150: Why can't I kill in Gnus based on the Newsgroups/Keywords/Control headers? Gnus will complain that the "Newsgroups:", "Keywords:", and "Control:" headers are "Unknown header" fields. For the "Newsgroups:" header, there is an easy workaround: kill on the "Xref" header instead, which will be present on any cross-posted article (as long as your site carries the cross-post group). If you really want to kill on one of these headers, you can do it like this: (gnus-kill nil "^Newsgroups: .*\\(bad\\.group\\|worse\\.group\\)")