+If the size spec is an integer instead of a floating point number,
+then that number will be used to say how many lines a buffer should
+occupy, not a percentage.
+
+If the @dfn{split} looks like something that can be @code{eval}ed (to be
+precise---if the @code{car} of the split is a function or a subr), this
+split will be @code{eval}ed. If the result is non-@code{nil}, it will
+be used as a split. This means that there will be three buffers if
+@code{gnus-carpal} is @code{nil}, and four buffers if @code{gnus-carpal}
+is non-@code{nil}.
+
+Not complicated enough for you? Well, try this on for size:
+
+@lisp
+(article (horizontal 1.0
+ (vertical 0.5
+ (group 1.0)
+ (gnus-carpal 4))
+ (vertical 1.0
+ (summary 0.25 point)
+ (summary-carpal 4)
+ (article 1.0))))
+@end lisp
+
+Whoops. Two buffers with the mystery 100% tag. And what's that
+@code{horizontal} thingie?
+
+If the first element in one of the split is @code{horizontal}, Gnus will
+split the window horizontally, giving you two windows side-by-side.
+Inside each of these strips you may carry on all you like in the normal
+fashion. The number following @code{horizontal} says what percentage of
+the screen is to be given to this strip.
+
+For each split, there @emph{must} be one element that has the 100% tag.
+The splitting is never accurate, and this buffer will eat any leftover
+lines from the splits.
+
+To be slightly more formal, here's a definition of what a valid split
+may look like:
+
+@example
+@group
+split = frame | horizontal | vertical | buffer | form
+frame = "(frame " size *split ")"
+horizontal = "(horizontal " size *split ")"
+vertical = "(vertical " size *split ")"
+buffer = "(" buf-name " " size *[ "point" ] *[ "frame-focus"] ")"
+size = number | frame-params
+buf-name = group | article | summary ...
+@end group
+@end example
+
+The limitations are that the @code{frame} split can only appear as the
+top-level split. @var{form} should be an Emacs Lisp form that should
+return a valid split. We see that each split is fully recursive, and
+may contain any number of @code{vertical} and @code{horizontal} splits.
+
+@vindex gnus-window-min-width
+@vindex gnus-window-min-height
+@cindex window height
+@cindex window width
+Finding the right sizes can be a bit complicated. No window may be less
+than @code{gnus-window-min-height} (default 1) characters high, and all
+windows must be at least @code{gnus-window-min-width} (default 1)
+characters wide. Gnus will try to enforce this before applying the
+splits. If you want to use the normal Emacs window width/height limit,
+you can just set these two variables to @code{nil}.
+
+If you're not familiar with Emacs terminology, @code{horizontal} and
+@code{vertical} splits may work the opposite way of what you'd expect.
+Windows inside a @code{horizontal} split are shown side-by-side, and
+windows within a @code{vertical} split are shown above each other.
+
+@findex gnus-configure-frame
+If you want to experiment with window placement, a good tip is to call
+@code{gnus-configure-frame} directly with a split. This is the function
+that does all the real work when splitting buffers. Below is a pretty
+nonsensical configuration with 5 windows; two for the group buffer and
+three for the article buffer. (I said it was nonsensical.) If you
+@code{eval} the statement below, you can get an idea of how that would
+look straight away, without going through the normal Gnus channels.
+Play with it until you're satisfied, and then use
+@code{gnus-add-configuration} to add your new creation to the buffer
+configuration list.
+
+@lisp
+(gnus-configure-frame
+ '(horizontal 1.0
+ (vertical 10
+ (group 1.0)
+ (article 0.3 point))
+ (vertical 1.0
+ (article 1.0)
+ (horizontal 4
+ (group 1.0)
+ (article 10)))))
+@end lisp
+
+You might want to have several frames as well. No prob---just use the
+@code{frame} split:
+
+@lisp
+(gnus-configure-frame
+ '(frame 1.0
+ (vertical 1.0
+ (summary 0.25 point frame-focus)
+ (article 1.0))
+ (vertical ((height . 5) (width . 15)
+ (user-position . t)
+ (left . -1) (top . 1))
+ (picon 1.0))))
+
+@end lisp
+
+This split will result in the familiar summary/article window
+configuration in the first (or ``main'') frame, while a small additional
+frame will be created where picons will be shown. As you can see,
+instead of the normal @code{1.0} top-level spec, each additional split
+should have a frame parameter alist as the size spec.
+@xref{Frame Parameters, , Frame Parameters, elisp, The GNU Emacs Lisp
+Reference Manual}. Under XEmacs, a frame property list will be
+accepted, too---for instance, @code{(height 5 width 15 left -1 top 1)}
+is such a plist.
+The list of all possible keys for @code{gnus-buffer-configuration} can
+be found in its default value.
+
+Note that the @code{message} key is used for both
+@code{gnus-group-mail} and @code{gnus-summary-mail-other-window}. If
+it is desirable to distinguish between the two, something like this
+might be used:
+
+@lisp
+(message (horizontal 1.0
+ (vertical 1.0 (message 1.0 point))
+ (vertical 0.24
+ (if (buffer-live-p gnus-summary-buffer)
+ '(summary 0.5))
+ (group 1.0))))
+@end lisp
+
+One common desire for a multiple frame split is to have a separate frame
+for composing mail and news while leaving the original frame intact. To
+accomplish that, something like the following can be done:
+
+@lisp
+(message
+ (frame 1.0
+ (if (not (buffer-live-p gnus-summary-buffer))
+ (car (cdr (assoc 'group gnus-buffer-configuration)))
+ (car (cdr (assoc 'summary gnus-buffer-configuration))))
+ (vertical ((user-position . t) (top . 1) (left . 1)
+ (name . "Message"))
+ (message 1.0 point))))
+@end lisp
+
+@findex gnus-add-configuration
+Since the @code{gnus-buffer-configuration} variable is so long and
+complicated, there's a function you can use to ease changing the config
+of a single setting: @code{gnus-add-configuration}. If, for instance,
+you want to change the @code{article} setting, you could say:
+
+@lisp
+(gnus-add-configuration
+ '(article (vertical 1.0
+ (group 4)
+ (summary .25 point)
+ (article 1.0))))
+@end lisp
+
+You'd typically stick these @code{gnus-add-configuration} calls in your
+@file{~/.gnus.el} file or in some startup hook---they should be run after
+Gnus has been loaded.
+
+@vindex gnus-always-force-window-configuration
+If all windows mentioned in the configuration are already visible, Gnus
+won't change the window configuration. If you always want to force the
+``right'' window configuration, you can set
+@code{gnus-always-force-window-configuration} to non-@code{nil}.
+
+If you're using tree displays (@pxref{Tree Display}), and the tree
+window is displayed vertically next to another window, you may also want
+to fiddle with @code{gnus-tree-minimize-window} to avoid having the
+windows resized.
+
+@subsection Example Window Configurations
+
+@itemize @bullet
+@item
+Narrow left hand side occupied by group buffer. Right hand side split
+between summary buffer (top one-sixth) and article buffer (bottom).
+
+@ifinfo
+@example
++---+---------+
+| G | Summary |
+| r +---------+
+| o | |
+| u | Article |
+| p | |
++---+---------+
+@end example
+@end ifinfo
+
+@lisp
+(gnus-add-configuration
+ '(article
+ (horizontal 1.0
+ (vertical 25 (group 1.0))
+ (vertical 1.0
+ (summary 0.16 point)
+ (article 1.0)))))
+
+(gnus-add-configuration
+ '(summary
+ (horizontal 1.0
+ (vertical 25 (group 1.0))
+ (vertical 1.0 (summary 1.0 point)))))
+@end lisp
+
+@end itemize
+
+
+@node Faces and Fonts
+@section Faces and Fonts
+@cindex faces
+@cindex fonts
+@cindex colors
+
+Fiddling with fonts and faces used to be very difficult, but these days
+it is very simple. You simply say @kbd{M-x customize-face}, pick out
+the face you want to alter, and alter it via the standard Customize
+interface.
+
+
+@node Compilation
+@section Compilation
+@cindex compilation
+@cindex byte-compilation
+
+@findex gnus-compile
+
+Remember all those line format specification variables?
+@code{gnus-summary-line-format}, @code{gnus-group-line-format}, and so
+on. By default, T-gnus will use the byte-compiled codes of these
+variables and we can keep a slow-down to a minimum. However, if you set
+@code{gnus-compile-user-specs} to @code{nil} (@code{t} by default),
+unfortunately, changing them will mean a quite significant slow-down.
+(The default values of these variables have byte-compiled functions
+associated with them, while the user-generated versions do not, of
+course.)
+
+To help with this, you can run @kbd{M-x gnus-compile} after you've
+fiddled around with the variables and feel that you're (kind of)
+satisfied. This will result in the new specs being byte-compiled, and
+you'll get top speed again. Note that T-gnus will not save these
+compiled specs in the @file{.newsrc.eld} file.
+
+@table @code
+@item gnus-compile-user-specs
+@vindex gnus-compile-user-specs
+If it is non-nil, the user-defined format specs will be byte-compiled
+automatically. The default value of this variable is @code{t}. It has
+an effect on the values of @code{gnus-*-line-format-spec}.
+@end table
+
+
+@node Mode Lines
+@section Mode Lines
+@cindex mode lines
+
+@vindex gnus-updated-mode-lines
+@code{gnus-updated-mode-lines} says what buffers should keep their mode
+lines updated. It is a list of symbols. Supported symbols include
+@code{group}, @code{article}, @code{summary}, @code{server},
+@code{browse}, and @code{tree}. If the corresponding symbol is present,
+Gnus will keep that mode line updated with information that may be
+pertinent. If this variable is @code{nil}, screen refresh may be
+quicker.
+
+@cindex display-time
+
+@vindex gnus-mode-non-string-length
+By default, Gnus displays information on the current article in the mode
+lines of the summary and article buffers. The information Gnus wishes
+to display (e.g. the subject of the article) is often longer than the
+mode lines, and therefore have to be cut off at some point. The
+@code{gnus-mode-non-string-length} variable says how long the other
+elements on the line is (i.e., the non-info part). If you put
+additional elements on the mode line (e.g. a clock), you should modify
+this variable:
+
+@c Hook written by Francesco Potorti` <pot@cnuce.cnr.it>
+@lisp
+(add-hook 'display-time-hook
+ (lambda () (setq gnus-mode-non-string-length
+ (+ 21
+ (if line-number-mode 5 0)
+ (if column-number-mode 4 0)
+ (length display-time-string)))))
+@end lisp
+
+If this variable is @code{nil} (which is the default), the mode line
+strings won't be chopped off, and they won't be padded either. Note
+that the default is unlikely to be desirable, as even the percentage
+complete in the buffer may be crowded off the mode line; the user should
+configure this variable appropriately for her configuration.
+
+
+@node Highlighting and Menus
+@section Highlighting and Menus
+@cindex visual
+@cindex highlighting
+@cindex menus
+
+@vindex gnus-visual
+The @code{gnus-visual} variable controls most of the Gnus-prettifying
+aspects. If @code{nil}, Gnus won't attempt to create menus or use fancy
+colors or fonts. This will also inhibit loading the @file{gnus-vis.el}
+file.
+
+This variable can be a list of visual properties that are enabled. The
+following elements are valid, and are all included by default:
+
+@table @code
+@item group-highlight
+Do highlights in the group buffer.
+@item summary-highlight
+Do highlights in the summary buffer.
+@item article-highlight
+Do highlights in the article buffer.
+@item highlight
+Turn on highlighting in all buffers.
+@item group-menu
+Create menus in the group buffer.
+@item summary-menu
+Create menus in the summary buffers.
+@item article-menu
+Create menus in the article buffer.
+@item browse-menu
+Create menus in the browse buffer.
+@item server-menu
+Create menus in the server buffer.
+@item score-menu
+Create menus in the score buffers.
+@item menu
+Create menus in all buffers.
+@end table
+
+So if you only want highlighting in the article buffer and menus in all
+buffers, you could say something like:
+
+@lisp
+(setq gnus-visual '(article-highlight menu))
+@end lisp
+
+If you want highlighting only and no menus whatsoever, you'd say:
+
+@lisp
+(setq gnus-visual '(highlight))
+@end lisp
+
+If @code{gnus-visual} is @code{t}, highlighting and menus will be used
+in all Gnus buffers.
+
+Other general variables that influence the look of all buffers include:
+
+@table @code
+@item gnus-mouse-face
+@vindex gnus-mouse-face
+This is the face (i.e., font) used for mouse highlighting in Gnus. No
+mouse highlights will be done if @code{gnus-visual} is @code{nil}.
+
+@end table
+
+There are hooks associated with the creation of all the different menus:
+
+@table @code
+
+@item gnus-article-menu-hook
+@vindex gnus-article-menu-hook
+Hook called after creating the article mode menu.
+
+@item gnus-group-menu-hook
+@vindex gnus-group-menu-hook
+Hook called after creating the group mode menu.
+
+@item gnus-summary-menu-hook
+@vindex gnus-summary-menu-hook
+Hook called after creating the summary mode menu.
+
+@item gnus-server-menu-hook
+@vindex gnus-server-menu-hook
+Hook called after creating the server mode menu.
+
+@item gnus-browse-menu-hook
+@vindex gnus-browse-menu-hook
+Hook called after creating the browse mode menu.
+
+@item gnus-score-menu-hook
+@vindex gnus-score-menu-hook
+Hook called after creating the score mode menu.
+
+@end table
+
+
+@node Buttons
+@section Buttons
+@cindex buttons
+@cindex mouse
+@cindex click
+
+Those new-fangled @dfn{mouse} contraptions is very popular with the
+young, hep kids who don't want to learn the proper way to do things
+these days. Why, I remember way back in the summer of '89, when I was
+using Emacs on a Tops 20 system. Three hundred users on one single
+machine, and every user was running Simula compilers. Bah!
+
+Right.
+
+@vindex gnus-carpal
+Well, you can make Gnus display bufferfuls of buttons you can click to
+do anything by setting @code{gnus-carpal} to @code{t}. Pretty simple,
+really. Tell the chiropractor I sent you.
+
+
+@table @code
+
+@item gnus-carpal-mode-hook
+@vindex gnus-carpal-mode-hook
+Hook run in all carpal mode buffers.
+
+@item gnus-carpal-button-face
+@vindex gnus-carpal-button-face
+Face used on buttons.
+
+@item gnus-carpal-header-face
+@vindex gnus-carpal-header-face
+Face used on carpal buffer headers.
+
+@item gnus-carpal-group-buffer-buttons
+@vindex gnus-carpal-group-buffer-buttons
+Buttons in the group buffer.
+
+@item gnus-carpal-summary-buffer-buttons
+@vindex gnus-carpal-summary-buffer-buttons
+Buttons in the summary buffer.
+
+@item gnus-carpal-server-buffer-buttons
+@vindex gnus-carpal-server-buffer-buttons
+Buttons in the server buffer.
+
+@item gnus-carpal-browse-buffer-buttons
+@vindex gnus-carpal-browse-buffer-buttons
+Buttons in the browse buffer.
+@end table
+
+All the @code{buttons} variables are lists. The elements in these list
+are either cons cells where the @code{car} contains a text to be displayed and
+the @code{cdr} contains a function symbol, or a simple string.
+
+
+@node Daemons
+@section Daemons
+@cindex demons
+@cindex daemons
+
+Gnus, being larger than any program ever written (allegedly), does lots
+of strange stuff that you may wish to have done while you're not
+present. For instance, you may want it to check for new mail once in a
+while. Or you may want it to close down all connections to all servers
+when you leave Emacs idle. And stuff like that.
+
+Gnus will let you do stuff like that by defining various
+@dfn{handlers}. Each handler consists of three elements: A
+@var{function}, a @var{time}, and an @var{idle} parameter.
+
+Here's an example of a handler that closes connections when Emacs has
+been idle for thirty minutes:
+
+@lisp
+(gnus-demon-close-connections nil 30)
+@end lisp
+
+Here's a handler that scans for @acronym{PGP} headers every hour when
+Emacs is idle:
+
+@lisp
+(gnus-demon-scan-pgp 60 t)
+@end lisp
+
+This @var{time} parameter and that @var{idle} parameter work together
+in a strange, but wonderful fashion. Basically, if @var{idle} is
+@code{nil}, then the function will be called every @var{time} minutes.
+
+If @var{idle} is @code{t}, then the function will be called after
+@var{time} minutes only if Emacs is idle. So if Emacs is never idle,
+the function will never be called. But once Emacs goes idle, the
+function will be called every @var{time} minutes.
+
+If @var{idle} is a number and @var{time} is a number, the function will
+be called every @var{time} minutes only when Emacs has been idle for
+@var{idle} minutes.
+
+If @var{idle} is a number and @var{time} is @code{nil}, the function
+will be called once every time Emacs has been idle for @var{idle}
+minutes.
+
+And if @var{time} is a string, it should look like @samp{07:31}, and
+the function will then be called once every day somewhere near that
+time. Modified by the @var{idle} parameter, of course.
+
+@vindex gnus-demon-timestep
+(When I say ``minute'' here, I really mean @code{gnus-demon-timestep}
+seconds. This is 60 by default. If you change that variable,
+all the timings in the handlers will be affected.)
+
+So, if you want to add a handler, you could put something like this in
+your @file{~/.gnus.el} file:
+
+@findex gnus-demon-add-handler
+@lisp
+(gnus-demon-add-handler 'gnus-demon-close-connections 30 t)
+@end lisp
+
+@findex gnus-demon-add-nocem
+@findex gnus-demon-add-scanmail
+@findex gnus-demon-add-rescan
+@findex gnus-demon-add-scan-timestamps
+@findex gnus-demon-add-disconnection
+Some ready-made functions to do this have been created:
+@code{gnus-demon-add-nocem}, @code{gnus-demon-add-disconnection},
+@code{gnus-demon-add-nntp-close-connection},
+@code{gnus-demon-add-scan-timestamps}, @code{gnus-demon-add-rescan}, and
+@code{gnus-demon-add-scanmail}. Just put those functions in your
+@file{~/.gnus.el} if you want those abilities.
+
+@findex gnus-demon-init
+@findex gnus-demon-cancel
+@vindex gnus-demon-handlers
+If you add handlers to @code{gnus-demon-handlers} directly, you should
+run @code{gnus-demon-init} to make the changes take hold. To cancel all
+daemons, you can use the @code{gnus-demon-cancel} function.
+
+Note that adding daemons can be pretty naughty if you over do it. Adding
+functions that scan all news and mail from all servers every two seconds
+is a sure-fire way of getting booted off any respectable system. So
+behave.
+
+
+@node NoCeM
+@section NoCeM
+@cindex nocem
+@cindex spam
+
+@dfn{Spamming} is posting the same article lots and lots of times.
+Spamming is bad. Spamming is evil.
+
+Spamming is usually canceled within a day or so by various anti-spamming
+agencies. These agencies usually also send out @dfn{NoCeM} messages.
+NoCeM is pronounced ``no see-'em'', and means what the name
+implies---these are messages that make the offending articles, like, go
+away.
+
+What use are these NoCeM messages if the articles are canceled anyway?
+Some sites do not honor cancel messages and some sites just honor cancels
+from a select few people. Then you may wish to make use of the NoCeM
+messages, which are distributed in the @samp{alt.nocem.misc} newsgroup.
+
+Gnus can read and parse the messages in this group automatically, and
+this will make spam disappear.
+
+There are some variables to customize, of course:
+
+@table @code
+@item gnus-use-nocem
+@vindex gnus-use-nocem
+Set this variable to @code{t} to set the ball rolling. It is @code{nil}
+by default.
+
+@item gnus-nocem-groups
+@vindex gnus-nocem-groups
+Gnus will look for NoCeM messages in the groups in this list. The
+default is
+@lisp
+("news.lists.filters" "news.admin.net-abuse.bulletins"
+ "alt.nocem.misc" "news.admin.net-abuse.announce")
+@end lisp
+
+@item gnus-nocem-issuers
+@vindex gnus-nocem-issuers
+There are many people issuing NoCeM messages. This list says what
+people you want to listen to. The default is
+@lisp
+("Automoose-1" "clewis@@ferret.ocunix.on.ca"
+ "cosmo.roadkill" "SpamHippo" "hweede@@snafu.de")
+@end lisp
+fine, upstanding citizens all of them.
+
+Known despammers that you can put in this list are listed at@*
+@uref{http://www.xs4all.nl/~rosalind/nocemreg/nocemreg.html}.
+
+You do not have to heed NoCeM messages from all these people---just the
+ones you want to listen to. You also don't have to accept all NoCeM
+messages from the people you like. Each NoCeM message has a @dfn{type}
+header that gives the message a (more or less, usually less) rigorous
+definition. Common types are @samp{spam}, @samp{spew}, @samp{mmf},
+@samp{binary}, and @samp{troll}. To specify this, you have to use
+@code{(@var{issuer} @var{conditions} @dots{})} elements in the list.
+Each condition is either a string (which is a regexp that matches types
+you want to use) or a list on the form @code{(not @var{string})}, where
+@var{string} is a regexp that matches types you don't want to use.
+
+For instance, if you want all NoCeM messages from Chris Lewis except his
+@samp{troll} messages, you'd say:
+
+@lisp
+("clewis@@ferret.ocunix.on.ca" ".*" (not "troll"))
+@end lisp
+
+On the other hand, if you just want nothing but his @samp{spam} and
+@samp{spew} messages, you'd say:
+
+@lisp
+("clewis@@ferret.ocunix.on.ca" (not ".*") "spew" "spam")
+@end lisp
+
+The specs are applied left-to-right.
+
+
+@item gnus-nocem-verifyer
+@vindex gnus-nocem-verifyer
+@findex pgg-verify-region
+This should be a function for verifying that the NoCeM issuer is who she
+says she is. The default is the function using @code{pgg-verify-region}
+shown below:
+
+@lisp
+(lambda ()
+ (pgg-verify-region (point-min) (point-max)))
+@end lisp
+
+It returns non-@code{nil} if the verification is successful, otherwise
+(including the case the NoCeM message was not signed) returns
+@code{nil}. If this is too slow and you don't care for verification
+(which may be dangerous), you can set this variable to @code{nil}.
+
+Formerly the default was @code{mc-verify}, which is a Mailcrypt
+function. While you can still use it, you can change it into the
+default function running with GnuPG if you are willing to add the
+@acronym{PGP} public keys to GnuPG's keyring.
+
+@item gnus-nocem-directory
+@vindex gnus-nocem-directory
+This is where Gnus will store its NoCeM cache files. The default is@*
+@file{~/News/NoCeM/}.
+
+@item gnus-nocem-expiry-wait
+@vindex gnus-nocem-expiry-wait
+The number of days before removing old NoCeM entries from the cache.
+The default is 15. If you make it shorter Gnus will be faster, but you
+might then see old spam.
+
+@item gnus-nocem-check-from
+@vindex gnus-nocem-check-from
+Non-@code{nil} means check for valid issuers in message bodies.
+Otherwise don't bother fetching articles unless their author matches a
+valid issuer; that is much faster if you are selective about the
+issuers.
+
+@item gnus-nocem-check-article-limit
+@vindex gnus-nocem-check-article-limit
+If non-@code{nil}, the maximum number of articles to check in any NoCeM
+group. NoCeM groups can be huge and very slow to process.
+
+@end table
+
+Using NoCeM could potentially be a memory hog. If you have many living
+(i. e., subscribed or unsubscribed groups), your Emacs process will grow
+big. If this is a problem, you should kill off all (or most) of your
+unsubscribed groups (@pxref{Subscription Commands}).
+
+
+@node Undo
+@section Undo
+@cindex undo
+
+It is very useful to be able to undo actions one has done. In normal
+Emacs buffers, it's easy enough---you just push the @code{undo} button.
+In Gnus buffers, however, it isn't that simple.
+
+The things Gnus displays in its buffer is of no value whatsoever to
+Gnus---it's all just data designed to look nice to the user.
+Killing a group in the group buffer with @kbd{C-k} makes the line
+disappear, but that's just a side-effect of the real action---the
+removal of the group in question from the internal Gnus structures.
+Undoing something like that can't be done by the normal Emacs
+@code{undo} function.
+
+Gnus tries to remedy this somewhat by keeping track of what the user
+does and coming up with actions that would reverse the actions the user
+takes. When the user then presses the @code{undo} key, Gnus will run
+the code to reverse the previous action, or the previous actions.
+However, not all actions are easily reversible, so Gnus currently offers
+a few key functions to be undoable. These include killing groups,
+yanking groups, and changing the list of read articles of groups.
+That's it, really. More functions may be added in the future, but each
+added function means an increase in data to be stored, so Gnus will
+never be totally undoable.
+
+@findex gnus-undo-mode
+@vindex gnus-use-undo
+@findex gnus-undo
+The undoability is provided by the @code{gnus-undo-mode} minor mode. It
+is used if @code{gnus-use-undo} is non-@code{nil}, which is the
+default. The @kbd{C-M-_} key performs the @code{gnus-undo}
+command, which should feel kinda like the normal Emacs @code{undo}
+command.
+
+
+@node Predicate Specifiers
+@section Predicate Specifiers
+@cindex predicate specifiers
+
+Some Gnus variables are @dfn{predicate specifiers}. This is a special
+form that allows flexible specification of predicates without having
+to type all that much.
+
+These specifiers are lists consisting of functions, symbols and lists.
+
+Here's an example:
+
+@lisp
+(or gnus-article-unseen-p
+ gnus-article-unread-p)
+@end lisp
+
+The available symbols are @code{or}, @code{and} and @code{not}. The
+functions all take one parameter.
+
+@findex gnus-make-predicate
+Internally, Gnus calls @code{gnus-make-predicate} on these specifiers
+to create a function that can be called. This input parameter to this
+function will be passed along to all the functions in the predicate
+specifier.
+
+
+@node Moderation
+@section Moderation
+@cindex moderation
+
+If you are a moderator, you can use the @file{gnus-mdrtn.el} package.
+It is not included in the standard Gnus package. Write a mail to
+@samp{larsi@@gnus.org} and state what group you moderate, and you'll
+get a copy.
+
+The moderation package is implemented as a minor mode for summary
+buffers. Put
+
+@lisp
+(add-hook 'gnus-summary-mode-hook 'gnus-moderate)
+@end lisp
+
+in your @file{~/.gnus.el} file.
+
+If you are the moderator of @samp{rec.zoofle}, this is how it's
+supposed to work:
+
+@enumerate
+@item
+You split your incoming mail by matching on
+@samp{Newsgroups:.*rec.zoofle}, which will put all the to-be-posted
+articles in some mail group---for instance, @samp{nnml:rec.zoofle}.
+
+@item
+You enter that group once in a while and post articles using the @kbd{e}
+(edit-and-post) or @kbd{s} (just send unedited) commands.
+
+@item
+If, while reading the @samp{rec.zoofle} newsgroup, you happen upon some
+articles that weren't approved by you, you can cancel them with the
+@kbd{c} command.
+@end enumerate
+
+To use moderation mode in these two groups, say:
+
+@lisp
+(setq gnus-moderated-list
+ "^nnml:rec.zoofle$\\|^rec.zoofle$")
+@end lisp
+
+
+@node Fetching a Group
+@section Fetching a Group
+@cindex fetching a group
+
+@findex gnus-fetch-group
+It is sometimes convenient to be able to just say ``I want to read this
+group and I don't care whether Gnus has been started or not''. This is
+perhaps more useful for people who write code than for users, but the
+command @code{gnus-fetch-group} provides this functionality in any case.
+It takes the group name as a parameter.
+
+
+@node Image Enhancements
+@section Image Enhancements
+
+XEmacs, as well as Emacs 21@footnote{Emacs 21 on MS Windows doesn't
+support images yet.}, is able to display pictures and stuff, so Gnus has
+taken advantage of that.
+
+@menu
+* X-Face:: Display a funky, teensy black-and-white image.
+* Face:: Display a funkier, teensier colored image.
+* Smileys:: Show all those happy faces the way they were meant to be shown.
+* Picons:: How to display pictures of what you're reading.
+* XVarious:: Other XEmacsy Gnusey variables.
+@end menu
+
+
+@node X-Face
+@subsection X-Face
+@cindex x-face
+
+@code{X-Face} headers describe a 48x48 pixel black-and-white (1 bit
+depth) image that's supposed to represent the author of the message.
+It seems to be supported by an ever-growing number of mail and news
+readers.
+
+@cindex x-face
+@findex gnus-article-display-x-face
+@vindex gnus-article-x-face-command
+@vindex gnus-article-x-face-too-ugly
+@iftex
+@iflatex
+\include{xface}
+@end iflatex
+@end iftex
+@c @anchor{X-Face}
+
+Decoding an @code{X-Face} header either requires an Emacs that has
+@samp{compface} support (which most XEmacs versions has), or that you
+have @samp{compface} installed on your system. If either is true,
+Gnus will default to displaying @code{X-Face} headers.
+
+The variable that controls this is the
+@code{gnus-article-x-face-command} variable. If this variable is a
+string, this string will be executed in a sub-shell. If it is a
+function, this function will be called with the face as the argument.
+If the @code{gnus-article-x-face-too-ugly} (which is a regexp) matches
+the @code{From} header, the face will not be shown.
+
+The default action under Emacs without image support is to fork off the
+@code{display} program@footnote{@code{display} is from the ImageMagick
+package. For the @code{uncompface} and @code{icontopbm} programs look
+for a package like @code{compface} or @code{faces-xface} on a GNU/Linux
+system.} to view the face.
+
+Under XEmacs or Emacs 21+ with suitable image support, the default
+action is to display the face before the @code{From} header. (It's
+nicer if XEmacs has been compiled with @code{X-Face} support---that
+will make display somewhat faster. If there's no native @code{X-Face}
+support, Gnus will try to convert the @code{X-Face} header using
+external programs from the @code{pbmplus} package and
+friends.@footnote{On a GNU/Linux system look for packages with names
+like @code{netpbm}, @code{libgr-progs} and @code{compface}.})
+
+(Note: @code{x-face} is used in the variable/function names, not
+@code{xface}).
+
+@noindent
+Face and variable:
+
+@table @code
+@item gnus-x-face
+@vindex gnus-x-face
+Face to show X-Face. The colors from this face are used as the
+foreground and background colors of the displayed X-Faces. The
+default colors are black and white.
+
+@item gnus-face-properties-alist
+@vindex gnus-face-properties-alist
+Alist of image types and properties applied to Face (@pxref{Face}) and
+X-Face images. The default value is @code{((pbm . (:face gnus-x-face))
+(png . nil))} for Emacs or @code{((xface . (:face gnus-x-face)))} for
+XEmacs. Here are examples:
+
+@lisp
+;; Specify the altitude of Face and X-Face images in the From header.
+(setq gnus-face-properties-alist
+ '((pbm . (:face gnus-x-face :ascent 80))
+ (png . (:ascent 80))))
+
+;; Show Face and X-Face images as pressed buttons.
+(setq gnus-face-properties-alist
+ '((pbm . (:face gnus-x-face :relief -2))
+ (png . (:relief -2))))
+@end lisp
+
+@pxref{Image Descriptors, ,Image Descriptors, elisp, The Emacs Lisp
+Reference Manual} for the valid properties for various image types.
+Currently, @code{pbm} is used for X-Face images and @code{png} is used
+for Face images in Emacs. Only the @code{:face} property is effective
+on the @code{xface} image type in XEmacs if it is built with the
+@samp{libcompface} library.
+@end table
+
+Gnus provides a few convenience functions and variables to allow
+easier insertion of X-Face headers in outgoing messages.
+
+@findex gnus-random-x-face
+@vindex gnus-convert-pbm-to-x-face-command
+@vindex gnus-x-face-directory
+@code{gnus-random-x-face} goes through all the @samp{pbm} files in
+@code{gnus-x-face-directory} and picks one at random, and then
+converts it to the X-Face format by using the
+@code{gnus-convert-pbm-to-x-face-command} shell command. The
+@samp{pbm} files should be 48x48 pixels big. It returns the X-Face
+header data as a string.
+
+@findex gnus-insert-random-x-face-header
+@code{gnus-insert-random-x-face-header} calls
+@code{gnus-random-x-face} and inserts a @samp{X-Face} header with the
+randomly generated data.
+
+@findex gnus-x-face-from-file
+@vindex gnus-convert-image-to-x-face-command
+@code{gnus-x-face-from-file} takes a GIF file as the parameter, and then
+converts the file to X-Face format by using the
+@code{gnus-convert-image-to-x-face-command} shell command.
+
+Here's how you would typically use the first function. Put something
+like the following in your @file{~/.gnus.el} file:
+
+@lisp
+(setq message-required-news-headers
+ (nconc message-required-news-headers
+ (list '(X-Face . gnus-random-x-face))))
+@end lisp
+
+Using the last function would be something like this:
+
+@lisp
+(setq message-required-news-headers
+ (nconc message-required-news-headers
+ (list '(X-Face . (lambda ()
+ (gnus-x-face-from-file
+ "~/My-face.gif"))))))
+@end lisp
+
+
+@node Face
+@subsection Face
+@cindex face
+
+@c #### FIXME: faces and x-faces'implementations should really be harmonized.
+
+@code{Face} headers are essentially a funkier version of @code{X-Face}
+ones. They describe a 48x48 pixel colored image that's supposed to
+represent the author of the message.
+
+@cindex face
+@findex gnus-article-display-face
+The contents of a @code{Face} header must be a base64 encoded PNG image.
+See @uref{http://quimby.gnus.org/circus/face/} for the precise
+specifications.
+
+The @code{gnus-face-properties-alist} variable affects the appearance of
+displayed Face images. @xref{X-Face}.
+
+Gnus provides a few convenience functions and variables to allow
+easier insertion of Face headers in outgoing messages.
+
+@findex gnus-convert-png-to-face
+@code{gnus-convert-png-to-face} takes a 48x48 PNG image, no longer than
+726 bytes long, and converts it to a face.
+
+@findex gnus-face-from-file
+@vindex gnus-convert-image-to-face-command
+@code{gnus-face-from-file} takes a JPEG file as the parameter, and then
+converts the file to Face format by using the
+@code{gnus-convert-image-to-face-command} shell command.
+
+Here's how you would typically use this function. Put something like the
+following in your @file{~/.gnus.el} file:
+
+@lisp
+(setq message-required-news-headers
+ (nconc message-required-news-headers
+ (list '(Face . (lambda ()
+ (gnus-face-from-file "~/face.jpg"))))))
+@end lisp
+
+
+@node Smileys
+@subsection Smileys
+@cindex smileys
+
+@iftex
+@iflatex
+\gnusfig{-3cm}{0.5cm}{\epsfig{figure=ps/BigFace,height=20cm}}
+\input{smiley}
+@end iflatex
+@end iftex
+
+@dfn{Smiley} is a package separate from Gnus, but since Gnus is
+currently the only package that uses Smiley, it is documented here.
+
+In short---to use Smiley in Gnus, put the following in your
+@file{~/.gnus.el} file:
+
+@lisp
+(setq gnus-treat-display-smileys t)
+@end lisp
+
+Smiley maps text smiley faces---@samp{:-)}, @samp{8-)}, @samp{:-(} and
+the like---to pictures and displays those instead of the text smiley
+faces. The conversion is controlled by a list of regexps that matches
+text and maps that to file names.
+
+@vindex smiley-regexp-alist
+The alist used is specified by the @code{smiley-regexp-alist}
+variable. The first item in each element is the regexp to be matched;
+the second element is the regexp match group that is to be replaced by
+the picture; and the third element is the name of the file to be
+displayed.
+
+The following variables customize where Smiley will look for these
+files:
+
+@table @code
+
+@item smiley-data-directory
+@vindex smiley-data-directory
+Where Smiley will look for smiley faces files.
+
+@item gnus-smiley-file-types
+@vindex gnus-smiley-file-types
+List of suffixes on smiley file names to try.
+
+@end table
+
+
+@node Picons
+@subsection Picons
+
+@iftex
+@iflatex
+\include{picons}
+@end iflatex
+@end iftex
+
+So@dots{} You want to slow down your news reader even more! This is a
+good way to do so. It's also a great way to impress people staring
+over your shoulder as you read news.
+
+What are Picons? To quote directly from the Picons Web site:
+
+@iftex
+@iflatex
+\margindex{}
+@end iflatex
+@end iftex
+
+@quotation
+@dfn{Picons} is short for ``personal icons''. They're small,
+constrained images used to represent users and domains on the net,
+organized into databases so that the appropriate image for a given
+e-mail address can be found. Besides users and domains, there are picon
+databases for Usenet newsgroups and weather forecasts. The picons are
+in either monochrome @code{XBM} format or color @code{XPM} and
+@code{GIF} formats.
+@end quotation
+
+@vindex gnus-picon-databases
+For instructions on obtaining and installing the picons databases,
+point your Web browser at
+@uref{http://www.cs.indiana.edu/picons/ftp/index.html}.
+
+If you are using Debian GNU/Linux, saying @samp{apt-get install
+picons.*} will install the picons where Gnus can find them.
+
+To enable displaying picons, simply make sure that
+@code{gnus-picon-databases} points to the directory containing the
+Picons databases.
+
+@vindex gnus-picon-style
+The variable @code{gnus-picon-style} controls how picons are displayed.
+If @code{inline}, the textual representation is replaced. If
+@code{right}, picons are added right to the textual representation.
+
+The following variables offer control over where things are located.
+
+@table @code
+
+@item gnus-picon-databases
+@vindex gnus-picon-databases
+The location of the picons database. This is a list of directories
+containing the @file{news}, @file{domains}, @file{users} (and so on)
+subdirectories. Defaults to @code{("/usr/lib/picon"
+"/usr/local/faces")}.
+
+@item gnus-picon-news-directories
+@vindex gnus-picon-news-directories
+List of subdirectories to search in @code{gnus-picon-databases} for
+newsgroups faces. @code{("news")} is the default.
+
+@item gnus-picon-user-directories
+@vindex gnus-picon-user-directories
+List of subdirectories to search in @code{gnus-picon-databases} for user
+faces. @code{("users" "usenix" "local" "misc")} is the default.
+
+@item gnus-picon-domain-directories
+@vindex gnus-picon-domain-directories
+List of subdirectories to search in @code{gnus-picon-databases} for
+domain name faces. Defaults to @code{("domains")}. Some people may
+want to add @samp{"unknown"} to this list.
+
+@item gnus-picon-file-types
+@vindex gnus-picon-file-types
+Ordered list of suffixes on picon file names to try. Defaults to
+@code{("xpm" "gif" "xbm")} minus those not built-in your Emacs.
+
+@end table
+
+
+@node XVarious
+@subsection Various XEmacs Variables
+
+@table @code
+@item gnus-xmas-glyph-directory
+@vindex gnus-xmas-glyph-directory
+This is where Gnus will look for pictures. Gnus will normally
+auto-detect this directory, but you may set it manually if you have an
+unusual directory structure.
+
+@item gnus-xmas-modeline-glyph
+@vindex gnus-xmas-modeline-glyph
+A glyph displayed in all Gnus mode lines. It is a tiny gnu head by
+default.
+
+@end table
+
+@subsubsection Toolbar
+
+@table @code
+
+@item gnus-use-toolbar
+@vindex gnus-use-toolbar
+This variable specifies the position to display the toolbar. If
+@code{nil}, don't display toolbars. If it is non-nil, it should be one
+of the symbols @code{default}, @code{top}, @code{bottom}, @code{right},
+and @code{left}. @code{default} means to use the default toolbar, the
+rest mean to display the toolbar on the place which those names show.
+The default is @code{default}.
+
+@item gnus-toolbar-thickness
+@vindex gnus-toolbar-thickness
+Cons of the height and the width specifying the thickness of a toolbar.
+The height is used for the toolbar displayed on the top or the bottom,
+the width is used for the toolbar displayed on the right or the left.
+The default is that of the default toolbar.
+
+@item gnus-group-toolbar
+@vindex gnus-group-toolbar
+The toolbar in the group buffer.
+
+@item gnus-summary-toolbar
+@vindex gnus-summary-toolbar
+The toolbar in the summary buffer.
+
+@item gnus-summary-mail-toolbar
+@vindex gnus-summary-mail-toolbar
+The toolbar in the summary buffer of mail groups.
+
+@end table
+
+@iftex
+@iflatex
+\margindex{}
+@end iflatex
+@end iftex
+
+
+@node Fuzzy Matching
+@section Fuzzy Matching
+@cindex fuzzy matching
+
+Gnus provides @dfn{fuzzy matching} of @code{Subject} lines when doing
+things like scoring, thread gathering and thread comparison.
+
+As opposed to regular expression matching, fuzzy matching is very fuzzy.
+It's so fuzzy that there's not even a definition of what @dfn{fuzziness}
+means, and the implementation has changed over time.
+
+Basically, it tries to remove all noise from lines before comparing.
+@samp{Re: }, parenthetical remarks, white space, and so on, are filtered
+out of the strings before comparing the results. This often leads to
+adequate results---even when faced with strings generated by text
+manglers masquerading as newsreaders.
+
+
+@node Thwarting Email Spam
+@section Thwarting Email Spam
+@cindex email spam
+@cindex spam
+@cindex UCE
+@cindex unsolicited commercial email
+
+In these last days of the Usenet, commercial vultures are hanging about
+and grepping through news like crazy to find email addresses they can
+foist off their scams and products to. As a reaction to this, many
+people have started putting nonsense addresses into their @code{From}
+lines. I think this is counterproductive---it makes it difficult for
+people to send you legitimate mail in response to things you write, as
+well as making it difficult to see who wrote what. This rewriting may
+perhaps be a bigger menace than the unsolicited commercial email itself
+in the end.
+
+The biggest problem I have with email spam is that it comes in under
+false pretenses. I press @kbd{g} and Gnus merrily informs me that I
+have 10 new emails. I say ``Golly gee! Happy is me!'' and select the
+mail group, only to find two pyramid schemes, seven advertisements
+(``New! Miracle tonic for growing full, lustrous hair on your toes!'')
+and one mail asking me to repent and find some god.
+
+This is annoying. Here's what you can do about it.
+
+@menu
+* The problem of spam:: Some background, and some solutions
+* Anti-Spam Basics:: Simple steps to reduce the amount of spam.
+* SpamAssassin:: How to use external anti-spam tools.
+* Hashcash:: Reduce spam by burning CPU time.
+* Filtering Spam Using The Spam ELisp Package::
+* Filtering Spam Using Statistics with spam-stat::
+@end menu
+
+@node The problem of spam
+@subsection The problem of spam
+@cindex email spam
+@cindex spam filtering approaches
+@cindex filtering approaches, spam
+@cindex UCE
+@cindex unsolicited commercial email
+
+First, some background on spam.
+
+If you have access to e-mail, you are familiar with spam (technically
+termed @acronym{UCE}, Unsolicited Commercial E-mail). Simply put, it
+exists because e-mail delivery is very cheap compared to paper mail,
+so only a very small percentage of people need to respond to an UCE to
+make it worthwhile to the advertiser. Ironically, one of the most
+common spams is the one offering a database of e-mail addresses for
+further spamming. Senders of spam are usually called @emph{spammers},
+but terms like @emph{vermin}, @emph{scum}, @emph{sociopaths}, and
+@emph{morons} are in common use as well.
+
+Spam comes from a wide variety of sources. It is simply impossible to
+dispose of all spam without discarding useful messages. A good
+example is the TMDA system, which requires senders
+unknown to you to confirm themselves as legitimate senders before
+their e-mail can reach you. Without getting into the technical side
+of TMDA, a downside is clearly that e-mail from legitimate sources may
+be discarded if those sources can't or won't confirm themselves
+through the TMDA system. Another problem with TMDA is that it
+requires its users to have a basic understanding of e-mail delivery
+and processing.
+
+The simplest approach to filtering spam is filtering, at the mail
+server or when you sort through incoming mail. If you get 200 spam
+messages per day from @samp{random-address@@vmadmin.com}, you block
+@samp{vmadmin.com}. If you get 200 messages about @samp{VIAGRA}, you
+discard all messages with @samp{VIAGRA} in the message. If you get
+lots of spam from Bulgaria, for example, you try to filter all mail
+from Bulgarian IPs.
+
+This, unfortunately, is a great way to discard legitimate e-mail. The
+risks of blocking a whole country (Bulgaria, Norway, Nigeria, China,
+etc.) or even a continent (Asia, Africa, Europe, etc.) from contacting
+you should be obvious, so don't do it if you have the choice.
+
+In another instance, the very informative and useful RISKS digest has
+been blocked by overzealous mail filters because it @strong{contained}
+words that were common in spam messages. Nevertheless, in isolated
+cases, with great care, direct filtering of mail can be useful.
+
+Another approach to filtering e-mail is the distributed spam
+processing, for instance DCC implements such a system. In essence,
+@var{N} systems around the world agree that a machine @var{X} in
+Ghana, Estonia, or California is sending out spam e-mail, and these
+@var{N} systems enter @var{X} or the spam e-mail from @var{X} into a
+database. The criteria for spam detection vary---it may be the number
+of messages sent, the content of the messages, and so on. When a user
+of the distributed processing system wants to find out if a message is
+spam, he consults one of those @var{N} systems.
+
+Distributed spam processing works very well against spammers that send
+a large number of messages at once, but it requires the user to set up
+fairly complicated checks. There are commercial and free distributed
+spam processing systems. Distributed spam processing has its risks as
+well. For instance legitimate e-mail senders have been accused of
+sending spam, and their web sites and mailing lists have been shut
+down for some time because of the incident.
+
+The statistical approach to spam filtering is also popular. It is
+based on a statistical analysis of previous spam messages. Usually
+the analysis is a simple word frequency count, with perhaps pairs of
+words or 3-word combinations thrown into the mix. Statistical
+analysis of spam works very well in most of the cases, but it can
+classify legitimate e-mail as spam in some cases. It takes time to
+run the analysis, the full message must be analyzed, and the user has
+to store the database of spam analyses. Statistical analysis on the
+server is gaining popularity. This has the advantage of letting the
+user Just Read Mail, but has the disadvantage that it's harder to tell
+the server that it has misclassified mail.
+
+Fighting spam is not easy, no matter what anyone says. There is no
+magic switch that will distinguish Viagra ads from Mom's e-mails.
+Even people are having a hard time telling spam apart from non-spam,
+because spammers are actively looking to fool us into thinking they
+are Mom, essentially. Spamming is irritating, irresponsible, and
+idiotic behavior from a bunch of people who think the world owes them
+a favor. We hope the following sections will help you in fighting the
+spam plague.
+
+@node Anti-Spam Basics
+@subsection Anti-Spam Basics
+@cindex email spam
+@cindex spam
+@cindex UCE
+@cindex unsolicited commercial email
+
+One way of dealing with spam is having Gnus split out all spam into a
+@samp{spam} mail group (@pxref{Splitting Mail}).
+
+First, pick one (1) valid mail address that you can be reached at, and
+put it in your @code{From} header of all your news articles. (I've
+chosen @samp{larsi@@trym.ifi.uio.no}, but for many addresses on the form
+@samp{larsi+usenet@@ifi.uio.no} will be a better choice. Ask your
+sysadmin whether your sendmail installation accepts keywords in the local
+part of the mail address.)
+
+@lisp
+(setq message-default-news-headers
+ "From: Lars Magne Ingebrigtsen <larsi@@trym.ifi.uio.no>\n")
+@end lisp
+
+Then put the following split rule in @code{nnmail-split-fancy}
+(@pxref{Fancy Mail Splitting}):
+
+@lisp
+(...
+ (to "larsi@@trym.ifi.uio.no"
+ (| ("subject" "re:.*" "misc")
+ ("references" ".*@@.*" "misc")
+ "spam"))
+ ...)
+@end lisp
+
+This says that all mail to this address is suspect, but if it has a
+@code{Subject} that starts with a @samp{Re:} or has a @code{References}
+header, it's probably ok. All the rest goes to the @samp{spam} group.
+(This idea probably comes from Tim Pierce.)
+
+In addition, many mail spammers talk directly to your @acronym{SMTP} server
+and do not include your email address explicitly in the @code{To}
+header. Why they do this is unknown---perhaps it's to thwart this
+thwarting scheme? In any case, this is trivial to deal with---you just
+put anything not addressed to you in the @samp{spam} group by ending
+your fancy split rule in this way:
+
+@lisp
+(
+ ...
+ (to "larsi" "misc")
+ "spam")
+@end lisp
+
+In my experience, this will sort virtually everything into the right
+group. You still have to check the @samp{spam} group from time to time to
+check for legitimate mail, though. If you feel like being a good net
+citizen, you can even send off complaints to the proper authorities on
+each unsolicited commercial email---at your leisure.
+
+This works for me. It allows people an easy way to contact me (they can
+just press @kbd{r} in the usual way), and I'm not bothered at all with
+spam. It's a win-win situation. Forging @code{From} headers to point
+to non-existent domains is yucky, in my opinion.
+
+Be careful with this approach. Spammers are wise to it.
+
+
+@node SpamAssassin
+@subsection SpamAssassin, Vipul's Razor, DCC, etc
+@cindex SpamAssassin
+@cindex Vipul's Razor
+@cindex DCC
+
+The days where the hints in the previous section were sufficient in
+avoiding spam are coming to an end. There are many tools out there
+that claim to reduce the amount of spam you get. This section could
+easily become outdated fast, as new products replace old, but
+fortunately most of these tools seem to have similar interfaces. Even
+though this section will use SpamAssassin as an example, it should be
+easy to adapt it to most other tools.
+
+Note that this section does not involve the @code{spam.el} package,
+which is discussed in the next section. If you don't care for all
+the features of @code{spam.el}, you can make do with these simple
+recipes.
+
+If the tool you are using is not installed on the mail server, you
+need to invoke it yourself. Ideas on how to use the
+@code{:postscript} mail source parameter (@pxref{Mail Source
+Specifiers}) follow.
+
+@lisp
+(setq mail-sources
+ '((file :prescript "formail -bs spamassassin < /var/mail/%u")
+ (pop :user "jrl"
+ :server "pophost"
+ :postscript
+ "mv %t /tmp/foo; formail -bs spamc < /tmp/foo > %t")))
+@end lisp
+
+Once you manage to process your incoming spool somehow, thus making
+the mail contain e.g.@: a header indicating it is spam, you are ready to
+filter it out. Using normal split methods (@pxref{Splitting Mail}):
+
+@lisp
+(setq nnmail-split-methods '(("spam" "^X-Spam-Flag: YES")
+ ...))
+@end lisp
+
+Or using fancy split methods (@pxref{Fancy Mail Splitting}):
+
+@lisp
+(setq nnmail-split-methods 'nnmail-split-fancy
+ nnmail-split-fancy '(| ("X-Spam-Flag" "YES" "spam")
+ ...))
+@end lisp
+
+Some people might not like the idea of piping the mail through various
+programs using a @code{:prescript} (if some program is buggy, you
+might lose all mail). If you are one of them, another solution is to
+call the external tools during splitting. Example fancy split method:
+
+@lisp
+(setq nnmail-split-fancy '(| (: kevin-spamassassin)
+ ...))
+(defun kevin-spamassassin ()
+ (save-excursion
+ (save-restriction
+ (widen)
+ (if (eq 1 (call-process-region (point-min) (point-max)
+ "spamc" nil nil nil "-c"))
+ "spam"))))
+@end lisp
+
+Note that with the nnimap back end, message bodies will not be
+downloaded by default. You need to set
+@code{nnimap-split-download-body} to @code{t} to do that
+(@pxref{Splitting in IMAP}).
+
+That is about it. As some spam is likely to get through anyway, you
+might want to have a nifty function to call when you happen to read
+spam. And here is the nifty function:
+
+@lisp
+ (defun my-gnus-raze-spam ()
+ "Submit SPAM to Vipul's Razor, then mark it as expirable."
+ (interactive)
+ (gnus-summary-show-raw-article)
+ (gnus-summary-save-in-pipe "razor-report -f -d")
+ (gnus-summary-mark-as-expirable 1))
+@end lisp
+
+@node Hashcash
+@subsection Hashcash
+@cindex hashcash
+
+A novel technique to fight spam is to require senders to do something
+costly and demonstrably unique for each message they send. This has
+the obvious drawback that you cannot rely on everyone in the world
+using this technique, since it is not part of the Internet standards,
+but it may be useful in smaller communities.
+
+While the tools in the previous section work well in practice, they
+work only because the tools are constantly maintained and updated as
+new form of spam appears. This means that a small percentage of spam
+will always get through. It also means that somewhere, someone needs
+to read lots of spam to update these tools. Hashcash avoids that, but
+instead prefers that everyone you contact through e-mail supports the
+scheme. You can view the two approaches as pragmatic vs dogmatic.
+The approaches have their own advantages and disadvantages, but as
+often in the real world, a combination of them is stronger than either
+one of them separately.
+
+@cindex X-Hashcash
+The ``something costly'' is to burn CPU time, more specifically to
+compute a hash collision up to a certain number of bits. The
+resulting hashcash cookie is inserted in a @samp{X-Hashcash:} header.
+For more details, and for the external application @code{hashcash} you
+need to install to use this feature, see
+@uref{http://www.hashcash.org/}. Even more information can be found
+at @uref{http://www.camram.org/}.
+
+If you wish to generate hashcash for each message you send, you can
+customize @code{message-generate-hashcash} (@pxref{Mail Headers, ,Mail
+Headers,message, The Message Manual}), as in:
+
+@lisp
+(setq message-generate-hashcash t)
+@end lisp
+
+You will need to set up some additional variables as well:
+
+@table @code
+
+@item hashcash-default-payment
+@vindex hashcash-default-payment
+This variable indicates the default number of bits the hash collision
+should consist of. By default this is 20. Suggested useful values
+include 17 to 29.
+
+@item hashcash-payment-alist
+@vindex hashcash-payment-alist
+Some receivers may require you to spend burn more CPU time than the
+default. This variable contains a list of @samp{(@var{addr}
+@var{amount})} cells, where @var{addr} is the receiver (email address
+or newsgroup) and @var{amount} is the number of bits in the collision
+that is needed. It can also contain @samp{(@var{addr} @var{string}
+@var{amount})} cells, where the @var{string} is the string to use
+(normally the email address or newsgroup name is used).
+
+@item hashcash-path
+@vindex hashcash-path
+Where the @code{hashcash} binary is installed. This variable should
+be automatically set by @code{executable-find}, but if it's @code{nil}
+(usually because the @code{hashcash} binary is not in your path)
+you'll get a warning when you check hashcash payments and an error
+when you generate hashcash payments.
+
+@end table
+
+Gnus can verify hashcash cookies, although this can also be done by
+hand customized mail filtering scripts. To verify a hashcash cookie
+in a message, use the @code{mail-check-payment} function in the
+@code{hashcash.el} library. You can also use the @code{spam.el}
+package with the @code{spam-use-hashcash} back end to validate hashcash
+cookies in incoming mail and filter mail accordingly (@pxref{Anti-spam
+Hashcash Payments}).
+
+@node Filtering Spam Using The Spam ELisp Package
+@subsection Filtering Spam Using The Spam ELisp Package
+@cindex spam filtering
+@cindex spam
+
+The idea behind @code{spam.el} is to have a control center for spam detection
+and filtering in Gnus. To that end, @code{spam.el} does two things: it
+filters new mail, and it analyzes mail known to be spam or ham.
+@dfn{Ham} is the name used throughout @code{spam.el} to indicate
+non-spam messages.
+
+Make sure you read the section on the @code{spam.el} sequence of
+events. See @xref{Spam ELisp Package Sequence of Events}.
+
+@cindex spam-initialize
+To use @code{spam.el}, you @strong{must} run the function
+@code{spam-initialize} to autoload @file{spam.el} and to install the
+@code{spam.el} hooks. There is one exception: if you use the
+@code{spam-use-stat} (@pxref{spam-stat spam filtering}) setting, you
+should turn it on before @code{spam-initialize}:
+
+@example
+(setq spam-use-stat t) ;; if needed
+(spam-initialize)
+@end example
+
+So, what happens when you load @file{spam.el}?
+
+First, some hooks will get installed by @code{spam-initialize}. There
+are some hooks for @code{spam-stat} so it can save its databases, and
+there are hooks so interesting things will happen when you enter and
+leave a group. More on the sequence of events later (@pxref{Spam
+ELisp Package Sequence of Events}).
+
+You get the following keyboard commands:
+
+@table @kbd
+
+@item M-d
+@itemx M s x
+@itemx S x
+@kindex M-d
+@kindex S x
+@kindex M s x
+@findex gnus-summary-mark-as-spam
+@code{gnus-summary-mark-as-spam}.
+
+Mark current article as spam, showing it with the @samp{$} mark.
+Whenever you see a spam article, make sure to mark its summary line
+with @kbd{M-d} before leaving the group. This is done automatically
+for unread articles in @emph{spam} groups.
+
+@item M s t
+@itemx S t
+@kindex M s t
+@kindex S t
+@findex spam-bogofilter-score
+@code{spam-bogofilter-score}.
+
+You must have Bogofilter installed for that command to work properly.
+
+@xref{Bogofilter}.
+
+@end table
+
+Also, when you load @file{spam.el}, you will be able to customize its
+variables. Try @code{customize-group} on the @samp{spam} variable
+group.
+
+@menu
+* Spam ELisp Package Sequence of Events::
+* Spam ELisp Package Filtering of Incoming Mail::
+* Spam ELisp Package Global Variables::
+* Spam ELisp Package Sorting and Score Display in Summary Buffer::
+* Spam ELisp Package Configuration Examples::
+* Blacklists and Whitelists::
+* BBDB Whitelists::
+* Gmane Spam Reporting::
+* Anti-spam Hashcash Payments::
+* Blackholes::
+* Regular Expressions Header Matching::
+* Bogofilter::
+* SpamAssassin back end::
+* ifile spam filtering::
+* spam-stat spam filtering::
+* SpamOracle::
+* Extending the Spam ELisp package::
+@end menu
+
+@node Spam ELisp Package Sequence of Events
+@subsubsection Spam ELisp Package Sequence of Events
+@cindex spam filtering
+@cindex spam filtering sequence of events
+@cindex spam
+You must read this section to understand how @code{spam.el} works.
+Do not skip, speed-read, or glance through this section.
+
+There are two @emph{contact points}, if you will, between
+@code{spam.el} and the rest of Gnus: checking new mail for spam, and
+leaving a group.
+
+Getting new mail in Gnus is done in one of two ways. You can either
+split your incoming mail or you can classify new articles as ham or
+spam when you enter the group.
+
+Splitting incoming mail is better suited to mail back ends such as
+@code{nnml} or @code{nnimap} where new mail appears in a single file
+called a @dfn{Spool File}. See @xref{Spam ELisp Package Filtering of
+Incoming Mail}.
+
+@vindex gnus-spam-autodetect
+@vindex gnus-spam-autodetect-methods
+For back ends such as @code{nntp} there is no incoming mail spool, so
+an alternate mechanism must be used. This may also happen for
+back ends where the server is in charge of splitting incoming mail, and
+Gnus does not do further splitting. The @code{spam-autodetect} and
+@code{spam-autodetect-methods} group parameters (accessible with
+@kbd{G c} and @kbd{G p} as usual), and the corresponding variables
+@code{gnus-spam-autodetect} and @code{gnus-spam-autodetect-methods}
+(accessible with @kbd{M-x customize-variable} as usual) can help.
+
+When @code{spam-autodetect} is used (you can turn it on for a
+group/topic or wholesale by regular expression matches, as needed), it
+hooks into the process of entering a group. Thus, entering a group
+with unseen or unread articles becomes the substitute for checking
+incoming mail. Whether only unseen articles or all unread articles
+will be processed is determined by the
+@code{spam-autodetect-recheck-messages}. When set to @code{t}, unread
+messages will be rechecked. You should probably stick with the
+default of only checking unseen messages.
+
+@code{spam-autodetect} grants the user at once more and less control
+of spam filtering. The user will have more control over each group's
+spam methods, so for instance the @samp{ding} group may have
+@code{spam-use-BBDB} as the autodetection method, while the
+@samp{suspect} group may have the @code{spam-use-blacklist} and
+@code{spam-use-bogofilter} methods enabled. Every article detected to
+be spam will be marked with the spam mark @samp{$} and processed on
+exit from the group as normal spam. The user has less control over
+the @emph{sequence} of checks, as he might with @code{spam-split}.
+
+When the newly split mail goes into groups, or messages are
+autodetected to be ham or spam, those groups must be exited (after
+entering, if needed) for further spam processing to happen. It
+matters whether the group is considered a ham group, a spam group, or
+is unclassified, based on its @code{spam-content} parameter
+(@pxref{Spam ELisp Package Global Variables}). Spam groups have the
+additional characteristic that, when entered, any unseen or unread
+articles (depending on the @code{spam-mark-only-unseen-as-spam}
+variable) will be marked as spam. Thus, mail split into a spam group
+gets automatically marked as spam when you enter the group.
+
+Thus, when you exit a group, the @code{spam-processors} are applied,
+if any are set, and the processed mail is moved to the
+@code{ham-process-destination} or the @code{spam-process-destination}
+depending on the article's classification. If the
+@code{ham-process-destination} or the @code{spam-process-destination},
+whichever is appropriate, are @code{nil}, the article is left in the
+current group.
+
+If a spam is found in any group (this can be changed to only non-spam
+groups with @code{spam-move-spam-nonspam-groups-only}), it is
+processed by the active @code{spam-processors} (@pxref{Spam ELisp
+Package Global Variables}) when the group is exited. Furthermore, the
+spam is moved to the @code{spam-process-destination} (@pxref{Spam
+ELisp Package Global Variables}) for further training or deletion.
+You have to load the @code{gnus-registry.el} package and enable the
+@code{spam-log-to-registry} variable if you want spam to be processed
+no more than once. Thus, spam is detected and processed everywhere,
+which is what most people want. If the
+@code{spam-process-destination} is @code{nil}, the spam is marked as
+expired, which is usually the right thing to do.
+
+If spam can not be moved---because of a read-only back end such as
+@acronym{NNTP}, for example, it will be copied.
+
+If a ham mail is found in a ham group, as determined by the
+@code{ham-marks} parameter, it is processed as ham by the active ham
+@code{spam-processor} when the group is exited. With the variables
+@code{spam-process-ham-in-spam-groups} and
+@code{spam-process-ham-in-nonham-groups} the behavior can be further
+altered so ham found anywhere can be processed. You have to load the
+@code{gnus-registry.el} package and enable the
+@code{spam-log-to-registry} variable if you want ham to be processed
+no more than once. Thus, ham is detected and processed only when
+necessary, which is what most people want. More on this in
+@xref{Spam ELisp Package Configuration Examples}.
+
+If ham can not be moved---because of a read-only back end such as
+@acronym{NNTP}, for example, it will be copied.
+
+If all this seems confusing, don't worry. Soon it will be as natural
+as typing Lisp one-liners on a neural interface@dots{} err, sorry, that's
+50 years in the future yet. Just trust us, it's not so bad.
+
+@node Spam ELisp Package Filtering of Incoming Mail
+@subsubsection Spam ELisp Package Filtering of Incoming Mail
+@cindex spam filtering
+@cindex spam filtering incoming mail
+@cindex spam
+
+To use the @code{spam.el} facilities for incoming mail filtering, you
+must add the following to your fancy split list
+@code{nnmail-split-fancy} or @code{nnimap-split-fancy}:
+
+@example
+(: spam-split)
+@end example
+
+Note that the fancy split may be called @code{nnmail-split-fancy} or
+@code{nnimap-split-fancy}, depending on whether you use the nnmail or
+nnimap back ends to retrieve your mail.
+
+Also, @code{spam-split} will not modify incoming mail in any way.
+
+The @code{spam-split} function will process incoming mail and send the
+mail considered to be spam into the group name given by the variable
+@code{spam-split-group}. By default that group name is @samp{spam},
+but you can customize @code{spam-split-group}. Make sure the contents
+of @code{spam-split-group} are an @emph{unqualified} group name, for
+instance in an @code{nnimap} server @samp{your-server} the value
+@samp{spam} will turn out to be @samp{nnimap+your-server:spam}. The
+value @samp{nnimap+server:spam}, therefore, is wrong and will
+actually give you the group
+@samp{nnimap+your-server:nnimap+server:spam} which may or may not
+work depending on your server's tolerance for strange group names.
+
+You can also give @code{spam-split} a parameter,
+e.g. @code{spam-use-regex-headers} or @code{"maybe-spam"}. Why is
+this useful?
+
+Take these split rules (with @code{spam-use-regex-headers} and
+@code{spam-use-blackholes} set):
+
+@example
+ nnimap-split-fancy '(|
+ (any "ding" "ding")
+ (: spam-split)
+ ;; @r{default mailbox}
+ "mail")
+@end example
+
+Now, the problem is that you want all ding messages to make it to the
+ding folder. But that will let obvious spam (for example, spam
+detected by SpamAssassin, and @code{spam-use-regex-headers}) through,
+when it's sent to the ding list. On the other hand, some messages to
+the ding list are from a mail server in the blackhole list, so the
+invocation of @code{spam-split} can't be before the ding rule.
+
+You can let SpamAssassin headers supersede ding rules, but all other
+@code{spam-split} rules (including a second invocation of the
+regex-headers check) will be after the ding rule:
+
+@example
+nnimap-split-fancy
+ '(|
+ ;; @r{all spam detected by @code{spam-use-regex-headers} goes to @samp{regex-spam}}
+ (: spam-split "regex-spam" 'spam-use-regex-headers)
+ (any "ding" "ding")
+ ;; @r{all other spam detected by spam-split goes to @code{spam-split-group}}
+ (: spam-split)
+ ;; @r{default mailbox}
+ "mail")
+@end example
+
+This lets you invoke specific @code{spam-split} checks depending on
+your particular needs, and to target the results of those checks to a
+particular spam group. You don't have to throw all mail into all the
+spam tests. Another reason why this is nice is that messages to
+mailing lists you have rules for don't have to have resource-intensive
+blackhole checks performed on them. You could also specify different
+spam checks for your nnmail split vs. your nnimap split. Go crazy.
+
+You should still have specific checks such as
+@code{spam-use-regex-headers} set to @code{t}, even if you
+specifically invoke @code{spam-split} with the check. The reason is
+that when loading @file{spam.el}, some conditional loading is done
+depending on what @code{spam-use-xyz} variables you have set. This
+is usually not critical, though.
+
+@emph{Note for IMAP users}
+
+The boolean variable @code{nnimap-split-download-body} needs to be
+set, if you want to split based on the whole message instead of just
+the headers. By default, the nnimap back end will only retrieve the
+message headers. If you use a @emph{statistical} filter,
+e.g. @code{spam-check-bogofilter}, @code{spam-check-ifile}, or
+@code{spam-check-stat} (the splitters that can benefit from the full
+message body), this variable will be set automatically. It is not set
+for non-statistical back ends by default because it will slow
+@acronym{IMAP} down.
+
+@xref{Splitting in IMAP}.
+
+@node Spam ELisp Package Global Variables
+@subsubsection Spam ELisp Package Global Variables
+@cindex spam filtering
+@cindex spam filtering variables
+@cindex spam variables
+@cindex spam
+
+@vindex gnus-spam-process-newsgroups
+The concepts of ham processors and spam processors are very important.
+Ham processors and spam processors for a group can be set with the
+@code{spam-process} group parameter, or the
+@code{gnus-spam-process-newsgroups} variable. Ham processors take
+mail known to be non-spam (@emph{ham}) and process it in some way so
+that later similar mail will also be considered non-spam. Spam
+processors take mail known to be spam and process it so similar spam
+will be detected later.
+
+The format of the spam or ham processor entry used to be a symbol,
+but now it is a @sc{cons} cell. See the individual spam processor entries
+for more information.
+
+@vindex gnus-spam-newsgroup-contents
+Gnus learns from the spam you get. You have to collect your spam in
+one or more spam groups, and set or customize the variable
+@code{spam-junk-mailgroups} as appropriate. You can also declare
+groups to contain spam by setting their group parameter
+@code{spam-contents} to @code{gnus-group-spam-classification-spam}, or
+by customizing the corresponding variable
+@code{gnus-spam-newsgroup-contents}. The @code{spam-contents} group
+parameter and the @code{gnus-spam-newsgroup-contents} variable can
+also be used to declare groups as @emph{ham} groups if you set their
+classification to @code{gnus-group-spam-classification-ham}. If
+groups are not classified by means of @code{spam-junk-mailgroups},
+@code{spam-contents}, or @code{gnus-spam-newsgroup-contents}, they are
+considered @emph{unclassified}. All groups are unclassified by
+default.
+
+@vindex gnus-spam-mark
+@cindex $
+In spam groups, all messages are considered to be spam by default:
+they get the @samp{$} mark (@code{gnus-spam-mark}) when you enter the
+group. If you have seen a message, had it marked as spam, then
+unmarked it, it won't be marked as spam when you enter the group
+thereafter. You can disable that behavior, so all unread messages
+will get the @samp{$} mark, if you set the
+@code{spam-mark-only-unseen-as-spam} parameter to @code{nil}. You
+should remove the @samp{$} mark when you are in the group summary
+buffer for every message that is not spam after all. To remove the
+@samp{$} mark, you can use @kbd{M-u} to ``unread'' the article, or
+@kbd{d} for declaring it read the non-spam way. When you leave a
+group, all spam-marked (@samp{$}) articles are sent to a spam
+processor which will study them as spam samples.
+
+Messages may also be deleted in various other ways, and unless
+@code{ham-marks} group parameter gets overridden below, marks @samp{R}
+and @samp{r} for default read or explicit delete, marks @samp{X} and
+@samp{K} for automatic or explicit kills, as well as mark @samp{Y} for
+low scores, are all considered to be associated with articles which
+are not spam. This assumption might be false, in particular if you
+use kill files or score files as means for detecting genuine spam, you
+should then adjust the @code{ham-marks} group parameter.
+
+@defvar ham-marks
+You can customize this group or topic parameter to be the list of
+marks you want to consider ham. By default, the list contains the
+deleted, read, killed, kill-filed, and low-score marks (the idea is
+that these articles have been read, but are not spam). It can be
+useful to also include the tick mark in the ham marks. It is not
+recommended to make the unread mark a ham mark, because it normally
+indicates a lack of classification. But you can do it, and we'll be
+happy for you.
+@end defvar
+
+@defvar spam-marks
+You can customize this group or topic parameter to be the list of
+marks you want to consider spam. By default, the list contains only
+the spam mark. It is not recommended to change that, but you can if
+you really want to.
+@end defvar
+
+When you leave @emph{any} group, regardless of its
+@code{spam-contents} classification, all spam-marked articles are sent
+to a spam processor, which will study these as spam samples. If you
+explicit kill a lot, you might sometimes end up with articles marked
+@samp{K} which you never saw, and which might accidentally contain
+spam. Best is to make sure that real spam is marked with @samp{$},
+and nothing else.
+
+@vindex gnus-ham-process-destinations
+When you leave a @emph{spam} group, all spam-marked articles are
+marked as expired after processing with the spam processor. This is
+not done for @emph{unclassified} or @emph{ham} groups. Also, any
+@strong{ham} articles in a spam group will be moved to a location
+determined by either the @code{ham-process-destination} group
+parameter or a match in the @code{gnus-ham-process-destinations}
+variable, which is a list of regular expressions matched with group
+names (it's easiest to customize this variable with @kbd{M-x
+customize-variable @key{RET} gnus-ham-process-destinations}). Each
+group name list is a standard Lisp list, if you prefer to customize
+the variable manually. If the @code{ham-process-destination}
+parameter is not set, ham articles are left in place. If the
+@code{spam-mark-ham-unread-before-move-from-spam-group} parameter is
+set, the ham articles are marked as unread before being moved.
+
+If ham can not be moved---because of a read-only back end such as
+@acronym{NNTP}, for example, it will be copied.
+
+Note that you can use multiples destinations per group or regular
+expression! This enables you to send your ham to a regular mail
+group and to a @emph{ham training} group.
+
+When you leave a @emph{ham} group, all ham-marked articles are sent to
+a ham processor, which will study these as non-spam samples.
+
+@vindex spam-process-ham-in-spam-groups
+By default the variable @code{spam-process-ham-in-spam-groups} is
+@code{nil}. Set it to @code{t} if you want ham found in spam groups
+to be processed. Normally this is not done, you are expected instead
+to send your ham to a ham group and process it there.
+
+@vindex spam-process-ham-in-nonham-groups
+By default the variable @code{spam-process-ham-in-nonham-groups} is
+@code{nil}. Set it to @code{t} if you want ham found in non-ham (spam
+or unclassified) groups to be processed. Normally this is not done,
+you are expected instead to send your ham to a ham group and process
+it there.
+
+@vindex gnus-spam-process-destinations
+When you leave a @emph{ham} or @emph{unclassified} group, all
+@strong{spam} articles are moved to a location determined by either
+the @code{spam-process-destination} group parameter or a match in the
+@code{gnus-spam-process-destinations} variable, which is a list of
+regular expressions matched with group names (it's easiest to
+customize this variable with @kbd{M-x customize-variable @key{RET}
+gnus-spam-process-destinations}). Each group name list is a standard
+Lisp list, if you prefer to customize the variable manually. If the
+@code{spam-process-destination} parameter is not set, the spam
+articles are only expired. The group name is fully qualified, meaning
+that if you see @samp{nntp:servername} before the group name in the
+group buffer then you need it here as well.
+
+If spam can not be moved---because of a read-only back end such as
+@acronym{NNTP}, for example, it will be copied.
+
+Note that you can use multiples destinations per group or regular
+expression! This enables you to send your spam to multiple @emph{spam
+training} groups.
+
+@vindex spam-log-to-registry
+The problem with processing ham and spam is that Gnus doesn't track
+this processing by default. Enable the @code{spam-log-to-registry}
+variable so @code{spam.el} will use @code{gnus-registry.el} to track
+what articles have been processed, and avoid processing articles
+multiple times. Keep in mind that if you limit the number of registry
+entries, this won't work as well as it does without a limit.
+
+@vindex spam-mark-only-unseen-as-spam
+Set this variable if you want only unseen articles in spam groups to
+be marked as spam. By default, it is set. If you set it to
+@code{nil}, unread articles will also be marked as spam.
+
+@vindex spam-mark-ham-unread-before-move-from-spam-group
+Set this variable if you want ham to be unmarked before it is moved
+out of the spam group. This is very useful when you use something
+like the tick mark @samp{!} to mark ham---the article will be placed
+in your @code{ham-process-destination}, unmarked as if it came fresh
+from the mail server.
+
+@vindex spam-autodetect-recheck-messages
+When autodetecting spam, this variable tells @code{spam.el} whether
+only unseen articles or all unread articles should be checked for
+spam. It is recommended that you leave it off.
+
+@node Spam ELisp Package Sorting and Score Display in Summary Buffer
+@subsubsection Spam ELisp Package Sorting and Score Display in Summary Buffer
+@cindex spam scoring
+@cindex spam sorting
+@cindex spam score summary buffer
+@cindex spam sort summary buffer
+@cindex spam
+
+You can display the spam score of articles in your summary buffer, and
+you can sort articles by their spam score.
+
+First you need to decide which back end you will be using. If you use
+the @code{spam-use-spamassassin},
+@code{spam-use-spamassassin-headers}, or @code{spam-use-regex-headers}
+back end, the @code{X-Spam-Status} header will be used. If you use
+@code{spam-use-bogofilter}, the @code{X-Bogosity} header will be used.
+If you use @code{spam-use-crm114}, any header that matches the CRM114
+score format will be used. As long as you set the appropriate back end
+variable to t @emph{before} you load @file{spam.el}, you will be
+fine. @code{spam.el} will automatically add the right header to the
+internal Gnus list of required headers.
+
+To show the spam score in your summary buffer, add this line to your
+@code{gnus.el} file (note @code{spam.el} does not do that by default
+so it won't override any existing @code{S} formats you may have).
+
+@lisp
+(defalias 'gnus-user-format-function-S 'spam-user-format-function-S)
+@end lisp
+
+Now just set your summary line format to use @code{%uS}. Here's an
+example that formats the spam score in a 5-character field:
+
+@lisp
+(setq gnus-summary-line-format
+ "%U%R %10&user-date; $%5uS %6k %B %(%4L: %*%-25,25a%) %s \n")
+@end lisp
+
+Finally, to sort by spam status, either do it globally: