-d turns on debugging of filing, headers, locking, matching, transmission. -r redirects stdout and stderr to /usr/lib/news/log and /usr/lib/news/errlog. -i redirects stdout only to /usr/lib/news/log. -n enables ``NNTP mode'' in which history entries are generated as articles are rejected. -s makes discarding an article a serious matter, justifying a non-zero exit status (for the benefit of inews). -x excludes excluded-site from the list of netnews neighbours to receive article(s).
Control messages, recognised by their Control: headers (or for backward compatibility ONLY a Newsgroups: header containing a single newsgroup ending in .ctl), are filed under the control pseudo-group only, but are forwarded as usual, by examining their Newsgroups: and Distribution: headers. Note that posting to the control pseudo-group will not cause a message to be treated as a control message; control is not a real newsgroup.
An article which contains an Also-Control: header is treated normally except that the contents of the header are executed as if they were the contents of a Control: header. Such an article is a form of hybrid message since it functions as an ordinary article yet also causes control functions to be executed. The Supersedes: header is a special case and is rewritten internally only to Also-Control: cancel.
Articles which contain no locally-known (to the active file) newsgroups yet accepted by the local subscription list are filed exactly once, in the junk pseudo-group, and forwarded as usual. If all newsgroups in the article are refused by the local subscription list or are refused by an x in active file entries, then the article will be discarded and not filed in junk.
Locally-generated articles need not be permitted by the local subscription list but are otherwise processed normally; this is for backward compatibility and perhaps to keep the local subscription list short by not requiring general and the like to be named.
A control message which cannot be filed in the control pseudo-group and which cannot be filed in the junk pseudo-group because junk is not in the active file will generate an error message which refers to the groups in its Newsgroups: header instead of referring to the control pseudo-group.
Relaynews could run faster in some circumstances and would be simpler if Control: were required to be the first header, if present, and if Newsgroups: were required to be the next.
The whole control message and hybrid message situation is a festering bug. Either control messages should be eliminated, or all forms of backward compatibility should be dropped (including Control: and Supersedes:) and only Also-Control: should be supported.