Chapter 3. Configuration
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# Chapter 3. Configuration

## 1. Location of Initialization Files

While the default configuration (or “preferences”) make Mutt usable right out of the box, it is often desirable to tailor Mutt to suit your own tastes. When Mutt is first invoked, it will attempt to read the “system” configuration file (defaults set by your local system administrator), unless the “-n” command line option is specified. This file is typically `/usr/local/share/mutt/Muttrc` or `/etc/Muttrc`. Mutt will next look for a file named `.muttrc` in your home directory. If this file does not exist and your home directory has a subdirectory named `.mutt`, Mutt tries to load a file named `.mutt/muttrc`. If still not found, Mutt will try `$XDG_CONFIG_HOME/mutt/muttrc`.

`.muttrc` is the file where you will usually place your commands to configure Mutt.

In addition, Mutt supports version specific configuration files that are parsed instead of the default files as explained above. For instance, if your system has a `Muttrc-0.88` file in the system configuration directory, and you are running version 0.88 of Mutt, this file will be sourced instead of the `Muttrc` file. The same is true of the user configuration file, if you have a file `.muttrc-0.88.6` in your home directory, when you run Mutt version 0.88.6, it will source this file instead of the default `.muttrc` file. The version number is the same which is visible using the “-v” command line switch or using the `show-version` key (default: V) from the index menu.

## 2. Starter Muttrc

Mutt is highly configurable because it's meant to be customized to your needs and preferences. However, this configurability can make it difficult when just getting started. A few sample muttrc files come with mutt, under `doc/mutt/samples/`. Among them, sample.muttrc-starter is a basic example config with a few suggested settings and pointers to useful programs.

## 3. Syntax of Initialization Files

An initialization file consists of a series of commands. Each line of the file may contain one or more commands. When multiple commands are used, they must be separated by a semicolon (“;”).

Example 3.1. Multiple configuration commands per line

    set realname='Mutt user' ; ignore x-

The hash mark, or pound sign (“#”), is used as a “comment” character. You can use it to annotate your initialization file. All text after the comment character to the end of the line is ignored.

Example 3.2. Commenting configuration files

    my_hdr X-Disclaimer: Why are you listening to me? # This is a comment

Single quotes (“'”) and double quotes (“"”) can be used to quote strings which contain spaces or other special characters. The difference between the two types of quotes is similar to that of many popular shell programs, namely that a single quote is used to specify a literal string (one that is not interpreted for shell variables or quoting with a backslash [see next paragraph]), while double quotes indicate a string for which should be evaluated. For example, backticks are evaluated inside of double quotes, but not for single quotes.

“\” quotes the next character, just as in shells such as bash and zsh. For example, if want to put quotes “"” inside of a string, you can use “\” to force the next character to be a literal instead of interpreted character.

Example 3.3. Escaping quotes in configuration files

    set realname="Michael \"MuttDude\" Elkins"

“\\” means to insert a literal “\” into the line. “\n” and “\r” have their usual C meanings of linefeed and carriage-return, respectively.

A “\” at the end of a line can be used to split commands over multiple lines as it “escapes” the line end, provided that the split points don't appear in the middle of command names. Lines are first concatenated before interpretation so that a multi-line can be commented by commenting out the first line only.

Example 3.4. Splitting long configuration commands over several lines

    set status_format="some very \
    long value split \
    over several lines"

It is also possible to substitute the output of a Unix command in an initialization file. This is accomplished by enclosing the command in backticks (``). In Example 3.5, “Using external command's output in configuration files”, the output of the Unix command “uname -a” will be substituted before the line is parsed. Since initialization files are line oriented, only the first line of output from the Unix command will be substituted.

Example 3.5. Using external command's output in configuration files

    my_hdr X-Operating-System: `uname -a`

To avoid the output of backticks being parsed, place them inside double quotes. In Example 3.6, “Preventing the output of backticks from being parsed”, the output of the gpg decryption is assigned directly to $imap_pass, so that special characters in the password (e.g.“'”, “#”, “$”) are not parsed and interpreted specially by mutt.

Example 3.6. Preventing the output of backticks from being parsed

    set imap_pass="`gpg --batch -q --decrypt ~/.mutt/account.gpg`"

Both environment variables and Mutt variables can be accessed by prepending “$” to the name of the variable. For example,

Example 3.7. Using environment variables in configuration files

    set record=+sent_on_$HOSTNAME

will cause Mutt to save outgoing messages to a folder named “sent_on_kremvax” if the environment variable `$HOSTNAME` is set to “kremvax.” (See $record for details.)

Mutt expands the variable when it is assigned, not when it is used. If the value of a variable on the right-hand side of an assignment changes after the assignment, the variable on the left-hand side will not be affected.

If $muttlisp_inline_eval is set, an unquoted parenthesis-enclosed expression will be evaluated as MuttLisp. See the Using MuttLisp section for more details.

Example 3.8. Using MuttLisp expresions

    set signature = \
      (if (equal $my_name "Kevin McCarthy") ~/kevin.sig ~/other.sig)

The commands understood by Mutt are explained in the next paragraphs. For a complete list, see the command reference.

All configuration files are expected to be in the current locale as specified by the $charset variable which doesn't have a default value since it's determined by Mutt at startup. If a configuration file is not encoded in the same character set the $config_charset variable should be used: all lines starting with the next are recoded from $config_charset to $charset.

This mechanism should be avoided if possible as it has the following implications:

- These variables should be set early in a configuration file with $charset preceding $config_charset so Mutt knows what character set to convert to.

- If $config_charset is set, it should be set in each configuration file because the value is global and not per configuration file.

- Because Mutt first recodes a line before it attempts to parse it, a conversion introducing question marks or other characters as part of errors (unconvertable characters, transliteration) may introduce syntax errors or silently change the meaning of certain tokens (e.g. inserting question marks into regular expressions).

## 4. Address Groups

Usage:

`group` [ `-group` `name` ...] { `-rx` `expr` ... | `-addr` `expr` ... }
`ungroup` [ `-group` `name` ...] { `*` | `-rx` `expr` ... | `-addr` `expr` ... }

Mutt supports grouping addresses logically into named groups. An address or address pattern can appear in several groups at the same time. These groups can be used in patterns (for searching, limiting and tagging) and in hooks by using group patterns. This can be useful to classify mail and take certain actions depending on in what groups the message is. For example, the mutt user's mailing list would fit into the categories “mailing list” and “mutt-related”. Using `send-hook`, the sender can be set to a dedicated one for writing mailing list messages, and the signature could be set to a mutt-related one for writing to a mutt list — for other lists, the list sender setting still applies but a different signature can be selected. Or, given a group only containing recipients known to accept encrypted mail, “auto-encryption” can be achieved easily.

The group command is used to directly add either addresses or regular expressions to the specified group or groups. The different categories of arguments to the group command can be in any order. The flags `-rx` and `-addr` specify what the following strings (that cannot begin with a hyphen) should be interpreted as: either a regular expression or an email address, respectively.

These address groups can also be created implicitly by the alias, lists, subscribe and alternates commands by specifying the optional `-group` option. For example,

    alternates -group me address1 address2
    alternates -group me -group work address3

would create a group named “me” which contains all your addresses and a group named “work” which contains only your work address address3. Besides many other possibilities, this could be used to automatically mark your own messages in a mailing list folder as read or use a special signature for work-related messages.

The ungroup command is used to remove addresses or regular expressions from the specified group or groups. The syntax is similar to the group command, however the special character `*` can be used to empty a group of all of its contents. As soon as a group gets empty because all addresses and regular expressions have been removed, it'll internally be removed, too (i.e. there cannot be an empty group). When removing regular expressions from a group, the pattern must be specified exactly as given to the group command or `-group` argument.

## 5. Defining/Using Aliases

Usage:

`alias` [ `-group` `name` ...] `key` `address` [ `address` ...]
`unalias` [ `-group` `name` ...] { `*` | `key` ... }

It's usually very cumbersome to remember or type out the address of someone you are communicating with. Mutt allows you to create “aliases” which map a short string to a full address.

### Note

If you want to create an alias for more than one address, you must separate the addresses with a comma (“,”).

The optional `-group` argument to alias causes the aliased address(es) to be added to the named group.

To add an alias:

    alias muttdude me@cs.hmc.edu (Michael Elkins)
    alias theguys manny, moe, jack

To remove an alias or aliases (“*” means all aliases):

    unalias muttdude
    unalias *

Unlike other mailers, Mutt doesn't require aliases to be defined in a special file. The alias command can appear anywhere in a configuration file, as long as this file is sourced. Consequently, you can have multiple alias files, or you can have all aliases defined in your `.muttrc`.

On the other hand, the `<create-alias>` function can use only one file, the one pointed to by the $alias_file variable (which is `~/.muttrc` by default). This file is not special either, in the sense that Mutt will happily append aliases to any file, but in order for the new aliases to take effect you need to explicitly source this file too.

Example 3.9. Configuring external alias files

    source /usr/local/share/Mutt.aliases
    source ~/.mail_aliases
    set alias_file=~/.mail_aliases

To use aliases, you merely use the alias at any place in Mutt where Mutt prompts for addresses, such as the To: or Cc: prompt. You can also enter aliases in your editor at the appropriate headers if you have the $edit_headers variable set.

In addition, at the various address prompts, you can use the tab character to expand a partial alias to the full alias. If there are multiple matches, Mutt will bring up a menu with the matching aliases. In order to be presented with the full list of aliases, you must hit tab without a partial alias, such as at the beginning of the prompt or after a comma denoting multiple addresses.

In the alias menu, you can select as many aliases as you want with the `select-entry` key (default: <Return>), and use the exit key (default: q) to return to the address prompt.

## 6. Changing the Default Key Bindings

Usage:

`bind` `map` `key` `function`

This command allows you to change the default key bindings (operation invoked when pressing a key).

map specifies in which menu the binding belongs. Multiple maps may be specified by separating them with commas (no additional whitespace is allowed). The currently defined maps are:

generic

  This is not a real menu, but is used as a fallback for all of the other menus except for the pager and editor modes. If a key is not defined in another menu, Mutt will look for a binding to use in this menu. This allows you to bind a key to a certain function in multiple menus instead of having multiple bind statements to accomplish the same task.

alias

  The alias menu is the list of your personal aliases as defined in your `.muttrc`. It is the mapping from a short alias name to the full email address(es) of the recipient(s).

attach

  The attachment menu is used to access the attachments on received messages.

browser

  The browser is used for both browsing the local directory structure, and for listing all of your incoming mailboxes.

editor

  The editor is used to allow the user to enter a single line of text, such as the To or Subject prompts in the `compose` menu.

index

  The index is the list of messages contained in a mailbox.

compose

  The compose menu is the screen used when sending a new message.

pager

  The pager is the mode used to display message/attachment data, and help listings.

pgp

  The pgp menu is used to select the OpenPGP keys used to encrypt outgoing messages.

smime

  The smime menu is used to select the OpenSSL certificates used to encrypt outgoing messages.

postpone

  The postpone menu is similar to the index menu, except is used when recalling a message the user was composing, but saved until later.

query

  The query menu is the browser for results returned by $query_command.

mix

  The mixmaster screen is used to select remailer options for outgoing messages (if Mutt is compiled with Mixmaster support).

key is the key (or key sequence) you wish to bind. To specify a control character, use the sequence \Cx, where x is the letter of the control character (for example, to specify control-A use “\Ca”). Note that the case of x as well as \C is ignored, so that \CA, \Ca, \cA and \ca are all equivalent. An alternative form is to specify the key as a three digit octal number prefixed with a “\” (for example \177 is equivalent to \c?). In addition, key may be a symbolic name as shown in Table 3.1, “Symbolic key names”.

Table 3.1. Symbolic key names

Symbolic name | Meaning
--- | ---
\t | tab
<tab> | tab
<backtab> | backtab / shift-tab
\r | carriage return
\n | newline
\e | escape
<esc> | escape
<up> | up arrow
<down> | down arrow
<left> | left arrow
<right> | right arrow
<pageup> | Page Up
<pagedown> | Page Down
<backspace> | Backspace
<delete> | Delete
<insert> | Insert
<enter> | Enter
<return> | Return
<home> | Home
<end> | End
<space> | Space bar
<f1> | function key 1
<f10> | function key 10

The `<what-key>` function can be used to explore keycode and symbolic names for other keys on your keyboard. Executing this function will display information about each key pressed, until terminated by `^G`.

key does not need to be enclosed in quotes unless it contains a space (“ ”) or semi-colon (“;”).

function specifies which action to take when key is pressed. For a complete list of functions, see the reference. Note that the bind expects function to be specified without angle brackets.

The special function `<noop>` unbinds the specified key sequence.

### 6.1. Terminal Keybindings

Some key bindings are controlled by the terminal, and so by default can't be bound inside Mutt. These may include `^C`, `^\`, `^Q`, `^S`, `^Z`, and on BSD/Mac `^Y`. These terminal settings can be viewed and changed using the `stty` program.

“`stty -a`” will list the bound characters (not all of them affect Mutt), and what actions they take when pressed. For example, you may see “`intr = ^C`” in its output. This means typing `^C` will send an interrupt signal. “`quit = ^\`” means typing `^\` (commonly also `^4`) will send a quit signal.

To unbind a key from an action, you invoke “stty action undef”. For example, “`stty quit undef`” will unbind `^\` (and `^4`) from sending the quit signal. Once unbound (e.g, by placing that line in your .bashrc, or in a Mutt wrapper script/function) you can use the key sequence in your Mutt bindings.

## 7. Changing the current working directory

Usage:

`cd` `directory`

The `cd` command changes Mutt's current working directory. This affects commands and functions like `source`, `change-folder`, and `save-entry` that use relative paths. Using `cd` without directory changes to your home directory.

## 8. Defining Aliases for Character Sets

Usage:

`charset-hook` `alias` `charset`
`iconv-hook` `charset` `local-charset`

The charset-hook command defines an alias for a character set. This is useful to properly display messages which are tagged with a character set name not known to Mutt.

The iconv-hook command defines a system-specific name for a character set. This is helpful when your systems character conversion library insists on using strange, system-specific names for character sets.

## 9. Setting Variables Based Upon Mailbox

Usage:

`folder-hook` `[!]regexp` `command`

It is often desirable to change settings based on which mailbox you are reading. The folder-hook command provides a method by which you can execute any configuration command. regexp is a regular expression specifying in which mailboxes to execute command before loading. If a mailbox matches multiple folder-hooks, they are executed in the order given in the `.muttrc`.

The regexp parameter has mailbox shortcut expansion performed on the first character. See Mailbox Matching in Hooks for more details.

### Note

If you use the “!” shortcut for $spoolfile at the beginning of the pattern, you must place it inside of double or single quotes in order to distinguish it from the logical not operator for the expression.

### Note

Settings are not restored when you leave the mailbox. For example, a command action to perform is to change the sorting method based upon the mailbox being read:

    folder-hook mutt "set sort=threads"

However, the sorting method is not restored to its previous value when reading a different mailbox. To specify a default command, use the pattern “.” before other folder-hooks adjusting a value on a per-folder basis because folder-hooks are evaluated in the order given in the configuration file.

### Note

The keyboard buffer will not be processed until after all hooks are run; multiple push or exec commands will end up being processed in reverse order.

The following example will set the sort variable to `date-sent` for all folders but to `threads` for all folders containing “mutt” in their name.

Example 3.10. Setting sort method based on mailbox name

    folder-hook . "set sort=date-sent"
    folder-hook mutt "set sort=threads"

## 10. Keyboard Macros

Usage:

`macro` `menu` `key` `sequence` [ `description` ]

Macros are useful when you would like a single key to perform a series of actions. When you press key in menu menu, Mutt will behave as if you had typed sequence. So if you have a common sequence of commands you type, you can create a macro to execute those commands with a single key or fewer keys.

menu is the map which the macro will be bound in. Multiple maps may be specified by separating multiple menu arguments by commas. Whitespace may not be used in between the menu arguments and the commas separating them.

key and sequence are expanded by the same rules as the key bindings with some additions. The first is that control characters in sequence can also be specified as ^x. In order to get a caret (“^”) you need to use ^^. Secondly, to specify a certain key such as up or to invoke a function directly, you can use the format <key name> and <function name>. For a listing of key names see the section on key bindings. Functions are listed in the reference.

The advantage with using function names directly is that the macros will work regardless of the current key bindings, so they are not dependent on the user having particular key definitions. This makes them more robust and portable, and also facilitates defining of macros in files used by more than one user (e.g., the system Muttrc).

Optionally you can specify a descriptive text after sequence, which is shown in the help screens if they contain a description.

### Note

Macro definitions (if any) listed in the help screen(s), are silently truncated at the screen width, and are not wrapped.

## 11. Using Color and Mono Video Attributes

Usage:

`color` `object` [ `attribute` ...] `foreground` `background`
`color` { `header` | `body` } [ `attribute` ...] `foreground` `background` `regexp`
`color` `index` [ `attribute` ...] `foreground` `background` `pattern`
`color` `compose` `composeobject` [ `attribute` ...] `foreground` `background`
`uncolor` { `index` | `header` | `body` } { `*` | `pattern` ... }

If your terminal supports color, you can spice up Mutt by creating your own color scheme. To define the color of an object (type of information), you must specify both a foreground color and a background color (it is not possible to only specify one or the other).

header and body match regexp in the header/body of a message, index matches pattern in the message index. Note that IMAP server-side searches (=b, =B, =h) are not supported for color index patterns.

When $header_color_partial is unset (the default), a header matched by regexp will have color applied to the entire header. When set, color is applied only to the exact text matched by regexp.

object can be one of:

- attachment

- bold (highlighting bold patterns in the body of messages)

- error (error messages printed by Mutt)

- hdrdefault (default color of the message header in the pager)

- indicator (arrow or bar used to indicate the current item in a menu)

- markers (the “+” markers at the beginning of wrapped lines in the pager)

- message (informational messages)

- normal

- prompt

- quoted (text matching $quote_regexp in the body of a message)

- quoted1, quoted2, ..., quotedN (higher levels of quoting)

- search (highlighting of words in the pager)

- signature

- status (mode lines used to display info about the mailbox or message)

- tilde (the “~” used to pad blank lines in the pager)

- tree (thread tree drawn in the message index and attachment menu)

- underline (highlighting underlined patterns in the body of messages)

composeobject can be one of:

- header

- security_encrypt

- security_sign

- security_both

- security_none

attribute can be one of the following:

- none

- bold

- underline

- reverse

- standout

foreground and background can be one of the following:

- white

- black

- green

- magenta

- blue

- cyan

- yellow

- red

- default

- colorx

The color name can optionally be prefixed with the keyword `bright` or `light` to make the color boldfaced or light (e.g., `brightred`). The precise behavior depends on the terminal and its configuration. In particular, the boldfaced/light difference and such background colors may be available only for terminals configured with at least 16 colors, as specified by the `$TERM` environment variable.

If your terminal supports it, the special keyword default can be used as a transparent color. The value brightdefault is also valid. If Mutt is linked against the S-Lang library, you also need to set the `$COLORFGBG` environment variable to the default colors of your terminal for this to work; for example (for Bourne-like shells):

    set COLORFGBG="green;black"
    export COLORFGBG

### Note

The S-Lang library requires you to use the lightgray and brown keywords instead of white and yellow when setting this variable.

### Note

The uncolor command can be applied to the index, header and body objects only. It removes entries from the list. You must specify the same pattern specified in the color command for it to be removed. The pattern “*” is a special token which means to clear the color list of all entries.

Mutt also recognizes the keywords color0, color1, ..., color N-1 (N being the number of colors supported by your terminal). This is useful when you remap the colors for your display (for example by changing the color associated with color2 for your xterm), since color names may then lose their normal meaning.

If your terminal does not support color, it is still possible change the video attributes through the use of the “mono” command. Usage:

`mono` `object` `attribute`
`mono` { `header` | `body` } `attribute` `regexp`
`mono` `index` `attribute` `pattern`
`mono` `compose` `composeobject` `attribute`
`unmono` { `index` | `header` | `body` } { `*` | `pattern` ... }

For object, composeobject, and attribute, see the color command.

## 12. Message Header Display

### 12.1. Header Display

When displaying a message in the pager, Mutt folds long header lines at $wrap columns. Though there're precise rules about where to break and how, Mutt always folds headers using a tab for readability. (Note that the sending side is not affected by this, Mutt tries to implement standards compliant folding.)

### 12.2. Selecting Headers

Usage:

`ignore` `pattern` [ `pattern` ...]
`unignore` { `*` | `pattern` ... }

Messages often have many header fields added by automatic processing systems, or which may not seem useful to display on the screen. This command allows you to specify header fields which you don't normally want to see in the pager.

You do not need to specify the full header field name. For example, “ignore content-” will ignore all header fields that begin with the pattern “content-”. “ignore *” will ignore all headers.

To remove a previously added token from the list, use the “unignore” command. The “unignore” command will make Mutt display headers with the given pattern. For example, if you do “ignore x-” it is possible to “unignore x-mailer”.

“unignore *” will remove all tokens from the ignore list.

Example 3.11. Header weeding

    # Sven's draconian header weeding
    ignore *
    unignore from date subject to cc
    unignore organization organisation x-mailer: x-newsreader: x-mailing-list:
    unignore posted-to:

### 12.3. Ordering Displayed Headers

Usage:

`hdr_order` `header` [ `header` ...]
`unhdr_order` { `*` | `header` ... }

With the hdr_order command you can specify an order in which Mutt will attempt to present these headers to you when viewing messages.

“unhdr_order *” will clear all previous headers from the order list, thus removing the header order effects set by the system-wide startup file.

Example 3.12. Configuring header display order

    hdr_order From Date: From: To: Cc: Subject:

## 13. Alternative Addresses

Usage:

`alternates` [ `-group` `name` ...] `regexp` [ `regexp` ...]
`unalternates` [ `-group` `name` ...] { `*` | `regexp` ... }

With various functions, Mutt will treat messages differently, depending on whether you sent them or whether you received them from someone else. For instance, when replying to a message that you sent to a different party, Mutt will automatically suggest to send the response to the original message's recipients — responding to yourself won't make much sense in many cases. (See $reply_to.)

Many users receive e-mail under a number of different addresses. To fully use Mutt's features here, the program must be able to recognize what e-mail addresses you receive mail under. That's the purpose of the alternates command: It takes a list of regular expressions, each of which can identify an address under which you receive e-mail.

As addresses are matched using regular expressions and not exact strict comparisons, you should make sure you specify your addresses as precise as possible to avoid mismatches. For example, if you specify:

    alternates user@example

Mutt will consider “`some-user@example`” as being your address, too which may not be desired. As a solution, in such cases addresses should be specified as:

    alternates '^user@example$'

The `-group` flag causes all of the subsequent regular expressions to be added to the named group.

The unalternates command can be used to write exceptions to alternates patterns. If an address matches something in an alternates command, but you nonetheless do not think it is from you, you can list a more precise pattern under an unalternates command.

To remove a regular expression from the alternates list, use the unalternates command with exactly the same regexp. Likewise, if the regexp for an alternates command matches an entry on the unalternates list, that unalternates entry will be removed. If the regexp for unalternates is “*”, all entries on alternates will be removed.

## 14. Mailing Lists

Usage:

`lists` [ `-group` `name` ...] `regexp` [ `regexp` ...]
`unlists` { `*` | `regexp` ... }
`subscribe` [ `-group` `name` ...] `regexp` [ `regexp` ...]
`unsubscribe` { `*` | `regexp` ... }

Mutt has a few nice features for handling mailing lists. In order to take advantage of them, you must specify which addresses belong to mailing lists, and which mailing lists you are subscribed to. Mutt also has limited support for auto-detecting mailing lists: it supports parsing `mailto:` links in the common `List-Post:` header which has the same effect as specifying the list address via the lists command (except the group feature). Once you have done this, the `<list-reply>` function will work for all known lists. Additionally, when you send a message to a known list and $followup_to is set, Mutt will add a Mail-Followup-To header. For unsubscribed lists, this will include your personal address, ensuring you receive a copy of replies. For subscribed mailing lists, the header will not, telling other users' mail user agents not to send copies of replies to your personal address.

### Note

The Mail-Followup-To header is a non-standard extension which is not supported by all mail user agents. Adding it is not bullet-proof against receiving personal CCs of list messages. Also note that the generation of the Mail-Followup-To header is controlled by the $followup_to configuration variable since it's common practice on some mailing lists to send Cc upon replies (which is more a group- than a list-reply).

More precisely, Mutt maintains lists of patterns for the addresses of known and subscribed mailing lists. Every subscribed mailing list is known. To mark a mailing list as known, use the list command. To mark it as subscribed, use subscribe.

You can use regular expressions with both commands. To mark all messages sent to a specific bug report's address on Debian's bug tracking system as list mail, for instance, you could say

    subscribe [0-9]+.*@bugs.debian.org

as it's often sufficient to just give a portion of the list's e-mail address.

Specify as much of the address as you need to remove ambiguity. For example, if you've subscribed to the Mutt mailing list, you will receive mail addressed to `mutt-users@mutt.org`. So, to tell Mutt that this is a mailing list, you could add `lists mutt-users@` to your initialization file. To tell Mutt that you are subscribed to it, add `subscribe mutt-users` to your initialization file instead. If you also happen to get mail from someone whose address is `mutt-users@example.com`, you could use `lists ^mutt-users@mutt\\.org$` or `subscribe ^mutt-users@mutt\\.org$` to match only mail from the actual list.

The `-group` flag adds all of the subsequent regular expressions to the named address group in addition to adding to the specified address list.

The “unlists” command is used to remove a token from the list of known and subscribed mailing-lists. Use “unlists *” to remove all tokens.

To remove a mailing list from the list of subscribed mailing lists, but keep it on the list of known mailing lists, use unsubscribe.

## 15. Using Multiple Spool Mailboxes

Usage:

`mbox-hook` `[!]regexp` `mailbox`

This command is used to move read messages from a specified mailbox to a different mailbox automatically when you quit or change folders. regexp is a regular expression specifying the mailbox to treat as a “spool” mailbox and mailbox specifies where mail should be saved when read.

The regexp parameter has mailbox shortcut expansion performed on the first character. See Mailbox Matching in Hooks for more details.

Note that execution of mbox-hooks is dependent on the $move configuration variable. If set to “no” (the default), mbox-hooks will not be executed.

Unlike some of the other hook commands, only the first matching regexp is used (it is not possible to save read mail in more than a single mailbox).

## 16. Monitoring Incoming Mail

Usage:

`mailboxes` [ [ `-poll` | `-nopoll` ] [ `-label` `label` | `-nolabel` ] `mailbox` ] [...]
`unmailboxes` { `*` | `mailbox` ... }

This command specifies folders which can receive mail and which will be checked for new messages periodically.

To disable polling, specify `-nopoll` before the mailbox name. The `-poll` argument can be used to reenable polling for an existing mailbox. If unspecified: a new mailbox will poll by default, while an existing mailbox will be unchanged.

The `-label` argument can be used to specify an alternative label to print in the sidebar or mailbox browser instead of the mailbox path. A label may be removed via the `-nolabel` argument. If unspecified, an existing mailbox label will be unchanged.

mailbox can either be a local file or directory (Mbox/Mmdf or Maildir/Mh). If Mutt was built with POP and/or IMAP support, mailbox can also be a POP/IMAP folder URL. The URL syntax is described in Section 1.2, “URL Syntax”, POP and IMAP are described in Section 3, “POP3 Support” and Section 4, “IMAP Support” respectively.

Mutt provides a number of advanced features for handling (possibly many) folders and new mail within them, please refer to Section 13, “New Mail Detection” for details (including in what situations and how often Mutt checks for new mail). Additionally, $new_mail_command can be used to run a command when new mail is detected.

The “unmailboxes” command is used to remove a token from the list of folders which receive mail. Use “unmailboxes *” to remove all tokens.

### Note

The folders in the mailboxes command are resolved when the command is executed, so if these names contain shortcut characters (such as “=” and “!”), any variable definition that affects these characters (like $folder and $spoolfile) should be set before the mailboxes command. If none of these shortcuts are used, a local path should be absolute as otherwise Mutt tries to find it relative to the directory from where Mutt was started which may not always be desired.

## 17. User-Defined Headers

Usage:

`my_hdr` `string`
`unmy_hdr` { `*` | `field` ... }

The my_hdr command allows you to create your own header fields which will be added to every message you send and appear in the editor if $edit_headers is set.

For example, if you would like to add an “Organization:” header field to all of your outgoing messages, you can put the command something like shown in Example 3.13, “Defining custom headers” in your `.muttrc`.

Example 3.13. Defining custom headers

    my_hdr Organization: A Really Big Company, Anytown, USA

### Note

Space characters are not allowed between the keyword and the colon (“:”). The standard for electronic mail (RFC2822) says that space is illegal there, so Mutt enforces the rule.

If you would like to add a header field to a single message, you should either set the $edit_headers variable, or use the `<edit-headers>` function (default: “E”) in the compose menu so that you can edit the header of your message along with the body.

To remove user defined header fields, use the unmy_hdr command. You may specify an asterisk (“*”) to remove all header fields, or the fields to remove. For example, to remove all “To” and “Cc” header fields, you could use:

    unmy_hdr to cc

## 18. Specify Default Save Mailbox

Usage:

`save-hook` `[!]pattern` `mailbox`

This command is used to override the default mailbox used when saving messages. mailbox will be used as the default if the message matches pattern, see Message Matching in Hooks for information on the exact format.

To provide more flexibility and good defaults, Mutt applies the expandos of $index_format to mailbox after it was expanded.

Example 3.14. Using %-expandos in save-hook

    # default: save all to ~/Mail/<author name>
    save-hook . ~/Mail/%F

    # save from me@turing.cs.hmc.edu and me@cs.hmc.edu to $folder/elkins
    save-hook me@(turing\\.)?cs\\.hmc\\.edu$ +elkins

    # save from aol.com to $folder/spam
    save-hook aol\\.com$ +spam

Also see the fcc-save-hook command.

## 19. Specify Default Fcc: Mailbox When Composing

Usage:

`fcc-hook` `[!]pattern` `mailbox`

This command is used to save outgoing mail in a mailbox other than $record. Mutt searches the initial list of message recipients for the first matching pattern and uses mailbox as the default Fcc: mailbox. If no match is found the message will be saved to $record mailbox.

To provide more flexibility and good defaults, Mutt applies the expandos of $index_format to mailbox after it was expanded.

See Message Matching in Hooks for information on the exact format of pattern.

    fcc-hook [@.]aol\\.com$ +spammers

...will save a copy of all messages going to the aol.com domain to the `+spammers' mailbox by default. Also see the fcc-save-hook command.

Multiple mailboxes may be specified by separating them with $fcc_delimiter, if set:

      set fcc_delimiter = ','
      fcc-hook 'foo@example\.com$' '+one,+two'

## 20. Specify Default Save Filename and Default Fcc: Mailbox at Once

Usage:

`fcc-save-hook` `[!]pattern` `mailbox`

This command is a shortcut, almost equivalent to doing both a fcc-hook and a save-hook with its arguments, including %-expansion on mailbox according to $index_format.

Note, however that the fcc-save-hook is not designed to take advantage of multiple mailboxes, as fcc-hook is. For correct behavior, you should use separate fcc and save hooks in that case.

## 21. Change Settings Based Upon Message Recipients

Usage:

`reply-hook` `[!]pattern` `command`
`send-hook` `[!]pattern` `command`
`send2-hook` `[!]pattern` `command`

These commands can be used to execute arbitrary configuration commands based upon recipients of the message. pattern is used to match the message, see Message Matching in Hooks for details. command is executed when pattern matches.

reply-hook is matched against the message you are replying to, instead of the message you are sending. send-hook is matched against all messages, both new and replies.

### Note

reply-hooks are matched before the send-hook, regardless of the order specified in the user's configuration file. However, you can inhibit send-hook in the reply case by using the pattern `'! ~Q'` (not replied, see Message Matching in Hooks) in the send-hook to tell when reply-hook have been executed.

send2-hook is matched every time a message is changed, either by editing it, or by using the compose menu to change its recipients or subject. send2-hook is executed after send-hook, and can, e.g., be used to set parameters such as the $sendmail variable depending on the message's sender address.

For each type of send-hook or reply-hook, when multiple matches occur, commands are executed in the order they are specified in the `.muttrc` (for that type of hook).

Example: `send-hook mutt "set mime_forward signature=''"`

Another typical use for this command is to change the values of the $attribution, $attribution_locale, and $signature variables in order to change the language of the attributions and signatures based upon the recipients.

### Note

send-hook's are only executed once after getting the initial list of recipients. They are not executed when resuming a postponed draft. Adding a recipient after replying or editing the message will not cause any send-hook to be executed, similarly if $autoedit is set (as then the initial list of recipients is empty). Also note that my_hdr commands which modify recipient headers, or the message's subject, don't have any effect on the current message when executed from a send-hook.

## 22. Change Settings Before Formatting a Message

Usage:

`message-hook` `[!]pattern` `command`

This command can be used to execute arbitrary configuration commands before viewing or formatting a message based upon information about the message. command is executed if the pattern matches the message to be displayed. When multiple matches occur, commands are executed in the order they are specified in the `.muttrc`.

See Message Matching in Hooks for information on the exact format of pattern.

Example:

    message-hook ~A 'set pager=builtin'
    message-hook '~f freshmeat-news' 'set pager="less \"+/^  subject: .*\""'

## 23. Choosing the Cryptographic Key of the Recipient

Usage:

`crypt-hook` `regexp` `keyid`

When encrypting messages with PGP/GnuPG or OpenSSL, you may want to associate a certain key with a given e-mail address automatically, either because the recipient's public key can't be deduced from the destination address, or because, for some reasons, you need to override the key Mutt would normally use. The crypt-hook command provides a method by which you can specify the ID of the public key to be used when encrypting messages to a certain recipient. You may use multiple crypt-hooks with the same regexp; multiple matching crypt-hooks result in the use of multiple keyids for a recipient. During key selection, Mutt will confirm whether each crypt-hook is to be used (unless the $crypt_confirmhook option is unset). If all crypt-hooks for a recipient are declined, Mutt will use the original recipient address for key selection instead.

The meaning of keyid is to be taken broadly in this context: You can either put a numerical key ID or fingerprint here, an e-mail address, or even just a real name.

## 24. Dynamically Changing $index_format using Patterns

Usage:

`index-format-hook` `name` `[!]pattern` `format-string`

This command is used to inject format strings dynamically into $index_format based on pattern matching against the current message.

The $index_format expando %@name@ specifies a placeholder for the injection. Index-format-hooks with the same name are matched using pattern against the current message. Matching is done in the order specified in the .muttrc, with the first match being used. The hook's format-string is then substituted and evaluated.

Because the first match is used, best practice is to put a catch-all ~A pattern as the last hook. Here is an example showing how to implement dynamic date formatting:

    set index_format="%4C %-6@date@ %-15.15F %Z (%4c) %s"

    index-format-hook  date  "~d<1d"    "%[%H:%M]"
    index-format-hook  date  "~d<1m"    "%[%a %d]"
    index-format-hook  date  "~d<1y"    "%[%b %d]"
    index-format-hook  date  "~A"       "%[%m/%y]"

Another example, showing a way to prepend to the subject. Note that without a catch-all ~A pattern, no match results in the expando being replaced with an empty string.

    set index_format="%4C %@subj_flags@%s"

    index-format-hook  subj_flags  "~f boss@example.com"    "** BOSS ** "
    index-format-hook  subj_flags  "~f spouse@example.com"  ":-) "

## 25. Adding Key Sequences to the Keyboard Buffer

Usage:

`push` `string`

This command adds the named string to the beginning of the keyboard buffer. The string may contain control characters, key names and function names like the sequence string in the macro command. You may use it to automatically run a sequence of commands at startup, or when entering certain folders. For example, Example 3.15, “Embedding push in folder-hook” shows how to automatically collapse all threads when entering a folder.

Example 3.15. Embedding push in folder-hook

    folder-hook . 'push <collapse-all>'

For using functions like shown in the example, it's important to use angle brackets (“<” and “>”) to make Mutt recognize the input as a function name. Otherwise it will simulate individual just keystrokes, i.e. “`push collapse-all`” would be interpreted as if you had typed “c”, followed by “o”, followed by “l”, ..., which is not desired and may lead to very unexpected behavior.

Keystrokes can be used, too, but are less portable because of potentially changed key bindings. With default bindings, this is equivalent to the above example:

    folder-hook . 'push \eV'

because it simulates that Esc+V was pressed (which is the default binding of `<collapse-all>`).

## 26. Executing Functions

Usage:

`exec` `function` [ `function` ...]

This command can be used to execute any function. Functions are listed in the function reference. “exec `function`” is equivalent to “`push <function>`”.

## 27. Message Scoring

Usage:

`score` `pattern` `value`
`unscore` { `*` | `pattern` ... }

The score commands adds value to a message's score if pattern matches it. pattern is a string in the format described in the patterns section (note: For efficiency reasons, patterns which scan information not available in the index, such as `~b`, `~B`, `~h`, `~M`, or `~X` may not be used). value is a positive or negative integer. A message's final score is the sum total of all matching score entries. However, you may optionally prefix value with an equal sign (“=”) to cause evaluation to stop at a particular entry if there is a match. Negative final scores are rounded up to 0.

The unscore command removes score entries from the list. You must specify the same pattern specified in the score command for it to be removed. The pattern “*” is a special token which means to clear the list of all score entries.

Scoring occurs as the messages are read in, before the mailbox is sorted. Because of this, patterns which depend on threading, such as ~=, ~$, and ~(), will not work by default. A workaround is to push the scoring command in a folder hook. This will cause the mailbox to be rescored after it is opened and input starts being processed:

    folder-hook . 'push "<enter-command>score ~= 10<enter>"'

## 28. Spam Detection

Usage:

`spam` `pattern` `format`
`nospam` { `*` | `pattern` }

Mutt has generalized support for external spam-scoring filters. By defining your spam patterns with the spam and `nospam` commands, you can limit, search, and sort your mail based on its spam attributes, as determined by the external filter. You also can display the spam attributes in your index display using the `%H` selector in the $index_format variable. (Tip: try `%?H?[%H] ?` to display spam tags only when they are defined for a given message.)

Note: the value displayed by `%H` and searched by `~H` is stored in the header cache. Mutt isn't smart enough to invalidate a header cache entry based on changing `spam` rules, so if you aren't seeing correct `%H` values, try temporarily turning off the header cache. If that fixes the problem, then once your spam rules are set to your liking, remove your stale header cache files and turn the header cache back on.

Your first step is to define your external filter's spam patterns using the spam command. pattern should be a regular expression that matches a header in a mail message. If any message in the mailbox matches this regular expression, it will receive a “spam tag” or “spam attribute” (unless it also matches a nospam pattern — see below.) The appearance of this attribute is entirely up to you, and is governed by the format parameter. format can be any static text, but it also can include back-references from the pattern expression. (A regular expression “back-reference” refers to a sub-expression contained within parentheses.) `%1` is replaced with the first back-reference in the regex, `%2` with the second, etc.

To match spam tags, mutt needs the corresponding header information which is always the case for local and POP folders but not for IMAP in the default configuration. Depending on the spam header to be analyzed, $imap_headers may need to be adjusted.

If you're using multiple spam filters, a message can have more than one spam-related header. You can define spam patterns for each filter you use. If a message matches two or more of these patterns, and the $spam_separator variable is set to a string, then the message's spam tag will consist of all the format strings joined together, with the value of $spam_separator separating them.

For example, suppose one uses DCC, SpamAssassin, and PureMessage, then the configuration might look like in Example 3.16, “Configuring spam detection”.

Example 3.16. Configuring spam detection

    spam "X-DCC-.*-Metrics:.*(....)=many"         "90+/DCC-%1"
    spam "X-Spam-Status: Yes"                     "90+/SA"
    spam "X-PerlMX-Spam: .*Probability=([0-9]+)%" "%1/PM"
    set spam_separator=", "

If then a message is received that DCC registered with “many” hits under the “Fuz2” checksum, and that PureMessage registered with a 97% probability of being spam, that message's spam tag would read `90+/DCC-Fuz2, 97/PM`. (The four characters before “=many” in a DCC report indicate the checksum used — in this case, “Fuz2”.)

If the $spam_separator variable is unset, then each spam pattern match supersedes the previous one. Instead of getting joined format strings, you'll get only the last one to match.

The spam tag is what will be displayed in the index when you use `%H` in the $index_format variable. It's also the string that the `~H` pattern-matching expression matches against for `<search>` and `<limit>` functions. And it's what sorting by spam attribute will use as a sort key.

That's a pretty complicated example, and most people's actual environments will have only one spam filter. The simpler your configuration, the more effective Mutt can be, especially when it comes to sorting.

Generally, when you sort by spam tag, Mutt will sort lexically — that is, by ordering strings alphanumerically. However, if a spam tag begins with a number, Mutt will sort numerically first, and lexically only when two numbers are equal in value. (This is like UNIX's `sort -n`.) A message with no spam attributes at all — that is, one that didn't match any of your spam patterns — is sorted at lowest priority. Numbers are sorted next, beginning with 0 and ranging upward. Finally, non-numeric strings are sorted, with “a” taking lower priority than “z”. Clearly, in general, sorting by spam tags is most effective when you can coerce your filter to give you a raw number. But in case you can't, Mutt can still do something useful.

The nospam command can be used to write exceptions to spam patterns. If a header pattern matches something in a spam command, but you nonetheless do not want it to receive a spam tag, you can list a more precise pattern under a nospam command.

If the pattern given to nospam is exactly the same as the pattern on an existing spam list entry, the effect will be to remove the entry from the spam list, instead of adding an exception. Likewise, if the pattern for a spam command matches an entry on the nospam list, that nospam entry will be removed. If the pattern for nospam is “*”, all entries on both lists will be removed. This might be the default action if you use spam and nospam in conjunction with a folder-hook.

You can have as many spam or nospam commands as you like. You can even do your own primitive spam detection within Mutt — for example, if you consider all mail from `MAILER-DAEMON` to be spam, you can use a spam command like this:

    spam "^From: .*MAILER-DAEMON"       "999"

## 29. Setting and Querying Variables

### 29.1. Variable Types

Mutt supports these types of configuration variables:

boolean

  A boolean expression, either “yes” or “no”.

number

  A signed integer number in the range -32768 to 32767.

number (long)

  A signed integer number in the range -2147483648 to 2147483647.

string

  Arbitrary text.

path

  A specialized string for representing paths including support for mailbox shortcuts (see Section 10, “Mailbox Shortcuts”) as well as tilde (“~”) for a user's home directory and more.

quadoption

  Like a boolean but triggers a prompt when set to “ask-yes” or “ask-no” with “yes” and “no” preselected respectively.

sort order

  A specialized string allowing only particular words as values depending on the variable.

regular expression

  A regular expression, see Section 2, “Regular Expressions” for an introduction.

folder magic

  Specifies the type of folder to use: mbox, mmdf, mh or maildir. Currently only used to determine the type for newly created folders.

e-mail address

  An e-mail address either with or without realname. The older “`user@example.org (Joe User)`” form is supported but strongly deprecated.

user-defined

  Arbitrary text, see Section 29.3, “User-Defined Variables” for details.

### 29.2. Commands

The following commands are available to manipulate and query variables:

Usage:

`set` { [ `no` | `inv` ] `variable` | `variable=value` } [...]
`toggle` `variable` [ `variable` ...]
`unset` `variable` [ `variable` ...]
`reset` `variable` [ `variable` ...]

This command is used to set (and unset) configuration variables. There are four basic types of variables: boolean, number, string and quadoption. boolean variables can be set (true) or unset (false). number variables can be assigned a positive integer value. string variables consist of any number of printable characters and must be enclosed in quotes if they contain spaces or tabs. You may also use the escape sequences “\n” and “\t” for newline and tab, respectively. quadoption variables are used to control whether or not to be prompted for certain actions, or to specify a default action. A value of yes will cause the action to be carried out automatically as if you had answered yes to the question. Similarly, a value of no will cause the action to be carried out as if you had answered “no.” A value of ask-yes will cause a prompt with a default answer of “yes” and ask-no will provide a default answer of “no.”

Prefixing a variable with “no” will unset it. Example: `set noaskbcc`.

For boolean variables, you may optionally prefix the variable name with `inv` to toggle the value (on or off). This is useful when writing macros. Example: `set invsmart_wrap`.

The toggle command automatically prepends the `inv` prefix to all specified variables.

The unset command automatically prepends the `no` prefix to all specified variables.

Using the `<enter-command>` function in the index menu, you can query the value of a variable by prefixing the name of the variable with a question mark:

    set ?allow_8bit

The question mark is actually only required for boolean and quadoption variables.

The reset command resets all given variables to the compile time defaults (hopefully mentioned in this manual). If you use the command set and prefix the variable with “&” this has the same behavior as the reset command.

With the reset command there exists the special variable “all”, which allows you to reset all variables to their system defaults.

### 29.3. User-Defined Variables

#### 29.3.1. Introduction

Along with the variables listed in the Configuration variables section, Mutt supports user-defined variables with names starting with `my_` as in, for example, `my_cfgdir`.

The set command either creates a custom `my_` variable or changes its value if it does exist already. The unset and reset commands remove the variable entirely.

Since user-defined variables are expanded in the same way that environment variables are (except for the shell-escape command and backtick expansion), this feature can be used to make configuration files more readable.

#### 29.3.2. Examples

The following example defines and uses the variable `my_cfgdir` to abbreviate the calls of the source command:

Example 3.17. Using user-defined variables for config file readability

    set my_cfgdir = $HOME/mutt/config

    source $my_cfgdir/hooks
    source $my_cfgdir/macros
    # more source commands...

A custom variable can also be used in macros to backup the current value of another variable. In the following example, the value of the $delete is changed temporarily while its original value is saved as `my_delete`. After the macro has executed all commands, the original value of $delete is restored.

Example 3.18. Using user-defined variables for backing up other config option values

    macro pager ,x '\
    <enter-command>set my_delete=$delete<enter>\
    <enter-command>set delete=yes<enter>\
    ...\
    <enter-command>set delete=$my_delete<enter>'

Since Mutt expands such values already when parsing the configuration file(s), the value of `$my_delete` in the last example would be the value of $delete exactly as it was at that point during parsing the configuration file. If another statement would change the value for $delete later in the same or another file, it would have no effect on `$my_delete`. However, the expansion can be deferred to runtime, as shown in the next example, when escaping the dollar sign.

Example 3.19. Deferring user-defined variable expansion to runtime

    macro pager <PageDown> "\
    <enter-command> set my_old_pager_stop=\$pager_stop pager_stop<Enter>\
    <next-page>\
    <enter-command> set pager_stop=\$my_old_pager_stop<Enter>\
    <enter-command> unset my_old_pager_stop<Enter>"

Note that there is a space between `<enter-command>` and the set configuration command, preventing Mutt from recording the macro's commands into its history.

### 29.4. Type Conversions

Variables are always assigned string values which Mutt parses into its internal representation according to the type of the variable, for example an integer number for numeric types. For all queries (including $-expansion) the value is converted from its internal type back into string. As a result, any variable can be assigned any value given that its content is valid for the target. This also counts for custom variables which are of type string. In case of parsing errors, Mutt will print error messages. Example 3.20, “Type conversions using variables” demonstrates type conversions.

Example 3.20. Type conversions using variables

    set my_lines = "5"                # value is string "5"
    set pager_index_lines = $my_lines # value is integer 5

    set my_sort = "date-received"     # value is string "date-received"
    set sort = "last-$my_sort"        # value is sort last-date-received

    set my_inc = $read_inc            # value is string "10" (default of $read_inc)
    set my_foo = $my_inc              # value is string "10"

These assignments are all valid. If, however, the value of `$my_lines` would have been “five” (or something else that cannot be parsed into a number), the assignment to `$pager_index_lines` would have produced an error message.

Type conversion applies to all configuration commands which take arguments. But please note that every expanded value of a variable is considered just a single token. A working example is:

    set my_pattern = "~A"
    set my_number = "10"

    # same as: score ~A +10
    score $my_pattern +$my_number

What does not work is:

    set my_mx = "+mailbox1 +mailbox2"
    mailboxes $my_mx +mailbox3

because the value of `$my_mx` is interpreted as a single mailbox named “+mailbox1 +mailbox2” and not two distinct mailboxes.

## 30. Reading Initialization Commands From Another File

Usage:

`source` `filename`

This command allows the inclusion of initialization commands from other files. For example, I place all of my aliases in `~/.mail_aliases` so that I can make my `~/.muttrc` readable and keep my aliases private.

If the filename begins with a tilde (“~”), it will be expanded to the path of your home directory.

If the filename ends with a vertical bar (“|”), then filename is considered to be an executable program from which to read input (e.g. `source ~/bin/myscript|`).

## 31. Removing Hooks

Usage:

`unhook` { `*` | `hook-type` }

This command permits you to flush hooks you have previously defined. You can either remove all hooks by giving the “*” character as an argument, or you can remove all hooks of a specific type by saying something like `unhook send-hook`.

## 32. Format Strings

### 32.1. Basic usage

Format strings are a general concept you'll find in several locations through the Mutt configuration, especially in the $index_format, $pager_format, $status_format, and other related variables. These can be very straightforward, and it's quite possible you already know how to use them.

The most basic format string element is a percent symbol followed by another character. For example, `%s` represents a message's Subject: header in the $index_format variable. The “expandos” available are documented with each format variable, but there are general modifiers available with all formatting expandos, too. Those are our concern here.

Some of the modifiers are borrowed right out of C (though you might know them from Perl, Python, shell, or another language). These are the `[-]m.n` modifiers, as in `%-12.12s`. As with such programming languages, these modifiers allow you to specify the minimum and maximum size of the resulting string, as well as its justification. If the “-” sign follows the percent, the string will be left-justified instead of right-justified. If there's a number immediately following that, it's the minimum amount of space the formatted string will occupy — if it's naturally smaller than that, it will be padded out with spaces. If a decimal point and another number follow, that's the maximum space allowable — the string will not be permitted to exceed that width, no matter its natural size. Each of these three elements is optional, so that all these are legal format strings: `%-12s`, `%4c`, `%.15F` and `%-12.15L`.

Mutt adds some other modifiers to format strings. If you use an equals symbol (`=`) as a numeric prefix (like the minus above), it will force the string to be centered within its minimum space range. For example, `%=14y` will reserve 14 characters for the %y expansion — that's the X-Label: header, in $index_format. If the expansion results in a string less than 14 characters, it will be centered in a 14-character space. If the X-Label for a message were “test”, that expansion would look like “ test ”.

There are two very little-known modifiers that affect the way that an expando is replaced. If there is an underline (“_”) character between any format modifiers (as above) and the expando letter, it will expands in all lower case. And if you use a colon (“:”), it will replace all decimal points with underlines.

### 32.2. Conditionals

Depending on the format string variable, some of its sequences can be used to optionally print a string if their value is nonzero. For example, you may only want to see the number of flagged messages if such messages exist, since zero is not particularly meaningful. To optionally print a string based upon one of the above sequences, the following construct is used:

    %?<sequence_char>?<optional_string>?

where sequence_char is an expando, and optional_string is the string you would like printed if sequence_char is nonzero. optional_string may contain other sequences as well as normal text, but you may not nest optional strings.

Here is an example illustrating how to optionally print the number of new messages in a mailbox in $status_format:

    %?n?%n new messages.?

You can also switch between two strings using the following construct:

    %?<sequence_char>?<if_string>&<else_string>?

If the value of sequence_char is non-zero, if_string will be expanded, otherwise else_string will be expanded.

### 32.3. Filters

Any format string ending in a vertical bar (“|”) will be expanded and piped through the first word in the string, using spaces as separator. The string returned will be used for display. If the returned string ends in %, it will be passed through the formatter a second time. This allows the filter to generate a replacement format string including % expandos.

All % expandos in a format string are expanded before the script is called so that:

Example 3.21. Using external filters in format strings

    set status_format="script.sh '%r %f (%L)'|"

will make Mutt expand `%r`, `%f` and `%L` before calling the script. The example also shows that arguments can be quoted: the script will receive the expanded string between the single quotes as the only argument.

A practical example is the `mutt_xtitle` script installed in the `samples` subdirectory of the Mutt documentation: it can be used as filter for $status_format to set the current terminal's title, if supported.

### 32.4. Padding

In most format strings, Mutt supports different types of padding using special %-expandos:

`%|X`

  When this occurs, Mutt will fill the rest of the line with the character `X`. For example, filling the rest of the line with dashes is done by setting:

      set status_format = "%v on %h: %B: %?n?%n&no? new messages %|-"

`%>X`

  Since the previous expando stops at the end of line, there must be a way to fill the gap between two items via the `%>X` expando: it puts as many characters `X` in between two items so that the rest of the line will be right-justified. For example, to not put the version string and hostname the above example on the left but on the right and fill the gap with spaces, one might use (note the space after `%>`):

      set status_format = "%B: %?n?%n&no? new messages %> (%v on %h)"

`%*X`

  Normal right-justification will print everything to the left of the `%>`, displaying padding and whatever lies to the right only if there's room. By contrast, “soft-fill” gives priority to the right-hand side, guaranteeing space to display it and showing padding only if there's still room. If necessary, soft-fill will eat text leftwards to make room for rightward text. For example, to right-justify the subject making sure as much as possible of it fits on screen, one might use (note two spaces after `%*` : the second ensures there's a space between the truncated right-hand side and the subject):

      set index_format="%4C %Z %{%b %d} %-15.15L (%?l?%4l&%4c?)%*  %s"

### 32.5. Bytes size display

Various format strings contain expandos that display the size of messages in bytes. This includes `%s` in $attach_format, `%l` in $compose_format, `%s` in $folder_format, `%c` in $index_format, and %l and %L in $status_format. There are four configuration variables that can be used to customize how the numbers are displayed.

$size_show_bytes will display the number of bytes when the size is < 1 kilobyte. When unset, kilobytes will be displayed instead.

$size_show_mb will display the number of megabytes when the size is >= 1 megabyte. When unset, kilobytes will be displayed instead (which could be a large number).

$size_show_fractions, will display numbers with a single decimal place for values from 0 to 10 kilobytes, and 1 to 10 megabytes.

$size_units_on_left will display the unit (“K” or “M”) to the left of the number, instead of the right if unset.

These variables also affect size display in a few other places, such as progress indicators and attachment delimiters in the pager.

## 33. Control allowed header fields in a mailto: URL

Usage:

`mailto_allow` { `*` | `header-field` ... }
`unmailto_allow` { `*` | `header-field` ... }

As a security measure, Mutt will only add user-approved header fields from a `mailto:` URL. This is necessary since Mutt will handle certain header fields, such as `Attach:`, in a special way. The `mailto_allow` and `unmailto_allow` commands allow the user to modify the list of approved headers.

Mutt initializes the default list to contain only the `Subject` and `Body` header fields, which are the only requirement specified by the `mailto:` specification in RFC2368.

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