NAIL(1)

NAME
nail - send and receive Internet mail

SYNOPSIS
nail [-BDdEFintv~] [-s subject] [-a attachment ] [-c cc-addr] [-b bcc-addr] [-r from-addr] [-h hops] [-A account] [-S variable[=value]] to-addr . . .
nail [-BDdeEHiInNRv~] [-T name] [-A account] [-S variable[=value]] -f [name]
nail [-BDdeEinNRv~] [-A account] [-S variable[=value]] [-u user]

DESCRIPTION
Nail is an intelligent mail processing system, which has a command syntax reminiscent of ed(1) with lines replaced by messages. It is based on Berkeley Mail 8.1, is intended to provide the functionality of the POSIX mailx command, and offers extensions for MIME, IMAP, POP3, SMTP, and S/MIME. Nail provides enhanced features for interactive use, such as caching and disconnected operation for IMAP, message threading, scoring, and filtering. It is also usable as a mail batch language, both for sending and receiving mail.

The following options are accepted:

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

-a file
    Attach the given file to the message.

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

-b address
    Send blind carbon copies to list. List should be a comma-separated list of names.

-c address
    Send carbon copies to list of users.

-D  Start in disconnected mode; see the description for the disconnected variable option.

-d  Enables debugging messages and disables the actual delivery of messages. Unlike -v, this option is intended for nail development only.

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

-E  If an outgoing message does not contain any text in its first or only message part, do not send it but discard it silently, effectively setting the skipemptybody variable at program startup. This is useful for sending messages from scripts started by cron(8).

-f [file]
    Read in the contents of the user's mbox (or the specified file) for processing; when nail is quit, it writes undeleted messages back to this file. The string file is handled as described for the folder command below.

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

-H  Print header summaries for all messages and exit.

-h hops
    Invoke sendmail with the specified hop count. This option has no effect when SMTP is used for sending mail.

-i  Ignore tty interrupt signals. This is particularly useful when using nail on noisy phone lines.

-I  Shows the `Newsgroup:' or `Article-Id:' fields in the header summary. Only applicable in combination with -f.

-n  Inhibits reading /etc/nail.rc upon startup. This option should be activated for nail scripts that are invoked on more than one machine, because the contents of that file may differ between them.

-N  Inhibits the initial display of message headers when reading mail or editing a mail folder.

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

-r address
    Sets the From address. Overrides any from variable specified in environment or startup files. Tilde escapes are disabled. The -r address options are passed to the mail transfer agent unless SMTP is used. This option exists for compatibility only; it is recommended to set the from variable directly instead.

-R  Opens any folders read-only.

-s subject
    Specify subject on command line (only the first argument after the -s flag is used as a subject; be careful to quote subjects containing spaces).

-S variable[=value]
    Sets the internal option variable and, in case of a string option, assigns value to it.

-T name
    Writes the `Message-Id:' and `Article-Id:' header fields of each message read in the file name. Implies -I. Compressed files are handled as described for the folder command below.

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

-u user
    Reads the mailbox of the given user name.

-v  Verbose mode. The details of delivery are displayed on the user's terminal.

-V  Print nail's version and exit.

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

  Sending mail
To send a message to one or more people, nail can be invoked with arguments which are the names of people to whom the mail will be sent. The user is then expected to type in his message, followed by an `control-D' at the beginning of a line. The section below Replying to or originating mail, describes some features of nail available to help when composing letters.

  Reading mail
In normal usage 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 user can move among the messages much as he moves between lines in ed(1), with the commands `+' and `-' moving backwards and forwards, and simple numbers.

  Disposing of mail
After examining a message the user can delete `d') the message or reply `r') to it. Deletion causes the nail program to forget about the message. This is not irreversible; the message can be undeleted `u') by giving its number, or the nail session can be aborted 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, while `delete 1-5' deletes messages 1 through 5. In sorted or threaded mode (see the sort and thread commands), `delete 1-5' deletes 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.

:k  All `killed' messages.

:j  All messages classified as junk.

.   The current message.

;   The message that was previously the current message.

,   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.

(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, 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

    ("real name" "source-route" "local-part" "domain-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))'; `(or a b c)' 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.

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

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

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

(subject string)
    All messages that contain string in the Subject: field.

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

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

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

(text string)
    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; date must be in the form d[d]-mon-yyyy, where d[d] is 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. "30-Aug-2004".

(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, 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 reply command 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 then, up to an end-of-file, defines the contents of the message. While the user is composing a message, 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 (see 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 nail session with 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. (See the -f option above).

  Personal and systemwide distribution lists
It is also possible to create a 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 by placing a line like
        alias cohorts bill ozalp jkf mark kridle@ucbcory
in the file .mailrc in the user's home directory. The current list of such aliases can be displayed with the alias command in nail. System wide distribution lists can be created by editing /etc/aliases, see aliases(5) and sendmail(8); these are kept in a different syntax. In mail the user sends, personal aliases will be expanded in mail sent to others so that they will be able to reply to the recipients. System wide aliases are not expanded when the mail is sent, but any reply returned to the machine will have the system wide alias expanded as all mail goes through sendmail.

  Recipient address specifications
When an address is used to name a recipient (in any of To, Cc, or Bcc), names of local mail folders and pipes to external commands can also be specified; the message text is then written to them. The rules are: Any name which starts with a `|' 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 `@' character is treated as a mail address; any other name which starts with a `+' character specifies a folder name; any other name which contains a `/' character but no `!' or `%' 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 below.

  Network mail (Internet / ARPA, UUCP, Berknet)
See mailaddr(7) for a description of network addresses. Nail has a number of options which can be set in the .mailrc file to alter its behavior; thus `set askcc' enables the askcc feature. (These options are summarized below).

  MIME types
For any outgoing attachment, 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 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, the first for text or international text files, the second for any file that contains formatting characters other than newlines and horizontal tabulators.

  Character sets
Nail normally detects the character set of the terminal using the LC_CTYPE locale setting. If the locale cannot be used appropriately, the ttycharset variable should be set to provide an explicit value. When reading messages, their text is converted to the terminal character set if possible. Unprintable characters and illegal byte sequences are detected and replaced by Unicode substitute characters or question marks unless the print-all-chars is set at initialization time.

The character set for outgoing messages is not necessarily the same as the one used on the terminal. If an outgoing text message contains characters not representable in US-ASCII, the character set being used must be declared within its header. Permissible values can be declared using the sendcharsets variable, separated by commas; nail tries each of the values in order and uses the first appropriate one. If the message contains characters that cannot be represented in any of the given character sets, the message will not be sent, and its text will be saved to the `dead.letter' file. Messages that contain NUL bytes are not converted.

Outgoing attachments are converted if they are plain text. If the sendcharsets variable contains more than one character set name, the ~@ tilde escape will ask for the character sets for individual attachments if it is invoked without arguments.

Best results are usually achieved when nail is run in a UTF-8 locale on a UTF-8 capable terminal. 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.

  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, nail types `applicable messages' and aborts the command. If the command begins with a # sign, the line is ignored.

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

•   An argument can be enclosed between paired double-quotes "" or single-quotes ''; 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:

-   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.

!   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 nail that the listed addresses all belong to the invoking user. When he replies to messages, 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 a 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
    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
    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 messages' originators by setting the smime-encrypt-user@host variable.

chdir
    (ch) Changes the user's working directory to that specified, if given. If no directory is given, then changes to the user's login directory.

classify
    (cl) Takes a list of messages and examines their contents for characteristics of junk mail using Bayesian filtering. Messages considered to be junk are then marked as such. The junk mail database is not changed.

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
    (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 messages it is used on 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
    (dec) For unencrypted messages, this command is identical to copy. Encrypted messages are first decrypted, if possible, and then copied.

Decrypt
    (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
        }

    Once defined, a macro can be explicitly invoked using the call command, or 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
    (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 information. 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 current mailbox available for disconnected use.

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

draft
    Takes a message list and marks each 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 folder command. The escape sequences `\a', `\b', `\c', `\f', `\n', `\r', `\t', `\v', `\\', and `\0num' are interpreted as with the echo(1) command.

edit
    (e) Takes a list of messages and points the text editor at each one 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 then 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 imap-list-depth variable.

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. # means the previous file, % means the invoking user's system mailbox, %user means user's system mailbox, & means the invoking user's mbox file, 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 e. g. by the mbox and save commands. If the name matches one of the strings defined with the shortcut command, it is replaced by its long form and expanded. If the name ends with .gz or .bz2, it is treated as compressed with gzip(1) or bzip2(1), respectively. Likewise, if name does not exist, but either name.gz or name.bz2 exists, the compressed file is used. If name refers to a directory with the subdirectories `tmp', `new', and `cur', 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 supported protocols are currently imap (IMAP v4r1), imaps (IMAP with SSL/TLS encryption), pop3 (POP3), and pop3s (POP3 with SSL/TLS encryption). 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 nail is connected to an IMAP server, a name of the form @mailbox refers to the mailbox on that server. If the `folder' variable refers to an IMAP account, the special name `%' selects the `INBOX' on that account.

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 forward command. This command has no effect when the forward-as-attachment option is set.

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

good
    (go) Takes a list of messages and marks all of them as not being junk mail. Data from these messages is then inserted into the junk mail database for future classification.

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

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. 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 nail's startup files can be executed conditionally depending on whether the user is sending or receiving mail with the if command. For example:
            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 command 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. If ignore is executed with no arguments, it lists the current set of ignored fields.

imap
    Sends command strings directly to the current IMAP server. 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
        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
        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 namespace prefix and a hierarchy separator is listed. Not all IMAP servers support this command.

inc Same as newmail.

junk
    (j) Takes a list of messages and marks all of them as junk mail. Data from these messages is then inserted into the junk mail database for future classification.

kill
    (k) Takes a list of messages and `kills' them. Killed messages are not printed in header summaries, and are ignored by the next command. The kill command also sets the score of the messages to negative infinity, so that subsequent score commands will not unkill them again. Killing is only effective for the current session on a folder; when it is quit, all messages are automatically unkilled.

list
    Prints the names of all available commands.

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 as argument login names and distribution group names and sends mail to those people.

mbox
    Indicate that a list of messages be sent to mbox in the user's home directory when nail is quit. This is the default action for messages if unless the hold option is set. 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.

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

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 CR) 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.

probability
    (prob) For each word given as argument, the contents of its junk mail database entry are printed.

quit
    (q) Terminates the session, saving all undeleted, unsaved messages in the user's mbox file in his login directory, 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 -f flag, 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 message. 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. If retain is executed with no arguments, it lists the current set of retained fields.

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
    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
    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.

score
    (sc) Takes a message list and a floating point number and adds the number to the score of each given message. All messages start at score 0 when a folder is opened. When the score of a message becomes negative, it is `killed' with the effects described for the kill command; otherwise if it was negative before and becomes positive, it is `unkilled'. Scores only refer to the currently opened instance of a folder.

set (se) With no arguments, prints all variable values, piped through the pager if the output does not fit on the screen. Otherwise, sets option. Arguments are of the form option=value (no space before or after =) or option. Quotation marks may be placed around any part of the assignment statement to quote blanks or tabs, i.e. `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. With no arguments, a list of defined shortcuts is printed.

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

size
    Takes a message list and prints out the size in characters of each message.

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.

    score
        Sort the messages by their score.

    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 thread command.

    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.

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 the mbox file. 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.

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. The group names no longer have any significance.

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 marks each message as a draft.

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.

ungood
    Takes a message list and undoes the effect of a good command that was previously applied on exactly these messages.

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

unjunk
    Takes a message list and undoes the effect of a junk command that was previously applied on exactly these messages.

unkill
    Takes a message list and `unkills' each message. Also sets the score of the messages to 0.

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
    (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, if 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; if the contents of the first part are not to be saved, `write /dev/null' can be used. For the second and subsequent parts, if the filename given starts with a `|' character, the part is piped through the remainder of the filename interpreted as a shell command. In non-interactive mode, only the parts of the multipart message that have a filename given in the part header are written, the other 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   Nail presents message headers in windowfuls as described under the headers command. The z 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 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 when composing messages to perform special functions. 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.

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

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

~<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. First, the user can edit all existing attachment data. 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, nail will ask for further attachments, until an empty file name is given. If filename arguments are specified, all of them are appended to the end of the attachment list. Filenames which contain white space can only be specified with the first method (no filename arguments).

~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.

~bname . . .
    Add the given names to the list of carbon copy recipients but do not make the names visible in the Cc: line (`blind' carbon copy).

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

~d  Read the file `dead.letter' from the user's home directory 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.

~fmessages
    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.

~Fmessages
    Identical to ~f, except all message headers and all 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 append text to the end or modify the field by using the current terminal erase and kill characters.

~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, and ORGANIZATION variables. If this tilde command has been used, changing the variables has no effect on the current message anymore.

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

~mmessages
    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 command) are not included. For MIME multipart messages, only the first printable part is included.

~Mmessages
    Identical to ~m, except all message headers and all 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. If the message text is longer than the screen size, it is piped through the pager.

~q  Abort the message being sent, copying the message to `dead.letter' in the user's home directory if save is set.

~rfilename
    Read the named file into the message.

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

~tname . . .
    Add the given names 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.

~wfilename
    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 to the `dead.letter' file.

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

~:nail-command
    Execute the given nail command. Not all commands, however, are allowed.

~_nail-command
    Identical to ~:.

~~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.

  Variable options
Options are controlled via set and unset commands, see their entries for a syntax description. An option is also set if it is passed to nail as part of the 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:

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 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, nail asks for files to attach at the end of each message. Responding with a newline indicates not to include an attachment.

askcc
    Causes the user to be prompted for additional carbon copy recipients (at the end of each message if askatend or bsdcompat is set). Responding with a newline indicates the user's satisfaction with the current list.

askbcc
    Causes the user to be prompted for additional blind carbon copy recipients (at the end of each message if askatend or bsdcompat is set). Responding with a newline indicates the user's satisfaction with the current list.

asksign
    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.

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', setting prompt to `& ', and changing the default pager to more.

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.

chained-junk-tokens
    Normally, the Bayesian junk mail filter bases its classifications on single word tokens extracted from messages. If this option is set, adjacent words are combined to pairs, which are then used as additional tokens. This usually improves the accuracy of the filter, but also increases the junk mail database five- to tenfold.

datefield
    The date in a header summary is normally the date of the mailbox `From ' line of the message. If this variable is set, the date as given in the `Date:' header field is used, converted to local time.

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

disconnected
    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.letter' 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 nail to interpret a period alone on a line as the terminator of a message the user is sending.

editheaders
    When a message is edited while being composed, its header is included in the editable text. `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, nail normally prints `No mail for user' and exits immediately. If this option is set, 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, and all of their parts are included. The fwdignore and fwdretain options are ignored when the forward-as-attachment option is set.

fullnames
    When replying to a message, 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.

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

ignoreeof
    An option related to dot is ignoreeof which makes nail refuse to accept a control-d as the end of a message. Ignoreeof also applies to nail command mode.

imap-use-starttls
    Causes 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 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 nail is quit. Setting this option causes all saved message to be retained.

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.

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.

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 any 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 n messages' is printed regardless of this variable, and message numbers may have changed.

noheader
    Setting the option noheader is the same as giving the -N flag on the command line.

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 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-use-apop
    If this variable is set, the APOP authentication method is used when a connection to a POP3 server is initiated. The advantage of this method over the usual USER/PASS authentication is that the password is not sent over the network in clear text. The connection fails if the server does not support the APOP command.

pop3-use-apop-user@host
    Enables pop3-use-apop for a specific account.

pop3-use-starttls
    Causes 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.

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, nail first tries to use the same character set of the original message for replies. If this fails, the sendcharsets variable is evaluated as usual.

Replyall
    Reverses the sense of reply and Reply commands.

save
    When the user aborts a message with two RUBOUT (interrupt characters) nail copies the partial letter to the file `dead.letter' in the home directory. This option is set by default.

searchheaders
    If this option is set, then a message-list specifier in the form `/x:y' will expand to all messages containing the substring `y' in the header field `x'. The string search is case insensitive.

sendwait
    When sending a message, wait until the mail transfer agent exits before accepting further commands. If the mail transfer agent returns a non-zero exit status, the exit status of nail will also be non-zero.

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

showname
    Causes 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 -E option).

smime-force-encryption
    Causes nail to refuse sending unencrypted messages.

smime-sign
    If this variable is set, outgoing messages are S/MIME signed 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
    Do not load the default CA locations when verifying S/MIME signed messages. Only applicable if S/MIME support is built using OpenSSL.

smtp-use-starttls
    Causes 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 cannot be automatically determined whether a server supports it or not.

ssl-no-default-ca
    Do not load the default CA locations to verify SSL/TLS server certificates. Only applicable if SSL/TLS support is built using OpenSSL.

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

stealthmua
    Inhibits the generation of the `Message-Id:' and `User-Agent:' header fields that include obvious references to 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.

verbose
    Setting the option verbose is the same as using the -v flag on the command line. When 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. 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. This is only possible for writable folders in mbox format. Setting this variable also disables MIME decoding and decryption for the editing commands.

  String Options

The string 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, unread but old, new but read, read and old, saved, preserved, mboxed, flagged, answered, draft, killed, start of a collapsed thread, collapsed, classified as junk. The default is `NUROSPMFATK+-J', or `NU *HMFATK+-J' 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.

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 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.

EDITOR
    Pathname of the text editor to use in the edit command and ~e escape. If not defined, then a default editor is used.

encoding
    The default MIME encoding to use in outgoing text messages and message parts. Valid values are 8bit or quoted-printable. The default is 8bit. In case the mail transfer system is not ESMTP compliant, quoted-printable should be used instead. If there is no need to encode a message, 7bit transfer mode is used, without regard to the value of this variable. Binary data is always encoded in base64 mode.

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

folder
    The name of the directory to use for storing folders of messages. All folder names that begin with `+' refer to files below that directory. If the directory name begins with a `/', nail considers it to be an absolute pathname; otherwise, the folder directory is found relative to the user's home directory.

    The directory name may also refer to an IMAP account; any names that begin with `+' then refer to IMAP mailboxes on that account. An IMAP folder is normally given in the form

        imaps://mylogin@imap.myisp.example

    In this case, the `+' and `@' prefixes for folder names have the same effect (see the folder command).

    Some IMAP servers do not accept the creation of mailboxes in the hierarchy base; they 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 (unless it is explicitly invoked within the called macro).

from
    The address (or a list of addresses) to put into the `From:' field of the message header. If replying to a message, 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), either this variable or hostname have to be set to get correct Message-ID header fields. 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. If it is set to the empty string, no heading is printed.

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

    %a | Message attributes.
    %c | The score of the message.
    %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.
    %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 ` '.
    %% | A `%' character.

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

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

imap-keepalive
    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
    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.

junkdb
    The location of the junk mail database. The string is treated like a folder name, as described for the folder command.

    The files in the junk mail database are normally stored in compress(1) format for saving space. If processing time is considered more important, uncompress(1) can be used to store them in plain form. Nail will then work using the uncompressed files.

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

MAIL
    Is used as the user's mailbox, if set. Otherwise, a system-dependent default is used. Can be a protocol:// string (see the folder command for more information).

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

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

maximum-unencoded-line-length
    Messages that contain lines longer than the value of this variable are encoded in quoted-printable even if they contain only ASCII characters. The maximum effective value is 950. If set to 0, all ASCII text messages are encoded in quoted-printable. S/MIME signed messages are always encoded in quoted-printable regardless of the value of this variable.

MBOX
    The name of the mbox file. It can be the name of a folder. The default is `mbox' in the user's home directory.

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/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 mailx implementations.

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

nss-config-dir
    A directory that contains the files certN.db to retrieve certificates, keyN.db to retrieve private keys, and secmod.db, where N is a digit. These are usually taken from Mozilla installations, so an appropriate value might be `~/.mozilla/firefox/default.clm'. Nail opens these files read-only and does not modify them. However, if the files are modified by Mozilla while nail is running, it will print a `Bad database' message. It may be necessary to create copies of these files that are exclusively used by nail then. Only applicable if S/MIME and SSL/TLS support is built using Network Security Services (NSS).

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 crt variable is set. The default paginator pg(1) or, in BSD compatibility mode, more(1) is used if this option is not defined.

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 it is replied to, its text is filtered through the value of this variable interpreted as a shell command. 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 nail is running on.

pop3-keepalive
    POP3 servers may 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.

quote
    If set, 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 command then. If the string allheaders is assigned, all headers are printed above the message body, and all MIME parts are included, thus quote acts like an automatic ~M command then.

record
    If defined, gives the pathname of the folder used to record all outgoing mail. If not defined, then outgoing mail is not so saved. When saving to this folder fails, the message is not sent but saved to the `dead.letter' file instead.

replyto
    A list of addresses to put into the `Reply-To:' field of the message header. If replying to a message, such addresses are handled as if they were in the alternates list.

screen
    When 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
    A comma-separated list of character set names that can be used in Internet mail. When a message that contains characters not representable in US-ASCII is prepared for sending, nail tries to convert its text to each of the given character sets in order and uses the first appropriate one. The default is `utf-8'.

    Character sets assigned to this variable should be ordered in ascending complexity. That is, the list should start with e.g. `iso-8859-1' for compatibility with older mail clients, might contain some other language-specific character sets, and should end with `utf-8' to handle messages that combine texts in multiple languages.

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 somebody other; 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. This should be used with care.

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

Sign
    A string for use with the ~A command.

sign
    A string for use with the ~a command.

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
    Specifies a directory with CA certificates for verification of S/MIME signed messages. The format is the same as described in SSL_CTX_load_verify_locations(3). Only applicable if S/MIME support is built using OpenSSL.

smime-ca-file
    Specifies a file with CA certificates for verification of S/MIME signed messages. The format is the same as described in SSL_CTX_load_verify_locations(3). Only applicable if S/MIME support is built using OpenSSL.

smime-cipher-user@host
    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; but even so, the recipient should upgrade his software in preference.

smime-crl-file
    Specifies a file that contains a CRL in PEM format to use when verifying S/MIME messages. Only applicable if S/MIME support is built using OpenSSL.

smime-crl-dir
    Specifies a directory that contains files with CRLs in PEM format to use when verifying S/MIME messages. Only applicable if S/MIME support is built using OpenSSL.

smime-encrypt-user@host
    If this variable is set, messages to user@host are encrypted before sending. If S/MIME support is built using OpenSSL, the value of the variable must be set to the name of a file that contains a certificate in PEM format. If S/MIME support is built using NSS, the value of this variable is ignored, but if multiple certificates for user@host are available, the smime-nickname-user@host variable should be set. Otherwise a certificate for the recipient is automatically retrieved from the certificate database, if possible.

    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-nickname-user@host
    Specifies the nickname of a certificate to be used when encrypting messages for user@host . Only applicable if S/MIME support is built using NSS.

smime-sign-cert
    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. Only applicable if S/MIME support is built using OpenSSL.

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. 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. Only applicable if S/MIME support is built using OpenSSL.

smime-sign-nickname
    Specifies that the named certificate be used for signing mail. If this variable is not set, but a single certificate matching the current from address is found in the database, that one is used automatically. Only applicable if S/MIME support is built using NSS.

smime-sign-nickname-user@host
    Overrides smime-sign-nickname for a specific address. Only applicable if S/MIME support is built using NSS.

smtp
    Normally, nail invokes sendmail(8) 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 their beginning on. This mode is configured by assigning smtps://server[:port] to the smtp variable.

    The SMTP transfer is executed in a child process; unless either the sendwait or the verbose variable is set, this process runs asynchronously. If it receives a TERM signal, it will abort and save the message to the `dead.letter' file.

smtp-auth
    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, depending on the from variable.

smtp-auth-password
    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, depending on the from variable.

smtp-auth-user
    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 or a matching smtp-auth-password-user@host can be found, nail will as for a password on the user's terminal.

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

ssl-ca-dir
    Specifies a directory with CA certificates for verification of SSL/TLS server certificates. See SSL_CTX_load_verify_locations(3) for more information. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-ca-file
    Specifies a file with CA certificates for verification of SSL/TLS server certificates. See SSL_CTX_load_verify_locations(3) for more information. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-cert
    Sets the file name for a SSL/TLS client certificate required by some servers. Only applicable if SSL/TLS support is built using OpenSSL.

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. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-cipher-list
    Specifies a list of ciphers for SSL/TLS connections. See ciphers(1) for more information. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-crl-file
    Specifies a file that contains a CRL in PEM format to use when verifying SSL/TLS server certificates. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-crl-dir
    Specifies a directory that contains files with CRLs in PEM format to use when verifying SSL/TLS server certificates. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-key
    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. Only applicable if SSL/TLS support is built using OpenSSL.

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. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-method
    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
    Gives the pathname to an entropy daemon socket, see RAND_egd(3).

ssl-rand-file
    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. Only applicable if SSL/TLS support is built using OpenSSL.

ssl-verify
    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.

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 nail operates on. There is normally no need to set this variable since nail can determine this automatically by looking at the LC_CTYPE locale setting; if this succeeds, the value is assigned at startup and will be displayed by the set command. Note that this is not necessarily a character set name that can be used in Internet messages.

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

ENVIRONMENT VARIABLES
Besides the variables described above, nail uses the following environment strings:

HOME
    The user's home directory.

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

MAILRC
    Is used as startup file instead of ~/.mailrc if set. When 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 set, it is read as startup file.

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/nail.rc
    System wide initialization file.

~/.mime.types
    Personal MIME types.

/etc/mime.types
    System wide MIME types.

EXAMPLES

  Getting started
The 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:

    $ nail bill@host.example

then type your message. 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 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 with a RUBOUT. Typing a single RUBOUT causes nail to print `(Interrupt -- one more to kill letter)'. Typing a second RUBOUT causes nail to save your partial letter on the file `dead.letter' in your home directory 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. Thus,

    $ nail sam@workstation.example bob@server.example
    Subject: Fees
    Tuition fees are due next Friday.  Don't forget!
    <Control-d>
    EOT
    $

will send the reminder to <sam@workstation.example>. and <bob@server.example>.

To read your mail, simply type

    $ nail

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. 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. 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  18/631 "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 to respond with, for example:

    Message  1:
    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 nail commands that operate on messages take a message number as an argument like the type command. For these commands, there is a notion of a current message. When you enter the 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 nail by simply typing a newline. As a special case, you can type a newline as your first command to nail to type the first message.

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

Note that 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>, you would do:

    mail frank@machine.example

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

Many features of nail can be tailored to your liking with the set command. The set command has two forms, depending on whether you are setting a binary option or a valued option. Binary options are either on or off. For example, the askcc option informs 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 nail uses to adapt to your tastes. For example, the record option tells nail where to save messages sent by you, and is specified by

    set record=Sent

for example. Note that no spaces are allowed in set record=Sent .

Nail includes a simple facility for maintaining groups of messages together in folders. To use the folder facility, you must tell 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 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 `/', 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 nail to the contents of a different folder. For example,

    folder +classwork

directs 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 simply:

    folder

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 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. 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
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 host name is `server.myisp.example' and your user name for that server is `mylogin', you can refer to this account using the folder command or -f command line option with
    imaps://mylogin@server.myisp.example
(This string is not necessarily the same as your Internet mail address.) You can replace `imaps://' with `imap://' if the server does not support SSL/TLS. (If SSL/TLS support is built using NSS, the nss-config-dir variable must be set before a connection can be initiated, see above). Use `pop3s://' or `pop3://' if the server does not offer IMAP. You should use IMAP if you can, though; first because it requires fewer network operations than POP3 to get the contents of the mailbox and is thus faster; and second because message attributes are maintained by the IMAP server, so you can easily distinguish new and old messages each time you connect. Even if the server does not accept IMAPS or POP3S connections, it is possible that it supports the STARTTLS method to make a session SSL/TLS encrypted after the initial connection has been performed, but before authentication begins. 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.

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. As the shortcut command is specific to this implementation of nail and will confuse other implementations, it should not be used in ~/.mailrc, instead, put
    set NAIL_EXTRA_RC=~/.nailrc
in ~/.mailrc and create a file ~/.nailrc containing the shortcut command above. You can then access your remote mailbox by invoking `nail -f myisp' on the command line, or by executing `fi myisp' within 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 nail-specific) is more appropriate than the shortcut command. You can put the following in ~/.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 `nail -A myisp' on the command line, or by executing `ac myisp' within 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.

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).

Nail supports different authentication methods for both IMAP and POP3. If Kerberos is used at your location, you can try to activate GSSAPI-based authentication by
    set imap-auth=gssapi
The advantage of this method is that nail does not need to know your password at all, nor needs to send sensitive data over the network. Otherwise, the options
    set imap-auth=cram-md5
    set pop3-use-apop
for IMAP and POP3, respectively, offer authentication methods that avoid to send the password in clear text over the network, which is especially important if SSL/TLS cannot be used. If the server does not offer any of these authentication methods, conventional user/password based authentication must be used. It is sometimes helpful to set the verbose option when authentication problems occur. Nail will display all data sent to the server in clear text on the screen with this option, including passwords. You should thus 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 startup file. All files within that directory can be overwritten or deleted by 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 nail is invoked with the -D option, 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
    $ openssl s_client </dev/null -showcerts -connect \
           server.myisp.example:imaps 2>&1 | tee log
(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 it is possible to fetch a forged certificate by this method. You can only completely rely on the authenticity of the CA certificate if you fetch it in a way that is trusted by other means, such as by personally receiving the certificate on storage media.)

  Creating a score file or message filter
The scoring commands are best separated from other configuration for clarity, and are mostly nail specific. It is thus recommended to put them in a separate file that is sourced from your NAIL_EXTRA_RC as follows:

    source ~/.scores

The .scores file could then look as follows:

    define list {
        score (subject "important discussion") +10
        score (subject "annoying discussion") -10
        score (from "nicefellow@goodnet") +15
        score (from "badguy@poornet") -5
        move (header x-spam-flag "+++++") +junk
    }
    set folder-hook-imap://user@host/public.list=list

In this scheme, you would see any mail from `nicefellow@goodnet', even if the surrounding discussion is annoying; but you normally would not see mail from `badguy@poornet', unless he participates in the important discussion. Messages that are marked with five or more plus characters in their `X-Spam-Flag' field (inserted by some server-side filtering software) are moved to the folder `junk' in the folder directory.

Be aware that all criteria in () lead to substring matches, so you would also score messages from e.g. `notsobadguy@poornetmakers' negative here. It is possible to select addresses exactly using "address" message specifications, but these cannot be executed remotely and will thus cause all headers to be downloaded from IMAP servers while looking for matches.

When searching messages on an IMAP server, best performance is usually achieved by sending as many criteria as possible in one large () specification, because each single such specification will result in a separate network operation.

  Activating the Bayesian filter
The Bayesian junk mail filter works by examining the words contained in messages. You decide yourself what a good and what a bad message is. Thus the resulting filter is your very personal one; once it is correctly set up, it will filter only messages similar to those previously specified by you.

To use the Bayesian filter, a location for the junk mail database must be defined first:

    set junkdb=~/.junkdb

The junk mail database does not contain actual words extracted from messages, but hashed representations of them. A foreign person who can read the database could only examine the frequency of previously known words in your mail.

If you have sufficient disk space (several 10 MB) available, it is recommended that you set the chained-junk-tokens option. The filter will then also consider two-word tokens, improving its accuracy.

A set of good messages and junk messages must now be available; it is also possible to use the incoming new messages for this purpose, although it will of course take some time until the filter becomes useful then. Do not underestimate the amount of statistical data needed; some hundred messages are typically necessary to get satisfactory results, and many thousand messages for best operation. You have to pass the good messages to the good command, and the junk messages to the junk command. If you ever accidentally mark a good message as junk or vice-versa, call the ungood or unjunk command to correct this.

Once a reasonable amount of statistics has been collected, new messages can be classified automatically. The classify command marks all messages that the filter considers to be junk, but it does not perform any action on them by default. It is recommended that you move these messages into a separate folder just for the case that false positives occur, or to pass them to the junk command later again to further improve the junk mail database. To automatically move incoming junk messages every time the inbox is opened, put lines like the following into your .scores file (or whatever name you gave to the file in the last example):

    define junkfilter {
        classify (smaller 20000) :n
        move :j +junk
    }
    set folder-hook-imap://user@host/INBOX=junkfilter

If you set the verbose option before running the classify command, nail prints the words it uses for calculating the junk status along with their statistical probabilities. This can help you to find out why some messages are not classified as you would like them to be. To see the statistical probability of a given word, use the probability command.

If a junk message was not recognized as such, use the junk command to correct this. Also if you encounter a false positive (a good message that was wrongly classified as junk), pass it to the good command.

Since the classify command must examine the entire text of all new messages in the respective folder, this will also cause all of them to be downloaded from the IMAP server. You should thus restrict the size of messages for automatic filtering. If server-based filtering is also available, you might try if that works for you first.

  Reading HTML mail
You need either the w3m or lynx utility or another command-line web browser that can write plain text to standard output.

    set pipe-text/html="w3m -dump -T text/html"

or

    set pipe-text/html="lynx -dump -force_html /dev/stdin"

will then 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, as with

    set pipe-application/pdf="cat >/tmp/nail$$.pdf; \
           acroread /tmp/nail$$.pdf; rm /tmp/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
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 nail does not directly accept if S/MIME support is built using OpenSSL. 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. 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 nail.

If S/MIME support is built using NSS, the PKCS#12 file must be installed using Mozilla (provided that nss-config-dir is set appropriately, see above), and no further action is necessary unless multiple user certificates for the same email address are installed. In this case, the smime-sign-nickname variable has to be set appropriately.

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 nail that it should use it for encryption:

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

If S/MIME support is built using NSS, the saved certificate must be installed using Mozilla. The value of the smime-encrypt-user@host is ignored then, but if multiple certificates for the recipient are available, the smime-nickname-user@host variable must be set.

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
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. Nail currently offers no mechanism to fetch CRLs, or to access them on the Internet, so you have to retrieve them by some external mechanism.

If S/MIME and SSL/TLS support are built using OpenSSL, nail accepts CRLs in PEM format only; CRLs in DER format must be converted, e.g. with the shell command

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

To tell 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, nail requires a CRL to be present for each CA that is used to verify a certificate.

If S/MIME and SSL/TLS support are built using NSS, CRLs can be imported in Mozilla applications (provided that nss-config-dir is set appropriately).

  Sending mail from scripts
If you want to send mail from scripts, you must be aware that 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 by invoking nail like

    MAILRC=/dev/null nail -n

You then need to create a configuration for nail for your script. This can be done by either pointing the MAILRC variable to a custom configuration file, or by passing the configuration in environment variables. Since many of the configuration options are not valid shell variables, the env command is useful in this situation. An invocation could thus look like

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

SEE ALSO
fmt(1), newaliases(1), openssl(1), pg(1), more(1), vacation(1), ssl(3), aliases(5), locale(7), mailaddr(7), sendmail(8)

NOTES

Variables in the environment passed to nail cannot be unset.

The character set conversion relies on the iconv(3) function. Its functionality differs widely between the various system environments nail runs on. If the message `Cannot convert from a to b' appears, either some characters within the message header or text 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 (e.g. en_US) or the ttycharset variable. In the second case, the sendcharsets and ttycharset variables must be set to the same value to inhibit character set conversion. If iconv() is not available at all, the value assigned to sendcharsets must match the character set that is used on the terminal.

Nail expects input text to be in Unix format, with lines separated by newline (^J, \n) characters only. Non-Unix text files that use carriage return (^M, \r) characters in addition will be treated as binary data; to send such files as text, strip these characters e. g. by

    tr -d '\015' <input | nail . . .

or fix the tools that generate them.

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 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, 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 nail is waiting for the operation to complete, the operation itself will be canceled. In this case, data that has not been fetched yet will have to be fetched before the next command can be performed. If the canceled operation was using an SSL/TLS encrypted channel, an error in the SSL transport will very likely result, and the connection is no longer usable.

As 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 a `dead.letter' file. This is usually not a problem if the SMTP server is located in the same local network as the computer on which 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.

Nail immediately contacts the SMTP server (or /usr/lib/sendmail) even when operating in disconnected mode. It would not make much sense for nail to defer outgoing mail since SMTP servers usually provide much more elaborated delay handling than 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.

The junk mail filter follows the concepts developed by Paul Graham in his articles, ``A Plan for Spam'', August 2002, <http://www.paulgraham.com/spam.html>, and ``Better Bayesian Filtering'', January 2003, <http://www.paulgraham.com/better.html>. Chained tokens are due to a paper by Jonathan A. Zdziarski, ``Advanced Language Classification using Chained Tokens'', February 2004, <http://www.nuclearelephant.com/papers/chained.html>.

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.

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.