Mutt has a built-in line editor for inputting text, e.g. email addresses or filenames. The keys used to manipulate text input are very similar to those of Emacs. See Table 2.2, “Most common line editor keys” for a full reference of available functions, their default key bindings, and short descriptions.

You can remap the editor functions using the bind command. For example, to make the <Delete> key delete the character in front of the cursor rather than under, you could use:

bind editor <delete> backspace

Mutt maintains a history for the built-in editor. The number of items is controlled by the $history variable and can be made persistent using an external file specified using $history_file. You may cycle through them at an editor prompt by using the <history-up> and/or <history-down> commands.

Mutt maintains several distinct history lists, one for each of the following categories:

Mutt automatically filters out repeated items from the history. It also mimics the behavior of some shells by ignoring items starting with a space. The latter feature can be useful in macros to not clobber the history's valuable entries with unwanted entries.

Common keys used to navigate through and manage messages in the index are shown in Table 2.3, “Most common message index keys”. How messages are presented in the index menu can be customized using the $index_format variable.

In addition to who sent the message and the subject, a short summary of the disposition of each message is printed beside the message number. Zero or more of the “flags” in Table 2.4, “Message status flags” may appear, some of which can be turned on or off using these functions: <set-flag> and <clear-flag> bound by default to “w” and “W” respectively.

Furthermore, the flags in Table 2.5, “Message recipient flags” reflect who the message is addressed to. They can be customized with the $to_chars variable.

By default, Mutt uses its builtin pager to display the contents of messages. The pager is very similar to the Unix program less though not nearly as featureful.

In addition to key bindings in Table 2.6, “Most common pager keys”, many of the functions from the index menu are also available in the pager, such as <delete-message> or <copy-message> (this is one advantage over using an external pager to view messages).

Also, the internal pager supports a couple other advanced features. For one, it will accept and translate the “standard” nroff sequences for bold and underline. These sequences are a series of either the letter, backspace (^H), the letter again for bold or the letter, backspace, “_” for denoting underline. Mutt will attempt to display these in bold and underline respectively if your terminal supports them. If not, you can use the bold and underline color objects to specify a color or mono attribute for them.

Additionally, the internal pager supports the ANSI escape sequences for character attributes. Mutt translates them into the correct color and character settings. The sequences Mutt supports are:

\e[Ps;Ps;..Ps;m

where Ps can be one of the codes shown in Table 2.7, “ANSI escape sequences”.

Mutt uses these attributes for handling text/enriched messages, and they can also be used by an external autoview script for highlighting purposes.

When the mailbox is sorted by threads, there are a few additional functions available in the index and pager modes as shown in Table 2.9, “Most common thread mode keys”.

See also: $strict_threads.

In addition, the index and pager menus have these interesting functions:

The bindings shown in Table 2.10, “Most common mail sending keys” are available in the index and pager to start a new message.

Bouncing a message sends the message as-is to the recipient you specify. Forwarding a message allows you to add comments or modify the message you are forwarding. These items are discussed in greater detail in the next chapter “Forwarding and Bouncing Mail.”

Mutt will then enter the compose menu and prompt you for the recipients to place on the “To:” header field. Next, it will ask you for the “Subject:” field for the message, providing a default if you are replying to or forwarding a message. See also $askcc, $askbcc, $autoedit, $bounce, $fast_reply, and $include for changing how Mutt asks these questions.

Mutt will then automatically start your $editor on the message body. If the $edit_headers variable is set, the headers will be at the top of the message in your editor. Any messages you are replying to will be added in sort order to the message, with appropriate $attribution, $indent_string and $post_indent_string. When forwarding a message, if the $mime_forward variable is unset, a copy of the forwarded message will be included. If you have specified a $signature, it will be appended to the message.

Once you have finished editing the body of your mail message, you are returned to the compose menu providing the functions shown in Table 2.11, “Most common compose menu keys” to modify, send or postpone the message.

The compose menu is also used to edit the attachments for a message which can be either files or other messages. The <attach-message> function to will prompt you for a folder to attach messages from. You can now tag messages in that folder and they will be attached to the message you are sending.

When editing the header because of $edit_headers being set, there are a several pseudo headers available which will not be included in sent messages.

If you have told mutt to PGP or S/MIME encrypt a message, it will guide you through a key selection process when you try to send the message. Mutt will not ask you any questions about keys which have a certified user ID matching one of the message recipients' mail addresses. However, there may be situations in which there are several keys, weakly certified user ID fields, or where no matching keys can be found.

In these cases, you are dropped into a menu with a list of keys from which you can select one. When you quit this menu, or mutt can't find any matching keys, you are prompted for a user ID. You can, as usually, abort this prompt using ^G. When you do so, mutt will return to the compose screen.

Once you have successfully finished the key selection, the message will be encrypted using the selected public keys when sent out.

Most fields of the entries in the key selection menu (see also $pgp_entry_format) have obvious meanings. But some explanations on the capabilities, flags, and validity fields are in order.

The flags sequence (%f) will expand to one of the flags in Table 2.12, “PGP key menu flags”.

The capabilities field (%c) expands to a two-character sequence representing a key's capabilities. The first character gives the key's encryption capabilities: A minus sign (“-”) means that the key cannot be used for encryption. A dot (“.”) means that it's marked as a signature key in one of the user IDs, but may also be used for encryption. The letter “e” indicates that this key can be used for encryption.

The second character indicates the key's signing capabilities. Once again, a “-” implies “not for signing”, “.” implies that the key is marked as an encryption key in one of the user-ids, and “s” denotes a key which can be used for signing.

Finally, the validity field (%t) indicates how well-certified a user-id is. A question mark (“?”) indicates undefined validity, a minus character (“-”) marks an untrusted association, a space character means a partially trusted association, and a plus character (“+”) indicates complete validity.

You may also have compiled mutt to co-operate with Mixmaster, an anonymous remailer. Mixmaster permits you to send your messages anonymously using a chain of remailers. Mixmaster support in mutt is for mixmaster version 2.04 (beta 45 appears to be the latest) and 2.03. It does not support earlier versions or the later so-called version 3 betas, of which the latest appears to be called 2.9b23.

To use it, you'll have to obey certain restrictions. Most important, you cannot use the Cc and Bcc headers. To tell Mutt to use mixmaster, you have to select a remailer chain, using the mix function on the compose menu.

The chain selection screen is divided into two parts. In the (larger) upper part, you get a list of remailers you may use. In the lower part, you see the currently selected chain of remailers.

You can navigate in the chain using the <chain-prev> and <chain-next> functions, which are by default bound to the left and right arrows and to the h and l keys (think vi keyboard bindings). To insert a remailer at the current chain position, use the <insert> function. To append a remailer behind the current chain position, use <select-entry> or <append>. You can also delete entries from the chain, using the corresponding function. Finally, to abandon your changes, leave the menu, or <accept> them pressing (by default) the Return key.

Note that different remailers do have different capabilities, indicated in the %c entry of the remailer menu lines (see $mix_entry_format). Most important is the “middleman” capability, indicated by a capital “M”: This means that the remailer in question cannot be used as the final element of a chain, but will only forward messages to other mixmaster remailers. For details on the other capabilities, please have a look at the mixmaster documentation.