Control 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.
Types of control messages
cancel
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.