The Newsgroups line specifies the newsgroup or newsgroups in which the message belongs. Multiple newsgroups may be specified, separated by a comma. Newsgroups specified must all be the names of existing newsgroups, as no new newsgroups will be created by simply posting to them.
Wildcards (e.g., the word all) are never allowed in a "Newsgroups" line. For example, a newsgroup comp.all is illegal, although a newsgroup rec.sport.football is permitted.
If a message is received with a Newsgroups line listing some valid newsgroups and some invalid newsgroups, a host should not remove invalid newsgroups from the list. Instead, the invalid newsgroups should be ignored. For example, suppose host A subscribes to the classes btl.all and comp.all, and exchanges news messages with host B, which subscribes to comp.all but not btl.all. Suppose A receives a message with Newsgroups: comp.unix,btl.general.
This message is passed on to B because B receives comp.unix, but B does not receive btl.general. A must leave the Newsgroups line unchanged. If it were to remove btl.general, the edited header could eventually re-enter the btl.all class, resulting in a message that is not shown to users subscribing to btl.general. Also, follow-ups from outside btl.all would not be shown to such users.
RFC1036: [Source:"RFC-1036"] [Last Changed:December 1987] [Copyright: 1987 M. Horton, R. Adams]
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