+(defcustom message-ignored-resent-headers
+ ;; `Delivered-To' needs to be removed because some mailers use it to
+ ;; detect loops, so if you resend a message to an address that ultimately
+ ;; comes back to you (e.g. a mailing-list to which you subscribe, in which
+ ;; case you may be removed from the list on the grounds that mail to you
+ ;; bounced with a "mailing loop" error).
+ "^Return-receipt\\|^X-Gnus\\|^Gnus-Warning:\\|^>?From \\|^Delivered-To:"