3.5.6 How to Alter the Behavior of mail

Following variables control the behavior of GNU mail:

append

Type: Boolean, Read-Only
Default: True

Messages saved in mbox are appended to the end rather than prepended. This is the default and cannot be changed. This variable exists only for compatibility with other mailx implementations.

appenddeadletter

Type: Boolean.
Default: False.

If this variable is True, the contents of canceled letter is appended to the user’s dead.letter file. Otherwise it overwrites its contents.

askbcc

Type: Boolean.
Default: False.

When set to True the user will be prompted to enter Bcc field before composing the message.

askcc

Type: Boolean.
Default: True.

When set to True the user will be prompted to enter Cc field before composing the message.

asksub

Type: Boolean.
Default: True in interactive mode, False otherwise.

When set to True the user will be prompted to enter Subject field before composing the message.

autoinc

Type: Boolean.
Default: True.

Automatically incorporate newly arrived messages.

autoprint

Type: Boolean.
Default: False.

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

bang

Type: Boolean.
Default: False.

When set, every occurrence of ! in arguments to ! command is replaced with the last executed command.

byname

Type: Boolean
Default: Unset

Record outgoing messages in a file named after the first recipient. The name is the login-name portion of the address found first on the ‘To:’ line in the mail header. This variable overrides the ‘record’ variable.

It is set by the --byname (-F) command line option.

datefield

Type: Boolean.
Default: False.

By default the date in a header summary is taken from the SMTP envelope of the message. Setting this variable tells mail to use the date from Date: header field, converted to local time. Notice, that for messages lacking this field mail will fall back to using SMTP envelope.

See fromfield.

charset

Type: string
Default: ‘auto’

The value of this variable is the character set used for input and output operations. If the value is ‘auto’, mail will try to deduce the name of the character set from the value of ‘LC_ALL’ environment variable. If the variable contains the character set part (e.g. ‘nb_NO.utf-8’), it will be used. Otherwise, mail will look up in its built-in database the value of the character for this language/territory combination. If ‘LC_ALL’ is not set, the ‘LANG’ environment variable is inspected.

The value of ‘charset’ controls both input and output operations. On input, it is used to set the value of the ‘charset’ parameter in the ‘Content-Type’ MIME header, if its value begins with ‘text/’ and ‘charset’ is not present.

On output, it is used to display values of the header fields encodied using RFC 2047. If the variable is unset, no decoding is performed and the fields are printed as they are. Otherwise, they are recoded to that character set.

cmd

Type: String.
Default: Unset.

Contains default shell command for pipe.

columns

Type: Numeric.
Default: Detected at startup by querying the terminal device. If this fails, the value of environment variable COLUMNS is used.

This variable contains the number of columns on terminal screen.

crt

Type: Boolean or Numeric
Default: True in interactive mode, False otherwise.

The variable crt determines the minimum number of lines the body of the message must contain in order to be piped through pager command specified by environment variable PAGER. If crt is set to a numeric value, this value is taken as the threshold. Otherwise, if crt is set without a value, then the height of the terminal screen is used to compute the threshold. The number of lines on screen is controlled by screen variable.

debug

Type: String to boolean
Default: Not set

Sets mailutils debug level. If set to string, the value must be a valid Mailutils debugging specification. See Debug Statement, for a description.

If unset (i.e. set nodebug), clears and disables all debugging information. If set to ‘true’ (i.e. set debug), sets maximum debugging (‘<trace7’) on mailbox and its underlying objects.

decode-fallback

Type: String.
Default: ‘none’.

This variable controls the way to represent characters that cannot be rendered using current character set. It can have three values:

‘none’

Such characters are not printed at all. The conversion process stops at the first character that cannot be rendered.

‘copy-pass’

The characters are displayed ‘as is’. Notice, that depending on your setup, this may screw-up your terminal settings.

‘copy-octal’

Unprintable characters are represented by their octal codes. Printable ones are printed ‘as is’.

debug

Type: Boolean
Default: Unset

This variable is not used. It exists for compatibility with other mailx implementations and for future use.

dot

Type: Boolean.
Default: False.

If True, causes mail to interpret a period alone on a line as the terminator of a message you are sending.

emptystart

Type: Boolean.
Default: False.

If the mailbox is empty, mail normally prints ‘No mail for user’ and exits immediately. If this option is set, mail will start no matter is the mailbox empty or not.

editheaders

Type: Boolean.
Default: False.

When set, mail will include message headers in the text to be the ~e and ~v escapes, thus allowing you to customize the headers.

escape

Type: String.
Default: ~

If defined, the first character of this option gives the character to denoting escapes.

flipr

Type: Boolean
Default: Unset

If set, the variable flipr swaps the meanings of reply and Reply commands (see Replying).

folder

Type: String.
Default: Unset.

The name of the directory to use for storing folders of messages. If unset, $HOME is assumed.

fromfield

Type: Boolean.
Default: True.

By default the sender address is taken from the ‘From’ header. Unsetting this variable tells mail to obtain it from the SMTP envelope, instead.

See datefield.

header

Type: Boolean.
Default: True, unless started with --nosum (-N) option.

Whether to run headers command automatically after entering interactive mode.

headline

Type: String
Default: ‘%>%a%4m %18f %16d %3l/%-5o %s’

Format string to use for the header summary. The ‘%’ character introduces a format specifier. The format specifier consists of optional alignment specifier (‘+’ or ‘-’ sign), optional output width and the specifier letter. Format specifiers are replaced on output with the corresponding piece of information from the message being described.

The ‘-’ character immediately following ‘%’ indicates that this field should be left aligned. The ‘+’ character indicates right alignment. Default alignment depends on the type of the specifier: the specifiers that produce numeric values (‘%l’, ‘%m’, and ‘%o’) are aligned to the right, whereas the ones producing string or date/time values are aligned to the left.

A number following ‘%’ or the alignment flag, indicates the field width.

Consider the ‘%m’ specifier as an example:

%m

Print current message number. Take as much screen columns as necessary for output.

%4m

%+4m

Print current message number. Use exactly 4 screen columns, truncating the output if it does not fit that width. Align the output to the right.

%-4m

Same as above, but align to the left.

Valid format specifiers are:

%a

Message attribute. One of the following letters, or a single horizontal space, if none of them applies:

‘M’	the message was copied to the mailbox (‘mbox’ command)
‘P’	the message was preserved (‘hold’ command)
‘*’	the message was saved (‘save’ or ‘Save’)
‘T’	the message was tagged (‘tag’)
‘R’	the message was read
‘N’	the message is new (was not seen)
‘U’	the message was seen, but wasn’t read

%d

The date when the message was received. It is determined from the message header set by the ‘datefield’ variable (see datefield). If that variable is not set, or the requested header is not present in the message, the date from the envelope is used.

The output is formatted according to the following format specification (see Date/time Format String):

%a %b %e %H:%M

I.e.: abbreviated weekday name, abbreviated month name, day of the month as a decimal number, followed by hour and minutes. All names are displayed according to the current locale.

%D{fmt}

Same as ‘%d’, but the date is formatted according to the date/time format fmt. It is essentially a C ‘strftime’ format string, described in detail in Date/time Format String.

For example:

set headline="%4m %20D{%Y-%m-%dT%H:%M:%S}"

Note, that the opening ‘{’ must follow the format letter without any intervening whitespace. If fmt contains ‘{’, ‘}’, or ‘\’, these characters must be escaped with backslash (e.g. ‘\{’).

%Df

A simplified form of the ‘%D’ specifier. It is equivalent to

%D{%f}

where f is a single ‘strftime’ specifier letter. It can be preceded by ‘E’ or ‘O’, if the Single UNIX Specification allows such usage (see conversion specs), e.g. ‘%DOU’.

Notice, that ‘%D’ not followed by a valid time format in either of the above forms is treated as unknown specifier.

%f

The email address of the message sender.

%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.

%>

A ‘>’ for the current message, otherwise a space.

%<

A ‘<’ for the current message, otherwise a space.

%%

A ‘%’ character.

hold

Type: Boolean.
Default: False.

Determines the location where to store the messages in state ‘read’ and (if the keepsave is also set) ‘saved’. When set, these messages will be retained in the system mailbox.

When not set (the default), such messages will be stored in the user’s personal mailbox.

See read messages, and See saved messages, for a detailed information on how such messages are processed when the mailbox is being closed.

See keepsave, for the discussion of the keepsave variable.

ignore

Type: Boolean.
Default: False.

When set to True, mail will ignore keyboard interrupts when composing messages. Otherwise an interrupt will be taken as a signal to abort composing.

ignoreeof

Type: Boolean.
Default: False.

Controls whether typing EOF character terminates the letter being composed.

indentprefix

Type: String.
Default: "\t" (a tab character).

String used by the ~m tilde escape for indenting quoted messages.

inplacealiases

Type: Boolean
Default: False

If set, mail will expand aliases in the address header field before entering send mode (see Composing Mail). By default, the address header fields are left intact while composing, the alias expansion takes place immediately before sending message.

keep

Type: Boolean, Read-Only
Default: True

Truncate the user’s system mailbox when it is empty, instead of removing it. This is the default and cannot be changed. This variable exists only for compatibility with other mailx implementations.

keepsave

Type: Boolean.
Default: False.

Controls whether saved messages should be retained. The location where they will be retained is controlled by the hold variable (see the hold variable).

This variable is in effect only when operating upon the user’s system mailbox.

See saved messages, for a detailed information on how the saved messages are processed when the mailbox is being closed.

mailx

Type: Boolean.
Default: False.

When set, enables mailx compatibility mode. This mode has the following effects:

• When composing a message mail will ask for Cc and Bcc addresses after composing the body. The default behavior is to ask for these values before composing the body.
• In send mode, if the composition was interrupted, mail will exit with zero status. By default it exits with zero status only if the message was sent successfully.

metamail

Type: Boolean or String.
Default: True.

This variable controls operation of decode command. If it is unset, decode will not attempt any interpretation of the content of message parts. Otherwise, if metamail is set to true, decode will use internal metamail support to interpret message parts. Finally, if metamail is assigned a string, this string is treated as command line of the external metamail command which will be used to display parts of a multipart message. For example:

# Disable MIME interpretation:
set nometamail
# Enable built-in MIME support:
set metamail
# Use external program to display MIME parts:
set metamail="metamail -m mail -p"

mime

Type: String
Default: Unset (false)

If set, this variable instructs mail to compose MIME messages.

It can be set from the command line using --mime option.

mimenoask

Type: String
Default: Empty

By default mail asks for confirmation before running interpreter to view a part of the multi-part message. If this variable is set, its value is treated as a comma-separated list of MIME types for which no confirmation is needed. Elements of this list may include shell-style globbing patterns, e.g. setting

set mimenoask=text/*,image/jpeg

will disable prompting before displaying any textual files, no matter what their subtype is, and before displaying files with type ‘image/jpeg’.

metoo

Type: Boolean.
Default: False.

Usually, when an alias 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.

mode

Type: String, Read-Only
Default: The name of current operation mode.

This variable keeps the name of the current operation mode. Its possible values are:

headers

The program is started with the --headers (-H) command line option (see Invoking Mail).

exist

The program is started with the --exist (-e) command line option (see Invoking Mail).

print

The program is started with the --print (-p) command line option (see Invoking Mail).

read

The program operates in read mode. This is the default.

send

The program operates in send mode. This means it was given one or more recipient addresses in the command line.

nullbody

Type: Boolean
Default: True

Controls whether mail accepts messages with an empty body. The default value, true, means such messages are sent, and a warning (traditionally saying ‘Null message body; hope that's ok’) is displayed. The text of the warning can be set using nullbodymsg variable (see below).

If nullbody is unset, mail will silently ignore such messages. This can be useful in crontab files, to avoid sending mails when nothing important happens. For example, the crontab entry below will send mail only if the utility some-prog outputs something on its standard output or error:

*/5 * * * * some-prog 2>&1 | \
   /bin/mail -E'set nonullbody' -s 'Periodic synchronization'

showenvelope

Type: Boolean
Default: Unset

If this variable is set, the print command will include the STMP envelope in its output.

nullbodymsg

Type: String
Default: Null message body; hope that’s ok

Keeps the text of the warning, displayed by mail before sending an empty message. When available, the translation of this text, in accordance with the current locale, is displayed.

Unsetting this variable disables the warning.

onehop

Type: Boolean
Default: Unset

This variable is not used. It exists for compatibility with other mailx implementations and for future use.

outfolder

Type: String.
Default: Unset.

Contains the directory in which files created by save, write, etc. commands will be stored. When unset, current directory is assumed.

PID

Type: String, Read-Only
Default: PID of the process.

PID of the current mail process.

page

Type: Boolean.
Default: False.

If set to True, the pipe command will emit a linefeed character after printing each message.

prompt

Type: String.
Default: "? "

Contains the command prompt sequence.

quiet

Type: Boolean
Default: Unset

This variable is not used. It exists for compatibility with other mailx implementations and for future use.

quit

Type: Boolean.
Default: False, unless started with --quit (-q) option.

When set, causes keyboard interrupts to terminate the program.

rc

Type: Boolean.
Default: True, unless started with --norc (-N) option.

When this variable is set, mail will read the system-wide configuration file upon startup. See Mail Configuration Files.

readonly

Type: Boolean
Default: False

When set, mailboxes are opened in readonly mode. In this mode, any mail commands that alter the contents of the mailbox are disabled. These commands include, but are not limited to: delete, save and mbox.

record

Type: String.
Default: Unset.

When set, any outgoing message will be saved to the named file.

recursivealiases

Type: Boolean
Default: True

When set, mail will expand aliases recursively.

regex

Type: Boolean.
Default: True.

Setting this to True enables use of regular expressions in ‘/.../’ message specifications.

replyprefix

Type: String
Default: ‘Re: ’

Sets the prefix that will be used when constructing the subject line of a reply message.

replyregex

Type: String
Default: ‘^re: *’

Sets the regular expression used to recognize subjects of reply messages. If the Subject header of the message matches this expression, the value of replyprefix will not be prepended to it before replying. The expression should be a POSIX extended regular expression. The comparison is case-insensitive.

For example, to recognize usual English, Polish, Norwegian and German reply subject styles, use:

set replyregex="^(re|odp|aw|ang)(\\[[0-9]+\\])?:[[:blank:]]"

(Notice the quoting of backslash characters).

return-address

Type: String
Default: unset

Sets the return email address to use when sending messages. If unset, the address is composed from the current user name and the host name.

save

Type: Boolean.
Default: True.

When set, the aborted messages will be stored in the user’s dead.file. See also appenddeadletter.

screen

Type: Numeric.
Default: Detected at startup by querying the terminal device. If this fails, the value of environment variable LINES is used.

This variable contains the number of lines on terminal screen.

sendmail

Type: String.
Default: sendmail:/usr/lib/sendmail

Contains URL of the mail transport agent.

sendwait

Type: Boolean
Default: Unset

This variable is not used. It exists for compatibility with other mailx implementations and for future use.

showto

Type: Boolean
Default: False

If the message was sent by the user, print its recipient address in the header summary.

Sign

Type: String.
Default: Unset.

Contains the filename holding users signature. The contents of this file is appended to the end of a message being composed by ~A escape.

sign

Type: String.
Default: Unset.

Contains the user’s signature. The contents of this variable is appended to the end of a message being composed by ~a escape. Use Sign variable, if your signature occupies more than one line.

showto

Type: Boolean
Default: unset

If this variable is set, mail will show To: addresses instead of From: for all messages that come from the user that invoked the program.

subject

Type: String.
Default: Unset.

Contains default subject line. This will be used when asksub is off.

toplines

Type: Numeric.
Default: 5

Number of lines to be displayed by top and Top commands.

variable-strict

varstrict

Type: Boolean.
Default: False.

Setting this variable enables strict control over variable settings. In this mode, mail refuses to set read-only variables. Also, if the user is trying to set an unknown variable, mail prints a warning.

See Setting and Unsetting the Variables.

variable-pretty-print

varpp

Type: Boolean.
Default: False.

If this variable is set, the listing output by set contains short descriptions before each variable. See Setting and Unsetting the Variables.

verbose

Type: Boolean.
Default: False.

When set, the actual delivery of messages is displayed on the user’s terminal.

xmailer

Type: Boolean.
Default: Set.

Controls whether the header ‘X-Mailer’ should be added to outgoing messages. The default value of this header is

X-Mailer: mail (GNU Mailutils 3.10)