Index: includes/unicode.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/unicode.inc,v
retrieving revision 1.26
diff -u -p -r1.26 unicode.inc
--- includes/unicode.inc	12 May 2007 06:08:56 -0000	1.26
+++ includes/unicode.inc	19 Jun 2007 00:41:25 -0000
@@ -236,13 +236,21 @@ function truncate_utf8($string, $len, $w
  * See http://www.rfc-editor.org/rfc/rfc2047.txt for more information.
  *
  * Notes:
- * - Only encode strings that contain non-ASCII characters.
+ * - Only encode strings that contain non-ASCII characters, unless the 
+ *   optional second parameter is defined, in which case quoted-string 
+ *   encoding will be performed on strings containing non-alphanumeric
+ *   characters.
  * - We progressively cut-off a chunk with truncate_utf8(). This is to ensure
  *   each chunk starts and ends on a character boundary.
  * - Using \n as the chunk separator may cause problems on some systems and may
  *   have to be changed to \r\n or \r.
+ *
+ * @param $string
+ *   The string to encode.
+ * @param $quoted
+ *   If set, perform quoted-string encoding of non-alphanumeric ASCII.
  */
-function mime_header_encode($string) {
+function mime_header_encode($string, $quoted = FALSE) {
   if (preg_match('/[^\x20-\x7E]/', $string)) {
     $chunk_size = 47; // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);
     $len = strlen($string);
@@ -256,6 +264,12 @@ function mime_header_encode($string) {
     }
     return trim($output);
   }
+  // Strings containing spaces and certain other characters must in some
+  // cases be quoted-string encoded.
+  if ($quoted && preg_match('/[^A-Za-z0-9_]/', $string)) {
+    // Escape double-quotes and backslashes.
+    return '"'. addcslashes($string, '\"') .'"';
+  }
   return $string;
 }