The most widely known message is cancel, with which a user may cancel an article sent by her earlier. This effectively removes the article from the spool directories, if it exists. The cancel message is forwarded to all sites that receive news from the groups affected, regardless of whether the article has been seen already or not. This is to take into account the possibility that the original article has been delayed over the cancellation message. Some news systems allow users to cancel other person's messages; this is of course a definite no-no.