deliver - deliver mail

deliver [ options ] address ...

The Deliver program collects a mail message from the standard input and delivers it. Deliver is capable of handling the delivery of all mail. However, Deliver is typically hung off the end of an existing mail system, where it handles the delivery of some or all local mail, a job usually done by /bin/mail (System V and BSD) or /usr/lib/mail/mail.local (Xenix).

The way Deliver handles each message is controlled by shell scripts which, given the message to be delivered and a list of addresses, produce as their output new lists of addresses. Such scripts, when called by Deliver, are called ``delivery files.'' Deliver allows a site administrator to write delivery files with global effects. In addition, each user may write a delivery file to control delivery of mail addressed to himself.

-b

Interpret arguments as mailbox filenames instead of addresses. The user who executes Deliver must have write permissions on all mailbox files. He may also need write permissions on their parent directories, depending on the existence of the mailbox files and the local locking protocol.

-n

Deliver to the given address(es), but do not run any delivery files. This option is most useful when Deliver is executed recursively, because it cannot cause infinite recursion.

-A

Collect the message, run delivery files and print the resolved address(es). Do not deliver the message. Note that when this option is specified, Deliver still collects a message from the standard input, because delivery files may vary their output based on message content. To test simple delivery files, redirect standard input from /dev/null.

-d

Turn on verbosity, collect the message and run delivery files. Do not deliver the message.

-v

Turn on verbosity while performing all tasks, including delivery.

-t

Do not remove temporary files before exiting.

-l localsender

Specify localsender as the name of the local sender, that is, the name of the user who invoked Deliver. This option is only believed if it is a valid user name with a user id equal to the real user id of the Deliver process. If it is invalid, or if it is not specified, then Deliver tries the values of the LOGNAME and USER environment variables, and then the login name corresponding to the tty on which Deliver is running. If none of these names matches the real user id, Deliver looks up the user name that corresponds to its real user id.

-r sender

Put sender on the generated From_ line. Default is to use the address on the From_ line in the input, or else the local sender.

-h hostname

Set the host name. The default is determined in a site-specific way, typically by asking the kernel.

-s system delivery file

Specify an alternate system delivery file. The default is /etc/deliver/sys.

-p post-user delivery file

Specify an alternate post-user delivery file. The default is /etc/deliver/post.

-e error delivery file

Specify an alternate error delivery file. The default is /etc/deliver/err.

-u user delivery file

Specify an alternate user delivery file. The default is .deliver (in each user's home directory).

For security reasons, specifying one or more of the options ``-h hostname'', ``-s sysdelfile'', ``-p postdelfile'', ``-e errdelfile'' or ``-u userdelfile'' disables setuid privileges. That is, Deliver revokes its setuid privileges before doing anything significant, just as if Deliver had been installed without the setuid bit turned on.

All command line options are put into environment variables, examined by Deliver on startup; thus all flags are propagated when Deliver is invoked recursively. Note that setting these environment variables is exactly equivalent to specifying the equivalent command line options; in particular, they can cause Deliver to disable setuid privileges as described in the previous paragraph.

For mail systems based on Smail 2.x, the LMAIL (local mailer) macro can be changed to call Deliver. For mail systems based on Smail 3.x or sendmail, a similar arrangement may be made; otherwise, individual users can invoke Deliver by mentioning it in their .forward files (e.g. ``|/usr/bin/deliver myname'').

For Xenix systems, Deliver may be used as a direct replacement for /usr/lib/mail/mail.local.

For stock Unix systems, it may be possible to make /bin/rmail a link to Deliver; however, this configuration has not been tested and is not recommended. After all, any postmaster motivated enough to install Deliver, and who wants something better than the standard /bin/rmail, should install Smail 2.x or 3.x.

When Deliver starts execution, it interprets its arguments in one of three ways.

(1) If the -b (mailbox) option is specified, then Deliver interprets its arguments as mailbox pathnames.

(3) If the -n option is specified, then Deliver interprets its arguments as addresses.

(3) If neither the -b nor the -n option is specified, Deliver uses the system, user and post-user delivery files (described below) to determine the address(es) to receive the message.

After attempting delivery, Deliver looks in its list of destinations for failures of any kind. If any failed destinations are found, and if the -n option is not specified, Deliver executes the error delivery file with the entire list of failed addresses as its arguments. If the error delivery file generates any destinations, Deliver attempts delivery to them. However, if such delivery fails, Deliver will not re-execute the error delivery file.

Delivery files are shell scripts executed by Deliver to determine the address(es) to receive a message. Note that delivery files have control over delivery to users and remote addresses, but not over delivery to explicitly named mailboxes. (See also the -b option.)

The default shell used to execute delivery files is configuration-dependent. Typically it is the Bourne shell (/bin/sh). However, you can arrange for Deliver to execute any given delivery file with any given shell by starting the delivery file with a ``#!'' line in the style of Berkeley UNIX. For example, if the first line of a delivery file is ``#!/bin/perl'', then Deliver will execute that delivery file with /bin/perl instead of /bin/sh.

The four kinds of delivery files are described below.

system delivery file

The system delivery file, if it exists, is created by the postmaster. By default, it is named ``/etc/deliver/sys''. It controls the delivery of all messages on the system where it is installed. It is executed with arguments of the name(s) specified on the Deliver command line. (Note, however, that arguments containing shell metacharacters are rejected before the system delivery file is run.)

user delivery file

Each user may create a user delivery file in his home directory. By default, it is named ``.deliver''. A user delivery file is always executed with exactly one argument: the name of the user in whose home directory the file is found.

post-user delivery file

The post-user delivery file, if it exists, is created by the postmaster. By default, it is named ``/etc/deliver/post''. It is executed after the system and user delivery files, but before any attempt at message delivery. Its arguments are those addresses which are about to receive the message, whether those addresses originated with Deliver command line arguments or with a system or user delivery file. This delivery file is particularly useful for implementing system-wide aliases, since it can modify or delete addresses generated by user delivery files, something the system delivery file cannot do.

error delivery file

The error delivery file, if it exists, is created by the postmaster. By default, it is named ``/etc/deliver/err''. After Deliver has attempted delivery to all requested destinations, and if delivery to one or more of those destinations failed, Deliver executes the error delivery file with arguments of all failed addresses. Note that failed addresses may contain whitespace, shell metacharacters or other strangeness -- be careful!

When Deliver runs a delivery file, it monitors the delivery file's standard output for delivery directives, one directive per line. Directives can take five forms:

user

Append the message to the given user's default mailbox. The location of a user's default mailbox is configuration-dependent.

user:mailbox

Append the message to the specified mailbox in the given user's context. If the mailbox name is not an absolute pathname, it is interpreted relative to the given user's home directory. Only the superuser may request delivery to a mailbox in another user's context.

user|command

Execute the specified command in the given user's context, and feed the message to its standard input. Only the superuser may request command execution in another user's context.

user?error message

Do not attempt delivery to the given user. Diagnostic messages, including the bounce notice (if any), will include the specified message. Only the superuser may report an error for another user.

host1!host2!user

Send the message with UUCP via the given bang path.

Note that the ``user:mailbox'', ``user|command'' and ``user?error message'' forms may omit the ``user'' part, in which case the current user context is assumed.

When Deliver executes a delivery file, it sets several environment variables, listed below. Note that these environment variables are both set and used by Deliver; therefore, all command line options automatically propagate when Deliver is run recursively (within a delivery file). The environment variable names set and used by Deliver are:

DELPID

The process id of the running Deliver process. Used by a child Deliver to determine its parent's process id.

DELLEVEL

The Deliver recursion level. Each time Deliver is called recursively, this value is incremented. When the maximum recursion level (default: eight) is exceeded, Deliver assumes infinite recursion and aborts.

DELFLAGS

The command line flags that do not take arguments, if any, that were specified on the Deliver command line.

HOSTNAME

The local host name, either the real hostname or a name specified with the -h option to Deliver.

SYSDELFILE

The system delivery filename.

POSTDELFILE

The post-user delivery filename.

ERRDELFILE

The error delivery filename.

USERDELFILE

The user delivery filename, relative to the home directory of each user.

LOCALSENDER

The local sender, that is, the user who invoked Deliver. This value is not believed by recursive Deliver processes, since the user who invokes the child may not be the same as the user who invoked the parent.

SENDER

The original sender of the message. This value can be the address specified with the -r option to Deliver, or the address given in the From_ line of the message, or the local sender.

HEADER

The name of the temporary file containing the message header.

BODY

The name of the temporary file containing the message body.

Recursive execution of Deliver is useful, especially when used with the the -b (mailbox) and -n (no delivery files) flags. For example, a user may wish to transform a message body before it is stored in a mailbox. This may be done with a user delivery file and recursive execution of Deliver. For example, the following user delivery file translates all incoming message bodies to lower case, and stores them in the user's default mailbox:

    ( cat $HEADER; tr '[A-Z]' '[a-z]' <$BODY ) | deliver -n "$1"

When Deliver executes a delivery file, it expects the delivery file to output a complete list of all addresses and/or mailboxes that should receive the message. Therefore, if a delivery file produces no output at all, Deliver assumes that there is a problem. In that case, to avoid total loss of the message, Deliver saves it in the ``undelivered mail'' mailbox, named ``Undel.mail'' in the home directory of the delivery file's owner. For the purpose of undelivered mail, system, post-user and error delivery files are considered to be owned by root. Therefore, the postmaster should occasionally check ``/Undel.mail'' for mail that went undelivered due to errors in the systemwide delivery files.

Sometimes a delivery file writer really does want Deliver to drop a message. For example, if a delivery file stores a message by running ``deliver -b'', then there's no need for the parent Deliver to save the message again. A delivery file can tell Deliver not to save the message by outputting the string ``DROP''. A delivery file's outputting ``DROP'' removes the undelivered mail safety net for that delivery file. Think of ``DROP'' as shorthand for: ``Trust me. I know what I'm doing.'' If the delivery file outputs any addresses before and/or after ``DROP'', then the ``DROP'' has no effect.

The example delivery file given above never generates any output. Therefore, it should always output ``DROP'':

    ( cat $HEADER; tr '[A-Z]' '[a-z]' <$BODY ) | deliver -n "$1"
    echo DROP

Note that the error delivery file is an exception to the ``DROP'' rule. After all, the error delivery file never receives valid addresses as arguments, so no output is expected (though it is allowed).

If Deliver is setuid root -- which it should be for normal operation -- then the system, post-user and error delivery files are executed as root. Be very careful about its permissions and its contents! Carelessness here can easily create a security problem.

All user delivery files are executed in the context of the user in whose home directory they reside. A user's ``context'' includes the uid, gid, and home directory as specified in /etc/passwd.

For security reasons, if a user's home directory is writable to the world, Deliver will ignore any delivery file that might be found there.

For security reasons, no user can request writing a specific mailbox under another user's context. Otherwise, any user could modify other users' private files.

For security reasons, Deliver will not write to a system mailbox if it has more than one hard link.

Deliver records its activity in two files: the ``delivery log'', named /var/log/deliver.log, and the ``error log'', named /var/log/deliver.errlog.

The deliver log is a record of activity of each Deliver process. Each delivery log entry include the users or mailboxes named on the command line, the users and/or mailboxes where delivery succeeded, and those where it failed.

The error log is a record of any problems encounted during delivery. Each error log entry includes all diagnostic output, a copy of the message header, and miscellaneous other information.

If you want a delivery log, you must create the delivery log file yourself. If the delivery log file does not exist, Deliver will not create it.

If Deliver is performing a ``dry run'' -- that is, if the -d (debug) or -A (print address) flag is specified -- it will not write to either log file.

If the -v (verbose) flag is specified, Deliver will not write to the error log.

Several preprocessor labels may be defined during compilation to control the method(s) used by Deliver to lock mailboxes. These labels are:

ML_DOTLOCK

Lock on exclusive creation of the mailbox name with ``.lock'' appended. (Version 7 and early BSD mailers use this method.)

ML_DOTMLK

Lock on exclusive creation of /tmp/basename.mlk, where basename is the last component of the mailbox pathname. (Xenix mailers use this method.)

ML_LOCKF

Exclusively lock mailbox with lockf().

ML_FCNTL

Exclusively lock mailbox with fcntl().

ML_LOCKING

Exclusively lock mailbox with locking().

Neither, one or both of ML_DOTLOCK and ML_DOTMLK may be specified. None or one of ML_LOCKF, ML_FCNTL or ML_LOCKING may be specified.

/etc/deliver/sys system delivery file

/etc/deliver/post post-user delivery file

/etc/deliver/err error delivery file

~user/.deliver user delivery file(s)

/var/log/deliver.log delivery log

/var/log/deliver.errlog error log

Please mail enhancements, enhancement requests, trouble reports, etc. to <chip@pobox.com>. See also the Debian GNU/Linux bug tracking system at http://www.debian.org/Bugs/.

header(1), mail(1), uux(1), smail(8), sendmail(8)