Agent Categories
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One of the main reasons to integrate the news transport layer into
the newsreader is to allow greater control over what articles to
download. There's not much point in downloading huge amounts of
articles, just to find out that you're not interested in reading any of
them. It's better to be somewhat more conservative in choosing what to
download, and then mark the articles for downloading manually if it
should turn out that you're interested in the articles anyway.
The main way to control what is to be downloaded is to create a
"category" and then assign some (or all) groups to this category.
Groups that do not belong in any other category belong to the `default'
category. Gnus has its own buffer for creating and managing categories.