Special kind of Usenet post used to control news servers
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 [1][2] and forbidden according to RFC 5537.[3] 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.
- ^ InterNetNews never supported all.all.ctl[clarification needed]. INN version 1.0 was released in 1990.
- ^ "Subject: cmsg" is described only in RFC 1036 (published in December 1987) but not in RFC 850 (published in June 1983). INN dropped this feature with version 2.3.
See INN Changes and Upgrade Information (Internet Archive).
- ^ RFC 5537, 5. Control Messages: [...] The presence of a Subject header field starting with the string "cmsg " MUST NOT cause an article to be interpreted as a control message. [...] Likewise, the presence of a <newsgroup-name> ending in ".ctl" in the Newsgroups header field or the presence of an Also-Control header field MUST NOT cause the article to be interpreted as a control message.