Are cancel messages the only way to delete a message?
No. Usenet is transitory; not every message will be on all news servers at all times. In fact, cancels are fairly rare; the cause of a missing message is very rarely a cancel. First of all, it takes some period of time for a message to propagate to all news servers that wish to carry the message. This is inherent in the Usenet system; messages take time to arrive. In some cases, they do not arrive at all. More commonly, messages are deleted after a certain period of time so that more messages can take their place – this process is known as expiration. The amount of time that a post exists varies from server to server, and is usually based on the size and content-type of the article and the newsgroups to which it was posted; servers typically save posts for anywhere from a day to several weeks. As this happens on all news servers and is not consistent, expiration is the number one cause of “missing” messages. As time goes on, the software itself has begun to change. Messages posted in H
