PIPE(8) PIPE(8)
NAME
pipe - Postfix delivery to external command
SYNOPSIS
pipe [generic Postfix daemon options] command_attributes...
DESCRIPTION
The pipe(8) daemon processes requests from the Postfix
queue manager to deliver messages to external commands.
This program expects to be run from the master(8) process
manager.
Message attributes such as sender address, recipient
address and next-hop host name can be specified as com-
mand-line macros that are expanded before the external
command is executed.
The pipe(8) daemon updates queue files and marks recipi-
ents as finished, or it informs the queue manager that
delivery should be tried again at a later time. Delivery
status reports are sent to the bounce(8), defer(8) or
trace(8) daemon as appropriate.
SINGLE-RECIPIENT DELIVERY
Some destinations cannot handle more than one recipient
per delivery request. Examples are pagers or fax machines.
In addition, multi-recipient delivery is undesirable when
prepending a Delivered-to: or X-Original-To: message
header.
To prevent Postfix from sending multiple recipients per
delivery request, specify
transport_destination_recipient_limit = 1
in the Postfix main.cf file, where transport is the name
in the first column of the Postfix master.cf entry for the
pipe-based delivery transport.
COMMAND ATTRIBUTE SYNTAX
The external command attributes are given in the master.cf
file at the end of a service definition. The syntax is as
follows:
chroot=pathname (optional)
Change the process root directory and working
directory to the named directory. This happens
before switching to the privileges specified with
the user attribute, and before executing the
optional directory=pathname directive. Delivery is
deferred in case of failure.
This feature is available as of Postfix 2.3.
directory=pathname (optional)
Change to the named directory before executing the
external command. The directory must be accessible
for the user specified with the user attribute (see
below). The default working directory is
$queue_directory. Delivery is deferred in case of
failure.
This feature is available as of Postfix 2.2.
eol=string (optional, default: \n)
The output record delimiter. Typically one would
use either \r\n or \n. The usual C-style backslash
escape sequences are recognized: \a \b \f \n \r \t
\v \ddd (up to three octal digits) and \\.
flags=BDFORXhqu.> (optional)
Optional message processing flags. By default, a
message is copied unchanged.
B Append a blank line at the end of each mes-
sage. This is required by some mail user
agents that recognize "From " lines only
when preceded by a blank line.
D Prepend a "Delivered-To: recipient" message
header with the envelope recipient address.
Note: for this to work, the transport_desti-
nation_recipient_limit must be 1 (see SIN-
GLE-RECIPIENT DELIVERY above for details).
The D flag also enforces loop detection
(Postfix 2.5 and later): if a message
already contains a Delivered-To: header with
the same recipient address, then the message
is returned as undeliverable. The address
comparison is case insensitive.
This feature is available as of Postfix 2.0.
F Prepend a "From sender time_stamp" envelope
header to the message content. This is
expected by, for example, UUCP software.
O Prepend an "X-Original-To: recipient" mes-
sage header with the recipient address as
given to Postfix. Note: for this to work,
the transport_destination_recipient_limit
must be 1 (see SINGLE-RECIPIENT DELIVERY
above for details).
This feature is available as of Postfix 2.0.
R Prepend a Return-Path: message header with
the envelope sender address.
X Indicate that the external command performs
final delivery. This flag affects the sta-
tus reported in "success" DSN (delivery sta-
tus notification) messages, and changes it
from "relayed" into "delivered".
This feature is available as of Postfix 2.5.
h Fold the command-line $original_recipient
and $recipient address domain part (text to
the right of the right-most @ character) to
lower case; fold the entire command-line
$domain and $nexthop host or domain informa-
tion to lower case. This is recommended for
delivery via UUCP.
q Quote white space and other special charac-
ters in the command-line $sender, $origi-
nal_recipient and $recipient address local-
parts (text to the left of the right-most @
character), according to an 8-bit transpar-
ent version of RFC 822. This is recommended
for delivery via UUCP or BSMTP.
The result is compatible with the address
parsing of command-line recipients by the
Postfix sendmail(1) mail submission command.
The q flag affects only entire addresses,
not the partial address information from the
$user, $extension or $mailbox command-line
macros.
u Fold the command-line $original_recipient
and $recipient address localpart (text to
the left of the right-most @ character) to
lower case. This is recommended for deliv-
ery via UUCP.
. Prepend "." to lines starting with ".". This
is needed by, for example, BSMTP software.
> Prepend ">" to lines starting with "From ".
This is expected by, for example, UUCP soft-
ware.
null_sender=replacement (default: MAILER-DAEMON)
Replace the null sender address (typically used for
delivery status notifications) with the specified
text when expanding the $sender command-line macro,
and when generating a From_ or Return-Path: message
header.
If the null sender replacement text is a non-empty
string then it is affected by the q flag for
address quoting in command-line arguments.
The null sender replacement text may be empty; this
form is recommended for content filters that feed
mail back into Postfix. The empty sender address is
not affected by the q flag for address quoting in
command-line arguments.
Caution: a null sender address is easily mis-parsed
by naive software. For example, when the pipe(8)
daemon executes a command such as:
Wrong: command -f$sender -- $recipient
the command will mis-parse the -f option value when
the sender address is a null string. For correct
parsing, specify $sender as an argument by itself:
Right: command -f $sender -- $recipient
This feature is available as of Postfix 2.3.
size=size_limit (optional)
Don't deliver messages that exceed this size limit
(in bytes); return them to the sender instead.
user=username (required)
user=username:groupname
Execute the external command with the rights of the
specified username. The software refuses to exe-
cute commands with root privileges, or with the
privileges of the mail system owner. If groupname
is specified, the corresponding group ID is used
instead of the group ID of username.
argv=command... (required)
The command to be executed. This must be specified
as the last command attribute. The command is exe-
cuted directly, i.e. without interpretation of
shell meta characters by a shell command inter-
preter.
In the command argument vector, the following
macros are recognized and replaced with correspond-
ing information from the Postfix queue manager
delivery request.
In addition to the form ${name}, the forms $name
and $(name) are also recognized. Specify $$ where
a single $ is wanted.
${client_address}
This macro expands to the remote client net-
work address.
This feature is available as of Postfix 2.2.
${client_helo}
This macro expands to the remote client HELO
command parameter.
This feature is available as of Postfix 2.2.
${client_hostname}
This macro expands to the remote client
hostname.
This feature is available as of Postfix 2.2.
${client_port}
This macro expands to the remote client TCP
port number.
This feature is available as of Postfix 2.5.
${client_protocol}
This macro expands to the remote client pro-
tocol.
This feature is available as of Postfix 2.2.
${domain}
This macro expands to the domain portion of
the recipient address. For example, with an
address user+foo@domain the domain is
domain.
This information is modified by the h flag
for case folding.
This feature is available as of Postfix 2.5.
${extension}
This macro expands to the extension part of
a recipient address. For example, with an
address user+foo@domain the extension is
foo.
A command-line argument that contains
${extension} expands into as many command-
line arguments as there are recipients.
This information is modified by the u flag
for case folding.
${mailbox}
This macro expands to the complete local
part of a recipient address. For example,
with an address user+foo@domain the mailbox
is user+foo.
A command-line argument that contains
${mailbox} expands to as many command-line
arguments as there are recipients.
This information is modified by the u flag
for case folding.
${nexthop}
This macro expands to the next-hop hostname.
This information is modified by the h flag
for case folding.
${original_recipient}
This macro expands to the complete recipient
address before any address rewriting or
aliasing.
A command-line argument that contains
${original_recipient} expands to as many
command-line arguments as there are recipi-
ents.
This information is modified by the hqu
flags for quoting and case folding.
This feature is available as of Postfix 2.5.
${recipient}
This macro expands to the complete recipient
address.
A command-line argument that contains
${recipient} expands to as many command-line
arguments as there are recipients.
This information is modified by the hqu
flags for quoting and case folding.
${sasl_method}
This macro expands to the name of the SASL
authentication mechanism in the AUTH command
when the Postfix SMTP server received the
message.
This feature is available as of Postfix 2.2.
${sasl_sender}
This macro expands to the SASL sender name
(i.e. the original submitter as per RFC
4954) in the MAIL FROM command when the
Postfix SMTP server received the message.
This feature is available as of Postfix 2.2.
${sasl_username}
This macro expands to the SASL user name in
the AUTH command when the Postfix SMTP
server received the message.
This feature is available as of Postfix 2.2.
${sender}
This macro expands to the envelope sender
address. By default, the null sender address
expands to MAILER-DAEMON; this can be
changed with the null_sender attribute, as
described above.
This information is modified by the q flag
for quoting.
${size}
This macro expands to Postfix's idea of the
message size, which is an approximation of
the size of the message as delivered.
${user}
This macro expands to the username part of a
recipient address. For example, with an
address user+foo@domain the username part is
user.
A command-line argument that contains
${user} expands into as many command-line
arguments as there are recipients.
This information is modified by the u flag
for case folding.
STANDARDS
RFC 3463 (Enhanced status codes)
DIAGNOSTICS
Command exit status codes are expected to follow the con-
ventions defined in <sysexits.h>. Exit status 0 means
normal successful completion.
Postfix version 2.3 and later support RFC 3463-style
enhanced status codes. If a command terminates with a
non-zero exit status, and the command output begins with
an enhanced status code, this status code takes precedence
over the non-zero exit status.
Problems and transactions are logged to syslogd(8). Cor-
rupted message files are marked so that the queue manager
can move them to the corrupt queue for further inspection.
SECURITY
This program needs a dual personality 1) to access the
private Postfix queue and IPC mechanisms, and 2) to exe-
cute external commands as the specified user. It is there-
fore security sensitive.
CONFIGURATION PARAMETERS
Changes to main.cf are picked up automatically as pipe(8)
processes run for only a limited amount of time. Use the
command "postfix reload" to speed up a change.
The text below provides only a parameter summary. See
postconf(5) for more details including examples.
RESOURCE AND RATE CONTROLS
In the text below, transport is the first field in a mas-
ter.cf entry.
transport_destination_concurrency_limit ($default_destina-
tion_concurrency_limit)
Limit the number of parallel deliveries to the same
destination, for delivery via the named transport.
The limit is enforced by the Postfix queue manager.
transport_destination_recipient_limit ($default_destina-
tion_recipient_limit)
Limit the number of recipients per message deliv-
ery, for delivery via the named transport. The
limit is enforced by the Postfix queue manager.
transport_time_limit ($command_time_limit)
Limit the time for delivery to external command,
for delivery via the named transport. The limit is
enforced by the pipe delivery agent.
Postfix 2.4 and later support a suffix that speci-
fies the time unit: s (seconds), m (minutes), h
(hours), d (days), w (weeks). The default time unit
is seconds.
MISCELLANEOUS CONTROLS
config_directory (see 'postconf -d' output)
The default location of the Postfix main.cf and
master.cf configuration files.
daemon_timeout (18000s)
How much time a Postfix daemon process may take to
handle a request before it is terminated by a
built-in watchdog timer.
delay_logging_resolution_limit (2)
The maximal number of digits after the decimal
point when logging sub-second delay values.
export_environment (see 'postconf -d' output)
The list of environment variables that a Postfix
process will export to non-Postfix processes.
ipc_timeout (3600s)
The time limit for sending or receiving information
over an internal communication channel.
mail_owner (postfix)
The UNIX system account that owns the Postfix queue
and most Postfix daemon processes.
max_idle (100s)
The maximum amount of time that an idle Postfix
daemon process waits for an incoming connection
before terminating voluntarily.
max_use (100)
The maximal number of incoming connections that a
Postfix daemon process will service before termi-
nating voluntarily.
process_id (read-only)
The process ID of a Postfix command or daemon
process.
process_name (read-only)
The process name of a Postfix command or daemon
process.
queue_directory (see 'postconf -d' output)
The location of the Postfix top-level queue direc-
tory.
recipient_delimiter (empty)
The separator between user names and address exten-
sions (user+foo).
syslog_facility (mail)
The syslog facility of Postfix logging.
syslog_name (see 'postconf -d' output)
The mail system name that is prepended to the
process name in syslog records, so that "smtpd"
becomes, for example, "postfix/smtpd".
SEE ALSO
qmgr(8), queue manager
bounce(8), delivery status reports
postconf(5), configuration parameters
master(5), generic daemon options
master(8), process manager
syslogd(8), system logging
LICENSE
The Secure Mailer license must be distributed with this
software.
AUTHOR(S)
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
PIPE(8)