NAME
mail, rmail - read mail or send mail to users

SYNOPSIS

  Sending mail:

mail [ -tw ] [ -m message_type ] recipient . . .

rmail [ -tw ] [ -m message_type ] recipient . . .

  Reading mail:

mail [ -ehpPqr ] [ -f file ]

  Forwarding mail:

mail -F recipient . . .

  Debugging:

mail [ -xdebug_level ] [ other_mail_options ] recipient . . .

mail -T mailsurr_file recipient . . .

DESCRIPTION

A recipient is usually a user name recognized by login(1). When recipients are named, mail assumes a message is being sent (except in the case of the -F option). It reads from the standard input up to an end-of-file (cntrl-d) or, if reading from a terminal device, until it reads a line consisting of just a period. When either of those indicators is received, mail adds the letter to the mailfile for each recipient.

A letter is composed of some header lines followed by a blank line followed by the message content. The header lines section of the letter consists of one or more UNIX postmarks:

    From sender date_and_time [remote from remote_system_name]

followed by one or more standardized message header lines of the form:

    keyword-name: [printable text]

where keyword-name is comprised of any printable, non-whitespace, characters other than colon (`:'). A Content-Length: header line, indicating the number of bytes in the message content will always be present. A Content-Type: header line that describes the type of the message content (such as text, binary, multipart, etc.) will always be present unless the letter consists of only header lines with no message content. Header lines may be contined on the following line if that line starts with white space.

  Sending mail:

The following command-line arguments affect SENDING mail:
-m  causes a Message-Type: line to be added to the message header with the value of message_type.
-t  causes a To: line to be added to the message header for each of the intended recipients.
-w  causes a letter to be sent to a remote recipient without waiting for the completion of the remote transfer program.

If a letter is found to be undeliverable, it is returned to the sender with diagnostics that indicate the location and nature of the failure. If mail is interrupted during input, the message is saved in the file dead.letter to allow editing and resending. dead.letter is always appended to, thus preserving any previous contents. The initial attempt to append to (or create) dead.letter will be in the current directory. If this fails, dead.letter will be appended to (or created in) the user's login directory. If the second attempt also fails, no dead.letter processing will be done.

rmail only permits the sending of mail; uucp(1C) uses rmail as a security precaution. Any application programs that generate mail messages should be sure to invoke rmail rather than mail for message transport and/or delivery.

If the local system has the Basic Networking Utilities installed, mail may be sent to a recipient on a remote system. There are numerous ways to address mail to recipients on remote systems depending on the transport mechanisms available to the local system. The two most prevalent addressing schemes are UUCP-style and Domain-style. With UUCP-style addressing, remote recipients are specified by prefixing the recipient name with the remote system name and an exclamation point (such as sysa!user). A series of system names separated by exclamation points can be used to direct a letter through an extended network (such as sysa!sysb!sysc!user). With Domain-style addressing, remote recipients are specified by appending an `@' and domain (and possibly sub-domain) information to the recipient name (such as user@sf.att.com). (The local System Administrator should be consulted for details on which addressing conventions are available on the local system.)

  Reading Mail:

The following command-line arguments affect READING mail:
-e  causes mail not to be printed. An exit value of 0 is returned if the user has mail; otherwise, an exit value of 1 is returned.
-h  causes a window of headers to be initially displayed rather than the latest message. The display is followed by the `?' prompt.
-p  causes all messages to be printed without prompting for disposition.
-P  causes all messages to be printed with all header lines displayed, rather than the default selective header line display.
-q  causes mail to terminate after interrupts. Normally an interrupt causes only the termination of the message being printed.
-r  causes messages to be printed in first-in, first-out order.
B-f file
    causes mail to use file (such as mbox) instead of the default mailfile.

mail, unless otherwise influenced by command-line arguments, prints a user's mail messages in last-in, first-out order. The default mode for printing messages is to display only those header lines of immediate interest. These include, but are not limited to, the UNIX From and >From postmarks, From:, Date:, Subject:, and Content-Length: header lines, and any recipient header lines such as To:, Cc:, Bcc:, etc. After the header lines have been displayed, mail will display the contents (body) of the message only if it contains no unprintable characters. Otherwise, mail will issue a warning statement about the message having binary content and not display the content. (This may be overridden via the p command. See below.)

For each message, the user is prompted with a ?, and a line is read from the standard input. The following commands are available to determine the disposition of the message:

#   Print the number of the current message.

-   Print previous message.

<new-line>, +, or n
    Print the next message.

!command
    Escape to the shell to do command.

a   Print message that arrived during the mail session.

d, or dp
    Delete the current message and print the next message.

d n Delete message number n. Do not go on to next message.

dq  Delete message and quit mail.

h   Display a window of headers around current message.

h n Display a window of headers around message number n.

h a Display headers of all messages in the user's mailfile.

h d Display headers of messages scheduled for deletion.

m [ persons ]
    Mail (and delete) the current message to the named person(s).

n   Print message number n.

p   Print current message again, overriding any indications of binary (that is, unprintable) content.

P   Override default brief mode and print current message again, displaying all header lines.

q, or cntrl-D
    Put undeleted mail back in the mailfile and quit mail.

r [ users ]
    Reply to the sender, and other user(s), then delete the message.

s [ files ]
    Save message in the named file(s) (mbox is default) and delete the message.

u [ n ]
    Undelete message number n (default is last read).

w [ files ]
    Save message contents, without any header lines, in the named files (mbox is default) and delete the message.

x   Put all mail back in the mailfile unchanged and exit mail.

y [ files ]
    Same as save.

?   Print a command summary.

When a user logs in, the presence of mail, if any, is usually indicated. Also, notification is made if new mail arrives while using mail.

The permissions of mailfile may be manipulated using chgrp in two ways to alter the function of mail. The other permissions of the file may be read-write (0666), read-only (0664), or neither read nor write (0660) to allow different levels of privacy. If changed to other than the default (mode 0660), the file will be preserved even when empty to perpetuate the desired permissions. (The administrator may override this file preservation using the DEL_EMPTY_MAILFILE option of mailcnfg.)

The group id of the mailfile must be mail to allow new messages to be delivered, and the mailfile must be writable by group mail.

  Forwarding mail:

The following command-line argument affects FORWARDING of mail:

-F recipients
    Causes all incoming mail to be forwarded to recipients. The mailbox must be empty.

The -F option causes the mailfile to contain a first line of:

    Forward to recipient. . .

Thereafter, all mail sent to the owner of the mailfile will be forwarded to each recipient.

An Auto-Forwarded-From: ... line will be added to the forwarded message's header. This is especially useful in a multi-machine environment to forward all a person's mail to a single machine, and to keep the recipient informed if the mail has been forwarded.

Installation and removal of forwarding is done with the -F invocation option. To forward all your mail to systema!user enter:

    mail -F systema!user

To forward to more than one recipient enter:

    mail -F "user1,user2@att.com,systemc!systemd!user3"

Note that when more than one recipient is specified, the entire list should be enclosed in double quotes so that it may all be interpreted as the operand of the -F option. The list can be up to 1024 bytes; either commas or white space can be used to separate users.

If the first character of any forwarded-to recipient name is the pipe symbol (`|'), the remainder of the line will be interpreted as a command to pipe the current mail message to. The command, known as a Personal Surrogate, will be executed in the environment of the recipient of the message (that is, basename of the mailfile). For example, if the mailfile is /var/mail/foo, foo will be looked up in /etc/passwd to determine the correct userID, groupID, and HOME directory. The command's environment will be set to contain only HOME, LOGNAME, TZ, PATH (= /usr/bin:), and SHELL (= /bin/sh), and the command will execute in the recipient's HOME directory. If the message recipient cannot be found in /etc/passwd, the command will not be executed and a non-delivery notification with appropriate diagnostics will be sent to the message's originator.

After the pipe symbol, escaped double quotes should be used to have strings with embedded whitespace be considered as single arguments to the command being executed. No shell syntax or metacharacters may be used unless the command specified is /bin/sh. For example,

    mail -F "|/bin/sh -c \"shell_command_line\""

will work, but is not advised since using double quotes and backslashes within the shell_command_line is difficult to do correctly and becomes tedious very quickly.

Certain %keywords are allowed within the piped-to command specification and will be textually substituted for before the command line is executed.

%R  Return path to the message originator.
%c  Value of the Content-Type: header line if present.
%S  Value of the Subject: header line if present.

If the command being piped to exits with any non-zero value, mail will assume that message delivery failed and will generate a non-delivery notification to the message's originator. It is allowable to forward mail to other recipients and pipe it to a command, as in

    mail -F "carol,joe,|myvacationprog %R"

Two UNIX System facilities that use the forwarding of messages to commands are notify(1), which causes asynchronous notification of new mail, and vacation(1), which provides an auto-answer capability for messages when the recipient will be unavailable for an extended period of time.

To remove forwarding enter:

    mail -F ""

The pair of double quotes is mandatory to set a NULL argument for the -F option.

In order for forwarding to work properly the mailfile should have mail as group ID, and the group permission should be read-write.

mail will exit with a return code of 0 if forwarding was successfully installed or removed.

  Debugging:

The following command-line arguments cause mail to provide DEBUGGING information:

-T mailsurr_file
    causes mail to display how it will parse and interpret the mailsurr file.
-xdebug_level
    causes mail to create a trace file containing debugging information.

The -T option requires an argument that will be taken as the pathname of a test mailsurr file. If NULL (as in -T ""), the system mailsurr file will be used. To use, type 'mail -T test_file recipient' and some trivial message (like "testing"), followed by a line with either just a dot (`.') or a cntrl-D. The result of using the -T option will be displayed on standard output and show the inputs and resulting transformations as mailsurr is processed by the mail command for the indicated recipient. Mail messages will never actually be sent or delivered when the -T option is used.

The -x option causes mail to create a file named /tmp/MLDBGprocess_id that contains debugging information relating to how mail processed the current message. The absolute value of debug_level controls the verboseness of the debug information. Zero implies no debugging. If debug_level is greater than zero, the debug file will be retained only if mail encountered some problem while processing the message. If debug_level is less than zero the debug file will always be retained. The debug_level specified via -x overrides any specification of DEBUG in /etc/mail/mailcnfg. The information provided by the -x option is esoteric and is probably only useful to System Administrators. The output produced by the -x option is a superset of that provided by the -T option.

  Delivery Notification
Several forms of notification are available for mail by including one of the following lines in the message header.

Transport-Options: [ /options ]

Default-Options: [ /options ]

>To: recipient [ /options ]

Where the ``/options'' may be one or more of the following:

/delivery
    Inform the sender that the message was successfully delivered to the recipient's mailbox.

/nodelivery
    Do not inform the sender of successful deliveries.

/ignore
    Do not inform the sender of unsuccessful deliveries.

/return
    Inform the sender if mail delivery fails. Return the failed message to the sender.

/report
    Same as /return except that the original message is not returned.

The default is /nodelivery/return. If contradictory options are used, the first will be recognized and later, conflicting, terms will be ignored.

FILES
dead.letter
    unmailable text
/etc/passwd
    to identify sender and locate recipients
/etc/mail/mailsurr
    routing / name translation information
/etc/mail/mailcnfg
    initialization information
$HOME/mbox
    saved mail
$MAIL
    variable containing path name of mailfile
/tmp/ma*
    temporary file
/tmp/MLDBG*
    debug trace file
/var/mail/*.lock
    lock for mail directory
/var/mail/:saved
    directory for holding temp files to prevent loss of data in the event of a system crash.
/var/mail/user
    incoming mail for user; that is, the mailfile

SEE ALSO
chmod(1), login(1), mailx(1), notify(1), write(1), vacation(1)

mail_pipe(1M), mailsurr(4), mailcnfg(4) in the System Administrator's Reference Manual.
User's Guide.

NOTES
The "Forward to recipient" feature may result in a loop. Local loops (messages sent to usera, which are forwarded to userb, which are forwarded to usera) will be detected immediately. Remote loops (mail sent to sys1!usera1 which is forwarded to sys2!userb, which is forwarded to sys1!usera) will also be detected, but only after the message has exceeded the built-in hop count limit of 20. Both cases of forwarding loops will result in a non-delivery notification being sent to the message originator.

As a security precaution, the equivalent of a chmod s+g is performed on the mailfile whenever forwarding is activated via the -F option, and a chmod s-g is done when forwarding is removed via the -F option. If the setGID mode bit is not set when mail attempts to forward an incoming message to a command, the operation will fail and a non-delivery report with appropriate diagnostics will be sent to the message's originator.

The interpretation and resulting action taken because of the header lines described in the Delivery Notifications section above will only occur if this version of mail is installed on the system where the delivery (or failure) happens. Earlier versions of mail may not support any types of delivery notification.

Conditions sometimes result in a failure to remove a lock file.

After an interrupt, the next message may not be printed; printing may be forced by typing a p.