Emanuel Berg [2013-07-04 13:18:03 +02:00] wrote:

> gnus-summary-cancel-article
>
> but it said
>
> Couldn't send message via news: 441 Invalid Control Message

My news server rejects Gnus's cancel messages unless I change the
control message's "Subject" field from "cmsg cancel" to "cancel". I do
this change automatically with message-cancel-hook (see below). Years
ago I browsed news server's control message group and learnt how to make
cancel messages work.


(add-hook 'message-cancel-hook 'tl-message-cancel-hook)

(defun tl-message-cancel-hook ()
  (save-excursion
    (save-restriction
      (save-match-data
        (message-narrow-to-head)
        (let ((case-fold-search nil))
          (when (re-search-forward "^Subject: \\(cmsg \\)cancel" nil t)
            (delete-region (match-beginning 1) (match-end 1))))))))