--- rcube_storage.php.original	2012-11-29 00:20:04.000000000 +0100
+++ rcube_storage.php.new	2012-12-09 01:32:52.000000000 +0100
@@ -64,6 +64,7 @@
         'MAIL-FOLLOWUP-TO',
         'MAIL-REPLY-TO',
         'RETURN-PATH',
+        'ENVELOPE-TO',
         'DELIVERED-TO',
     );