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(gnus)Threading

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Threading
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   Gnus threads articles by default.  "To thread" is to put responses
to articles directly after the articles they respond to--in a
hierarchical fashion.

   Threading is done by looking at the `References' headers of the
articles.  In a perfect world, this would be enough to build pretty
trees, but unfortunately, the `References' header is often broken or
simply missing.  Weird news propagation exacerbates the problem, so one
has to employ other heuristics to get pleasing results.  A plethora of
approaches exists, as detailed in horrible detail in Note: Customizing
Threading.

   First, a quick overview of the concepts:

"root"
     The top-most article in a thread; the first article in the thread.

"thread"
     A tree-like article structure.

"sub-thread"
     A small(er) section of this tree-like structure.

"loose threads"
     Threads often lose their roots due to article expiry, or due to
     the root already having been read in a previous session, and not
     displayed in the summary buffer.  We then typically have many
     sub-threads that really belong to one thread, but are without
     connecting roots.  These are called loose threads.

"thread gathering"
     An attempt to gather loose threads into bigger threads.

"sparse threads"
     A thread where the missing articles have been "guessed" at, and are
     displayed as empty lines in the summary buffer.

Customizing Threading

Variables you can change to affect the threading.

Thread Commands

Thread based commands in the summary buffer.