\%S-NAIL(1)

." ."

NAME
\%S-nail v14.4.5 - send and receive Internet mail

SYNOPSIS
\%s-nail [-BDdEFintv~] [-A account] [-a attachment] [-b bcc-addr] [-c cc-addr] [-O mta-option] [-q quote-file] [-r from-addr] [-S variable[=value]] [-s subject] to-addr ...
\%s-nail [-BDdEeHiNnRv~#] [-A account] [-S variable[=value]] -f [file]
\%s-nail [-BDdEeiNnRv~#] [-A account] [-S variable[=value]] [-u user]

DESCRIPTION
\%S-nail is a mail processing system with a command syntax reminiscent of ed(1) with lines replaced by messages. It is based on Heirloom mailx that is based upon Berkeley Mail 8.1, is intended to provide the functionality of the POSIX mailx(1) command and offers (mostly optional) extensions for IDNA, MIME, S/MIME, SMTP, POP3 and IMAP. It is usable as a mail batch language.

In the following list of supported command line options, -D, -d, -E, -i, -N and -v are implemented by means of setting the respective option, as via -S.

-A account
    Executes an account command (see below) for account after the startup files have been read.

-a file
    Attach the given file to the message. The same filename conventions as described in the section Commands apply.

-B  Make standard input and standard output line-buffered.

-b address
    Send blind carbon copies to the given list of addresses. Sending mail below goes into more detail on that.

-c address
    Send carbon copies to the given list of addresses.

-D  [Optional] Set the disconnected variable.

-d  Set the debug variable, which enables debug messages and disables message delivery. Note that this is not a real `sandbox' mode.

-E  Set the skipemptybody variable and thus discard messages with an empty message part body. This is useful for sending messages from scripts.

-e  Just check if mail is present in the system mailbox. If yes, return an exit status of zero, a non-zero value otherwise.

-F  Save the message to send in a file named after the local part of the first recipient's address.

-f [file]
    Read in the contents of the user's mbox (or the specified file) for processing; when \%S-nail is quit, it writes undeleted messages back to this file. The string file is interpreted as described for the folder command below. Note that file is not a direct argument to the flag -f, but is instead taken from the command line after option processing has been completed.

-H  Print header summaries for all messages and exit.

-i  Set the ignore variable to ignore tty interrupt signals.

-N  Unset the header variable and thus inhibits the initial display of message headers when reading mail or editing a mail folder.

-n  Inhibits reading \%/etc/s-nail.rc upon startup. This option should be activated for \%S-nail scripts that are invoked on more than one machine, because the contents of that file may differ between them. (The same behaviour can be achieved by setting the NAIL_NO_SYSTEM_RC environment variable.)

-O mta-option
    Pass the given option through to the mail-transfer-agent (MTA). This option has no effect when mail is send via SMTP. E.g., use `-O-h -Onumber' to specify the hop count for an old sendmail(1). Options set like that persist for an entire (interactive) session.

-q file
    Start the message with the contents of the specified file. May be given in send mode only.

-R  Opens any folders read-only.

-r address
    Sets the envelope sender address by passing an -r option to the MTA when a message is send. If a non-empty address argument is given it'll be checked for validity and then fixated to the given value, but otherwise the content of the variable from will be used for that purpose – i.e., it'll be passed through to the MTA via the -r option whenever a message is send. A valid non-empty value will also be set as if an additional `-Sfrom=VALUE' option had been used and therefore affect sending of messages via SMTP (as a consideration for `From:').

-S variable[=value]
    Sets the internal option variable and, in case of a value option, assigns value to it. Even though options set via -S may be overwritten from within resource files, the command line setting will be reestablished after all resources have been loaded.

-s subject
    Specify the subject on the command line (be careful to quote subjects containing spaces).

-t  The message to be sent is expected to contain a message header with `To:', `Cc:', or `Bcc:' fields giving its recipients and `Subject:' giving the subject of the message. Recipients and subject specified on the command line are ignored.

-u user
    Reads the mailbox of the given user name. Note that using this option changes the expansion of `%' so that dynamical changes of the folder variables etc. are not reflected.

-V  Print \%S-nail's version and exit.

-v  Sets the verbose option, which enables more verbose messages.

-~  Enable tilde escapes even if not in interactive mode.

-#  This sets multiple options to prepare \%S-nail for working in batch mode (most likely in non-interactive mode): dot, emptystart, noheader, sendwait; it also enables processing of tilde escapes. E.g., the following should send an email message to `alias'.

        printf 'm alias\n~s Subject\nBody\n.\nx\n' | MAILRC=/dev/null s-nail -n -#

  Sending mail
To send a message to one or more people, \%S-nail can be invoked with arguments which are the names of people to whom the mail will be sent. These names may be alias es, plain addresses or full address specifications including user names and comments, in which case care for proper quoting may be necessary. If this manual refers to a list of addresses, then \%S-nail expects a comma-separated list of such names. The section Recipient address specifications below explains the interpretation of names in more detail. The user is then expected to type in his message, followed by a `control-D' at the beginning of a line. The section Replying to or originating mail describes some features of \%S-nail available to help when composing letters.

  Reading mail
In normal usage \%S-nail is given no arguments and checks the user's mail out of the post office, then prints out a one line header of each message found. The current message is initially the first message (numbered 1) and can be printed using the print command, which can be abbreviated `p'. The commands `p+' and `p-' move forward to the next and backward to the previous message, respectively, and messages can be addressed directly by specifying their message number, as in `p 1'.

  Disposing of mail
After examining a message the user can delete (`d') the message or reply (`r') to it. Deletion causes the \%S-nail program to forget about the message. This is not irreversible; one can undelete (`u') the message by giving its number, or the \%S-nail session can be ended by giving the exit (`x') command. Deleted messages will, however, usually disappear never to be seen again.

  Specifying messages
Commands such as print and delete can be given a list of message numbers as arguments to apply to a number of messages at once. Thus `delete 1 2' deletes messages 1 and 2, whereas `delete 1-5' will delete the messages 1 through 5. In sorted or threaded mode (see the sort and thread commands), `delete 1-5' will delete the messages that are located between (and including) messages 1 through 5 in the sorted/threaded order, as shown in the header summary. The following special message names exist:

:n  All new messages.

:o  All old messages (any not in state read or new).

:u  All unread messages.

:d  All deleted messages (for the undelete command).

:r  All read messages.

:f  All `flagged' messages.

:a  All answered messages (cf. the markanswered variable).

:t  All messages marked as draft.

:s  [Optional] All messages classified as spam.

file ....
    The current message.

file ...;
    The message that was previously the current message.

file ...,
    The parent message of the current message, that is the message with the Message-ID given in the `In-Reply-To:' field or the last entry of the `References:' field of the current message.

-   The next previous undeleted message, or the next previous deleted message for the undelete command. In sorted/threaded mode, the next previous such message in the sorted/threaded order.

+   The next undeleted message, or the next deleted message for the undelete command. In sorted/threaded mode, the next such message in the sorted/threaded order.

^   The first undeleted message, or the first deleted message for the undelete command. In sorted/threaded mode, the first such message in the sorted/threaded order.

$   The last message. In sorted/threaded mode, the last message in the sorted/threaded order.

&x  In threaded mode, selects the message addressed with x, where x is any other message specification, and all messages from the thread that begins at it. Otherwise it is identical to x. If x is omitted, the thread beginning with the current message is selected.

*   All messages.

`   All messages that were included in the message list for the previous command.

/string
    All messages that contain string in the subject field (case ignored). See also the searchheaders variable. If string is empty, the string from the previous specification of that type is used again.

address
    All messages from address. By default, this is a case-sensitive search for the complete email address. If the allnet variable is set, only the local part of the addresses is evaluated for the comparison. Otherwise if the showname variable is set, a case-sensitive search for the complete real name of a sender is performed. The IMAP-style `(from address)' expression can be used instead if substring matches are desired.

(criterion)
    All messages that satisfy the given IMAP-style SEARCH criterion. This addressing mode is available with all types of folders; for folders not located on IMAP servers, or for servers unable to execute the SEARCH command, \%S-nail will perform the search locally. Strings must be enclosed by double quotes `"' in their entirety if they contain white space or parentheses; within the quotes, only backslash `\' is recognized as an escape character. All string searches are case-insensitive. When the description indicates that the `envelope' representation of an address field is used, this means that the search string is checked against both a list constructed as

        (namesourcelocal-partdomain-part)

    for each address, and the addresses without real names from the respective header field. Criteria can be nested using parentheses.

(criterion1 criterion2 ... criterionN)
    All messages that satisfy all of the given criteria.

(or criterion1 criterion2)
    All messages that satisfy either criterion1 or criterion2, or both. To connect more than two criteria using `or', (or) specifications have to be nested using additional parentheses, as with `(or a (or b c))', since `(or a b c)' really means `((a or b) and c)'. For a simple `or' operation of independent criteria on the lowest nesting level, it is possible to achieve similar effects by using three separate criteria, as with `(a) (b) (c)'.

(not criterion)
    All messages that do not satisfy criterion.

(bccstring)
    All messages that contain string in the `envelope' representation of the `Bcc:' field.

(ccstring)
    All messages that contain string in the `envelope' representation of the `Cc:' field.

(fromstring)
    All messages that contain string in the `envelope' representation of the `From:' field.

(subjectstring)
    All messages that contain string in the `Subject:' field.

(tostring)
    All messages that contain string in the `envelope' representation of the `To:' field.

(header namestring)
    All messages that contain string in the specified Name: field.

(bodystring)
    All messages that contain string in their body.

(textstring)
    All messages that contain string in their header or body.

(larger size)
    All messages that are larger than size (in bytes).

(smaller size)
    All messages that are smaller than size (in bytes).

(before date)
    All messages that were received before date, which must be in the form d[d]-mon-yyyy, where `d' denotes the day of the month as one or two digits, `mon' is the name of the month – one of `Jan', `Feb', `Mar', `Apr', `May', `Jun', `Jul', `Aug', `Sep', `Oct', `Nov', or `Dec', and `yyyy' is the year as four digits, e.g., ``28-Dec-2012''.

(on date)
    All messages that were received on the specified date.

(since date)
    All messages that were received since the specified date.

(sentbefore date)
    All messages that were sent on the specified date.

(senton date)
    All messages that were sent on the specified date.

(sentsince date)
    All messages that were sent since the specified date.

()  The same criterion as for the previous search. This specification cannot be used as part of another criterion. If the previous command line contained more than one independent criterion then the last of those criteria is used.

A practical method to read a set of messages is to issue a from command with the search criteria first to check for appropriate messages, and to read each single message then by typing ``' repeatedly.

  Replying to or originating mail
The command reply can be used to set up a response to a message, sending it back to the person who it was from. Text the user types in, up to an end-of-file, defines the contents of the message. While the user is composing a message \%S-nail treats lines beginning with the character `~' specially. For instance, typing `~m' (alone on a line) will place a copy of the current message into the response right shifting it by a tabstop (more about the indentprefix variable below). Other escapes will set up subject fields, add and delete recipients to the message, attach files to it and allow the user to escape to an editor to revise the message or to a shell to run some commands. (These options are given in the summary below.)

  Ending a mail processing session
The user can end a \%S-nail session by issuing the quit (`q') command. Messages which have been examined go to the user's mbox file unless they have been deleted, in which case they are discarded. Unexamined messages go back to the post office. (Also see the -f option above.)

  Personal and systemwide distribution lists
It is also possible to create personal distribution lists so that, for instance, the user can send mail to `cohorts' and have it go to a group of people. Such lists can be defined via the alias command by, e.g., placing lines like

    alias cohorts bill ozalp jkf mark kridle@ucbcory

in the file \%~/.mailrc in the user's home directory. Using alias without arguments lists all the currently known aliases.

System wide distribution lists can be created by editing /etc/aliases (see aliases(5) and sendmail(1) ), which are kept in a different syntax and will be used by the MTA (mail-transfer-agent) rather than by \%S-nail. Personal aliases will be expanded by \%S-nail before the message is sent. System wide aliases are not expanded when the mail is sent by \%S-nail, but any reply returned to the machine will have the system wide alias expanded as all mail goes through the MTA.

  Recipient address specifications
When an address is used to name a recipient (in `To:', `Cc:', or `Bcc:'), names of local mail folders and pipes to external commands may also be specified – the message text is then written to them. The rules are: Any name which starts with a `|' (vertical bar) character specifies a pipe – the command string following the `|' is executed and the message is sent to its standard input; any other name which contains a `@' (at sign) character is treated as a mail address; any other name which starts with a `+' (plus sign) character specifies a folder name; any other name which contains a `/' (slash) character but no `!' (exclamation mark) or `%' (percent sign) character before also specifies a folder name; what remains is treated as a mail address. Compressed folders are handled as described for the folder command.

  Network mail (Internet / ARPA, UUCP, Berknet)
See mailaddr(7) for a description of network addresses. If support for IDNA (internationalized domain names for applications) has been compiled into \%S-nail, then the domain name part of network addresses will be converted via IDNA mechanisms as necessary, effectively treating it as a name in the ttycharset character set; see Character sets for the complete picture about character sets.

\%S-nail has a number of options which can be set in the \%~/.mailrc file to alter its behavior; e.g., set askcc enables the askcc feature, and set idna-disable will disable the mentioned IDNA conversion even if support is available. (These options are summarized below.)

  MIME types
For any outgoing attachment \%S-nail tries to determine the content type. It does this by reading MIME type files whose lines have the following syntax:

    type/subtype extension [extension ...]

where `type/subtype' are strings describing the file contents, and `extension' is the part of a filename starting after the last dot. Any line not immediately beginning with an ASCII alphabetical character is ignored by \%S-nail. If \%S-nail cannot find any MIME type files, it will use a restricted set of builtin mappings. The mimetypes command can be used to show the list of mime types known to \%S-nail. If there is a match with the `extension' of the file to attach, the given `type/subtype' pair is used. Otherwise, or if the filename has no extension, the content types `text/plain' or `application/octet-stream' are used, dependent upon file content inspection.

  Character sets
\%S-nail normally detects the character set of the terminal by using mechanisms that are controlled by the `LC_CTYPE' locale setting, if such are supported; the variable ttycharset will be set to the detected terminal character set and will thus show up in the output of the command set.

A user supplied ttycharset value is not overwritten by this detection mechanism; this feature must be used if the detection doesn't work properly, and it may be used to adjust the name of the locale character set. E.g., on BSD systems one may use a locale with the character set `ISO8859-1', which is not a valid name for this character set; to be on the safe side, one may set ttycharset to the correct name, `ISO-8859-1'.

Note that changing the value doesn't mean much beside that, since several aspects of the real character set are implied by the locale environment of the system, and that stays unaffected by the content of an overwritten ttycharset variable. (This is mostly an issue when interactively using \%S-nail, though. It is actually possible to send mail in a completely "faked" locale environment.)

If no character set conversion capabilities have been compiled into \%S-nail (i.e., no iconv(3) library has been found), then ttycharset will be the only supported character set, and it is simply assumed that it can be used to exchange 8 bit messages, and the rest of this section does not apply; it may however still be necessary to explicitly set it if automatic detection fails, since in that case it defaults to `ISO-8859-1'.

When reading messages, their text is converted into ttycharset as necessary in order to display them on the users terminal. Unprintable characters and illegal byte sequences are detected and replaced by proper substitution characters (unless the variable print-all-chars was set once \%S-nail was started).

When sending messages all their parts and attachments are classified. Whereas no character set conversion is performed on those parts which appear to be binary data, the character set being used must be declared within the MIME header of an outgoing text part if it contains characters that do not conform to the set of characters that are allowed by the email standards. Permissible values for character sets can be declared using the sendcharsets variable, which is expected to contain a (comma-separated list of) character set (names), and the charset-8bit variable, which is used as a catch-all last-resort fallback.

All the specified character sets are tried in order unless the conversion of the part or attachment succeeds. If none of the tried (8 bit) character sets is capable to represent the content of the part or attachment, then the message will not be sent and its text will be saved to DEAD. Note that some character set conversions will never fail, even if the result is incorrect; e.g., `ISO-8859-1' is capable to represent any 8 bit message.

In general, if the message `Cannot convert from a to b' appears, either some characters are not appropriate for the currently selected (terminal) character set, or the needed conversion is not supported by the system. In the first case, it is necessary to set an appropriate `LC_CTYPE' locale and/or the variable ttycharset.

The best results are usually achieved when \%S-nail is run in a UTF-8 locale on a UTF-8 capable terminal, in which case the full Unicode spectrum of characters is available. In this setup characters from various countries can be displayed, while it is still possible to use more simple character sets for sending to retain maximum compatibility with older mail clients.

  Line editor
[Optional] \%S-nail can be configured to support a command line editor and command history lists which are saved in between sessions. One may link against fully-fledged external editor libraries (editline(3), readline(3) ), or use the builtin editor instead, which should work in all environments which comply to ISO C (ISO/IEC 9899:1990/Amendment 1:1995). (Note, however, that commands that are based upon rightwise movement may not work on every terminal. If you encounter that issue, use the line-editor-cursor-right variable to enforce a different terminal control sequence.)

The builtin editor supports the following operations; the notation `^-character' stands for the combination of the `control' key plus the mentioned character, e.g., `^A' means ``hold control key while adding an A key on top of it'':

^A  Go to the start of the line.

^B  History backward step.

^D  Forward delete the character under the cursor; quits \%S-nail if used on the empty line, unless the ignoreeof option is set.

^E  Go to the end of the line.

^F  History forward step.

^G  Cancel current operation, full reset. If there is an active history search or tabulator expansion then this command will first reset that, reverting to the former line content; thus a second reset is needed for a full reset in this case. In all cases \%S-nail will reset a possibly used multibyte character input state machine.

^H  The same as `backspace': backward delete one character.

^I  The same as `horizontal tabulator': try to expand the ``word'' before the cursor. Here ``expansion'' refers to the \%S-nail expansion, as documented for folder, and thus includes shell word expansion (as a last step). (Note that this is a real ``expansion'', not what one expects from ``tab-completion''.)

^J  The same as `RETURN': complete this line of input.

^K  Delete all characters from the cursor to the end of the line.

^L  Repaint the line.

^O  Move the cursor left one character.

^P  Move the cursor right one character.

^R  Complete the current line from (the remaining older) history entries.

^U  The same as `^A' followed by `^K'.

^W  Delete the characters from the one preceding the cursor to the preceding word boundary.

^X  Move the cursor forward one word boundary.

^Y  Move the cursor backward one word boundary.

Regardless of the actually present command line editor history entries will be created for lines entered in command mode only, and creation of such an entry can be forcefully suppressed by starting the line with a space character. Also refer to the documentation of emptystart, line-editor-cursor-right, line-editor-disable, NAIL_HISTFILE and NAIL_HISTSIZE.

  Commands
Each command is typed on a line by itself, and may take arguments following the command word. The command need not be typed in its entirety – the first command which matches the typed prefix is used. For commands which take message lists as arguments, if no message list is given, then the next message forward which satisfies the command's requirements is used. If there are no messages forward of the current message, the search proceeds backwards, and if there are no good messages at all, \%S-nail types `no applicable messages' and aborts the command. If the command begins with a `#' (number sign) character, the line is ignored.

The arguments to commands can be quoted, using the following methods:

•   An argument can be enclosed between paired double-quotes `"argument"' or single-quotes `'argument''; any white space, shell word expansion, or backslash characters within the quotes are treated literally as part of the argument. A double-quote will be treated literally within single-quotes and vice versa. These special properties of the quote marks occur only when they are paired at the beginning and end of the argument.

•   A backslash outside of the enclosing quotes is discarded and the following character is treated literally as part of the argument.

•   An unquoted backslash at the end of a command line is discarded and the next line continues the command.

Filenames, where expected, are subjected to the following transformations, in sequence:

•   If the filename begins with an unquoted plus sign, and the folder variable is defined, the plus sign will be replaced by the value of the folder variable followed by a slash. If the folder variable is unset or is set to null, the filename will be unchanged.

•   Shell word expansions are applied to the filename. If more than a single pathname results from this expansion and the command is expecting one file, an error results.

The following commands are provided:

~   Interprets the remainder of the word as a macro name and passes it through to the call command; e.g., `~mymacro' is a shorter synonym for `call mymacro'.

-   Print out the preceding message. If given a numeric argument n, goes to the n'th previous message and prints it.

?   Prints a brief summary of commands. [Optional] Given an argument a synopsis for the command in question is printed instead.

!   Executes the shell (see sh(1) and csh(1) ) command which follows.

|   A synonym for the pipe command.

account
    (ac) Creates, selects or lists an email account. An account is formed by a group of commands, primarily of those to set variables. With two arguments, of which the second is a `{', the first argument gives an account name, and the following lines create a group of commands for that account until a line containing a single `}' appears. With one argument the previously created group of commands for the account name is executed, and a folder command is executed for the system mailbox or inbox of that account. Without arguments the list of accounts and their contents are printed. As an example,

           account myisp {
              set folder=imaps://mylogin@imap.myisp.example
              set record=+Sent
              set from="myname@myisp.example (My Name)"
              set smtp=smtp.myisp.example
           }

    creates an account named `myisp' which can later be selected by specifying `account myisp'.

alias
    (a) With no arguments, prints out all currently-defined aliases. With one argument, prints out that alias. With more than one argument, creates a new alias or changes an old one.

alternates
    (alt) The alternates command is useful if the user has accounts on several machines. It can be used to inform \%S-nail that the listed addresses all belong to the invoking user. When replying to messages \%S-nail will not send a copy of the message to any of the addresses listed on the alternates list. If the alternates command is given with no argument, the current set of alternate names is displayed.

answered
    (ans) Takes a message list and marks each message as having been answered. This mark has no technical meaning in the mail system; it just causes messages to be marked in the header summary, and makes them specially addressable.

cache
    [Optional] Only applicable to cached IMAP mailboxes; takes a message list and reads the specified messages into the IMAP cache.

call
    Calls a macro (see the define command).

cd  Same as chdir.

certsave
    [Optional] Only applicable to S/MIME signed messages. Takes a message list and a file name and saves the certificates contained within the message signatures to the named file in both human-readable and PEM format. The certificates can later be used to send encrypted messages to the respective message senders by setting smime-encrypt-user@host variables.

chdir
    (ch) Changes the user's working directory to the specified one, or to the user's login directory, if none was given.

collapse
    (coll) Only applicable to threaded mode. Takes a message list and makes all replies to these messages invisible in header summaries, unless they are in state `new'.

connect
    [Optional] (conn) If operating in disconnected mode on an IMAP mailbox, switch to online mode and connect to the mail server while retaining the mailbox status. See the description of the disconnected variable for more information.

copy
    (c) The copy command does the same thing that save does except that it does not mark the given messages for deletion when the user quits. Compressed files and IMAP mailboxes are handled as described for the folder command.

Copy
    (C) Similar to copy, but saves the messages in a file named after the local part of the sender address of the first message.

decrypt
    [Optional] (dec) For unencrypted messages, this command is identical to copy. Encrypted messages are first decrypted, if possible, and then copied.

Decrypt
    P (Dec) Similar to decrypt, but saves the messages in a file named after the local part of the sender address of the first message.

define
    (def) Defines a macro. A macro definition is a sequence of commands in the following form:

           define name {
              command1
              command2
              ...
              commandN
           }

    A defined macro can be explicitly invoked using call or ~, or it can be implicitly invoked by setting the folder-hook or folder-hook-fullname variables.

defines
    Prints the currently defined macros including their contents.

delete
    (d) Takes a list of messages as argument and marks them all as deleted. Deleted messages will not be saved in `mbox', nor will they be available for most other commands.

discard
    Same as ignore.

disconnect
    [Optional] (disco) If operating in online mode on an IMAP mailbox, switch to disconnected mode while retaining the mailbox status. See the description of the disconnected variable for more. A list of messages may optionally be given as argument; the respective messages are then read into the cache before the connection is closed. Thus `disco *' makes the entire mailbox available for disconnected use.

dp or dt
    Deletes the current message and prints the next message. If there is no next message, \%S-nail says `at EOF'.

draft
    Takes a message list and marks each given message as a draft. This mark has no technical meaning in the mail system; it just causes messages to be marked in the header summary, and makes them specially addressable.

echo
    Echoes its arguments, resolving special names as documented for the command folder. The escape sequences `\a', `\b', `\c', `\f', `\n', `\r', `\t', `\v', `\\', and `\0octal-num' are interpreted just as they are by printf(1) (proper quoting provided).

edit
    (e) Point the text editor at each message from the given list in turn. Modified contents are discarded unless the writebackedited variable is set.

else
    Marks the end of the then-part of an if statement and the beginning of the part to take effect if the condition of the if statement is false.

endif
    Marks the end of an if statement.

exit
    (ex or x) Effects an immediate return to the Shell without modifying the user's system mailbox, his `mbox' file, or his edit file in -f.

file
    (fi) The same as folder.

flag
    (fl) Takes a message list and marks the messages as `flagged' for urgent/special attention. This mark has no technical meaning in the mail system; it just causes messages to be highlighted in the header summary, and makes them specially addressable.

folders
    With no arguments, list the names of the folders in the folder directory. With an existing folder as an argument, lists the names of folders below the named folder; e.g. the command `folders @' lists the folders on the base level of the current IMAP server. See also the variable imap-list-depth.

folder
    (fold) The folder command switches to a new mail file or folder. With no arguments, it tells the user which file he is currently reading. If an argument is given, it will write out changes (such as deletions) the user has made in the current file and read in the new file. Some special conventions are recognized for the name argument:

    #   (number sign) means the previous file,

    %   (percent sign) means the invoking user's system mailbox (or the value of folder for IMAP folders),

    %user
        means the system mailbox of `user' (and never the value of folder, regardless of its actual setting),

    &   (ampersand) means the invoking user's `mbox' file (see MBOX ) and

    +file
        means a `file' in the folder directory.

    %:filespec
        expands to the same value as `filespec', but the file is handled as a system mailbox by, e.g., the mbox and save commands.

    If the name matches one of the strings defined with the command shortcut, it is replaced by its long form and expanded. If the name ends with `.gz' or `.bz2' it is treated as being compressed with gzip(1) or bzip2(1), respectively. Likewise, if `name' does not exist, but either `name.gz' or `name.bz2' does, then the compressed file is used. If `name' refers to a directory with the subdirectories `tmp', `new', and `cur', then it is treated as a folder in `maildir' format. A name of the form

        protocol://[user@]host[:port][/file]

    is taken as an Internet mailbox specification. The (optionally) supported protocols are `imap' (IMAP v4r1), `imaps' (IMAP with SSL/TLS encrypted transport), `pop3' (POP3) and `pop3s' (POP3 with SSL/TLS encrypted transport). If `user' contains special characters, in particular `/' or `%', they must be escaped in URL notation, as `%2F' or `%25'. The optional `file' part applies to IMAP only; if it is omitted, the default `INBOX' is used.

    If \%S-nail is connected to an IMAP server, a name of the form `@mailbox' refers to the `mailbox' on that server, but otherwise a `@' prefix has no special meaning.

Followup
    (F) Similar to Respond, but saves the message in a file named after the local part of the first recipient's address.

followup
    (fo) Similar to respond, but saves the message in a file named after the local part of the first recipient's address.

followupall
    Similar to followup, but responds to all recipients regardless of the flipr and Replyall variables.

followupsender
    Similar to Followup, but responds to the sender only regardless of the flipr and Replyall variables.

forward
    (fwd) Takes a message and the address of a recipient and forwards the message to him. The text of the original message is included in the new one, with the value of the fwdheading variable printed before. The fwdignore and fwdretain commands specify which header fields are included in the new message. Only the first part of a multipart message is included unless the forward-as-attachment option is set.

Forward
    (Fwd) Similar to forward, but saves the message in a file named after the local part of the recipient's address.

from
    (f) Takes a list of messages and prints their message headers, piped through the pager if the output does not fit on the screen.

fwdignore
    Specifies which header fields are to be ignored with the command forward. This command has no effect when the forward-as-attachment option is set.

fwdretain
    Specifies which header fields are to be retained with the command forward. fwdretain overrides fwdignore. This command has no effect when the forward-as-attachment option is set.

headers
    (h) Lists the current range of headers, which is an 18-message group. If a `+' argument is given the next 18-message group is printed, likewise the previous is printed if the argument was `-'.

help
    A synonym for `?'.

hold
    (ho, also preserve) Takes a message list and marks each message therein to be saved in the user's system mailbox instead of in `mbox'. Does not override the delete command. \%S-nail deviates from the POSIX standard with this command, as a next command issued after hold will display the following message, not the current one.

if  Commands in \%S-nail's startup files can be executed conditionally depending on whether the user is sending or receiving mail with the if command, e.g.:

           if receive
              commands ...
           endif

    An else form is also available:

           if receive
              commands ...
           else
              commands ...
           endif

    Note that the only allowed conditions are `receive', `send' and `term' (execute if standard input is a tty).

ignore
    Add the list of header fields named to the ignored list. Header fields in the ignore list are not printed on the terminal when a message is printed. This command is very handy for suppression of certain machine-generated header fields. The Type and Print commands can be used to print a message in its entirety, including ignored fields. It lists the current set of ignored fields if no arguments were given.

imap
    [Optional] Sends command strings directly to the current IMAP server. \%S-nail operates always in IMAP `selected state' on the current mailbox; commands that change this will produce undesirable results and should be avoided. Useful IMAP commands are:

    create
        Takes the name of an IMAP mailbox as an argument and creates it.

    getquotaroot
        (RFC 2087) Takes the name of an IMAP mailbox as an argument and prints the quotas that apply to the mailbox. Not all IMAP servers support this command.

    namespace
        (RFC 2342) Takes no arguments and prints the Personal Namespaces, the Other User's Namespaces and the Shared Namespaces. Each namespace type is printed in parentheses; if there are multiple namespaces of the same type, inner parentheses separate them. For each namespace a prefix and a hierarchy separator is listed. Not all IMAP servers support this command.

inc Same as newmail.

list
    Prints the names of all available commands, alphabetically sorted.

Mail
    (M) Similar to mail, but saves the message in a file named after the local part of the first recipient's address.

mail
    (m) Takes a (list of) recipient address(es) as (an) argument(s), or asks on standard input if none were given; then collects the remaining mail content and sends it out.

mbox
    The given message list is to be sent to `mbox' when \%S-nail is quit. This is the default action unless the hold option is set. \%S-nail deviates from the POSIX standard with this command, as a next command issued after mbox will display the following message, not the current one.

mimetypes
    Either (show or) clear the mime.types(5) cache. In the former case all sources are loaded first as necessary. The mimetypes-load-control option can be used to fine-tune loading of the sources.

move
    (mv) Acts like copy but marks the messages for deletion if they were transferred successfully.

more
    Takes a message list and invokes the PAGER on that list, printing a form-feed (`\f') in between messages.

More
    Like more, but also prints ignored header fields and all MIME parts.

Move
    (Mv) Similar to move, but moves the messages to a file named after the local part of the sender address of the first message.

newmail
    Checks for new mail in the current folder without committing any changes before. If new mail is present, a message is printed. If the header variable is set, the headers of each new message are also printed.

next
    (n) (like `+' or `ENTER') Goes to the next message in sequence and types it. With an argument list, types the next matching message.

New Same as unread.

new Same as unread.

online
    Same as connect.

noop
    If the current folder is located on an IMAP or POP3 server, a `NOOP' command is sent. Otherwise, no operation is performed.

Pipe
    (Pi) Like pipe but also pipes ignored header fields and all parts of MIME `multipart/alternative' messages.

pipe
    (pi) Takes a message list and a shell command and pipes the messages through the command. Without an argument the current message is piped through the command given by the cmd variable. If the page variable is set, every message is followed by a formfeed character.

preserve
    (pre) A synonym for hold.

Print
    (P) Like print but also prints out ignored header fields and all parts of MIME `multipart/alternative' messages. See also print, ignore and retain.

print
    (p) Takes a message list and types out each message on the user's terminal. If the message is a MIME multipart message, all parts with a content type of `text' or `message' are shown, the other are hidden except for their headers. Messages are decrypted and converted to the terminal character set if necessary.

quit
    (q) Terminates the session, saving all undeleted, unsaved messages in the current `mbox', preserving all messages marked with hold or preserve or never referenced in his system mailbox, and removing all other messages from his system mailbox. If new mail has arrived during the session, the message `You have new mail' is given. If given while editing a mailbox file with the command line flag -f, then the edit file is rewritten. A return to the shell is effected, unless the rewrite of edit file fails, in which case the user can escape with the exit command.

redirect
    (red) Same as resend.

Redirect
    (Red) Same as Resend.

remove
    (rem) Removes the named folders. The user is asked for confirmation in interactive mode.

rename
    (ren) Takes the name of an existing folder and the name for the new folder and renames the first to the second one. Both folders must be of the same type and must be located on the current server for IMAP.

Reply
    (R) Reply to originator. Does not reply to other recipients of the original message.

reply
    (r) Takes a message list and sends mail to the sender and all recipients of the specified messages. The default message must not be deleted.

replyall
    Similar to reply, but responds to all recipients regardless of the flipr and Replyall variables.

replysender
    Similar to Reply, but responds to the sender only regardless of the flipr and Replyall variables.

Resend
    Like resend, but does not add any header lines. This is not a way to hide the sender's identity, but useful for sending a message again to the same recipients.

resend
    Takes a list of messages and a user name and sends each message to the named user. `Resent-From:' and related header fields are prepended to the new copy of the message.

Respond
    Same as Reply.

respond
    Same as reply.

respondall
    Same as replyall.

respondsender
    Same as replysender.

retain
    Add the list of header fields named to the retained list. Only the header fields in the retain list are shown on the terminal when a message is printed, all other header fields are suppressed. The Type and Print commands can be used to print a message in its entirety. The current set of retained fields is shown if retain is used without arguments.

Save
    (S) Similar to save, but saves the messages in a file named after the local part of the sender of the first message instead of taking a filename argument.

save
    (s) Takes a message list and a filename and appends each message in turn to the end of the file. If no filename is given, the `mbox' file is used. The filename in quotes, followed by the line count and character count is echoed on the user's terminal. If editing a system mailbox the messages are marked for deletion. Compressed files and IMAP mailboxes are handled as described for the -f command line option above.

savediscard
    Same as saveignore.

saveignore
    Is to save what ignore is to print and type. Header fields thus marked are filtered out when saving a message by save or when automatically saving to `mbox'. This command should only be applied to header fields that do not contain information needed to decode the message, as MIME content fields do. If saving messages on an IMAP account ignoring fields makes it impossible to copy the data directly on the server, thus operation usually becomes much slower.

saveretain
    Is to save what retain is to print and type. Header fields thus marked are the only ones saved with a message when saving by save or when automatically saving to `mbox'. saveretain overrides saveignore. The use of this command is strongly discouraged since it may strip header fields that are needed to decode the message correctly.

set (se) With no arguments, prints all variable values. Otherwise, sets an option. Arguments are of the form `option=value' (no space before or after `='), or plain `option' if there is no value. Quotation marks may be placed around any part of the assignment statement to quote blanks or tabs, e.g.,

        set indentprefix="->"

    If an argument begins with `no', as in `set nosave', the effect is the same as invoking the unset command with the remaining part of the variable (`unset save').

seen
    Takes a message list and marks all messages as having been read.

shell
    (sh) Invokes an interactive version of the shell.

shortcut
    Defines a shortcut name and its string for expansion, as described for the folder command. If used without arguments the currently defined shortcuts are printed.

show
    (Sh) Like print, but performs neither MIME decoding nor decryption so that the raw message text is shown.

size
    Print the size in characters of each message of the given message-list.

sort
    Create a sorted representation of the current folder, and change the next command and the addressing modes such that they refer to messages in the sorted order. Message numbers are the same as in regular mode. If the header variable is set, a header summary in the new order is also printed. Possible sorting criteria are:

    date
        Sort the messages by their `Date:' field, that is by the time they were sent.

    from
        Sort messages by the value of their `From:' field, that is by the address of the sender. If the showname variable is set, the sender's real name (if any) is used.

    size
        Sort the messages by their size.

    spam
        [Optional] Sort the message by their spam score, as has been classified via the command spamrate.

    status
        Sort the messages by their message status (new, read, old, etc.).

    subject
        Sort the messages by their subject.

    thread
        Create a threaded order, as with the command thread.

    to  Sort messages by the value of their `To:' field, that is by the address of the recipient. If the showname variable is set, the recipient's real name (if any) is used.

    If no argument is given, the current sorting criterion is printed.

source
    The source command reads commands from a file.

spamclear
    [Optional] Takes a list of messages and clears their ``is-spam'' flag.

spamforget
    [Optional] Takes a list of messages and forces the spam detector to forget it has ever used them to train its Bayesian filter, wether as `ham' or `spam'.

spamham
    [Optional] Takes a list of messages and teaches them to the spam detector as being `ham'. This also clears the ``is-spam'' flag of the messages in question.

spamrate
    [Optional] Takes a list of messages and rates them using the configured spam detector, setting their ``is-spam'' flag as appropriate. Note that the messages are not modified, and due to that the rating will get lost once the mailbox is left. Refer to the manual section Handling spam for the complete picture of spam handling in \%S-nail.

spamset
    [Optional] Takes a list of messages and sets their ``is-spam'' flag.

spamspam
    [Optional] Takes a list of messages and teaches them to the spam detector as being `spam'. This also sets the ``is-spam'' flag of the messages in question.

thread
    (th) Create a threaded representation of the current folder, i.e. indent messages that are replies to other messages in the header display and change the next command and the addressing modes such that they refer to messages in the threaded order. Message numbers are the same as in unthreaded mode. If the header variable is set, a header summary in threaded order is also printed.

top Takes a message list and prints the top few lines of each. The number of lines printed is controlled by the variable toplines and defaults to five.

touch
    Takes a message list and marks the messages for saving in `mbox'. \%S-nail deviates from the POSIX standard with this command, as a next command issued after `mbox' will display the following message instead of the current one.

Type
    (T) Identical to the Print command.

type
    (t) A synonym for print.

unalias
    Takes a list of names defined by alias commands and discards the remembered groups of users.

unanswered
    Takes a message list and marks each message as not having been answered.

uncollapse
    (unc) Only applicable to threaded mode. Takes a message list and makes the message and all replies to it visible in header summaries again. When a message becomes the current message, it is automatically made visible. Also when a message with collapsed replies is printed, all of these are automatically uncollapsed.

undef
    Undefines each of the named macros. It is not an error to use a name that does not belong to one of the currently defined macros.

undelete
    (u) Takes a message list and marks each message as not being deleted.

undraft
    Takes a message list and undraft s each message.

unflag
    Takes a message list and marks each message as not being flagged.

unfwdignore
    Removes the header field names from the list of ignored fields for the forward command.

unfwdretain
    Removes the header field names from the list of retained fields for the forward command.

unignore
    Removes the header field names from the list of ignored fields.

Unread
    Same as unread.

unread
    (U) Takes a message list and marks each message as not having been read.

unretain
    Removes the header field names from the list of retained fields.

unsaveignore
    Removes the header field names from the list of ignored fields for saving.

unsaveretain
    Removes the header field names from the list of retained fields for saving.

unset
    Takes a list of option names and discards their remembered values; the inverse of set.

unshortcut
    Deletes the shortcut names given as arguments.

unsort
    Disable sorted or threaded mode (see the sort and thread commands), return to normal message order and, if the header variable is set, print a header summary.

unthread
    (unth) Same as unsort.

verify
    [Optional] (verif) Takes a message list and verifies each message. If a message is not an S/MIME signed message, verification will fail for it. The verification process checks if the message was signed using a valid certificate, if the message sender's email address matches one of those contained within the certificate, and if the message content has been altered.

visual
    (v) Takes a message list and invokes the display editor on each message. Modified contents are discarded unless the writebackedited variable is set.

write
    (w) For conventional messages the body without all headers is written. The output is decrypted and converted to its native format as necessary. If the output file exists, the text is appended. If a message is in MIME multipart format its first part is written to the specified file as for conventional messages, and the user is asked for a filename to save each other part. For convience saving of each part may be skipped by giving an empty value; the same result can also be achieved by writing it to /dev/null. For the second and subsequent parts a leading `|' character causes the part to be piped to the remainder of the user input interpreted as a shell command; otherwise the user input is expanded as usually for folders, e.g., tilde expansion is performed. In non-interactive mode, only the parts of the multipart message that have a filename given in the part header are written, the others are discarded. The original message is never marked for deletion in the originating mail folder. For attachments, the contents of the destination file are overwritten if the file previously existed. No special handling of compressed files is performed.

xit (x) A synonym for exit.

z   \%S-nail presents message headers in windowfuls as described under the headers command. This command scrolls to the next window of messages. If an argument is given, it specifies the window to use. A number prefixed by `+' or `-' indicates that the window is calculated in relation to the current position. A number without a prefix specifies an absolute window number, and a `$' lets \%S-nail scroll to the last window of messages.

Z   Similar to z, but scrolls to the next or previous window that contains at least one new or `flagged' message.

  Tilde escapes
Here is a summary of the tilde escapes, which are used to perform special functions when composing messages. Tilde escapes are only recognized at the beginning of lines. The name `tilde escape' is somewhat of a misnomer since the actual escape character can be set by the option escape.

~~ string
    Insert the string of text in the message prefaced by a single `~'. (If the escape character has been changed, that character must be doubled in order to send it at the beginning of a line.)

~! command
    Execute the indicated shell command, then return to the message.

~.  Same effect as typing the end-of-file character.

~: \%S-nail-command or ~_ \%S-nail-command
    Execute the given \%S-nail command. Not all commands, however, are allowed.

~?  Write a summary of command escapes.

~< filename
    Identical to ~r.

~<! command
    command is executed using the shell. Its standard output is inserted into the message.

~@ [filename...]
    With no arguments, edit the attachment list interactively. If an attachment's file name is left empty, that attachment is deleted from the list. When the end of the attachment list is reached, \%S-nail will ask for further attachments until an empty name is given. If a given file name solely consists of the number sign `#' followed by a valid message number of the currently active mailbox, the given message is attached as a MIME `message/rfc822' and the rest of this section does not apply.

    If character set conversion has been compiled into \%S-nail, then this mode gives the user the option to specify input and output character sets, unless the file extension indicates binary content, in which case \%S-nail asks wether this step shall be skipped for the attachment in question. If not skipped, then the charset that succeeds to represent the attachment data will be used in the `charset=' MIME parameter of the mail message.

    •   If input and output character sets are specified, then the conversion is performed on the fly. The user will be asked repeatedly until the desired conversion succeeds.

    •   If only an output character set is specified, then the input is assumed to be in the ttycharset charset and will be converted to the given output charset on the fly. The user will be asked repeatedly until the desired conversion succeeds.

    •   If no character sets are specified at all then the algorithm that is documented in the section Character sets is applied, but directly and on the fly. The user will be asked repeatedly until the desired conversion succeeds.

    •   Finally, if an input-, but no output character set is specified, then no conversion is ever performed, but the `charset=' MIME parameter will still be set to the user input.

    Without character set conversion support, \%S-nail will ask for the input character set only, and it'll set the `charset=' MIME parameter to the given input, if any; if no user input is seen then the ttycharset character set will be used for the `charset=' parameter instead. Note that the file extension check isn't performed in this mode, since no conversion will take place anyway.

    Note that in non-interactive mode, for reproduceabilities sake, there will always be two questions for each attachment, regardless of wether character set conversion is available and what the file extension is. The first asks for the filename, and the second asks for the input character set to be passed through to the `charset=' MIME parameter; no conversion will be tried if there is input to the latter question, otherwise the usual conversion algorithm, as above, is applied. For message attachments, the answer to the second question is completely ignored.

    If filename arguments are specified, they are treated as a comma separated list of files, which are all expanded and appended to the end of the attachment list. (Filenames with commas, or with leading or trailing whitespace can only be added via the command line or the first method. Message attachments can only be added via the first method; filenames which clash with message numbers can only be added via the command line or the second method.) In this mode the (text) attachments are assumed to be in ttycharset encoding, and will be evaluated as documented in the section Character sets.

~A  Inserts the string contained in the Sign variable (same as `~i Sign'). The escape sequences `\t' (tabulator) and `\n' (newline) are understood.

~a  Inserts the string contained in the sign variable (same as `~i sign'). The escape sequences `\t' (tabulator) and `\n' (newline) are understood.

~b name ...
    Add the given names to the list of blind carbon copy recipients.

~c name ...
    Add the given names to the list of carbon copy recipients.

~d  Read the file specified by the DEAD variable into the message.

~e  Invoke the text editor on the message collected so far. After the editing session is finished, the user may continue appending text to the message.

~f messages
    Read the named messages into the message being sent. If no messages are specified, read in the current message. Message headers currently being ignored (by the ignore or retain command) are not included. For MIME multipart messages, only the first printable part is included.

~F messages
    Identical to `~f', except that all message headers and MIME parts are included.

~h  Edit the message header fields `To:', `Cc:', `Bcc:', and `Subject:' by typing each one in turn and allowing the user to edit the field.

~H  Edit the message header fields `From:', `Reply-To:', `Sender:' and `Organization:' in the same manner as described for ~h. The default values for these fields originate from the from, replyto, sender and ORGANIZATION variables.

~i variable
    Insert the value of the specified variable into the message, adding a newline character at the end. The message remains unaltered if the variable is unset or empty. The escape sequences `\t' (tabulator) and `\n' (newline) are understood.

~m messages
    Read the named messages into the message being sent, indented by a tab or by the value of indentprefix. If no messages are specified, read the current message. Message headers currently being ignored (by the ignore or retain commands) are not included. For MIME multipart messages, only the first printable part is included.

~M messages
    Identical to `~m', except that all message headers and MIME parts are included.

~p  Print out the message collected so far, prefaced by the message header fields and followed by the attachment list, if any.

~q  Abort the message being sent, copying it to the file specified by the DEAD variable if save is set.

~r filename
    Read the named file into the message.

~s string
    Cause the named string to become the current subject field.

~t name ...
    Add the given name(s) to the direct recipient list.

~v  Invoke an alternate editor (defined by the VISUAL option) on the message collected so far. Usually, the alternate editor will be a screen editor. After the editor is quit, the user may resume appending text to the end of the message.

~w filename
    Write the message onto the named file. If the file exists, the message is appended to it.

~x  Same as `~q', except that the message is not saved at all.

~| command
    Pipe the message through the specified filter command. If the command gives no output or terminates abnormally, retain the original text of the message. E.g., the command fmt(1) is often used as a rejustifying filter.

  Variable options
Options are controlled via set and unset commands, see the corresponding entries for a syntax description. An option is also set if it is passed to \%S-nail as part of the program environment (this is not restricted to specific variables as in the POSIX standard). A value given in a startup file overrides a value imported from the environment. Options may be either binary, in which case it is only significant to see whether they are set or not; or string, in which case the actual value is of interest.

  Binary options
The binary options include the following:

add-file-recipients
    When file or pipe recipients have been specified, mention them in the corresponding address fields of the message instead of silently stripping them from their recipient list. By default such addressees are not mentioned.

allnet
    Causes only the local part to be evaluated when comparing addresses.

append
    Causes messages saved in mbox to be appended to the end rather than prepended. This should always be set.

ask or asksub
    Causes \%S-nail to prompt for the subject of each message sent. If the user responds with simply a newline, no subject field will be sent.

askatend
    Causes the prompts for `Cc:' and `Bcc:' lists to appear after the message has been edited.

askattach
    If set, \%S-nail asks for files to attach at the end of each message. An empty line finalizes the list.

askcc
    Causes the user to be prompted for additional carbon copy recipients (at the end of each message if askatend or bsdcompat are set). An empty line finalizes the list.

askbcc
    Causes the user to be prompted for additional blind carbon copy recipients (at the end of each message if askatend or bsdcompat are set). An empty line finalizes the list.

asksign
    [Optional] Causes the user to be prompted if the message is to be signed at the end of each message. The smime-sign variable is ignored when this variable is set.

autocollapse
    Causes threads to be collapsed automatically when threaded mode is entered (see the collapse command).

autoinc
    Same as newmail.

autoprint
    Causes the delete command to behave like `dp -'; thus, after deleting a message the next one will be typed automatically.

autothread
    Causes threaded mode (see the thread command) to be entered automatically when a folder is opened.

bang
    Enables the substitution of `!' by the contents of the last command line in shell escapes.

batch-exit-on-error
    If the batch mode has been enabled via the -# command line option, then this variable will be consulted whenever \%S-nail completes one operation (returns to the command prompt); if it is set then \%S-nail will terminate if the last operation generated an error.

bsdannounce
    Causes automatic display of a header summary after executing a folder command.

bsdcompat
    Sets some cosmetical features to traditional BSD style; has the same affect as setting askatend and all other variables prefixed with `bsd' as well as setting prompt to `& '.

bsdflags
    Changes the letters printed in the first column of a header summary to traditional BSD style.

bsdheadline
    Changes the display of columns in a header summary to traditional BSD style.

bsdmsgs
    Changes some informational messages to traditional BSD style.

bsdorder
    Causes the `Subject:' field to appear immediately after the `To:' field in message headers and with the `~h' tilde command.

bsdset
    Changes the output format of the set command to traditional BSD style.

debug
    Prints debugging messages and disables the actual delivery of messages. Unlike verbose, this option is intended for \%S-nail development only.

disconnected
    [Optional] When an IMAP mailbox is selected and this variable is set, no connection to the server is initiated. Instead, data is obtained from the local cache (see imap-cache ). Mailboxes that are not present in the cache and messages that have not yet entirely been fetched from the server are not available; to fetch all messages in a mailbox at once, the command `copy * /dev/null' can be used while still in online mode. Changes that are made to IMAP mailboxes in disconnected mode are queued and committed later when a connection to that server is opened in online mode. This procedure is not completely reliable since it cannot be guaranteed that the IMAP unique identifiers (UIDs) on the server still match the ones in the cache at that time. Data is saved to DEAD when this problem occurs.

disconnected-user@host
    The specified account is handled as described for the disconnected variable above, but other accounts are not affected.

dot The binary option dot causes \%S-nail to interpret a period alone on a line as the terminator of a message the user is sending.

editalong
    If this variable is set then the editor is started automatically when composing a message in an interactive mode, as if the `~e' tilde command had been specified. The editheaders variable is implied for this automatically spawned editor session.

editheaders
    When a message is edited while being composed, its header is included in the editable text. The `To:', `Cc:', `Bcc:', `Subject:', `From:', `Reply-To:', `Sender:', and 'Organization:' fields are accepted within the header, other fields are ignored.

emptybox
    If set, an empty mailbox file is not removed. This may improve the interoperability with other mail user agents when using a common folder directory.

emptystart
    If the mailbox is empty \%S-nail normally prints `No mail for user' and exits immediately. If this option is set \%S-nail starts even with an empty mailbox.

flipr
    Exchanges the Respond with the respond commands and vice-versa.

forward-as-attachment
    Original messages are normally sent as inline text with the forward command, and only the first part of a multipart message is included. With this option messages are sent as MIME `message/rfc822' attachments with all of their parts included. The fwdignore and fwdretain options are ignored when the forward-as-attachment option is set.

fullnames
    When replying to a message \%S-nail normally removes the comment parts of email addresses, which by convention contain the full names of the recipients. If this variable is set such stripping is not performed, and comments are retained.

header
    Causes the header summary to be written at startup and after commands that affect the number of messages or the order of messages in the current folder; enabled by default.

hold
    This option is used to hold messages in the system mailbox by default.

idna-disable
    [Optional] Can be used to turn off the automatic conversion of domain names according to the rules of IDNA (internationalized domain names for applications). Since the IDNA code assumes domain names are specified with the ttycharset character set, an UTF-8 locale charset is required to represent all possible international domain names (before conversion, that is).

ignore
    Causes interrupt signals from the terminal to be ignored and echoed as `@'s.

ignoreeof
    An option related to dot is ignoreeof, which makes \%S-nail refuse to accept a `control-D' as the end of a message. This option also applies to \%S-nail command mode.

imap-use-starttls
    [Optional] Causes \%S-nail to issue a `STARTTLS' command to make an unencrypted IMAP session SSL/TLS encrypted. This functionality is not supported by all servers, and is not used if the session is already encrypted by the IMAPS method.

imap-use-starttls-user@host
    Activates imap-use-starttls for a specific account.

keep
    This option causes \%S-nail to truncate the user's system mailbox instead of deleting it when it is empty. This should always be set since it prevents malicious users from creating fake mail folders in a world-writable spool directory.

keepsave
    When a message is saved it is usually discarded from the originating folder when \%S-nail is quit. Setting this option causes all saved message to be retained.

line-editor-disable
    Turn off any enhanced command line editing capabilities (see Line editor for more).

markanswered
    When a message is replied to and this variable is set, it is marked as having been answered. This mark has no technical meaning in the mail system; it just causes messages to be marked in the header summary, and makes them specially addressable.

message-id-disable
    By setting this option the generation of `Message-ID:' can be completely suppressed, effectively leaving this task up to the mail-transfer-agent (MTA) or the SMTP server. (According to RFC 5321 your SMTP server is not required to add this field by itself, so you should ensure that it accepts messages without a `Message-ID'.)

metoo
    Usually, when a group is expanded that contains the sender, the sender is removed from the expansion. Setting this option causes the sender to be included in the group.

mime-allow-text-controls
    When sending messages, each part of the message is MIME-inspected in order to classify the `Content-Type:' and `Content-Transfer-Encoding:' that is required to send this part over mail transport, i.e., a computation rather similar to what the file(1) command produces when used with the --mime option.

    This classification however treats text files which are encoded in UTF-16 (often found for HTML files) and similar character sets as binary octet-streams, forcefully changing any `text/plain' or `text/html' specification to `application/octet-stream'; if that actually happens, then a yet unset charset MIME parameter is set to `binary', effectively making it impossible for the receiving MUA to automatically interpret the contents of the part.

    If this option is set, and the data was unambiguously identified as text data at first glance (by a `.txt' or `.html' file extension), then the original `Content-Type:' will not be overwritten.

mime-counter-evidence
    Normally the `Content-Type:' field is used to decide how to treat a messages MIME part. Some MUAs however don't use mime.types(5) or a similar mechanism to correctly classify content, but simply specify `application/octet-stream', even for plain text attachments like `text/diff'. If this variable is set then \%S-nail will use the file extension of attachments to classify such MIME message parts, if possible.

newmail
    Checks for new mail in the current folder each time the prompt is printed. For IMAP mailboxes the server is then polled for new mail, which may result in delayed operation if the connection to the server is slow. A `maildir' folder must be re-scanned to determine if new mail has arrived.

    If this variable is set to the special value `nopoll' an IMAP server is not actively asked for new mail, but new mail may still be detected and announced with any other IMAP command that is sent to the server. A `maildir' folder is not scanned, then.

    In either case the IMAP server may send notifications about messages that have been deleted on the server by another process or client. In this case, `Expunged X messages' is printed regardless of this variable, and message numbers may have changed.

noheader
    Setting this option is the same as using the command line option -N.

outfolder
    Causes the filename given in the record variable and the sender-based filenames for the Copy and Save commands to be interpreted relative to the directory given in the folder variable rather than to the current directory, unless it is set to an absolute pathname.

page
    If set, each message the pipe command prints out is followed by a formfeed character.

piperaw
    Send messages to the pipe command without performing MIME and character set conversions.

pop3-bulk-load
    [Optional] When accessing a POP3 server \%S-nail loads the headers of the messages, and only requests the message bodies on user request. For the POP3 protocol this means that the message headers will be downloaded twice. If this option is set then \%S-nail will download only complete messages from POP3 servers instead. It may be useful to define a macro that temporarily sets this option, then accesses a POP3 account that is known to only get small text messages, and then unsets this variable again.

pop3-no-apop
    [Optional] Unless this variable is set the `APOP' authentication method will be used when connecting to a POP3 server that advertises support. The advantage of APOP over `USER/PASS' authentication is that the password is not sent in clear text over the wire and that only a single packet is sent for the user/password tuple.

pop3-no-apop-user@host
    Disables usage of the `APOP' authentication method (see pop3-no-apop) for a specific account.

pop3-use-starttls
    [Optional] Causes \%S-nail to issue a `STLS' command to make an unencrypted POP3 session SSL/TLS encrypted. This functionality is not supported by all servers, and is not used if the session is already encrypted by the POP3S method.

pop3-use-starttls-user@host
    Activates pop3-use-starttls for a specific account.

print-all-chars
    This option causes all characters to be considered printable. It is only effective if given in a startup file. With this option set some character sequences in messages may put the user's terminal in an undefined state when printed; it should only be used as a last resort if no working system locale can be found.

print-alternatives
    When a MIME message part of type `multipart/alternative' is displayed and it contains a subpart of type `text/plain', other parts are normally discarded. Setting this variable causes all subparts to be displayed, just as if the surrounding part was of type `multipart/mixed'.

quiet
    Suppresses the printing of the version when first invoked.

quote-as-attachment
    If this is set, then the original message is added in its entirety as a `message/rfc822' MIME attachment when replying to a message. Note this works regardless of the setting of quote.

recipients-in-cc
    On group replies, specify only the sender of the original mail in `To:' and mention it's other recipients in the secondary `Cc:'.

record-resent
    If both this variable and the record variable are set, the resend and Resend commands save messages to the record folder as it is normally only done for newly composed messages.

reply-in-same-charset
    If this variable is set \%S-nail first tries to use the same character set of the original message for replies. If this fails, the mechanism described in Character sets is evaluated as usual.

Replyall
    Reverses the sense of reply and Reply commands.

rfc822-body-from_
    This variable can be used to force the display of a so-called `From_' line for messages that are embedded into an envelope mail via the `message/rfc822' MIME mechanism.

save
    When the user aborts a message with two `RUBOUT' (interrupt) characters, \%S-nail will copy the partial letter to the file DEAD. This option is set by default.

searchheaders
    Expand message-list specifiers in the form `/x:y' to all messages containing the substring `y' in the header field `x'. The string search is case insensitive.

sendcharsets-else-ttycharset
    [Optional] If this variable is set, but sendcharsets is not, then \%S-nail acts as if sendcharsets had been set to the value of the variable ttycharset. In effect this combination passes through the message data in the character set of the current locale (given that ttycharset hasn't been set manually), i.e., without converting it to the charset-8bit fallback character set. Thus, mail message text will be in `ISO-8859-1' encoding when send from within a `ISO-8859-1' locale, and in `UTF-8' encoding when send from within an `UTF-8' locale.

sendwait
    When sending a message wait until the MTA exits before accepting further commands. If the MTA returns a non-zero exit status, the exit status of \%s-nail will also be non-zero.

showlast
    Setting this option causes \%S-nail to start at the last message instead of the first one when opening a mail folder.

showname
    Causes \%S-nail to use the sender's real name instead of the plain address in the header field summary and in message specifications.

showto
    Causes the recipient of the message to be shown in the header summary if the message was sent by the user.

skipemptybody
    If an outgoing message does not contain any text in its first or only message part, do not send it but discard it silently (see also the command line option -E ).

smime-force-encryption
    [Optional] Causes \%S-nail to refuse sending unencrypted messages.

smime-sign
    [Optional] S/MIME sign outgoing messages with the user's private key. Signing a message enables a recipient to verify that the sender used a valid certificate, that the email addresses in the certificate match those in the message header and that the message content has not been altered. It does not change the message text, and people will be able to read the message as usual.

smime-no-default-ca
    [Optional] Don't load default CA locations when verifying S/MIME signed messages.

smtp-use-starttls
    [Optional] Causes \%S-nail to issue a `STARTTLS' command to make an SMTP session SSL/TLS encrypted. Not all servers support this command – because of common implementation defects it can't be automatically determined whether a server supports it or not.

ssl-no-default-ca
    [Optional] Don't load default CA locations to verify SSL/TLS server certificates.

ssl-v2-allow
    [Optional] Accept SSLv2 connections. These are normally not allowed because this protocol version is insecure.

keep-content-length
    When (editing messages and) writing MBOX mailbox files \%S-nail can be told to keep the `Content-Length:' and `Lines:' header fields that some MUAs generate by setting this variable. Since \%S-nail does neither use nor update these non-standardized header fields (which in itself shows one of their conceptual problems), stripping them should increase interoperability in between MUAs that work with with same mailbox files. Note that, if this is not set but writebackedited, as below, is, a possibly performed automatic stripping of these header fields already marks the message as being modified.

verbose
    Setting the option verbose is the same as using the command line option -v. When \%S-nail runs in verbose mode details of the actual message delivery and protocol conversations for IMAP, POP3, and SMTP, as well as of other internal processes, are displayed on the user's terminal. This is sometimes useful to debug problems. \%S-nail prints all data that is sent to remote servers in clear texts, including passwords, so care should be taken that no unauthorized option can view the screen if this option is enabled.

writebackedited
    If this variable is set messages modified using the edit or visual commands are written back to the current folder when it is quit; it is only honoured for writable folders in `mbox' format, though. Note that the editor will be pointed to the raw message content in that case, i.e., neither MIME decoding nor decryption will have been performed, and proper RFC 4155 `From ' quoting of newly added or edited content is also left as an excercise to the user.

  Value options
The value options include the following:

attrlist
    A sequence of characters to print in the `attribute' column of a header summary, each for one type of messages in the following order: new (N), unread but old (U), new but read (R), read and old (O), saved (S), preserved (P), mboxed (M), flagged (F), answered (A), draft (T), start of a collapsed thread (+), collapsed (-), classified as spam ($). The default is `NUROSPMFAT+-$', or `NU *HMFAT+-$' if bsdflags or the SYSV3 environment variable are set.

autobcc
    Specifies a list of recipients to which a blind carbon copy of each outgoing message will be sent automatically.

autocc
    Specifies a list of recipients to which a carbon copy of each outgoing message will be sent automatically.

autosort
    Causes sorted mode (see the sort command) to be entered automatically with the value of this option as sorting method when a folder is opened.

charset-7bit
    The value that should appear in the `charset=' parameter of `Content-Type:' MIME header fields when no character set conversion of the message data was performed. This defaults to `US-ASCII', and the chosen character set should be `US-ASCII' compatible.

charset-8bit
    [Optional] The default 8 bit character set that is used if sendcharsets is not set or no character set therein was capable to represent the content of a message. Defaults to `UTF-8'. If no character set conversion capabilities are available in \%S-nail then the only supported character set is ttycharset. Refer to the section Character sets for the complete picture of character set conversion in \%S-nail.

cmd The default value for the pipe command.

crt The valued option crt is used as a threshold to determine how long a message must be before PAGER is used to read it. If crt is set without a value then the height of the terminal screen stored in the system is used to compute the threshold (see LINES and stty(1) ).

DEAD
    The name of the file to use for saving aborted messages. This defaults to `dead.letter' in the user's home directory.

datefield
    The date in a header summary is normally the date of the mailbox `From ' line of the message. If this variable is set, then the date as given in the `Date:' field is used, converted to local time. It is possible to control the display of the date by assigning a value, in which case the strftime(3) function will be used to format the date accordingly. Please read your system manual for the available formats. Note that the `%n' format should not be used, because \%S-nail doesn't take embedded newlines into account when calculating how many lines fit onto the screen.

datefield-markout-older
    This option, when set in addition to datefield, modifies the display of messages that are not really current in a way that is rather comparable to the -l option of the POSIX ls(1) command. The interpretation of the value is identical to what has been described for datefield.

EDITOR
    Pathname of the text editor to use in the edit command and ~e tilde escape. A default editor is used if this value is not defined.

encoding
    The default MIME encoding to use in outgoing text messages and message parts. Valid values are the default `quoted-printable', `8bit' and `base64'. `8bit' may cause problems with mail transfers that are not ESMTP compliant. If there is no need to encode a message, `7bit' transfer mode is always used regardless of this variable. Binary data is always encoded as `base64'.

escape
    If defined, the first character of this option gives the character to use in place of `~' to denote tilde escapes.

folder
    The name of the directory to use for storing folders of messages. All folder names that begin with `+' refer to files below it. The same special conventions as documented for the folder command may be used when specifying a new value for folder, but be aware that the expansion is fully performed immediately. E.g., if the expanded name refers to an IMAP account, all names that begin with `+' refer to IMAP mailboxes below the folder target box.

    Note: some IMAP servers do not accept the creation of mailboxes in the hierarchy base, but require that they are created as subfolders of `INBOX' – with such servers a folder name of the form

        imaps://mylogin@imap.myisp.example/INBOX.

    should be used (the last character is the server's hierarchy delimiter). Folder names prefixed by `+' will then refer to folders below `INBOX', while folder names prefixed by `@' refer to folders below the hierarchy base. See the imap namespace command for a method to detect the appropriate prefix and delimiter.

folder-hook
    When a folder is opened and this variable is set, the macro corresponding to the value of this variable is executed. The macro is also invoked when new mail arrives, but message lists for commands executed from the macro only include newly arrived messages then.

folder-hook-fullname
    When a folder named `fullname' is opened, the macro corresponding to the value of this variable is executed. Unlike other folder specifications, the fully expanded name of a folder, without metacharacters, is used to avoid ambiguities. The macro specified with folder-hook is not executed if this variable is effective for a folder (but it can be call ed from within the actually executed macro).

from
    The address (or a list of addresses) to put into the `From:' field of the message header. If replying to messages these addresses are handled as if they were in the alternates list. If the machine's hostname is not valid at the Internet (for example at a dialup machine), then either this variable or hostname have to be set or \%S-nail will not generate `Message-ID:' header fields but leave that task up to a (then obviously present) local Mail Transfer Agent (MTA). If from contains more than one address, the sender variable must also be set.

fwdheading
    The string to print before the text of a message with the forward command (unless the forward-as-attachment variable is set). Defaults to `-------- Original Message --------' if unset. No heading is printed if it is set to the empty string.

headline
    A format string to use for the header summary, similar to printf(3) formats. A `%' character introduces a format specifier. It may be followed by a number indicating the field width. If the (possibly implicitly implied) field width is negative, the field is to be left-aligned. Valid format specifiers are:

    %a  Message attributes.

    %d  The date when the message was received.

    %e  The indenting level in threaded mode.

    %f  The address of the message sender.

    %i  The message thread structure. (Note that this format doesn't support a field width.)

    %l  The number of lines of the message.

    %m  Message number.

    %o  The number of octets (bytes) in the message.

    %s  Message subject (if any).

    %S  Message subject (if any) in double quotes.

    %t  The position in threaded/sorted order.

    %>  A `>' for the current message, otherwise ` '.

    %<  A `<' for the current message, otherwise ` '.

    %$  The spam score of the message, as has been classified via the command spamrate.

    %%  A `%' character.

    The default is `%>%a%m %-18f %16d %4l/%-5o %i%-s', or `%>%a%m %20-f %16d %3l/%-5o %i%-S' if bsdcompat is set.

hostname
    Use this string as hostname when expanding local addresses instead of the value obtained from uname(2) and getaddrinfo(3). Note that this must be set explicitly to become used for the generation of `Message-ID:' fields.

imap-auth
    [Optional] Sets the IMAP authentication method. Valid values are `login' for the usual password-based authentication (the default), `cram-md5', which is a password-based authentication that does not send the password over the network in clear text, and `gssapi' for GSSAPI-based authentication.

imap-auth-user@host
    Sets the IMAP authentication method for a specific account.

imap-cache
    [Optional] Enables caching of IMAP mailboxes. The value of this variable must point to a directory that is either existent or can be created by \%S-nail. All contents of the cache can be deleted by \%S-nail at any time; it is not safe to make assumptions about them.

imap-keepalive
    [Optional] IMAP servers may close the connection after a period of inactivity; the standard requires this to be at least 30 minutes, but practical experience may vary. Setting this variable to a numeric `value' greater than 0 causes a `NOOP' command to be sent each `value' seconds if no other operation is performed.

imap-list-depth
    [Optional] When retrieving the list of folders on an IMAP server, the folders command stops after it has reached a certain depth to avoid possible infinite loops. The value of this variable sets the maximum depth allowed. The default is 2. If the folder separator on the current IMAP server is a slash `/', this variable has no effect and the folders command does not descend to subfolders.

indentprefix
    String used by the `~m' and `~M' tilde escapes and by the quote option for indenting messages, in place of the normal tab character (`^I'). Be sure to quote the value if it contains spaces or tabs.

LISTER
    Pathname of the directory lister to use in the folders command when operating on local mailboxes. Default is /bin/ls.

line-editor-cursor-right
    [Optional] If the builtin line editor is used, actions which are based on rightwise movement may not work on some terminals. If you encounter such problems, set this variable to the terminal control sequence that is necessary to move the cursor one column to the right. The default is `\033[C', which should work for most terminals. Less often occur `\033OC' and `\014'. Note that `ESCAPE' and other control character have to be written as shell-style escape sequences, e.g., `\033' for `ESCAPE'.

MAIL
    Is used as the user's mailbox, if set. Otherwise, a system-dependent default is used. Supports a logical subset of the special conventions that are documented for the folder command and the folder option.

MBOX
    The name of the mbox file. Supports a logical subset of the special conventions that are documented for the folder command and the folder option. The fallback default is `mbox' in the user's home directory.

mimetypes-load-control
    This option can be used to control which of the mime.types(5) MIME type databases are loaded by \%S-nail. If the letter `u' (or `U') is part of this options value, then the user's personal ~/.mime.types file will be loaded (if it exists); likewise the letter `s' (or `S') controls loading of the system wide /etc/mime.types. If this option is not set \%S-nail will try to load both files instead. Incorporation of the MIME types that are compiled into \%S-nail cannot be suppressed.

NAIL_EXTRA_RC
    The name of an optional startup file to be read after \%~/.mailrc. This variable is ignored if it is imported from the environment; it has an effect only if it is set in \%/etc/s-nail.rc or \%~/.mailrc to allow bypassing the configuration with, e.g., `MAILRC=/dev/null'. Use this file for commands that are not understood by other \%S-nail implementations.

NAIL_HEAD
    A string to put at the beginning of each new message. The escape sequences `\t' (tabulator) and `\n' (newline) are understood.

NAIL_HISTFILE
    [Optional] If a command line editor is available then this can be set to name the (expandable) path of the location of a permanent history file.

NAIL_HISTSIZE
    [Optional] If a command line editor is available this value restricts the amount of history entries that are saved into a set and valid NAIL_HISTFILE. A value of less than 0 disables this feature; note that loading and incorporation of NAIL_HISTFILE upon program startup can also be suppressed by doing this. An unset or invalid value, or 0, causes a default value to be used. Dependent on the available line editor this will also define the number of history entries in memory; it is also editor-specific wether runtime updates of this value will be honoured.

NAIL_TAIL
    A string to put at the end of each new message. The escape sequences `\t' (tabulator) and `\n' (newline) are understood.

newfolders
    If this variable has the value `maildir', newly created local folders will be in `maildir' format.

ORGANIZATION
    The value to put into the `Organization:' field of the message header.

PAGER
    Pathname of the program to use in the more command or when the crt variable is set. The default paginator is more(1).

password-user@host
    Set the password for `user' when connecting to `host'. If no such variable is defined for a host, the user will be asked for a password on standard input. Specifying passwords in a startup file is generally a security risk; the file should be readable by the invoking user only.

pipe-content/subcontent
    When a MIME message part of `content/subcontent' type is displayed or is replied to, its text is filtered through the value of this variable interpreted as a shell command.

    The special value `@' can be used to force interpretation of the message part as plain text, e.g., `set pipe-application/pgp-signature=@' will henceforth treat signatures as plain text and display them ``as is''.

    Also, if a normal shell command is prefixed with `@', then the command will only be used to prepare the MIME message part if the message is displayed by itself, but not when multiple messages are displayed at once.

    Finally, if a normal shell command is prefixed with `@&', then, in addition to what has been described for the plain `@' shell command prefix, the command will be run asynchronously, i.e., without blocking \%S-nail, which may be a handy way to display a, e.g., PDF file while also continuing to read the mail message.

    Special care must be taken when using such commands as mail viruses may be distributed by this method; if messages of type `application/x-sh' were filtered through the shell, for example, a message sender could easily execute arbitrary code on the system \%S-nail is running on.

pop3-keepalive
    [Optional] POP3 servers close the connection after a period of inactivity; the standard requires this to be at least 10 minutes, but practical experience may vary. Setting this variable to a numeric `value' greater than 0 causes a `NOOP' command to be sent each `value' seconds if no other operation is performed.

prompt
    The string printed when a command is accepted. Defaults to `? ', or to `& ' if the bsdcompat variable is set. The same XSI escape sequences that are understood by the echo command may be used within prompt. As a \%S-nail specific addition, the escape sequence `\?' will expand to `1' if the last command failed, and to `0' otherwise.

quote
    If set, \%S-nail starts a replying message with the original message prefixed by the value of the variable indentprefix. Normally, a heading consisting of `Fromheaderfield wrote:' is printed before the quotation. If the string `noheading' is assigned to the quote variable, this heading is omitted. If the string `headers' is assigned, the headers selected by the ignore/retain commands are printed above the message body, thus quote acts like an automatic `~m' tilde escape command, then. If the string `allheaders' is assigned, all headers are printed above the message body and all MIME parts are included, making quote act like an automatic `~M' command. Also see quote-as-attachment.

quote-fold
    [Optional] Can be set in addition to indentprefix. Setting this turns on a more fancy quotation algorithm in that leading quotation characters are compressed and overlong lines are folded. quote-fold can be set to either one or two (space separated) numeric values, which are interpreted as the maximum (goal) and the minimum line length, respectively, in a spirit rather equal to the fmt(1) program, but line-, not paragraph-based. If not set explicitly the minimum will reflect the goal algorithmically. The goal can't be smaller than the length of indentprefix plus some additional pad. Necessary adjustments take place silently.

record
    If defined, gives the pathname of the folder used to record all outgoing mail. If not defined, then outgoing mail is not saved. When saving to this folder fails the message is not sent, but instead saved to DEAD.

replyto
    A list of addresses to put into the `Reply-To:' field of the message header. Members of this list are handled as if they were in the alternates list.

screen
    When \%S-nail initially prints the message headers it determines the number to print by looking at the speed of the terminal. The faster the terminal, the more it prints. This option overrides this calculation and specifies how many message headers are printed. This number is also used for scrolling with the z command.

sendcharsets
    [Optional] A comma-separated list of character set names that can be used in outgoing Internet mail. If no character set conversion capabilities are compiled into \%S-nail then the only supported charset is ttycharset. Also see sendcharsets-else-ttycharset and refer to the section Character sets for the complete picture of character set conversion in \%S-nail.

sender
    An address that is put into the `Sender:' field of outgoing messages. This field needs not normally be present. It is, however, required if the `From:' field contains more than one address. It can also be used to indicate that a message was sent on behalf of someone else – in this case, `From:' should contain the address of the person that took responsibility for the message, and `Sender:' should contain the address of the person that actually sent the message. The sender address is handled as if it were in the alternates list.

sendmail
    To use an alternate mail delivery system, set this option to the full pathname of the program to use. It may be necessary to set sendmail-progname in addition.

sendmail-progname
    Many systems use a so-called mailwrapper(8) environment to ensure compatibility with sendmail(1). This works by inspecting the name that was used to invoke the mail delivery system. If this variable is set then the mailwrapper (the program that is actually executed when calling `sendmail') will treat its contents as that name. The default is `sendmail'.

SHELL
    Pathname of the shell to use in the! command and the `~!' tilde escape. A default shell is used if this option is not defined.

Sign
    A string for use with the `~A' tilde escape.

sign
    A string for use with the `~a' tilde escape.

signature
    Must correspond to the name of a readable file if set. The file's content is then appended to each singlepart message and to the first part of each multipart message. Be warned that there is no possibility to edit the signature for an individual message.

smime-ca-dir
    [Optional] Specifies a directory with CA certificates in PEM (Privacy Enhanced Mail) format for verification of S/MIME signed messages.

smime-ca-file
    [Optional] Specifies a file with CA certificates in PEM format for verification of S/MIME signed messages.

smime-cipher-user@host
    [Optional] Specifies a cipher to use when generating S/MIME encrypted messages for `user@host'. Valid ciphers are `rc2-40' (RC2 with 40 bits), `rc2-64' (RC2 with 64 bits), `des' (DES, 56 bits) and `des-ede3' (3DES, 112/168 bits). The default is 3DES. It is not recommended to use the other ciphers unless a recipient's client is actually unable to handle 3DES since they are comparatively weak.

smime-crl-file
    [Optional] Specifies a file that contains a CRL in PEM format to use when verifying S/MIME messages.

smime-crl-dir
    [Optional] Specifies a directory that contains files with CRLs in PEM format to use when verifying S/MIME messages.

smime-encrypt-user@host
    [Optional] If this variable is set, messages to `user@host' are encrypted before sending. The value of the variable must be set to the name of a file that contains a certificate in PEM format.

    If a message is sent to multiple recipients, each of them for whom a corresponding variable is set will receive an individually encrypted message; other recipients will continue to receive the message in plain text unless the smime-force-encryption variable is set. It is recommended to sign encrypted messages, i.e., to also set the smime-sign variable.

smime-sign-cert
    [Optional] Points to a file in PEM format that contains the user's private key as well as his certificate. Both are used with S/MIME for signing and decrypting messages.

smime-sign-cert-user@host
    Overrides smime-sign-cert for the specific addresses. When signing messages and the value of the from variable is set to `user@host', the specific file is used. When decrypting messages, their recipient fields (`To:' and `Cc:') are searched for addresses for which such a variable is set. \%S-nail always uses the first address that matches, so if the same message is sent to more than one of the user's addresses using different encryption keys, decryption might fail.

smime-sign-include-certs
    [Optional] If used, this must be set to a comma-separated list of files, each of which containing a single certificate in PEM format to be included in the S/MIME message in addition to the smime-sign-cert certificate. This is most useful for long certificate chains if it is desired to aid the receiving party's verification process.

smime-sign-include-certs-user@host
    Overrides smime-sign-include-certs for the specific addresses. Refer to the discussion of smime-sign-cert-user@host for more on this topic.

smtp
    [Optional] Normally \%S-nail invokes sendmail(1) directly to transfer messages. If the smtp variable is set, a SMTP connection to the server specified by the value of this variable is used instead. If the SMTP server does not use the standard port, a value of `server:port' can be given, with `port' as a name or as a number.

    There are two possible methods to get SSL/TLS encrypted SMTP sessions: First, the `STARTTLS' command can be used to encrypt a session after it has been initiated, but before any user-related data has been sent; see smtp-use-starttls above. Second, some servers accept sessions that are encrypted from begin on. This mode is configured by assigning `smtps://server[:port]' to the smtp variable.

    The SMTP transfer is executed in a child process, which runs asynchronously unless either the sendwait or the verbose variable is set. If it receives a TERM signal, it will abort and save the message to DEAD.

smtp-auth
    [Optional] Sets the SMTP authentication method. If set to `login', or if unset and smtp-auth-user is set, `AUTH LOGIN' is used. If set to `cram-md5', `AUTH CRAM-MD5' is used; if set to `plain', `AUTH PLAIN' is used. Otherwise, no SMTP authentication is performed.

smtp-auth-user@host
    Overrides smtp-auth for specific values of sender addresses, dependend upon the variable from.

smtp-auth-password
    [Optional] Sets the global password for `SMTP AUTH'. Both user and password have to be given for `AUTH LOGIN' and `AUTH CRAM-MD5'.

smtp-auth-password-user@host
    Overrides smtp-auth-password for specific values of sender addresses, dependent upon the variable from.

smtp-auth-user
    [Optional] Sets the global user name for `SMTP AUTH'. Both user and password have to be given for `AUTH LOGIN' and `AUTH CRAM-MD5'. If this variable is set but neither smtp-auth-password nor a matching smtp-auth-password-user@host can be found, \%S-nail will ask for a password on the user's terminal.

smtp-auth-user-user@host
    Overrides smtp-auth-user for specific values of sender addresses, dependent upon the variable from.

spam-command
    [Optional] The path to the spam detector. Note that the path is not expanded, but used ``as is''. A fallback path will have been compiled into the \%S-nail binary if the spamc(1) executable had been found during compilation.

spam-host
    [Optional] Can be used to specify the host on which spamd(1) listens for connections; if not set, defaults to `localhost'.

spam-maxsize
    [Optional] Spam detectors like spamc(1) decline to work with messages which exceed a specific size; if this variable is set then \%S-nail won't even try to pass messages which exceed the given limit. The default is 420000 bytes.

spam-port
    [Optional] Can be used to explicitly specify the port on which spamd(1) listens for connections.

spam-socket
    [Optional] If the spam detector listens on a path-based UNIX domain socket, then setting this variable to the fully qualified path will force its usage for communication.

spam-user
    [Optional] This can be used to support multiple, per-used configuration files of the spam detector. Note that \%S-nail doesn't automatically set this to reflect a possibly set -u option.

ssl-ca-dir
    [Optional] Specifies a directory with CA certificates in PEM (Pricacy Enhanced Mail) for verification of of SSL/TLS server certificates. See SSL_CTX_load_verify_locations(3) for more information.

ssl-ca-file
    [Optional] Specifies a file with CA certificates in PEM format for verification of SSL/TLS server certificates. See SSL_CTX_load_verify_locations(3) for more information.

ssl-cert
    [Optional] Sets the file name for a SSL/TLS client certificate required by some servers.

ssl-cert-user@host
    Sets an account-specific file name for a SSL/TLS client certificate required by some servers. Overrides ssl-cert for the specified account.

ssl-cipher-list
    [Optional] Specifies a list of ciphers for SSL/TLS connections. See ciphers(1) for more information.

ssl-crl-file
    [Optional] Specifies a file that contains a CRL in PEM format to use when verifying SSL/TLS server certificates.

ssl-crl-dir
    [Optional] Specifies a directory that contains files with CRLs in PEM format to use when verifying SSL/TLS server certificates.

ssl-key
    [Optional] Sets the file name for the private key of a SSL/TLS client certificate. If unset, the name of the certificate file is used. The file is expected to be in PEM format.

ssl-key-user@host
    Sets an account-specific file name for the private key of a SSL/TLS client certificate. Overrides ssl-key for the specified account.

ssl-method
    [Optional] Selects a SSL/TLS protocol version; valid values are `ssl2', `ssl3', and `tls1'. If unset, the method is selected automatically, if possible.

ssl-method-user@host
    Overrides ssl-method for a specific account.

ssl-rand-egd
    [Optional] Gives the pathname to an entropy daemon socket, see RAND_egd(3).

ssl-rand-file
    [Optional] Gives the pathname to a file with entropy data, see RAND_load_file(3). If the file is a regular file writable by the invoking user, new data is written to it after it has been loaded.

ssl-verify
    [Optional] Sets the action to be performed if an error occurs during SSL/TLS server certificate validation. Valid values are `strict' (fail and close connection immediately), `ask' (ask whether to continue on standard input), `warn' (print a warning and continue), `ignore' (do not perform validation). The default is `ask'.

ssl-verify-user@host
    Overrides ssl-verify for a specific account.

stealthmua
    If only set without an assigned value, then this option inhibits the generation of the `Message-Id:' and `User-Agent:' header fields that include obvious references to \%S-nail. There are two pitfalls associated with this: First, the message id of outgoing messages is not known anymore. Second, an expert may still use the remaining information in the header to track down the originating mail user agent. If set to the value `noagent', then the mentioned `Message-Id:' suppression doesn't occur.

toplines
    If defined, gives the number of lines of a message to be printed out with the top command; normally, the first five lines are printed.

ttycharset
    The character set of the terminal \%S-nail operates on, and the one and only supported character set that \%S-nail can use if no character set conversion capabilities have been compiled into it, in which case it defaults to `ISO-8859-1' unless it can deduce a value from the `LC_CTYPE' locale environment. Refer to the section Character sets for the complete picture about character sets.

VISUAL
    Pathname of the text editor to use in the visual command and `~v' tilde escape.

ENVIRONMENT
Besides the variables described above, \%S-nail uses the following environment variables:

COLUMNS
    The user's preferred width in column positions for the terminal screen or window (only used during startup).

HOME
    The user's home directory.

LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES
    See locale(7).

LINES
    The user's preferred number of lines on a page or the vertical screen or window size in lines (only used during startup).

MAILRC
    Is used as a startup file instead of \%~/.mailrc if set. When \%S-nail scripts are invoked on behalf of other users, this variable should be set to /dev/null to avoid side-effects from reading their configuration files.

NAILRC
    If this variable is set and MAILRC is not, it is treated as a startup configuration file and read.

NAIL_NO_SYSTEM_RC
    If this variable is set then reading of \%/etc/s-nail.rc at startup is inhibited, i.e., the same effect is achieved as if \%S-nail had been started up with the option -n.

SYSV3
    Changes the letters printed in the first column of a header summary.

TMPDIR
    Used as directory for temporary files instead of /tmp, if set.

FILES

\%~/.mailrc
    File giving initial commands.

\%/etc/s-nail.rc
    System wide initialization file.

~/.mime.types
    Personal MIME types.

/etc/mime.types
    System wide MIME types.

EXAMPLES

  Getting started
The \%S-nail command has two distinct usages, according to whether one wants to send or receive mail. Sending mail is simple: to send a message to a user whose email address is, say, `<bill@host.example>', use the shell command:

    $ \%s-nail bill@host.example

then type your message. \%S-nail will prompt you for a message `Subject:' first; after that, lines typed by you form the body of the message. When you reach the end of the message, type an EOT (`control-D') at the beginning of a line, which will cause \%S-nail to echo `EOT' and return you to the shell.

If, while you are composing the message you decide that you do not wish to send it after all, you can abort the letter by typing two `RUBOUT' (interrupt) characters. Typing a single `RUBOUT' causes \%S-nail to print `(Interrupt -- one more to kill letter)'. Typing a second `RUBOUT' causes \%S-nail to save your partial letter on the file DEAD and abort the letter. Once you have sent mail to someone, there is no way to undo the act, so be careful.

If you want to send the same message to several other people, you can list their email addresses on the command line.

    $ \%s-nail sam@workstation.example bob@server.example
    Subject: Fees
    Tuition fees are due next Friday.  Don't forget!
    <control-D>
    EOT
    $

will sendout to `<sam@workstation.example>' and `<bob@server.example>'. To read your mail, simply type

    $ \%s-nail

\%S-nail will respond by typing its version number and date and then listing the messages you have waiting. Then it will type a prompt and await your command. The messages are assigned numbers starting with 1 – you refer to the messages with these numbers. \%S-nail keeps track of which messages are `new' (have been sent since you last read your mail) and `read' (have been read by you). New messages have an `N' next to them in the header listing and old, but unread messages have a `U' next to them. \%S-nail keeps track of new/old and read/unread messages by putting a header field called `Status' into your messages.

To look at a specific message, use the type command, which may be abbreviated to simply `t'. For example, if you had the following messages:

    O 1 drfoo@myhost.example Wed Sep  1 19:52   5/421 "Fees"
    O 2 sam@friends.example  Thu Sep  2 00:08  30/895

you could examine the first message by giving the command:

    type 1

which might cause \%S-nail to respond with, for example:

    [-- Message  1 -- 5 lines, 421 bytes --]:
    From drfoo@myhost.example Wed Sep  1 19:52:25 2004
    Subject: Fees
    Status: R
    Tuition fees are due next Wednesday.  Don't forget!

Many \%S-nail commands that operate on messages take a message number as an argument, just as the shown type command. For these commands, there is a notion of a current message. When you enter the \%S-nail program, the current message is initially the first (or the first recent) one. Thus, you can often omit the message number and use, for example, `t` to type the current message. As a further shorthand, you can type a message by simply giving its message number – hence `1` would type the first message.

Frequently, it is useful to read the messages in your mailbox in order, one after another. You can read the next message in \%S-nail by simply typing a newline. As a special case, you can type a newline as your first command to \%S-nail to type the first message.

If, after typing a message, you wish to immediately send a reply, you can do so with the command reply. This command, like type, takes a message number as an argument. \%S-nail then begins a message addressed to the user who sent you the message and let you type in your letter in reply, followed by a `<control-D>' at the beginning of a line, as before.

Note that \%S-nail copies the subject header from the original message. This is useful in that correspondence about a particular matter will tend to retain the same subject heading, making it easy to recognize. If there are other header fields in the message, like `Cc:', the information found will also be used.

Sometimes you will receive a message that has been sent to several people and wish to reply only to the person who sent it. Reply (with a capital `R') replies to a message, but sends a copy to the sender only.

If you wish, while reading your mail, to send a message to someone, but not as a reply to one of your messages, you can send the message directly with the mail command, which takes as arguments the names of the recipients you wish to send to. For example, to send a message to `<frank@machine.example>':

    mail frank@machine.example

To delete a message from the mail folder, you can use the command delete. In addition to not saving deleted messages, \%S-nail will not let you type them, either. The effect is to make the message disappear altogether, along with its number.

Many features of \%S-nail can be tailored to your liking with the set command; it has two forms, depending on whether you are setting a `binary' or a `valued' option. Binary options are either on or off – for example, the askcc option informs \%S-nail that each time you send a message, you want it to prompt you for a `Cc:' header to be included in the message. To set the askcc option, you would type

    set askcc

Valued options are values which \%S-nail uses to adapt to your tastes. For example, the record option tells \%S-nail where to save messages sent by you, and is specified by, e.g.,

    set record=Sent

Note that no spaces are allowed in `set record=Sent'.

\%S-nail includes a simple facility for maintaining groups of messages together in folders. To use the folder facility, you must tell \%S-nail where you wish to keep your folders. Each folder of messages will be a single file. For convenience, all of your folders are kept in a single directory of your choosing. To tell \%S-nail where your folder directory is, put a line of the form

    set folder=letters

in your \%~/.mailrc file. If, as in the example above, your folder directory does not begin with a `/', \%S-nail will assume that your folder directory is to be found starting from your home directory.

Anywhere a file name is expected, you can use a folder name, preceded with `+'. For example, to put a message into a folder with the save command, you can use:

    save +classwork

to save the current message in the `classwork' folder. If the `classwork' folder does not yet exist, it will be created. Note that messages which are saved with the save command are automatically removed from your system mailbox.

In order to make a copy of a message in a folder without causing that message to be removed from your system mailbox, use the copy command, which is identical in all other respects to the save command.

The folder command can be used to direct \%S-nail to the contents of a different folder. For example,

    folder +classwork

directs \%S-nail to read the contents of the `classwork' folder. All of the commands that you can use on your system mailbox are also applicable to folders, including type, delete, and reply. To inquire which folder you are currently editing, use `folder' without arguments. And to list your current set of folders, use the folders command.

Finally, the help command is available to print out a brief summary of the most important \%S-nail commands.

While typing in a message to be sent to others it is often useful to be able to invoke the text editor on the partial message, print the message, execute a shell command, or do some other auxiliary function. \%S-nail provides these capabilities through `tilde escapes', which consist of a tilde (`~') at the beginning of a line, followed by a single character which indicates the function to be performed. For example, to print the text of the message so far, use:

    ~p

which will print a line of dashes, the recipients of your message, and the text of the message so far. A list of the most important tilde escapes is available with `~?'.

  IMAP or POP3 client setup
[Optional] First you need the following data from your ISP: the host name of the IMAP or POP3 server, user name and password for this server, and a notice whether the server uses SSL/TLS encryption. Assuming the SSL/TLS secured host name of your IMAP account is `server.myisp.example' and your user name for that server is `mylogin', you could refer to this account using the folder command or the -f command line option with

    imaps://mylogin@server.myisp.example

(This string is not necessarily the same as your Internet mail address.) Even if the server does not accept IMAPS or POP3S connections, it is possible that it supports the `STARTTLS' method of upgrading already connected, but not yet authenticated sessions to use SSL/TLS encryption. The only reliable method to see if this works is to try it; enter one of

    set imap-use-starttls
    set pop3-use-starttls

before you initiate the connection, dependent on the actual protocol.

As you probably want messages to be deleted from this account after saving them, prefix it with `%:'. The shortcut command can be used to avoid typing that many characters every time you want to connect:

    shortcut myisp %:imaps://mylogin@server.myisp.example

You might want to put this string into a startup file. shortcut is one of those commands that are specific to \%S-nail and will thus confuse other implementations of POSIX mailx(1), so it should possibly not be placed in \%~/.mailrc. Instead, put

    set NAIL_EXTRA_RC=.\%s-nailrc

in \%~/.mailrc and create a file ~/.\%s-nailrc containing all the commands that are specific to \%S-nail. You can then access your remote mailbox by invoking

    \%s-nail -f myisp

on the command line, or by executing

    fi myisp

within \%S-nail. If you want to use more than one IMAP mailbox on a server, or if you want to use the IMAP server for mail storage too, the account command (which is also \%S-nail-specific) is possibly more appropriate. You can put the following in ~/.\%s-nailrc:

    account myisp {
       set folder=imaps://mylogin@server.myisp.example
       set record=+Sent MBOX=+mbox outfolder
    }

and can then access incoming mail for this account by invoking `\%s-nail -A myisp' on the command line or by executing `ac myisp' within \%S-nail. After that, a command like `copy 1 +otherfolder' will refer to `otherfolder' on the IMAP server. In particular, `fi &' will change to the `mbox' folder, and `fi +Sent' will show your recorded sent mail, with both folders located on the IMAP server.

\%S-nail will ask you for a password string each time you connect to a remote account. If you can reasonably trust the security of your workstation, you can give this password in the startup file as

    set password-mylogin@server.myisp.example="SECRET"

You should change the permissions of this file to 0600, see chmod(1).

\%S-nail supports different authentication methods for both IMAP and POP3. If Kerberos is used at your location, you can try to activate (the optional) GSSAPI-based authentication via

    set imap-auth=gssapi

The advantage of this method is that \%S-nail doesn't need to know your password at all, nor does it have to send sensitive data over the network. If that isn't possible, try to use authentication methods that at least avoid sending the password in clear over the wire, which is especially important if SSL/TLS cannot be used, e.g.,

    set imap-auth=cram-md5

For POP3 \%S-nail will try to use the `APOP' mechanism automatically unless explicitly disabled. If the server does not offer any such authentication methods, conventional user/password based authentication must be used. It is sometimes helpful, especially when setting up an account or when there are authentification problems, to enable verbosity by setting the verbose option – \%S-nail will display all data sent to the server in clear text on the screen when this option is set. (Because this may also include passwords you should take care that no unauthorized person can look at your terminal when this option is set.)

If you regularly use the same workstation to access IMAP accounts, you can greatly enhance performance by enabling local caching of IMAP messages. For any message that has been fully or partially fetched from the server, a local copy is made and is used when the message is accessed again, so most data is transferred over the network once only. To enable the IMAP cache, select a local directory name and put

    set imap-cache=~/localdirectory

in the (\%S-nail-specific) startup file. All files within that directory can be overwritten or deleted by \%S-nail at any time, so you should not use the directory to store other information.

Once the cache contains some messages, it is not strictly necessary anymore to open a connection to the IMAP server to access them. When \%S-nail is invoked with the option -D, or when the disconnected variable is set, only cached data is used for any folder you open. Messages that have not yet been completely cached are not available then, but all other messages can be handled as usual. Changes made to IMAP mailboxes in disconnected mode are committed to the IMAP server next time it is used in online mode. Synchronizing the local status with the status on the server is thus partially within your responsibility; if you forget to initiate a connection to the server again before you leave your location, changes made on one workstation are not available on others. Also if you alter IMAP mailboxes from a workstation while uncommitted changes are still pending on another, the latter data may become invalid. The same might also happen because of internal server status changes. You should thus carefully evaluate this feature in your environment before you rely on it.

Many servers will close the connection after a short period of inactivity – use one of

    set pop3-keepalive=30
    set imap-keepalive=240

to send a keepalive message each 30 seconds for POP3, or each 4 minutes for IMAP.

If you encounter problems connecting to a SSL/TLS server, try the ssl-rand-egd and ssl-rand-file variables (see the OpenSSL FAQ for more information) or specify the protocol version with ssl-method. Contact your ISP if you need a client certificate or if verification of the server certificate fails. If the failed certificate is indeed valid, fetch its CA certificate by executing the shell command

    $ </dev/null openssl s_client -showcerts -connect \
          server.myisp.example:imaps 2>&1 | tee log.txt

(see s_client(1) ) and put it into the file specified with ssl-ca-file. The data you need is located at the end of the certificate chain within (and including) the `BEGIN CERTIFICATE' and `END CERTIFICATE' lines. Note that the example above is insecure! One should use the `-verify' and `-CAfile' options of s_client(1) to be ``on the safe side'' regarding the fetched certificates.

  Reading HTML mail
You need either the elinks(1) or lynx(1) utility or another command-line web browser that can write plain text to standard output.

    set pipe-text/html="elinks -force-html -dump 1"
    set pipe-text/html="lynx -stdin -dump -force_html"

will cause HTML message parts to be converted into a more friendly form.

  Viewing PDF attachments
Most PDF viewers do not accept input directly from a pipe. It is thus necessary to store the attachment in a temporary file first:

    set pipe-application/pdf="@&cat >/tmp/\%s-nail$$.pdf; \
          acroread /tmp/\%s-nail$$.pdf; rm /tmp/\%s-nail$$.pdf"

Note that security defects are discovered in PDF viewers from time to time. Automatical command execution like this can compromise your system security, in particular if you stay not always informed about such issues.

  Signed and encrypted messages with S/MIME
[Optional] S/MIME provides two central mechanisms: message signing and message encryption. A signed message contains some data in addition to the regular text. The data can be used to verify that the message was sent using a valid certificate, that the sender's address in the message header matches that in the certificate, and that the message text has not been altered. Signing a message does not change its regular text; it can be read regardless of whether the recipient's software is able to handle S/MIME. It is thus usually possible to sign all outgoing messages if so desired. Encryption, in contrast, makes the message text invisible for all people except those who have access to the secret decryption key. To encrypt a message, the specific recipient's public encryption key must be known. It is thus not possible to send encrypted mail to people unless their key has been retrieved from either previous communication or public key directories. A message should always be signed before it is encrypted. Otherwise, it is still possible that the encrypted message text is altered.

A central concept to S/MIME is that of the certification authority (CA). A CA is a trusted institution that issues certificates. For each of these certificates it can be verified that it really originates from the CA, provided that the CA's own certificate is previously known. A set of CA certificates is usually delivered with OpenSSL and installed on your system. If you trust the source of your OpenSSL software installation, this offers reasonable security for S/MIME on the Internet. In general, a certificate cannot be more secure than the method its CA certificate has been retrieved with, though. Thus if you download a CA certificate from the Internet, you can only trust the messages you verify using that certificate as much as you trust the download process.

The first thing you need for participating in S/MIME message exchange is your personal certificate, including a private key. The certificate contains public information, in particular your name and your email address, and the public key that is used by others to encrypt messages for you, and to verify signed messages they supposedly received from you. The certificate is included in each signed message you send. The private key must be kept secret. It is used to decrypt messages that were previously encrypted with your public key, and to sign messages.

For personal use it is recommended that you get a S/MIME certificate from one of the major CAs on the Internet using your WWW browser. (Many CAs offer such certificates for free.) You will usually receive a combined certificate and private key in PKCS#12 format which \%S-nail does not directly accept. To convert it to PEM format, use the following shell command:

    $ openssl pkcs12 -in cert.p12 -out cert.pem -clcerts -nodes

If you omit the `-nodes' parameter, you can specifiy an additional `PEM pass phrase' for protecting the private key. \%S-nail will then ask you for that pass phrase each time it signs or decrypts a message. You can then use

    set smime-sign-cert-myname@myisp.example=cert.pem

to make this private key and certificate known to \%S-nail. You can now sign outgoing messages. Just use

    set smime-sign

to do so. From each signed message you send, the recipient can fetch your certificate and use it to send encrypted mail back to you. Accordingly if somebody sends you a signed message, you can do the same. First use the verify command to check the validity of the certificate. After that, retrieve the certificate and tell \%S-nail that it should use it for encryption:

    certsave filename
    set smime-encrypt-user@host=filename

You should carefully consider if you prefer to store encrypted messages in decrypted form. If you do, anybody who has access to your mail folders can read them, but if you do not, you might be unable to read them yourself later if you happen to lose your private key. The decrypt command saves messages in decrypted form, while the save, copy, and move commands leave them encrypted.

Note that neither S/MIME signing nor encryption applies to message subjects or other header fields. Thus they may not contain sensitive information for encrypted messages, and cannot be trusted even if the message content has been verified. When sending signed messages, it is recommended to repeat any important header information in the message text.

  Using CRLs with S/MIME or SSL/TLS
[Optional] Certification authorities (CAs) issue certificate revocation lists (CRLs) on a regular basis. These lists contain the serial numbers of certificates that have been declared invalid after they have been issued. Such usually happens because the private key for the certificate has been compromised, because the owner of the certificate has left the organization that is mentioned in the certificate, etc. To seriously use S/MIME or SSL/TLS verification, an up-to-date CRL is required for each trusted CA. There is otherwise no method to distinguish between valid and invalidated certificates. \%S-nail currently offers no mechanism to fetch CRLs, nor to access them on the Internet, so you have to retrieve them by some external mechanism.

\%S-nail accepts CRLs in PEM format only; CRLs in DER format must be converted, like, e.g.:

    $ openssl crl -inform DER -in crl.der -out crl.pem

To tell \%S-nail about the CRLs, a directory that contains all CRL files (and no other files) must be created. The smime-crl-dir or ssl-crl-dir variables, respectively, must then be set to point to that directory. After that, \%S-nail requires a CRL to be present for each CA that is used to verify a certificate.

  Handling spam
[Optional] \%S-nail can make use of spam detection and learning facilities – more precisely, SpamAssassin (<http://spamassassin.apache.org>). A very comprehensive documentation of spamassassin(1) can be found at the O'Reilly Commons (<http://commons.oreilly.com/wiki/index.php/SpamAssassin>).

Currently \%S-nail supports interaction with spamassassin(1) only via its daemonized spamd(1) / spamc(1) server / client pair, which means that, in order to detect and work with spam through \%S-nail, an instance of the spamd(1) daemon must be running (the examples are equivalent):

    $ spamd -i localhost:2142 -i /tmp/.spamsock -d [-L] [-l]
    $ spamd --listen=localhost:2142 --listen=/tmp/.spamsock \
        --daemonize [--local] [--allow-tell]

Note that if spamd(1) should only listen on a local, path-based UNIX domain socket instead of offering its service over the network, it maybe necessary to use a single --socketpath option instead of the shown --listen. In order to support training of the Bayesian classifier through \%S-nail, spamd(1) must have been started with the --allow-tell option.

Once spamd(1) is running \%S-nail can classify messages by using the client side program, spamc(1), as in:

    $ \%s-nail -Sspam-command=/usr/local/bin/spamc \
        -Sspam-socket=/tmp/.spamsock -Sspam-maxsize=500000

The commands offered are spamclear and spamset, which simply set an ``is-spam'' flag that can be used for, e.g., message selection, spamrate, which passes messages through to the spam detector in order to gain a spam score and conditionally set the ``is-spam'' flag accordingly, as well as the Bayesian filter related spamforget, spamham and spamspam.

Because messages must exist on local storage in order to be scored (or used for Bayesian filter training), it is possibly a good idea to perform the local spam check last:

    define spamdelhook {
    	# Server side DCC
    	spamset (header x-dcc-brand-metrics "bulk")
    	# Server-side spamassassin(1)
    	spamset (header x-spam-flag "YES")
    	del :s # TODO we HAVE to be able to do `spamrate :u ! :s'
    	# And finally the local spamc(1)
    	spamrate :u
    	del :s
    }
    set folder-hook-FOLDER=spamdelhook

See also the documentation for the variables spam-command, spam-host, spam-port, spam-socket, spam-user and spam-maxsize.

  Sending mail from scripts
If you want to send mail from scripts, you must be aware that \%S-nail reads the user's configuration files by default. So unless your script is only intended for your own personal use (as, e.g., a cron job), you need to circumvent this:

    MAILRC=/dev/null \%s-nail -n

You then need to create a script-local configuration for \%S-nail. This can be done by either pointing the MAILRC variable to a custom configuration file, by passing the configuration in environment variables, or by using the -S command line option to specify options. Since many configuration options are not valid shell variables, the env(1) command is useful if the approach via environment variables is used:

    env MAILRC=/dev/null from=scriptreply@domain smtp=host \
        smtp-auth-user=login smtp-auth-password=secret \
        smtp-auth=login \%s-nail -n -s "subject" \
        -a attachment_file recipient@domain < content_file

SEE ALSO
file(1), fmt(1), more(1), newaliases(1), openssl(1), printf(1), sendmail(1), sh(1,) spamassassin(1), spamc(1), spamd(1), vacation(1), editline(3), iconv(3), readline(3), setlocale(3), ssl(3), aliases(5), locale(7), mailaddr(7), mailwrapper(8)

IMPLEMENTATION NOTES
The character set conversion uses and relies upon the iconv(3) function. Its functionality differs widely between the various system environments \%S-nail runs on.

Limitations with IMAP mailboxes are: It is not possible to edit messages, but it is possible to append them. Thus to edit a message, create a local copy of it, edit it, append it, and delete the original. The line count for the header display is only appropriate if the entire message has been downloaded from the server. The marking of messages as `new' is performed by the IMAP server; use of the exit command instead of quit will not cause it to be reset, and if the autoinc/newmail variables are unset, messages that arrived during a session will not be in state `new' anymore when the folder is opened again. Also if commands queued in disconnected mode are committed, the IMAP server will delete the `new' flag for all messages in the changed folder, and new messages will appear as unread when it is selected for viewing later. The `flagged', `answered', and `draft' attributes are usually permanent, but some IMAP servers are known to drop them without notification. Message numbers may change with IMAP every time before the prompt is printed if \%S-nail is notified by the server that messages have been deleted by some other client or process. In this case, `Expunged n messages' is printed, and message numbers may have changed.

Limitations with POP3 mailboxes are: It is not possible to edit messages, they can only be copied and deleted. The line count for the header display is only appropriate if the entire message has been downloaded from the server. The status field of a message is maintained by the server between connections; some servers do not update it at all, and with a server that does, the `exit' command will not cause the message status to be reset. The `newmail' command and the `newmail' variable have no effect. It is not possible to rename or to remove POP3 mailboxes.

If a `RUBOUT' (interrupt) is typed while an IMAP or POP3 operation is in progress, \%S-nail will wait until the operation can be safely aborted, and will then return to the command loop and print the prompt again. When a second `RUBOUT' is typed while \%S-nail is waiting for the operation to complete, the operation itself will be cancelled. In this case, data that has not been fetched yet will have to be fetched before the next command can be performed. If the cancelled operation was using an SSL/TLS encrypted channel, an error in the SSL transport will very likely result and render the connection unusable.

As \%S-nail is a mail user agent, it provides only basic SMTP services. If it fails to contact its upstream SMTP server, it will not make further attempts to transfer the message at a later time, and it does not leave other information about this condition than an error message on the terminal and an entry in DEAD. This is usually not a problem if the SMTP server is located in the same local network as the computer on which \%S-nail is run. However, care should be taken when using a remote server of an ISP; it might be better to set up a local SMTP server then which just acts as a proxy.

\%S-nail immediately contacts the SMTP server (or sendmail(1) ) even when operating in disconnected mode. It would not make much sense for \%S-nail to defer outgoing mail since SMTP servers usually provide much more elaborated delay handling than \%S-nail could perform as a client. Thus the recommended setup for sending mail in disconnected mode is to configure a local SMTP server such that it sends outgoing mail as soon as an external network connection is available again, i.e., to advise it to do that from a network startup script.

HISTORY
A mail command appeared in Version 1 AT&T Unix. Berkeley Mail was written in 1978 by Kurt Shoens. This man page is derived from from The Mail Reference Manual originally written by Kurt Shoens. ``Heirloom Mailx'' enhancements are maintained and documented by Gunnar Ritter. ``S-nail'' enhancements are maintained and documented by Steffen "Daode" Nurpmeso.

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology – Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright © 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at <http://www.opengroup.org/unix/online.html>. Redistribution of this material is permitted so long as this notice remains intact.

AUTHORS
Kurt Shoens, Christos Zoulas, Gunnar Ritter, Steffen "Daode" Nurpmeso <sdaoden@users.sf.net>

BUGS
Variables in the environment passed to \%S-nail cannot be unset.