\input texinfo.tex @c -*-texinfo-*- @c %**start of header @setfilename mu4e.info @settitle mu4e user manual @documentencoding utf-8 @c %**end of header @include version.texi @titlepage @title @t{mu4e} - an e-mail client for emacs @author{Dirk-Jan C. Binnema} @end titlepage @dircategory Emacs @direntry * mu4e: (mu4e). An email client for emacs based on mu. @end direntry @copying Copyright @copyright{} 2012 Dirk-Jan C. Binnema @quotation Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License.'' @end quotation @end copying @node Top @top mu4e Manual Welcome to @t{mu4e}! @t{mu4e} (@emph{mu-for-emacs}) is an e-mail client for GNU Emacs (version 23 and later). It is built on top of the @t{mu} e-mail search engine. This manual describes how to set up and use @t{mu4e}. This manual has been updated for @t{mu}/@t{mu4e} version @emph{@value{mu4e-version}}. @menu * Introduction:: * Getting started:: * Running mu4e:: * Searching mail:: * Interaction with other tools:: * Example configuration:: * FAQ - Frequently Anticipated Questions:: * Known issues / missing features:: Appendices * How it works:: Some notes about the implementation of mu4e * Logging and debugging:: How to debug problems in @t{mu4e} * GNU Free Documentation License:: The license of this manual. @end menu @node Introduction @chapter Introduction In this chapter some prelimary thoughs about the how and why of @t{mu4e}. @menu * Why another e-mail client?:: * Other mail clients:: * What mu4e does and doesn't do:: @end menu @node Why another e-mail client? @section Why another e-mail client? Why would the world need another e-mail client? Well, I'm not sure the world really @emph{needs} another one, but maybe @emph{I} do! I spend a @emph{lot} of time, professionally and privately, dealing with e-mail -- having an efficient e-mail client is essential for me. Since none of the existing ones worked they I wanted, I created my own. Still, while having been created for such selfish motives, @t{mu4e} tries hard to be as useful as possible for all its users - suggestions are very welcome and are acted upon. @node Other mail clients @section Other mail clients Under the hood, @t{mu4e} is fully search-based, similar to programs such as @t{notmuch}@footnote{@url{http://notmuchmail.org}}, @t{md}@footnote{@url{https://github.com/nicferrier/md}} and @t{sup}@footnote{@url{http://sup.rubyforge.org/}}. The user-interface is quite different though. @t{mu4e}'s mail handling (deleting, moving etc.) is inspired by @emph{Wanderlust}@footnote{@url{http://www.gohome.org/wl/}} (another emacs-based e-mail client), @t{mutt}@footnote{@url{http://www.mutt.org/}} and @t{dired}, while it takes some cues from @emph{GMail}. @t{mu4e} tries to keep all the 'state' in your maildirs, so one can switch between clients, synchronize over @abbr{IMAP} or backup with @t{rsync} -- if you delete the database, you won't lose any information. @node What mu4e does and doesn't do @section What mu4e does and doesn't do @t{mu}, and, by extension, @t{mu4e}, do @emph{not} deal with getting your e-mail messages from a mail server; instead, this task is delegated to other tools, such as @t{offlineimap}@footnote{@url{http://offlineimap.org/}}, @t{isync}@footnote{@url{http://isync.sourceforge.net/}} or @t{fetchmail}@footnote{@url{http://www.fetchmail.info/}}. As long as the messages end up in a Maildir, @t{mu4e}/@t{mu} are happy to deal with them. @t{mu4e} also does @emph{not} implement sending messages; instead, it depends on the true-and-tested @emph{smtpmail}, which is part of @t{emacs}. In addition, @t{mu4e} piggybacks on Gnus' message editor; @inforef{Top,Gnus message editor,message}. Thus, many of the traditional things an e-mail client needs to do, are subcontracted to other tools. This leaves @t{mu4e} to concentrate on what it does best: quick message searching, reading mails, replying them, moving messages around and so on. @node Getting started @chapter Getting started In this chapter, we go through installing @t{mu4e} and see how to set it up. After we have succeeded in @ref{Getting mail}, and @ref{Indexing your messages}, we discuss @ref{Basic configuration}. After going through these steps, @t{mu4e} should be ready for use. @menu * Installation:: * Getting mail:: * Indexing your messages:: * Sending mail:: * Queuing mail:: * Basic configuration:: @end menu @node Installation @section Installation @t{mu4e} is part of @t{mu} - by installing the latter, the former will be installed as well. At the time of writing, there are no distribution packages for @t{mu4e} yet, so we are assuming installation from source packages. First, you need make sure you have the necessary dependencies. On a Debian or Ubuntu system, you can get these with: @example sudo apt-get install libgmime-2.4-dev libxapian-dev # emacs if you don't have it yet sudo apt-get install emacs23 # optional sudo apt-get install guile-2.0-dev html2text xdg-utils @end example Installation follows the normal sequence of: @example $ tar xvfz mu-.tar.gz # use the specific version $ cd mu- $./configure && make $ sudo make install @end example After this, @t{mu} and @t{mu4e} should be installed @footnote{there's a hard dependency between versions of @t{mu4e} and @t{mu} - you cannot combine different versions.}, and be available from the command line and emacs (respectively). You may need to restart @t{emacs} so it can pick up @t{mu4e}. @subsection mu4e and emacs customization There is @emph{experimental} support for using the @t{emacs} customization system in @t{mu4e}, but for now we recommend setting the values manually. Please refer to @ref{Example configuration} for a couple of examples of this. @node Getting mail @section Getting mail In order for @t{mu} (and, by extension, @t{mu4e}) to work, we need to have our e-mail messages stored in a Maildir. If you were already using Maildirs, you are lucky; otherwise, you will need to get your mail there in some way. If you are using some external @abbr{IMAP} or @abbr{POP} server, you can use tools like @t{getmail}, @t{offlineimap} or @t{isync} to download your message into a Maildir-directory (@file{~/Maildir}, usually). If you are using a local mail-server (such as @emph{Postfix} or @t{qmail}), you can teach them to deliver into a Maildir as well, maybe in combination with @t{procmail}. A bit of googling should be able to provide you with the details; also there is full example of setting @t{mu4e} up with @t{offlineimap} and Gmail; @pxref{Gmail configuration}. You can do all of the mail retrieval @emph{outside} of @t{emacs}/@t{mu4e}, but you can also do it from the @t{mu4e}. For that, set the variable @code{mu4e-get-mail-command} to the command you want to use for retrieving mail, which you can then access from the @ref{Main view}. You can also have this command run periodically (in the background), by setting the variable @code{mu4e-update-interval} to the number of seconds between such updates. If set to @code{nil}, it will not update at all. Note that if you make changes to @code{mu4e-update-interval}, @code{mu4e} must be restarted before the change will take effect. @node Indexing your messages @section Indexing your messages After you have succeeded in @ref{Getting mail}, we need to @emph{index} the messages. That is - we need to scan the Maildir and store the information about the mails into a special database. We can do that from @code{mu4e} -- @ref{Main view}, but this first time, it's better to run it from the command line, as it may be easier to recognize problems. Assuming that your Maildir is at @file{~/Maildir}, you should give the following command: @example $ mu index --maildir=~/Maildir @end example This should scan your @file{~/Maildir}@footnote{In most cases, you do not even have to provide the @t{--maildir=~/Maildir}; see the @t{mu-index} man-page for details} and fill the database, and give progress information while doing so. The first time you index your mail may take a few minutes (for thousands of e-mails), afterwards it is much faster since it only has to scan the differences. Note that indexing is discussed at length in the @t{mu-index} man page. After the indexing is finished, you can quickly test if everything worked, by trying some command line searches, for example @example $ mu find hello @end example which should list all messages that match @t{hello}. For some more examples of searches @xref{Queries}, or check the @t{mu-find} and @t{mu-easy} man pages. If all of this worked well, we are almost ready to start @t{mu4e}; we only need set up @ref{Sending mail}. @node Sending mail @section Sending mail @t{mu4e} re-uses Gnu's @t{message mode} @inforef{message}, for writing mail and inherits the setup for @emph{sending} mail from that. For sending mail using @abbr{SMTP}, @t{mu4e} uses Emacs' standard @t{smtpmail} package -- @inforef{smtpmail}. This package support many different ways to send mail, please refer to its documentation for the details. Here we only provide some simple examples - and @ref{Example configuration}. A very minimal setup could look something like: @lisp ;; tell message-mode how to send mail (setq message-send-mail-function 'smtpmail-send-it) ;; if our mail server lives at smtp.example.org; if you have a local ;; mail-server, simply use 'localhost' here. (setq smtpmail-smtp-server "smtp.example.org") @end lisp Note, since @t{mu4e} uses the same @t{message mode} and @t{smtpmail} that Gnus uses, any setting for those will also work for @t{mu4e}. By default, @t{mu4e} puts a copy of any messages you sent in the folder you set for @code{mu4e-sent-folder}. In some case, this may not be what you want - for example, when using GMail+@abbr{IMAP} (but @emph{not} with GMail+@abbr{POP3}), this interferes with GMail's handling of the sent messages folder, and you may end up with duplicate messages. For this, since @t{mu4e} 0.9.8.3, there is the variable @code{mu4e-sent-messages-behavior}, which takes a symbol. The default is @code{'sent} which, as mentioned, causes the message to be copied to your sent-messages folder. Other possible values are @code{'trash} (so the sent message is copied to the trash-folder (@code{mu4e-trash-folder}), and @code{'delete} to simply discard the message altogether. Thus, for GMail-IMAP you can add the following to your settings: @verbatim ;; don't save message to Sent Messages, GMail/IMAP will take care of this (setq mu4e-sent-messages-behavior 'trash) @end verbatim @node Queuing mail @section Queuing mail If you cannot send mail directly, for example because you are currently offline, you can @emph{queue} the mail, and send it when you have restored your internet connection. You can control this from the @t{mu4e} @xref{Main view}. To allow for queuing, you need to tell @t{smtpmail} where you want to do this. For example: @lisp (setq smtpmail-queue-mail nil ;; start in non-queuing mode smtpmail-queue-dir "~/Maildir/queue/cur") @end lisp For convenience, we locate the queue directory somewhere in our normal Maildir. If you want to use queued mail, you should create this directory before starting @t{mu4e}. The @command{mu mkdir} command can be handy here, so for example: @verbatim $ mu mkdir ~/Maildir/queue $ touch ~/Maildir/queue/.noindex @end verbatim The @command{touch} command tells @t{mu} to ignore this directory for indexing, which makes sense since it contains @t{smtpmail} meta-data rather than 'normal' messages. Also, see the @t{mu-mkdir} and @t{mu-index} man pages. @emph{Warning}: when you switch on queued-mode, your messages will not reach their destination until you switch it off again; so, be careful not to do so accidentally. @node Basic configuration @section Basic configuration The last thing to do before running @t{mu4e} is setting up some basic configuration. A good place to put this would be in your @file{~/.emacs} file. First some more extensive configuration, @xref{Example configuration}. First, we need to load @t{mu4e}: @example (require 'mu4e) @end example Then, we need to tell @t{mu4e} where it can find your Maildir, and some special folders. So, for example: @lisp (setq mu4e-maildir "~/Maildir" ;; top-level Maildir mu4e-sent-folder "/sent" ;; where do i keep sent mail? mu4e-drafts-folder "/drafts" ;; where do i keep half-written mail? mu4e-trash-folder "/trash") ;; where do i move deleted mail? @end lisp @code{mu4e-maildir} take an actual filesystem-path, the other folder names are all relative to @code{mu4e-maildir}. @node Running mu4e @chapter Running mu4e After the following the steps in @ref{Getting started}, we should now have a working @t{mu4e} setup. In this chapter, we'll give a tour of the @t{mu4e} program, and show its use. @t{mu4e} consists of a number of views; the diagram shows how they relate to each other, and the default key-bindings to get from one view to the next. In the next sections we will describe what these keys actually @emph{do}. @menu * Main view:: * Headers view:: * Message view:: * Editor view:: @end menu @example ---------------------------------------------------------------------------- [C] +--------+ [RFCE] --------> | editor | <-------- / +--------+ \ / [RFCE]^ \ / | \ +-------+ [sjbB]+---------+ [RET] +---------+ | main | <---> | headers | <----> | message | +-------+ [q] +---------+ [qbBjs]+---------+ [sjbB] ^ [.] | [q] V +-----+ | raw | +-----+ Default bindings ---------------- R: Reply s: search .: raw view (toggle) F: Forward j: jump-to-maildir q: quit C: Compose b: bookmark-search E: Edit B: bookmark-search (edit-first) ---------------------------------------------------------------------------- @end example @node Main view @section Main view After you have installed @t{mu4e} (@pxref{Getting started}), you can start it with @code{M-x mu4e}. This will do some checks to ensure everything is set up correctly, and then show the @t{mu4e} main view. This looks something like the following: @verbatim ---------------------------------------------------------------------------- * mu4e - mu for emacs version x.x Basics * [j]ump to some maildir * enter a [s]earch query * [C]ompose a new message Bookmarks * [bu] Unread messages * [bt] Today's messages * [bw] Last 7 days * [bp] Messages with images Misc * [U]pdate email & database * toggle [m]ail sending mode (direct) * [f]lush queued mail * [H]elp * [q]uit mu4e ---------------------------------------------------------------------------- @end verbatim In the below, we assume the default key bindings here. If you've changed those, well, mutatis mutandis. @subsection Basic actions First, the @emph{Basics}: @itemize @item @t{[j]ump to some maildir} means that after pressing @key{j}, @t{mu4e} will ask you for a maildir to jump to. These are the maildirs you set in @ref{Basic configuration}. @item @t{enter a [s]earch query} means that after pressing @key{s} you will be asked for a search query, and after entering one, the results will be shown. @xref{Searching mail}. @item @t{[C]ompose a new message} means that after pressing @key{C}, you will be thrown in a message-editing buffer, where you can compose a new message. @end itemize @subsection Bookmarks Next come the @emph{Bookmarks}.These are set with the variable @code{mu4e-bookmarks}; what you see in the above example are the @emph{default} bookmarks - you can add your own and/or replace the default ones. @xref{Bookmarks}. In short, you can view the list of messages matching a bookmark by pressing @key{b} followed by the shortcut for this bookmark. If you'd like to edit the bookmarked query first, use @key{B}. @subsection Miscellaneous Finally, there are some @emph{Misc} actions: @itemize @item @t{[U]pdate email & database} will execute whatever is in the variable @code{mu4e-get-mail-command}, and afterwards update the @t{mu} database; @pxref{Indexing your messages}. See @ref{Getting mail} for details. @item @t{toggle [m]ail sending mode (direct)} will toggle between sending mail directly, and queuing it first (for example, when you are offline), and @t{[f]lush queued mail} will flush any queued mail. This item is visible only if you have actually set up mail-queuing. @xref{Queuing mail}. @item @t{[H]elp} will show help information for this view. @item Finally, @t{[q]uit mu4e} will quit @t{mu4e}. @end itemize @node Headers view @section Headers view The headers view shows the results of search queries. There is a line for each matching message, each showing a number of fields describing the corresponding message. This looks something like the following: @verbatim ---------------------------------------------------------------------------------- Date Flgs From/To Subject 2011-12-16 18:38 uN To Edmund Dantès + Re: Extension security? 2011-12-16 21:44 uN Abbé Busoni + Re: Extension security? 2011-12-17 03:14 uN Pierre Morrel + Re: Extension security? 2011-12-17 04:04 uN Jacopo + Re: Extension security? 2011-12-17 14:36 uN Mercédès + Re: Extension security? 2011-12-18 06:05 uN Beachamp \ Re: Extension security? 2011-12-16 18:23 uN Albert de Moncerf + Re: [O] A presentation tool 2011-12-17 01:53 usaN Gaspard Caderousse \ Re: [O] A presentation tool 2011-12-16 16:31 uN Baron Danglars | [O] imaxima? End of search results ---------------------------------------------------------------------------------- @end verbatim @subsection Some notes Some notes to explain what you see in the example: @itemize @item The fields shown in the headers view can be influenced by customizing the variable @t{mu4e-headers-fields} @item You can change the date format by customizing @t{mu4e-headers-date-format} @item The letters in the 'Flags' field correspond to the following: D=draft, F=flagged, N=new, P=passed (i.e.., forwarded), R=replied, S=seen, T=trashed, a=has-attachment, x=encrypted, s=signed, u=unread. @item The From/To field shows the sender of the message unless the sender matches the regular expression in @t{mu4e-user-mail-address-regexp}, in which the header will show @t{To} followed by the recipient. @item The subject field displays the discussion threads according to the @emph{JWZ mail threading algorithm}@footnote{@url{http://www.jwz.org/doc/threading.html}}. @end itemize @subsection Keybindings Using the default key bindings, you can do various things with these messages; these actions are also listed in the @t{Headers} menu in the Emacs menu bar. @verbatim key description --- ----------- n,p go to next, previous message y select the message view (if it's visible) j jump to maildir b,B jump to bookmark (/ edit first) d mark for moving to the trash folder DEL,D mark for immediate deletion m mark for moving to another maildir folder u unmark message at point R,F,C reply/forward/compose E edit (only allowed for draft messages) | pipe message through shell command d mark for moving to the trash folder DEL,D mark for immediate deletion m mark for moving to another maildir folder o mark message as unread r mark message as read u unmark message at point U unmark *all* messages x execute actions for the marked messages RET open the message at point in the message view H get help q,z leave the headers buffer @end verbatim @subsection Marking messages Note, all mark/unmark commands support the current @emph{region} (i.e., selection) -- so, for example, if you the select a number of message and then press @key{DEL}, all selected message will be marked for deletion. The two-step mark-execute sequence is similar to what @t{dired} and a number of other emacs-based programs do. @t{mu4e} tries to be as quick as possible while still trying to protect you from accidents. When you try to do a new search, or refresh the headers buffer while you still have marked messages, normally you will be asked what to do with those marks -- whether to @emph{apply} them before leaving, @emph{ignore} them or to @emph{cancel} the operation. This behavior can be influenced with the variable @code{`mu4e-headers-leave-behavior'} -- see its documentation. @subsection Split view @emph{Split view} refers to viewing the @ref{Headers view} and the @ref{Message view} next to each other, with the message selected in the former, visible in the latter. Earlier versions of @t{mu4e} only showed one of the views at the same time, but split view is the default after version 0.8.3.1. You can influence the way the splitting works by setting the variable @code{mu4e-split-view} in your configuration to one of 3 values: @itemize @item @t{horizontal} (this is the default): display the message view below the header view @item @t{vertical}: display the message view on the right side of the header view @item anything else: don't do any splitting @end itemize When splitting horizontally, you can determine the number of visible header lines with with the variable @t{mu4e-headers-visible-lines} (default value: 8). When split vertically you can use @t{mu4e-headers-visible-columns} (default value: 30) to set the number of visible columns. When the message view window is selected, you cannot use the arrow keys for moving to the next / previous message (like you can in the headers view), since those are already assigned to cursor movement in the message. However, instead can use the @key{p} (or @key{M-up}) and @key{n} (or @key{M-down}) keys for moving to the previous and the next message, respectively. These keys also work in the headers view. You can change the selected window from the headers-view to the message-view and vice-versa with @code{mu4e-select-other-view}, bound to @key{y}. @node Message view @section Message view After selecting a message in the @ref{Headers view}, it will be shown in the message view, for example: @verbatim ---------------------------------------------------------------------------- From: info@galatians.net To: "Paul" paul@hotmail.com Subject: Re: some thoughts Flags: (seen attach) Date: Mon 19 Jan 2004 09:39:42 AM EET Maildir: /inbox Attachments(2): [1]DSCN4961.JPG(1.3M), [2]DSCN4962.JPG(1.4M) Hi Paul, How are you? Sorry we didn't get back to you sooner and sorry for the top-quoting. We're still debating your last message; anyway, here are some recent pics. And here's a link: http://example.com[1] All the best! On Sun 21 Dec 2003 09:06:34 PM EET, Paul wrote: [....] ---------------------------------------------------------------------------- @end verbatim Some notes: @itemize @item You can determine which header fields are shown by setting the variable @code{mu4e-view-fields}. @item You can customize the date format by setting the variable @code{mu4e-date-format-long}, using the same format that @code{format-time-string} uses. @item If you only want to see the name and not the e-mail address of the contacts in address fields, you can set @option{mu4e-view-show-addresses} to @t{nil}. This will hide the addresses for contacts that also have a name. The e-mail address is still available as a tool-tip. @item The body text can be line-wrapped (toggle between wrapped/not-wrapped with @key{w}) and/or cited parts can be hidden (toggle between hidden/not-hidden with @key{h}. If you want to do this by default when viewing messages, you can set, respectively, @code{mu4e-view-wrap-lines} and @code{mu4e-view-hide-cited} to @code{t}. @footnote{If you have installed the @t{filladapt} package (@url{http://www.wonderworks.com/download/filladapt.el}), @t{mu4e} will use it for line-wrapping, as it generally does a better job than the default mechanism emacs provides.} @end itemize @subsection Keybindings You can find most things you can do with this message in the @emph{View} menu, or by using the keyboard; the default bindings are: @verbatim key description --- ----------- n,p go to next, previous message y select the headers view (if it's visible) j jump to maildir b,B jump to bookmark (/ edit first) d mark for moving to the trash folder DEL,D mark for immediate deletion m mark for moving to another maildir folder u unmark message at point R,F,C reply/forward/compose E edit (only allowed for draft messages) . show the raw message view. 'q' takes you back. g go to (visit) numbered URL (using `browse-url') (or: or RET with point on url) e extract (save) attachment (asks for number) (or: or RET with point on attachment) o open attachment (asks for number) (or: or S-RET with point on attachment) a additional attachment handling w toggle line wrapping h toggle showing cited parts H get help q,z leave the message view @end verbatim Note that @key{x}, which means 'execute actions on marked messages' is not available in this view, to reduce the risk of accidents. You need to go back to the headers view to effectuate the actions. @subsection Opening and saving attachments By default, when opening attachments, @t{mu4e} uses the the @t{xdg-open}-program @footnote{@url{http://portland.freedesktop.org/wiki/}} or (on MacOS) the @t{open} program. If you want to use another program, you can specify this by setting the @t{MU_PLAY_PROGRAM} environment variable. When extracting (saving) attachments (with @key{e}), the default directory for saving them is your home directory (@file{~/}); you can change this using the variable @code{mu4e-attachment-dir}, for example: @lisp (setq mu4e-attachment-dir (file-name-expand "~/Downloads")) @end lisp @subsection Additional actions on attachments When you press @key{a} (@code{mu4e-view-handle-attachment}), @t{mu4e} lets you choose from a list with some more actions to perform on attachments: @itemize @item @t{open-with} (@key{w}): open the attachment with some arbitrary program. For example, suppose you have received a message with a picture attachment; then, @t{a w 1 RET gimp RET} will open that attachment in The Gimp. @item @t{pipe} (@key{|}: process the attachment with some Unix shell-pipe and see the results. Suppose you receive a patch file, and would like to get an overview of the changes, using the @t{diffstat} program. You can use something like: @t{a | 1 RET diffstat -b RET}. @item @t{emacs} (@key{e}): open the attachment in your running @t{emacs} . For example, if you receive some text file you'd like to open in @t{emacs}: @t{a e 1 RET}. @end itemize Note that all of these actions work on @emph{temporary copy} of the attachment. @subsection Displaying rich-text messages For displaying messages, @t{mu4e} normally prefers the plain-text version for messages consisting of both a plain-text and an html (rich-text) version of its body-text. If there is only an html-version, or if the plaint-text version is too short in comparison with the html part, @t{mu4e} tries to convert the html into plain-text for display. The default way to do that is to use the Emacs built-in @code{html2text} function, but if you set the variable @code{mu4e-html2text-command} to some external program, that program will be used. This program is expected to take html from standard input and write plain text in @t{utf-8} encoding on standard output. An obvious choice for this is the program that is actually @emph{called} @t{html2text}@footnote{@url{http://www.mbayer.de/html2text/}}, which you could set up with something like the following in your initialization files: @lisp (setq mu4e-html2text-command "html2text -utf8 -width 72") @end lisp Normally, @t{mu4e} prefers the text-version of an e-mail message to determine the message body. You can change this by setting @code{mu4e-view-prefer-html}. @node Editor view @section Editor view For its editor, @t{mu4e} re-uses Gnu's @t{message-mode}. For example, when replying to a message, the editor view looks something like the following: @verbatim ---------------------------------------------------------------------------- From: Rupert the Monkey Reply-To: rupert@example.com To: Wally the Walrus In-reply-to: <201201160918.47080.ssdfz@example.com> Subject: Re: Eau-qui d'eau qui? --text follows this line-- On Mon 16 Jan 2012 10:18:47 AM EET, Wally the Walrus wrote: > Hi Rupert, > > Dude - how are things? > > Later -- wally. ---------------------------------------------------------------------------- @end verbatim Since @t{mu4e} uses @t{gnu}'s message editor, for documentation @inforef{Message}. Also, @pxref{Sending mail}. There are many key-bindings available, here are some of the essential ones (you can use the menu to find more): @subsection Some useful keybindings @verbatim key description --- ----------- C-c C-c send message C-c C-d save to drafts and leave C-c C-k kill the message C-c C-w insert signature C-c C-a attach a file (pro-tip: drag & drop works as well) @end verbatim @node Searching mail @chapter Searching mail @t{mu4e} is fully search-based; this means that all the lists of messages you see, are the result of some query. Even if you 'jump to a folder', in fact you are executing a search query for messages that happen to have the property of being in a certain folder. Queries normally return only up to @code{mu4e-search-results-limit} (which defaults to 1000) results. You get @emph{all} results when you prefix your search commands (such as with @code{mu4e-search}, @code{mu4e-search-bookmark}, @code{mu4e-search-bookmark-edit-first} and @code{mu4e-jump-to-maildir} with @kbd{C-u}. This limit was introduced in earlier versions of @t{mu4e}, where @t{emacs} could become slow when there were many matches. This is no longer the case (post @t{mu4e} version 0.9.8.3), but since it is still faster to limit the number of matches, the limit remains. @menu * Queries:: * Bookmarks:: * Maildir searches:: @end menu @node Queries @section Queries The queries you can execute are the same ones that @code{mu find} understands. Please refer to the @code{mu-find} and @code{mu-easy} man pages for details and more examples. @verbatim # get all messages about bananas bananas # get all messages about bananas from john with an attachment from:john flag:attach bananas # get all messages with subject wombat in June 2009 subject:wombat date:20090601..20090630 # get all messages with PDF attachments in the /projects folder maildir:/projects mime:application/pdf # get all important messages which are signed: flag:signed prio:high # get all messages from Jim without an attachment: from:jim AND NOT flag:attach # get all unread messages where the subject mentions Ångström: subject:angstrom flag:unread # get all unread messages between Mar-2002 and Aug-2003 about some bird date:20020301..20030831 nightingale flag:unread # get today's messages date:today..now # get all messages we got in the last two weeks regarding emacs date:2w..now emacs # get mails with a subject soccer, Socrates, society... # note: the '*' wildcard can only appear as the rightmost character in the term subject:soc* # get all mails with attachment with filenames starting with 'pic' # note: the '*' wildcard can only appear as the rightmost character in the term file:pic* # get all messages with PDF attachments: mime:application/pdf # get all messages with image attachments: # note: the '*' wildcard can only appear as the rightmost character in the term mime:image/* @end verbatim @node Bookmarks @section Bookmarks If you have queries that you use often, you may want to store them as @emph{bookmarks}. These bookmarks then show up in the main view, and you can invoke them in other places as well. Bookmark searches are available in the main view @ref{Main view}, header view @xref{Headers view}, and message view @xref{Message view}, using (by default) the key @key{b} (@code{mu4e-search-bookmark}). @subsection Setting up bookmarks @code{mu4e} provides some default bookmarks, which you can override. The definition of the default bookmarks is instructive here: @lisp (defvar mu4e-bookmarks '( ("flag:unread AND NOT flag:trashed" "Unread messages" ?u) ("date:today..now" "Today's messages" ?t) ("date:7d..now" "Last 7 days" ?w) ("mime:image/*" "Messages with images" ?p)) "A list of pre-defined queries; these will show up in the main screen. Each of the list elements is a three-element list of the form (QUERY DESCRIPTION KEY), where QUERY is a string with a mu query, DESCRIPTION is a short description of the query (this will show up in the UI), and KEY is a shortcut key for the query.") @end lisp You can replaces these, or add your own items, by putting in your configuration (@file{~/.emacs}) something like: @lisp (add-to-list 'mu4e-bookmarks '("size:5M..500M" "Big messages" ?b)) @end lisp This prepends your bookmark to the list, and assigns the key @key{b} to it. If you want to @emph{append} your bookmark, you can use @code{t} as the third argument to @code{add-to-list}. In the various @t{mu4e} views, pressing @key{b} will list all the bookmarks defined in the echo area, with the shortcut key highlighted. So, to invoke the bookmark we just defined (to get the list of "Big Messages"), all you need to type is @key{bb}. @subsection Editing bookmarks before searching There is also @code{mu4e-search-bookmark-edit-first} (key @key{B}), which lets you edit the search query with some bookmark already filled in. This can be useful if you have many similar queries, but need to change some parameter. For example, you could have a bookmark @t{"NOT maildir:/Trash AND"}@footnote{Not a valid search query by itself} and add whatever you want to search for to that. Or, to do a query limited to the messages of today, all you need to type is @key{Bt} (using the @t{Today's messages}-bookmark, see above). @node Maildir searches @section Maildir searches Maildir searches are quite similar to bookmark searches (see @ref{Bookmarks}), with the difference being that the target is always a maildir -- maildir queries provide a 'traditional' folder-like interface to a search-based e-mail client. By default, maildir searches are available in the @ref{Main view}, @ref{Headers view}, and @ref{Message view}, with the key @key{j} (@code{mu4e-jump-to-maildir}). @subsection Setting up maildir shortcuts You can do Maildir searches manually (e.g. with a query like @code{maildir:/myfolder}) but since it is so common, @t{mu4e} offers a quicker way to do this. To enable this, you need to set the variable @t{mu4e-maildir-shortcuts} to list of maildirs you'd like to have quick access to, for example: @lisp (setq mu4e-maildir-shortcuts '( ("/inbox" . ?i) ("/archive" . ?a) ("/lists" . ?l) ("/work" . ?w) ("/sent" . ?s)) @end lisp This would set @key{i} as a shortcut for the @t{/inbox} folder; so effectively a query @t{maildir:/inbox}. There is a special shortcut @key{o} for @emph{other} (so don't use that one for your own shortcuts!), which allows you to choose from @emph{all} maildirs. Each of the folder names is relative to your top-level maildir directory; so if you keep your mail in @file{~/Maildir}, @file{/inbox} would refer to @file{~/Maildir/inbox}. Having these shortcuts allows you to jump around your folder very quickly - for example, getting to the @t{/lists} folder only requires you to type @key{jl}. The very same shortcuts are used by the @code{mu4e-mark-for-move} (default shortcut @key{m}); so, for example, if you want to move a message the @t{/archive} folder, you can do so by typing @key{ma}. @node Interaction with other tools @chapter Interaction with other tools In this chapter we discuss some ways in ways in which @t{mu4e} can cooperate with other tools. @menu * Creating org-mode links:: * Maintaining an address-book with org-contacts:: * Getting new mail notifications with Sauron:: * Speedbar support:: * Citations with mu-cite:: @end menu @node Creating org-mode links @section Creating org-mode links It can be useful to include links to e-mail messages or even search queries in your org-mode files. @t{mu4e} supports this with the @t{org-mu4e} module; you can set it up by adding it to your configuration: @lisp (require 'org-mu4e) @end lisp After this, you can use the normal @t{org-mode} mechanisms to store links: @t{M-x org-store-link} will store a link to a particular message when you're in Message view (@ref{Message view}), and a link to a query when you are in Headers view (@ref{Headers view}). You can insert these link later with @t{M-x org-insert-link}. Then, you can go to the query or message the link points to with either @t{M-x org-agenda-open-link} in agenda buffers, or @t{M-x org-open-at-point} elsewhere - both are typically bound to @kbd{C-c C-o}. @node Maintaining an address-book with org-contacts @section Maintaining an address-book with org-contacts To manage your addresses using @t{org-mode}, there is @t{org-contacts}@footnote{@url{http://julien.danjou.info/software/org-contacts.el}}. You can use it with a @t{capture}-template: @verbatim ("c" "contacts" entry (file "contacts.org") "* %(mu4e-view-snarf-from 'name) :PROPERTIES: :EMAIL: %(mu4e-view-snarf-from 'email) :NICK: :BIRTHDAY: :END:\n\n") @end verbatim After setting this up, you can use @t{M-x org-capture RET c} to get a template for a new contact based on` the 'From:' address. @node Getting new mail notifications with Sauron @section Getting new mail notifications with Sauron The emacs-package Sauron@footnote{Sauron can be found at @url{https://github.com/djcb/sauron}, or in the Marmalade package-repository at @url{http://http://marmalade-repo.org/}.} (by the same author) can be used to get notifications about new mails. If you put something like the below script in your @t{crontab} (or have some other way of having it execute every @emph{n} minutes, you will receive notifications in the sauron-buffer when new messages arrive. @verbatim #!/bin/sh # put the path to your Inbox folder here CHECKDIR="/home/$LOGNAME/Maildir/Inbox" sauron-msg () { DBUS_COOKIE="/home/$LOGNAME/.sauron-dbus" if test "x$DBUS_SESSION_BUS_ADDRESS" = "x"; then if test -e $DBUS_COOKIE; then export DBUS_SESSION_BUS_ADDRESS="`cat $DBUS_COOKIE`" fi fi if test -n "x$DBUS_SESSION_BUS_ADDRESS"; then dbus-send --session \ --dest="org.gnu.Emacs" \ "/org/gnu/Emacs/Sauron" \ "org.gnu.Emacs.Sauron.AddMsgEvent" \ string:shell uint32:3 string:"$1" fi } for f in `find $CHECKDIR -mmin -2 -a -type f`; do subject=`$MU view $f | grep '^Subject:' | sed 's/^Subject://'` sauron-msg "mail: $subject" done @end verbatim Note, you should put something like: @lisp (setq sauron-dbus-cookie t) @end lisp in your setup, which allows the script to find the D-Bus session bus. @node Speedbar support @section Speedbar support @code{speedbar} is an emacs-extension that shows navigational information for an emacs buffer in a separate frame. Using @code{mu4e-speedbar}, @t{mu4e} lists your bookmarks and maildir folders and allows for one-click access to them. @t{mu4e} loads @t{mu4e-speedbar} automatically; all you need to do to activate it is @code{M-x speedbar}. Then, when then going to the @ref{Main view}, the speedbar-frame will be updated with your bookmarks and maildirs. @code{mu4e-speedbar} was contributed by Antono Vasiljev. @node Citations with mu-cite @section Citations with @t{mu-cite} Note, apart from its name @t{mu-cite} is a project totally unconnected to @t{mu}/@t{mu4e}. @t{mu-cite} is a package to control the way message citations look like (i.e., the message you responded to when you reply to them or forward them), with its latest version available at @url{http://www.jpl.org/elips/mu/}. After installation of the @t{mu-cite}, you can use something like the following to make it work with @t{mu4e}: @lisp (require 'mu-cite) (setq message-cite-function 'mu-cite-original) (setq mu-cite-top-format '("On " date ", " full-name " wrote:\n\n")) (setq mu-cite-prefix-format '(" > "))) @end lisp @node Example configuration @chapter Example configuration In this chapter, we show some example configurations. @menu * Minimal configuration:: * Longer configuration:: * Gmail configuration:: @end menu @node Minimal configuration @section Minimal configuration An (almost) minimal configuration for @t{mu4e} might look something like this: @lisp ;; example configuration for mu-for-emacs (mu4e) (require 'mu4e) ;; happily, below settings are all /optional/ ;; Only needed if your maildir is _not_ ~/Maildir ;;(setq mu4e-maildir "/home/user/Maildir") ;; these must start with a "/", and must exist ;; (i.e.. /home/user/Maildir/sent must exist) ;; you use e.g. 'mu mkdir' to make the Maildirs if they don't ;; already exist ;; below are the defaults; if they do not exist yet, mu4e will offer to ;; create them ;; (setq mu4e-sent-folder "/sent") ;; (setq mu4e-drafts-folder "/drafts") ;; (setq mu4e-trash-folder "/trash") ;; for the settings for outgoing mail consult the section 'Longer configuration' @end lisp @node Longer configuration @section Longer configuration @lisp ;; example configuration for mu-for-emacs (mu4e) (require 'mu4e) (setq ;; a regular expression that matches all email address uses by the user; ;; this allows us to correctly determine if user is the sender of some message mu4e-user-mail-address-regexp "foo@@bar\.com\\|cuux@@example\.com" ;; path to our Maildir directory mu4e-maildir "/home/user/Maildir" ;; the next are relative to `mu4e-maildir' mu4e-sent-folder "/sent" mu4e-drafts-folder "/drafts" mu4e-trash-folder "/trash" ;; the maildirs you use frequently; access them with 'j' ('jump') mu4e-maildir-shortcuts '( ("/archive" . ?a) ("/inbox" . ?i) ("/work" . ?w) ("/sent" . ?s)) ;; when you want to use some external command for text->html conversion, ;; i.e., the 'html2text' program mu4e-html2text-command "html2text" ;; the headers to show in the headers list -- a pair of the field + its ;; width, with `nil' meaning 'unlimited' (better only use that for ;; the last field. These are the defaults: mu4e-headers-fields '( (:date . 25) (:flags . 6) (:from . 22) (:subject . nil)) ;; program to get mail; alternatives are 'fetchmail', 'getmail' ;; isync or your own shellscript. called when 'U' is pressed in ;; main view mu4e-get-mail-command "offlineimap" ;; general emacs mail settings; used when composing e-mail mu4e-reply-to-address "foo@@bar.com" user-mail-address "foo@@bar.com" user-full-name "Foo X. Bar" ;; include in message with C-c C-w message-signature (concat "Foo X. Bar\n" "http://www.example.com\n") ;; smtp mail setting message-send-mail-function 'smtpmail-send-it smtpmail-default-smtp-server "smtp.example.com" smtpmail-smtp-server ""smtp.example.com" smtpmail-local-domain "example.com" ;; if you need offline mode, set these -- and create the queue dir ;; with 'mu mkdir', i.e.. mu mkdir /home/user/Maildir/queue smtpmail-queue-mail nil smtpmail-queue-dir "/home/user/Maildir/queue/cur") @end lisp @node Gmail configuration @section Gmail configuration @emph{Gmail} is a popular e-mail provider; let's see how we can make it work with @t{mu4e}. First of all, we need a program to get the e-mail from Gmail on our local machine; for this we use @t{offlineimap}; on Debian (and derivatives like Ubuntu), this is as easy as: @verbatim sudo apt-get install offlineimap @end verbatim Then, create a configuration for @t{offlineimap}, i.e. a file @file{~/.offlineimaprc}: @verbatim [general] accounts = Gmail maxsyncaccounts = 3 [Account Gmail] localrepository = Local remoterepository = Remote [Repository Local] type = Maildir localfolders = ~/Maildir [Repository Remote] type = IMAP remotehost = imap.gmail.com remoteuser = USERNAME@gmail.com remotepass = PASSWORD ssl = yes maxconnections = 1 realdelete = no @end verbatim Of course, you need replace @t{USERNAME} and @t{PASSWORD} with your actual GMail username and password. After this, you should be able to download your mail: @verbatim $ offlineimap OfflineIMAP 6.3.4 Copyright 2002-2011 John Goerzen & contributors. Licensed under the GNU GPL v2+ (v2 or any later version). Account sync Gmail: ***** Processing account Gmail Copying folder structure from IMAP to Maildir Establishing connection to imap.gmail.com:993. Folder sync [Gmail]: Syncing INBOX: IMAP -> Maildir Syncing [Gmail]/All Mail: IMAP -> Maildir Syncing [Gmail]/Drafts: IMAP -> Maildir Syncing [Gmail]/Sent Mail: IMAP -> Maildir Syncing [Gmail]/Spam: IMAP -> Maildir Syncing [Gmail]/Starred: IMAP -> Maildir Syncing [Gmail]/Trash: IMAP -> Maildir Account sync Gmail: ***** Finished processing account Gmail @end verbatim We can now run @t{mu} to make sure things work: @verbatim $ mu index mu: indexing messages under /home/foo/Maildir [/home/foo/.mu/xapian] | processing mail; processed: 520; updated/new: 520, cleaned-up: 0 mu: elapsed: 3 second(s), ~ 173 msg/s mu: cleaning up messages [/home/foo/.mu/xapian] / processing mail; processed: 520; updated/new: 0, cleaned-up: 0 mu: elapsed: 0 second(s) @end verbatim Note that we can run both the @t{offlineimap} and the @t{mu index} from within @t{mu4e}, but running it from the command line makes it a bit easier to see what is going on. Now, let's make a @t{mu4e} configuration for this: @lisp (require 'mu4e) ;; default ;; (setq mu4e-maildir (expand-file-name "~/Maildir")) (setq mu4e-drafts-folder "/[Gmail].Drafts") (setq mu4e-sent-folder "/[Gmail].Sent Mail") (setq mu4e-trash-folder "/[Gmail].Trash") ;; don't save message to Sent Messages, GMail/IMAP will take care of this (setq mu4e-sent-messages-behavior 'delete) ;; setup some handy shortcuts (setq mu4e-maildir-shortcuts '( ("/INBOX" . ?i) ("/[Gmail].Sent Mail" . ?s) ("/[Gmail].Trash" . ?t) ("/[Gmail].All Mail" . ?a))) ;; allow for updating mail using 'U' in the main view: (setq mu4e-get-mail-command "offlineimap") ;; something about ourselves (setq user-mail-address "USERNAME@@gmail.com" user-full-name "Foo X. Bar" ;; include in message with C-c C-w message-signature (concat "Foo X. Bar\n" "http://www.example.com\n")) ;; sending mail -- replace USERNAME with your gmail username ;; also, make sure the gnutls command line utils are installed ;; package 'gnutls-bin' in Debian/Ubuntu (require 'smtpmail) (setq message-send-mail-function 'smtpmail-send-it starttls-use-gnutls t smtpmail-starttls-credentials '(("smtp.gmail.com" 587 nil nil)) smtpmail-auth-credentials '(("smtp.gmail.com" 587 "USERNAME@@gmail.com" nil)) smtpmail-default-smtp-server "smtp.gmail.com" smtpmail-smtp-server "smtp.gmail.com" smtpmail-smtp-service 587) @end lisp And that's it -- put the above in your @file{~/.emacs} (obviously you need to change @t{USERNAME} etc. to your own), and restart @t{emacs}, and run @kbd{M-x mu4e}. Using these setting you can quickly switch to your Inbox -- press @kbd{ji}. Then, when you want archive some messages, move them to the 'All Mail' folder by pressing @kbd{ma}. @node FAQ - Frequently Anticipated Questions @chapter FAQ - Frequently Anticipated Questions In this chapter we list a number of actual and anticipated questions and their answers. @itemize @item @emph{How can I quickly delete/move/trash a lot of messages?} You can select ('mark' in emacs-speak) the messages; the actions you then take (e.g., @key{DEL} for delete, @key{m} for move and @key{t} for trash) will apply to @emph{all} selected messages @item @emph{How can I use @t{BBDB}?} Currently, there is no built-in for address management with @t{BBDB}; instead, we recommend @ref{Maintaining an address-book with org-contacts} for now. @item @emph{mu4e only seems to return a subset of all matches - how can I get all?}. Yes, for speed reasons (and because, if you are like the author, you usually don't need thousands of matches), @t{mu4e} returns only up to the value of the variable @code{m4ue-search-result-limit} matches. You can customize that variable, or simply press the emacs prefix @kbd{C-u} before your search command to get all matches. In other words, when you press @t{C-u s hello} you will get all matches, while @t{s hello} only gets you up-to-a-limited-number matches. Same for the other search based commands, @code{mu4e-jump-to-maildir} (default: @key{j}) and @code{mu4e-search-bookmark} (default: @key{b}). @item @emph{How can I easily include attachments in the messages I write?} Drag-and-drop. @item @emph{When I try do run @t{mu index} while @t{mu4e} is running I get errors like @t{mu: mu_store_new_writable: xapian error 'Unable to get write lock on ~/.mu/xapian: already locked'}. What can I do about this?} You get this error because the underlying Xapian database allows itself to be opened in read-write mode only once. There is not much @t{mu4e} can do about this, but what you can do is telling @t{mu} to (gracefully) terminate: @verbatim pkill -2 -u $UID mu # send SIGINT sleep 1 mu index @end verbatim @t{mu4e} will automatically restart @t{mu} when it needs it. In practice, this seems to work quite well. @item @emph{Can I automatically execute the actions on marked messages when leaving the headers buffer?} Yes you can -- see the documentation on @t{mu4e-headers-leave-behavior}. @item @emph{Can I automatically apply word-wrapping (and hiding cited parts) when viewing a message?} Yes -- see the documentation on @t{mu4e-view-wrap-lines} (and @t{mu4e-view-hide-cited}). You can always toggle between the two states with @key{w} and @key{h}, respectively. @item @emph{Is there context-sensitive help available?} Yes - pressing @key{H} in most cases should point you to the right spot in this manual. @end itemize @node Known issues / missing features @chapter Known issues / missing features In this chapter we list a number of known issue and/or missing features in @t{mu4e}. Thus, users won't have to search in vain for things that are not there (yet), and the author can use it as a todo-list. @itemize @item @emph{Thread handling is incomplete.} While threads are calculated and are visible in the headers buffer, there is no functionality to manipulate them (e.g., collapse the thread, or delete a whole thread at once). But note that you can manipulate a number of consecutive messages at once by selecting them, and then using one of the manipulation commands, such as @code{mu4e-mark-for-move} or @code{mu4e-mark-for-delete}. @item @emph{No support for crypto when reading mail}. Currently, you cannot conveniently read encrypted mail or check signatures (it should be possible with e.g. EPA though, @inforef{Top, EasyPG Assistant, epa}.) For outgoing messages, it should work though, using the built-in mechanisms. @item @emph{One cannot influence the sorting of messages}. Messages are sorted according to thread, then descending by date. It would be nice if it could be sorted in other ways as well. @item @emph{The key-bindings are @emph{somewhat} hard-coded} That is, the main menu assumes the default key-bindings, as do the clicks-on-bookmarks. @item @emph{Attachments are not accessible in draft/sent messages}. Currently, attachments in saved messages are special strings, which are transformed into the actual attachments when sending. However, you cannot access them afterwards. @end itemize @node How it works @appendix How it works While not necessarily interesting for all users of @t{mu4e}, for some it may be interesting to know how @t{mu4e} does its job. @menu * High-level overview:: * mu server:: * Reading from the server:: @end menu @node High-level overview @section High-level overview On a high level, we can summarize the structure of the @t{mu4e} system using some ascii-art: @example +---------+ | emacs | | +------+ +----| mu4e | --> send mail (smtpmail) +------+ | A V | ---/ search, view, move mail +---------+ \ | mu | +---------+ | A V | +---------+ | Maildir | <--- receive mail (fetchmail, +---------+ offlineimap, ...) @end example In words: @itemize @item Your e-mail messages are stored in a Maildir-directory (typically, @file{~/Maildir}), and new mail comes in using tools like @t{fetchmail}, @t{offlineimap}, or through a local mail servers (such as @t{qmail} or Postfix). @item @t{mu} indexes these messages periodically, so you can quickly search for them. @t{mu} can run in a special @t{server}-mode, where it provides services to client software. @item @t{mu4e}, which runs inside @t{emacs} is such a client; it communicates with @t{mu} (in its @t{server}-mode to search for messages, and manipulate them. @item @t{mu4e} uses the facilities offered by @t{emacs} (the Gnus message editor and @t{smtpmail}) to send messages. @end itemize @node mu server @section @t{mu server} @t{mu4e} is based on the @t{mu} e-mail searching/indexer. The latter is a C-program; there are different ways to communicate with a client that is emacs-based. One way to implement this, would be to call the @t{mu} command-line tool with some parameters and then parse the output. In fact, that is how some tools do it, and it was the first approach -- @t{mu4e} would invoke e.g., @t{mu find} and process the output in emacs. However, with approach, we need to load the entire e-mail @emph{Xapian} database (in which the message is stored) for each invocation. Wouldn't it be nicer to keep a running @t{mu} instance around? Indeed, it would - and thus, the @t{mu server} sub-command was born. Running @t{mu server}, you get a sort-of shell, in which you can give commands to @t{mu}, which will then spit out the results/errors. @t{mu server} is not meant for humans, but it can be used manually, which is great for debugging. @node Reading from the server @section Reading from the server In the design, the next question was what format @t{mu} should use for its output for @t{mu4e} (@t{emacs}) to process. Some other programs use @abbr{JSON} here, but it seemed easier (and possibly, more efficient) just to talk to @t{emacs} in its native language: @emph{s-expressions} (to be precise: @emph{plists}), and interpret those using the @t{emacs}-function @code{read-from-string}. So, now let's look how we process the data from @t{mu server} in emacs. We'll leave out a lot of detail, @t{mu4e}-specifics, and look at a bit more generic approach. The first is to create a process with, for example, @code{start-process}, and then register a filter function for it, which will be invoked whenever the process has some chunk of output. Something like: @lisp (let ((proc (start-process ))) (set-process-filter proc 'my-process-filter) (set-process-sentinel proc 'my-process-sentinel)) @end lisp Note, the process sentinel is invoked when the process is terminated -- so there you can clean things up. The function =my-process-filter= is a user-defined function that takes the process and the chunk of output as arguments; in @t{mu4e} it looks something like (pseudo-lisp): @lisp (defun my-process-filter (proc str) ;; mu4e-buf: a global string variable to which data gets appended ;; as we receive it (setq mu4e-buf (concat mu4e-buf str)) (when )) @end lisp @code{} de-multiplexes the s-expression we got. For example, if the s-expression looks like an e-mail message header, it will be processed by the header-handling function, which will append it to the header list. If the s-expression looks like an error message, it will be reported to the user. And so on. The language between frontend and backend is documented in the @t{mu-server} man-page. If you set @t{mu4e-debug} to @t{t}, @t{mu4e} will log all the messages that go between frontend and backend in a special @t{*mu4e-log*} buffer. @subsection Example: ping-pong As an example of this, let's look at the @t{ping-pong}-sequence. When @t{mu4e} starts, it sends a command @t{ping} to the the @t{mu server} backend, to learn about its version. @t{mu server} then responds with a @t{pong} s-expression to provide this information (this is implemented in @file{mu-cmd-server.c}). We start this sequence when @t{mu4e} is invoked (when the program is started). It call @t{mu4e-proc-ping}, and registers a (lambda) function for @t{mu4e-proc-pong-func}, so it will retrieve the response. @verbatim -> ping <- (pong "mu" :version "x.x.x" :doccount 10000) @end verbatim When we receive such a @t{pong} (in @file{mu4e-proc.el}), the lambda function we registered will be called, and it check the version we got from the @t{pong} with the version we expected, and raises an error, if they differ. @node Logging and debugging @appendix Logging and debugging As explained in @ref{How it works}, @t{mu4e} communicates with its backend (@t{mu server}) by sending commands and receiving responses (s-expressions). For debugging purposes, it can be very useful to see this data. For this reason, @t{mu4e} can log all these messages. Note that the 'protocol' is documented to some extent in the @t{mu-server} manpage. You can enable (and disable) logging with @t{M-x mu4e-toggle-logging}. The log-buffer is called @t{*mu4e-log-buffer*}, and in the @ref{Main view}, @ref{Headers view} and @t{Message view}, there's a keybinding @key{$} that will take you there. You can quit it by pressing @key{q}. Logging can be a bit resource-intensive, so you may not want to leave it on all the time. By default, the log only maintains the most recent 1200 lines. Note, @t{mu} itself keeps a log as well, you can find this it in @t{/log/mu.log}, typically @t{~/.mu/log/mu.log}. @node GNU Free Documentation License @appendix GNU Free Documentation License @include fdl.texi @bye