disposition-notification'));
     $compose->setTXTBody(rc_wordwrap($body, 75, "\r\n"));
     $compose->addAttachment($report, 'message/disposition-notification', 'MDNPart2.txt', false, '7bit', 'inline');