Cancel message

Control messages are a special kind of Usenet post that are used to control news servers. They differ from ordinary posts by a header field named Control. The body of the field contains control name and arguments.

There are two historical alternatives to header field Control. They are not supported by contemporary software and forbidden according to RFC 5537. However, the traditional format of the subject line is widely used in addition to the Control header: the subject line consists of the word "cmsg" followed by control name and arguments.

A cancel message requests the deletion of a specific article. The body of the Control field contains one argument, the Message-ID of the article to delete.

According to RFC 1036 only the author of the target message or the local news administrator is allowed to send a cancel. To verify authorization the From: line (or Sender: line, if it exists) of the cancel message must match the target article. This verification does not work well in modern day Usenet and is rarely used.

Additional hierarchy specific rules (see Breidbart Index) allow cancelbots to send third-party cancels to remove spam.

A newgroup message is issued to create a new Usenet newsgroup. The body of the Control field contains one mandatory argument, the name of the new group. The second argument is optional. If present it consists of the keyword moderated. The body of the message typically contains tagline, charter and rationale.

If the group already exists, only the status of the group is changed, i.e. whether it is moderated or nor not.

Typically newgroup messages having a correct digital signature are executed automatically. In some hierarchies (alt.*, free.*, de.alt.*) unsigned newgroup messages just serve as formalized proposal to create a new group. Objections to the proposal are then expressed with a rmgroup.

In many cases newgroup messages are archived by the Internet Systems Consortium.

A rmgroup message is issued to remove a newsgroup. The body of the Control field contains one mandatory argument, the name of the group to remove.

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