The Also-Control header content marks the article as being a control message IN ADDITION to being a normal news article, and specifies the desired actions:
Also-Control-content = Control-content
An article with an Also-Control header is filed and passed on normally, but the content of the Also-Control header is processed as if it were found in a Control header.
NOTE: It is sometimes desirable to piggyback con- trol actions on a normal article, so that the article will be filed normally but will also be acted on as a control message. This header is essentially a generalization of Supersedes.
NOTE: Be warned that some old relayers do not implement Also-Control.
参考: 古い中継者は Also-Control を実装していないことに注意せよ。
An article with an Also-Control header MUST not have a Control or Supersedes header.
Also-Control 頭のついた記事は Control 頭や Supersedes 頭も つけてはいけません。
[1] draft-usefor-articleにより廃止
usefor-article は、新しい代理者(の実装者)は無視するべきとしています。