+@node Searching
+@section Searching
+
+@menu
+* nnir:: Searching on IMAP, with swish, namazu, etc.
+* nnmairix:: Searching maildir, MH or mbox with Mairix.
+@end menu
+
+@cindex Searching
+
+FIXME: This node is a stub.
+
+FIXME: Add a brief overview of Gnus search capabilities. A brief
+comparison of nnir, nnmairix, contrib/gnus-namazu would be nice
+as well.
+
+FIXME: Explain difference to @ref{Searching for Articles}, add reference
+and back-reference.
+
+@node nnir
+@subsection nnir
+
+FIXME: As a first step, convert the commentary of @file{nnir} to texi.
+@cindex nnir
+
+@node nnmairix
+@subsection nnmairix
+
+@cindex mairix
+@cindex nnmairix
+This paragraph describes how to set up mairix and the back end
+@code{nnmairix} for indexing and searching your mail from within
+Gnus. Additionally, you can create permanent ``smart'' groups which are
+bound to mairix searches and are automatically updated.
+
+@menu
+* About mairix:: About the mairix mail search engine
+* nnmairix requirements:: What you will need for using nnmairix
+* What nnmairix does:: What does nnmairix actually do?
+* Setting up mairix:: Set up your mairix installation
+* Configuring nnmairix:: Set up the nnmairix back end
+* nnmairix keyboard shortcuts:: List of available keyboard shortcuts
+* Propagating marks:: How to propagate marks from nnmairix groups
+* nnmairix tips and tricks:: Some tips, tricks and examples
+* nnmairix caveats:: Some more stuff you might want to know
+@end menu
+
+@c FIXME: The markup in this section might need improvement.
+@c E.g. adding @samp, @var, @file, @command, etc.
+@c Cf. (info "(texinfo)Indicating")
+
+@node About mairix
+@subsubsection About mairix
+
+Mairix is a tool for indexing and searching words in locally stored
+mail. It was written by Richard Curnow and is licensed under the
+GPL. Mairix comes with most popular GNU/Linux distributions, but it also
+runs under Windows (with cygwin), Mac OS X and Solaris. The homepage can
+be found at
+@uref{http://www.rpcurnow.force9.co.uk/mairix/index.html}
+
+Though mairix might not be as flexible as other search tools like
+swish++ or namazu, which you can use via the @code{nnir} back end, it
+has the prime advantage of being incredibly fast. On current systems, it
+can easily search through headers and message bodies of thousands and
+thousands of mails in well under a second. Building the database
+necessary for searching might take a minute or two, but only has to be
+done once fully. Afterwards, the updates are done incrementally and
+therefore are really fast, too. Additionally, mairix is very easy to set
+up.
+
+For maximum speed though, mairix should be used with mails stored in
+@code{Maildir} or @code{MH} format (this includes the @code{nnml} back
+end), although it also works with mbox. Mairix presents the search
+results by populating a @emph{virtual} maildir/MH folder with symlinks
+which point to the ``real'' message files (if mbox is used, copies are
+made). Since mairix already presents search results in such a virtual
+mail folder, it is very well suited for using it as an external program
+for creating @emph{smart} mail folders, which represent certain mail
+searches.
+
+@node nnmairix requirements
+@subsubsection nnmairix requirements
+
+Mairix searches local mail---that means, mairix absolutely must have
+direct access to your mail folders. If your mail resides on another
+server (e.g. an @acronym{IMAP} server) and you happen to have shell
+access, @code{nnmairix} supports running mairix remotely, e.g. via ssh.
+
+Additionally, @code{nnmairix} only supports the following Gnus back
+ends: @code{nnml}, @code{nnmaildir}, and @code{nnimap}. You must use
+one of these back ends for using @code{nnmairix}. Other back ends, like
+@code{nnmbox}, @code{nnfolder} or @code{nnmh}, won't work.
+
+If you absolutely must use mbox and still want to use @code{nnmairix},
+you can set up a local @acronym{IMAP} server, which you then access via
+@code{nnimap}. This is a rather massive setup for accessing some mbox
+files, so just change to MH or Maildir already... However, if you're
+really, really passionate about using mbox, you might want to look into
+the package @file{mairix.el}, which comes with Emacs 23.
+
+@node What nnmairix does
+@subsubsection What nnmairix does
+
+The back end @code{nnmairix} enables you to call mairix from within Gnus,
+either to query mairix with a search term or to update the
+database. While visiting a message in the summary buffer, you can use
+several pre-defined shortcuts for calling mairix, e.g. to quickly
+search for all mails from the sender of the current message or to
+display the whole thread associated with the message, even if the
+mails are in different folders.
+
+Additionally, you can create permanent @code{nnmairix} groups which are bound
+to certain mairix searches. This way, you can easily create a group
+containing mails from a certain sender, with a certain subject line or
+even for one specific thread based on the Message-ID. If you check for
+new mail in these folders (e.g. by pressing @kbd{g} or @kbd{M-g}), they
+automatically update themselves by calling mairix.
+
+You might ask why you need @code{nnmairix} at all, since mairix already
+creates the group, populates it with links to the mails so that you can
+then access it with Gnus, right? Well, this @emph{might} work, but often
+does not---at least not without problems. Most probably you will get
+strange article counts, and sometimes you might see mails which Gnus
+claims have already been canceled and are inaccessible. This is due to
+the fact that Gnus isn't really amused when things are happening behind
+its back. Another problem can be the mail back end itself, e.g. if you
+use mairix with an @acronym{IMAP} server (I had Dovecot complaining
+about corrupt index files when mairix changed the contents of the search
+group). Using @code{nnmairix} should circumvent these problems.
+
+@code{nnmairix} is not really a mail back end---it's actually more like
+a wrapper, sitting between a ``real'' mail back end where mairix stores
+the searches and the Gnus front end. You can choose between three
+different mail back ends for the mairix folders: @code{nnml},
+@code{nnmaildir} or @code{nnimap}. @code{nnmairix} will call the mairix
+binary so that the search results are stored in folders named
+@code{zz_mairix-<NAME>-<NUMBER>} on this mail back end, but it will
+present these folders in the Gnus front end only with @code{<NAME>}.
+You can use an existing mail back end where you already store your mail,
+but if you're uncomfortable with @code{nnmairix} creating new mail
+groups alongside your other mail, you can also create e.g. a new
+@code{nnmaildir} or @code{nnml} server exclusively for mairix, but then
+make sure those servers do not accidentally receive your new mail
+(@pxref{nnmairix caveats}). A special case exists if you want to use
+mairix remotely on an IMAP server with @code{nnimap}---here the mairix
+folders and your other mail must be on the same @code{nnimap} back end.
+
+@node Setting up mairix
+@subsubsection Setting up mairix
+
+First: create a backup of your mail folders (@pxref{nnmairix caveats}).
+
+Setting up mairix is easy: simply create a @file{.mairixrc} file with
+(at least) the following entries:
+
+@example
+# Your Maildir/MH base folder
+base=~/Maildir
+@end example
+
+This is the base folder for your mails. All the following directories
+are relative to this base folder. If you want to use @code{nnmairix}
+with @code{nnimap}, this base directory has to point to the mail
+directory where the @acronym{IMAP} server stores the mail folders!
+
+@example
+maildir= ... your maildir folders which should be indexed ...
+mh= ... your nnml/mh folders which should be indexed ...
+mbox = ... your mbox files which should be indexed ...
+@end example
+
+This specifies all your mail folders and mbox files (relative to the
+base directory!) you want to index with mairix. Note that the
+@code{nnml} back end saves mails in MH format, so you have to put those
+directories in the @code{mh} line. See the example at the end of this
+section and mairixrc's man-page for further details.
+
+@example
+omit=zz_mairix-*
+@end example
+
+@vindex nnmairix-group-prefix
+This should make sure that you don't accidentally index the mairix
+search results. You can change the prefix of these folders with the
+variable @code{nnmairix-group-prefix}.
+
+@example
+mformat= ... 'maildir' or 'mh' ...
+database= ... location of database file ...
+@end example
+
+The @code{format} setting specifies the output format for the mairix
+search folder. Set this to @code{mh} if you want to access search results
+with @code{nnml}. Otherwise choose @code{maildir}.
+
+To summarize, here is my shortened @file{.mairixrc} file as an example:
+
+@example
+base=~/Maildir
+maildir=.personal:.work:.logcheck:.sent
+mh=../Mail/nnml/*...
+mbox=../mboxmail/mailarchive_year*
+mformat=maildir
+omit=zz_mairix-*
+database=~/.mairixdatabase
+@end example
+
+In this case, the base directory is @file{~/Maildir}, where all my Maildir
+folders are stored. As you can see, the folders are separated by
+colons. If you wonder why every folder begins with a dot: this is
+because I use Dovecot as @acronym{IMAP} server, which again uses
+@code{Maildir++} folders. For testing nnmairix, I also have some
+@code{nnml} mail, which is saved in @file{~/Mail/nnml}. Since this has
+to be specified relative to the @code{base} directory, the @code{../Mail}
+notation is needed. Note that the line ends in @code{*...}, which means
+to recursively scan all files under this directory. Without the three
+dots, the wildcard @code{*} will not work recursively. I also have some
+old mbox files with archived mail lying around in @file{~/mboxmail}.
+The other lines should be obvious.
+
+See the man page for @code{mairixrc} for details and further options,
+especially regarding wildcard usage, which may be a little different
+than you are used to.
+
+Now simply call @code{mairix} to create the index for the first time.
+Note that this may take a few minutes, but every following index will do
+the updates incrementally and hence is very fast.
+
+@node Configuring nnmairix
+@subsubsection Configuring nnmairix
+
+In group mode, type @kbd{G b c}
+(@code{nnmairix-create-server-and-default-group}). This will ask you for all
+necessary information and create a @code{nnmairix} server as a foreign
+server. You will have to specify the following:
+
+@itemize @bullet
+
+@item
+The @strong{name} of the @code{nnmairix} server---choose whatever you
+want.
+
+@item
+The name of the @strong{back end server} where mairix should store its
+searches. This must be a full server name, like @code{nnml:mymail}.
+Just hit @kbd{TAB} to see the available servers. Currently, servers
+which are accessed through @code{nnmaildir}, @code{nnimap} and
+@code{nnml} are supported. As explained above, for locally stored
+mails, this can be an existing server where you store your mails.
+However, you can also create e.g. a new @code{nnmaildir} or @code{nnml}
+server exclusively for @code{nnmairix} in your secondary select methods
+(@pxref{Finding the News}). If you use a secondary @code{nnml} server
+just for mairix, make sure that you explicitly set the server variable
+@code{nnml-get-new-mail} to @code{nil}, or you might loose mail
+(@pxref{nnmairix caveats}). If you want to use mairix remotely on an
+@acronym{IMAP} server, you have to choose the corresponding
+@code{nnimap} server here.
+
+@item
+@vindex nnmairix-mairix-search-options
+The @strong{command} to call the mairix binary. This will usually just
+be @code{mairix}, but you can also choose something like @code{ssh
+SERVER mairix} if you want to call mairix remotely, e.g. on your
+@acronym{IMAP} server. If you want to add some default options to
+mairix, you could do this here, but better use the variable
+@code{nnmairix-mairix-search-options} instead.
+
+@item
+The name of the @strong{default search group}. This will be the group
+where all temporary mairix searches are stored, i.e. all searches which
+are not bound to permanent @code{nnmairix} groups. Choose whatever you
+like.
+
+@item
+If the mail back end is @code{nnimap} or @code{nnmaildir}, you will be
+asked if you work with @strong{Maildir++}, i.e. with hidden maildir
+folders (=beginning with a dot). For example, you have to answer
+@samp{yes} here if you work with the Dovecot @acronym{IMAP}
+server. Otherwise, you should answer @samp{no} here.
+
+@end itemize
+
+@node nnmairix keyboard shortcuts
+@subsubsection nnmairix keyboard shortcuts
+
+In group mode:
+
+@table @kbd
+
+@item G b c
+@kindex G b c (Group)
+@findex nnmairix-create-server-and-default-group
+Creates @code{nnmairix} server and default search group for this server
+(@code{nnmairix-create-server-and-default-group}). You should have done
+this by now (@pxref{Configuring nnmairix}).
+
+@item G b s
+@kindex G b s (Group)
+@findex nnmairix-search
+Prompts for query which is then sent to the mairix binary. Search
+results are put into the default search group which is automatically
+displayed (@code{nnmairix-search}).
+
+@item G b m
+@kindex G b m (Group)
+@findex nnmairix-widget-search
+Allows you to create a mairix search or a permanent group more
+comfortably using graphical widgets, similar to a customization
+group. Just try it to see how it works (@code{nnmairix-widget-search}).
+
+@item G b i
+@kindex G b i (Group)
+@findex nnmairix-search-interactive
+Another command for creating a mairix query more comfortably, but uses
+only the minibuffer (@code{nnmairix-search-interactive}).
+
+@item G b g
+@kindex G b g (Group)
+@findex nnmairix-create-search-group
+Creates a permanent group which is associated with a search query
+(@code{nnmairix-create-search-group}). The @code{nnmairix} back end
+automatically calls mairix when you update this group with @kbd{g} or
+@kbd{M-g}.
+
+@item G b q
+@kindex G b q (Group)
+@findex nnmairix-group-change-query-this-group
+Changes the search query for the @code{nnmairix} group under cursor
+(@code{nnmairix-group-change-query-this-group}).
+
+@item G b t
+@kindex G b t (Group)
+@findex nnmairix-group-toggle-threads-this-group
+Toggles the 'threads' parameter for the @code{nnmairix} group under cursor,
+i.e. if you want see the whole threads of the found messages
+(@code{nnmairix-group-toggle-threads-this-group}).
+
+@item G b u
+@kindex G b u (Group)
+@findex nnmairix-update-database
+@vindex nnmairix-mairix-update-options
+Calls mairix binary for updating the database
+(@code{nnmairix-update-database}). The default parameters are @code{-F}
+and @code{-Q} for making this as fast as possible (see variable
+@code{nnmairix-mairix-update-options} for defining these default
+options).
+
+@item G b r
+@kindex G b r (Group)
+@findex nnmairix-group-toggle-readmarks-this-group
+Keep articles in this @code{nnmairix} group always read or unread, or leave the
+marks unchanged (@code{nnmairix-group-toggle-readmarks-this-group}).
+
+@item G b d
+@kindex G b d (Group)
+@findex nnmairix-group-delete-recreate-this-group
+Recreate @code{nnmairix} group on the ``real'' mail back end
+(@code{nnmairix-group-delete-recreate-this-group}). You can do this if
+you always get wrong article counts with a @code{nnmairix} group.
+
+@item G b a
+@kindex G b a (Group)
+@findex nnmairix-group-toggle-allowfast-this-group
+Toggles the @code{allow-fast} parameters for group under cursor
+(@code{nnmairix-group-toggle-allowfast-this-group}). The default
+behavior of @code{nnmairix} is to do a mairix search every time you
+update or enter the group. With the @code{allow-fast} parameter set,
+mairix will only be called when you explicitly update the group, but not
+upon entering. This makes entering the group faster, but it may also
+lead to dangling symlinks if something changed between updating and
+entering the group which is not yet in the mairix database.
+
+@item G b p
+@kindex G b p (Group)
+@findex nnmairix-group-toggle-propmarks-this-group
+Toggle marks propagation for this group
+(@code{nnmairix-group-toggle-propmarks-this-group}). (@pxref{Propagating
+marks}).
+
+@item G b o
+@kindex G b o (Group)
+@findex nnmairix-propagate-marks
+Manually propagate marks (@code{nnmairix-propagate-marks}); needed only when
+@code{nnmairix-propagate-marks-upon-close} is set to @code{nil}.
+
+@end table
+
+In summary mode:
+
+@table @kbd
+
+@item $ m
+@kindex $ m (Summary)
+@findex nnmairix-widget-search-from-this-article
+Allows you to create a mairix query or group based on the current
+message using graphical widgets (same as @code{nnmairix-widget-search})
+(@code{nnmairix-widget-search-from-this-article}).
+
+@item $ g
+@kindex $ g (Summary)
+@findex nnmairix-create-search-group-from-message
+Interactively creates a new search group with query based on the current
+message, but uses the minibuffer instead of graphical widgets
+(@code{nnmairix-create-search-group-from-message}).
+
+@item $ t
+@kindex $ t (Summary)
+@findex nnmairix-search-thread-this-article
+Searches thread for the current article
+(@code{nnmairix-search-thread-this-article}). This is effectively a
+shortcut for calling @code{nnmairix-search} with @samp{m:msgid} of the
+current article and enabled threads.
+
+@item $ f
+@kindex $ f (Summary)
+@findex nnmairix-search-from-this-article
+Searches all messages from sender of the current article
+(@code{nnmairix-search-from-this-article}). This is a shortcut for
+calling @code{nnmairix-search} with @samp{f:From}.
+
+@item $ o
+@kindex $ o (Summary)
+@findex nnmairix-goto-original-article
+(Only in @code{nnmairix} groups!) Tries determine the group this article
+originally came from and displays the article in this group, so that
+e.g. replying to this article the correct posting styles/group
+parameters are applied (@code{nnmairix-goto-original-article}). This
+function will use the registry if available, but can also parse the
+article file name as a fallback method.
+
+@item $ u
+@kindex $ u (Summary)
+@findex nnmairix-remove-tick-mark-original-article
+Remove possibly existing tick mark from original article
+(@code{nnmairix-remove-tick-mark-original-article}). (@pxref{nnmairix
+tips and tricks}).
+
+@end table
+
+@node Propagating marks
+@subsubsection Propagating marks
+
+First of: you really need a patched mairix binary for using the marks
+propagation feature efficiently. Otherwise, you would have to update
+the mairix database all the time. You can get the patch at
+
+@uref{http://www.randomsample.de/mairix-maildir-patch.tar}
+
+You need the mairix v0.21 source code for this patch; everything else
+is explained in the accompanied readme file. If you don't want to use
+marks propagation, you don't have to apply these patches, but they also
+fix some annoyances regarding changing maildir flags, so it might still
+be useful to you.
+
+With the patched mairix binary, you can use @code{nnmairix} as an
+alternative to mail splitting (@pxref{Fancy Mail Splitting}). For
+example, instead of splitting all mails from @samp{david@@foobar.com}
+into a group, you can simply create a search group with the query
+@samp{f:david@@foobar.com}. This is actually what ``smart folders'' are
+all about: simply put everything in one mail folder and dynamically
+create searches instead of splitting. This is more flexible, since you
+can dynamically change your folders any time you want to. This also
+implies that you will usually read your mails in the @code{nnmairix}
+groups instead of your ``real'' mail groups.
+
+There is one problem, though: say you got a new mail from
+@samp{david@@foobar.com}; it will now show up in two groups, the
+``real'' group (your INBOX, for example) and in the @code{nnmairix}
+search group (provided you have updated the mairix database). Now you
+enter the @code{nnmairix} group and read the mail. The mail will be
+marked as read, but only in the @code{nnmairix} group---in the ``real''
+mail group it will be still shown as unread.
+
+You could now catch up the mail group (@pxref{Group Data}), but this is
+tedious and error prone, since you may overlook mails you don't have
+created @code{nnmairix} groups for. Of course, you could first use
+@code{nnmairix-goto-original-article} (@pxref{nnmairix keyboard
+shortcuts}) and then read the mail in the original group, but that's
+even more cumbersome.
+
+Clearly, the easiest way would be if marks could somehow be
+automatically set for the original article. This is exactly what
+@emph{marks propagation} is about.
+
+Marks propagation is deactivated by default. You can activate it for a
+certain @code{nnmairix} group with
+@code{nnmairix-group-toggle-propmarks-this-group} (bound to @kbd{G b
+p}). This function will warn you if you try to use it with your default
+search group; the reason is that the default search group is used for
+temporary searches, and it's easy to accidentally propagate marks from
+this group. However, you can ignore this warning if you really want to.
+
+With marks propagation enabled, all the marks you set in a @code{nnmairix}
+group should now be propagated to the original article. For example,
+you can now tick an article (by default with @kbd{!}) and this mark should
+magically be set for the original article, too.
+
+A few more remarks which you may or may not want to know:
+
+@vindex nnmairix-propagate-marks-upon-close
+Marks will not be set immediately, but only upon closing a group. This
+not only makes marks propagation faster, it also avoids problems with
+dangling symlinks when dealing with maildir files (since changing flags
+will change the file name). You can also control when to propagate marks
+via @code{nnmairix-propagate-marks-upon-close} (see the doc-string for
+details).
+
+Obviously, @code{nnmairix} will have to look up the original group for every
+article you want to set marks for. If available, @code{nnmairix} will first use
+the registry for determining the original group. The registry is very
+fast, hence you should really, really enable the registry when using
+marks propagation. If you don't have to worry about RAM and disc space,
+set @code{gnus-registry-max-entries} to a large enough value; to be on
+the safe side, choose roughly the amount of mails you index with mairix.
+
+@vindex nnmairix-only-use-registry
+If you don't want to use the registry or the registry hasn't seen the
+original article yet, @code{nnmairix} will use an additional mairix
+search for determining the file name of the article. This, of course, is
+way slower than the registry---if you set hundreds or even thousands of
+marks this way, it might take some time. You can avoid this situation by
+setting @code{nnmairix-only-use-registry} to t.
+
+Maybe you also want to propagate marks the other way round, i.e. if you
+tick an article in a "real" mail group, you'd like to have the same
+article in a @code{nnmairix} group ticked, too. For several good
+reasons, this can only be done efficiently if you use maildir. To
+immediately contradict myself, let me mention that it WON'T work with
+@code{nnmaildir}, since @code{nnmaildir} stores the marks externally and
+not in the file name. Therefore, propagating marks to @code{nnmairix}
+groups will usually only work if you use an IMAP server which uses
+maildir as its file format.
+
+@vindex nnmairix-propagate-marks-to-nnmairix-groups
+If you work with this setup, just set
+@code{nnmairix-propagate-marks-to-nnmairix-groups} to @code{t} and see what
+happens. If you don't like what you see, just set it to @code{nil} again. One
+problem might be that you get a wrong number of unread articles; this
+usually happens when you delete or expire articles in the original
+groups. When this happens, you can recreate the @code{nnmairix} group on the
+back end using @kbd{G b d}.
+
+@node nnmairix tips and tricks
+@subsubsection nnmairix tips and tricks
+
+@itemize
+@item
+Checking Mail
+
+@findex nnmairix-update-groups
+I put all my important mail groups at group level 1. The mairix groups
+have group level 5, so they do not get checked at start up (@pxref{Group
+Levels}).
+
+I use the following to check for mails:
+
+@lisp
+(defun my-check-mail-mairix-update (level)
+ (interactive "P")
+ ;; if no prefix given, set level=1
+ (gnus-group-get-new-news (or level 1))
+ (nnmairix-update-groups "mairixsearch" t t)
+ (gnus-group-list-groups))
+
+(define-key gnus-group-mode-map "g" 'my-check-mail-mairix-update)
+@end lisp
+
+Instead of @samp{"mairixsearch"} use the name of your @code{nnmairix}
+server. See the doc string for @code{nnmairix-update-groups} for
+details.
+
+@item
+Example: search group for ticked articles
+
+For example, you can create a group for all ticked articles, where the
+articles always stay unread:
+
+Hit @kbd{G b g}, enter group name (e.g. @samp{important}), use
+@samp{F:f} as query and do not include threads.
+
+Now activate marks propagation for this group by using @kbd{G b p}. Then
+activate the always-unread feature by using @kbd{G b r} twice.
+
+So far so good---but how do you remove the tick marks in the @code{nnmairix}
+group? There are two options: You may simply use
+@code{nnmairix-remove-tick-mark-original-article} (bound to @kbd{$ u}) to remove
+tick marks from the original article. The other possibility is to set
+@code{nnmairix-propagate-marks-to-nnmairix-groups} to @code{t}, but see the above
+comments about this option. If it works for you, the tick marks should
+also exist in the @code{nnmairix} group and you can remove them as usual,
+e.g. by marking an article as read.
+
+When you have removed a tick mark from the original article, this
+article should vanish from the @code{nnmairix} group after you have updated the
+mairix database and updated the group. Fortunately, there is a function
+for doing exactly that: @code{nnmairix-update-groups}. See the previous code
+snippet and the doc string for details.
+
+@item
+Dealing with auto-subscription of mail groups
+
+As described before, all @code{nnmairix} groups are in fact stored on
+the mail back end in the form @samp{zz_mairix-<NAME>-<NUMBER>}. You can
+see them when you enter the back end server in the server buffer. You
+should not subscribe these groups! Unfortunately, these groups will
+usually get @emph{auto-subscribed} when you use @code{nnmaildir} or
+@code{nnml}, i.e. you will suddenly see groups of the form
+@samp{zz_mairix*} pop up in your group buffer. If this happens to you,
+simply kill these groups with C-k. For avoiding this, turn off
+auto-subscription completely by setting the variable
+@code{gnus-auto-subscribed-groups} to @code{nil} (@pxref{Filtering New
+Groups}), or if you like to keep this feature use the following kludge
+for turning it off for all groups beginning with @samp{zz_}:
+
+@lisp
+(setq gnus-auto-subscribed-groups
+ "^\\(nnml\\|nnfolder\\|nnmbox\\|nnmh\\|nnbabyl\\|nnmaildir\\).*:\\([^z]\\|z$\\|\\z[^z]\\|zz$\\|zz[^_]\\|zz_$\\).*")
+@end lisp
+
+@end itemize
+
+@node nnmairix caveats
+@subsubsection nnmairix caveats
+
+@itemize
+@item
+You can create a secondary @code{nnml} server just for nnmairix, but then
+you have to explicitly set the corresponding server variable
+@code{nnml-get-new-mail} to @code{nil}. Otherwise, new mail might get
+put into this secondary server (and would never show up again). Here's
+an example server definition:
+
+@lisp
+(nnml "mairix" (nnml-directory "mairix") (nnml-get-new-mail nil))
+@end lisp
+
+(The @code{nnmaildir} back end also has a server variabe
+@code{get-new-mail}, but its default value is @code{nil}, so you don't
+have to explicitly set it if you use a @code{nnmaildir} server just for
+mairix.)
+
+@item
+If you use the Gnus registry: don't use the registry with
+@code{nnmairix} groups (put them in
+@code{gnus-registry-unfollowed-groups}). Be @emph{extra careful} if
+you use @code{gnus-registry-split-fancy-with-parent}; mails which are
+split into @code{nnmairix} groups are usually gone for good as soon as
+you check the group for new mail (yes, it has happened to me...).
+
+@item
+Therefore: @emph{Never ever} put ``real'' mails into @code{nnmairix}
+groups (you shouldn't be able to, anyway).
+
+@item
+If you use the Gnus agent (@pxref{Gnus Unplugged}): don't agentize
+@code{nnmairix} groups (though I have no idea what happens if you do).
+
+@item
+mairix does only support us-ascii characters.
+
+@item
+@code{nnmairix} uses a rather brute force method to force Gnus to
+completely reread the group on the mail back end after mairix was
+called---it simply deletes and re-creates the group on the mail
+back end. So far, this has worked for me without any problems, and I
+don't see how @code{nnmairix} could delete other mail groups than its
+own, but anyway: you really should have a backup of your mail
+folders.
+
+@item
+All necessary information is stored in the group parameters
+(@pxref{Group Parameters}). This has the advantage that no active file
+is needed, but also implies that when you kill a @code{nnmairix} group,
+it is gone for good.
+
+@item
+@findex nnmairix-purge-old-groups
+If you create and kill a lot of @code{nnmairix} groups, the
+``zz_mairix-*'' groups will accumulate on the mail back end server. To
+delete old groups which are no longer needed, call
+@code{nnmairix-purge-old-groups}. Note that this assumes that you don't
+save any ``real'' mail in folders of the form
+@code{zz_mairix-<NAME>-<NUMBER>}. You can change the prefix of
+@code{nnmairix} groups by changing the variable
+@code{nnmairix-group-prefix}.
+
+@item
+The following only applies if you @emph{don't} use the mentioned patch
+for mairix (@pxref{Propagating marks}):
+
+A problem can occur when using @code{nnmairix} with maildir folders and
+comes with the fact that maildir stores mail flags like @samp{Seen} or
+@samp{Replied} by appending chars @samp{S} and @samp{R} to the message
+file name, respectively. This implies that currently you would have to
+update the mairix database not only when new mail arrives, but also when
+mail flags are changing. The same applies to new mails which are indexed
+while they are still in the @samp{new} folder but then get moved to
+@samp{cur} when Gnus has seen the mail. If you don't update the database
+after this has happened, a mairix query can lead to symlinks pointing to
+non-existing files. In Gnus, these messages will usually appear with
+``(none)'' entries in the header and can't be accessed. If this happens
+to you, using @kbd{G b u} and updating the group will usually fix this.
+
+@end itemize
+
projects / gnus / blobdiff