diff --git a/core/includes/unicode.inc b/core/includes/unicode.inc
index a2ff76b..3af3183 100644
--- a/core/includes/unicode.inc
+++ b/core/includes/unicode.inc
@@ -331,12 +331,12 @@ function truncate_utf8($string, $max_length, $wordsafe = FALSE, $add_ellipsis =
  */
 function mime_header_encode($string) {
   if (preg_match('/[^\x20-\x7E]/', $string)) {
-    $chunk_size = 47; // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);
+    $chunk_size = 45; // floor((75 - strlen("=?UTF-8?B??=\r\n ")) * 0.75);
     $len = strlen($string);
     $output = '';
     while ($len > 0) {
       $chunk = drupal_truncate_bytes($string, $chunk_size);
-      $output .= ' =?UTF-8?B?' . base64_encode($chunk) . "?=\n";
+      $output .= ' =?UTF-8?B?' . base64_encode($chunk) . "?=\r\n ";
       $c = strlen($chunk);
       $string = substr($string, $c);
       $len -= $c;