PIPE(8)PIPE(8)NAMEpipe - Postfix delivery to external command
SYNOPSISpipe [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 command-line macros that are expanded
before the external command is executed.
The pipe(8) daemon updates queue files and marks recipients as fin‐
ished, 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 external commands cannot handle more than one recipient per deliv‐
ery request. Examples of such transports are pagers or fax machines.
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 com‐
mand. The directory must be accessible for the user specified
with the user attribute (see below). The default working direc‐
tory is $queue_directory. Delivery is deferred in case of fail‐
ure.
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 recog‐
nized: \a \b \f \n \r \t \v \ddd (up to three octal digits) and
\\.
flags=BDFORhqu.> (optional)
Optional message processing flags. By default, a message is
copied unchanged.
B Append a blank line at the end of each message. 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_destination_recipient_limit must be 1.
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" message header with
the recipient address as given to Postfix. Note: for this
to work, the transport_destination_recipient_limit must
be 1.
This feature is available as of Postfix 2.0.
R Prepend a Return-Path: message header with the envelope
sender address.
h Fold the command-line $recipient domain name and $nexthop
host name to lower case. This is recommended for deliv‐
ery via UUCP.
q Quote white space and other special characters in the
command-line $sender and $recipient address localparts
(text to the left of the right-most @ character), accord‐
ing to an 8-bit transparent version of RFC 822. This is
recommended for delivery via UUCP or BSMTP.
The result is compatible with the address parsing of com‐
mand-line recipients by the Postfix sendmail(1) mail sub‐
mission command.
The q flag affects only entire addresses, not the partial
address information from the $user, $extension or $mail‐
box command-line macros.
u Fold the command-line $recipient address localpart (text
to the left of the right-most @ character) to lower case.
This is recommended for delivery 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 software.
null_sender=replacement (default: MAILER-DAEMON)
Replace the null sender address, which is typically used for
delivery status notifications, with the specified text when
expanding the $sender command-line macro, and when generating a
From_ or Return-Path: message header.
If the null sender replacement text is a non-empty string then
it is affected by the q flag for address quoting in command-line
arguments.
The null sender replacement text may be empty; this form is rec‐
ommended for content filters that feed mail back into Postfix.
The empty sender address is not affected by the q flag for
address quoting in command-line arguments.
Caution: a null sender address is easily mis-parsed by naive
software. For example, when the pipe(8) daemon executes a com‐
mand such as:
command -f$sender -- $recipient (bad)
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:
command -f $sender -- $recipient (good)
This feature is available with Postfix 2.3 and later.
size=size_limit (optional)
Messages greater in size than this limit (in bytes) will be
returned to the sender as undeliverable.
user=username (required)
user=username:groupname
Execute the external command with the rights of the specified
username. The software refuses to execute 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 executed directly, i.e. with‐
out interpretation of shell meta characters by a shell command
interpreter.
In the command argument vector, the following macros are recog‐
nized and replaced with corresponding information from the Post‐
fix 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 network address.
This is available in Postfix 2.2 and later.
${client_helo}
This macro expands to the remote client HELO command
parameter.
This is available in Postfix 2.2 and later.
${client_hostname}
This macro expands to the remote client hostname.
This is available in Postfix 2.2 and later.
${client_protocol}
This macro expands to the remote client protocol.
This is available in Postfix 2.2 and later.
${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 fold‐
ing.
${mailbox}
This macro expands to the complete local part of a recip‐
ient 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 recipi‐
ents.
This information is modified by the u flag for case fold‐
ing.
${nexthop}
This macro expands to the next-hop hostname.
This information is modified by the h flag for case fold‐
ing.
${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 SASL authentication mechanism
used during the reception of the message. An empty string
is passed if the message has been received without SASL
authentication.
This is available in Postfix 2.2 and later.
${sasl_sender}
This macro expands to the SASL sender name (i.e. the
original submitter as per RFC 2554) used during the
reception of the message.
This is available in Postfix 2.2 and later.
${sasl_username}
This macro expands to the SASL user name used during the
reception of the message. An empty string is passed if
the message has been received without SASL authentica‐
tion.
This is available in Postfix 2.2 and later.
${sender}
This macro expands to the envelope sender address. By
default, the null sender address expands to MAILER-DAE‐
MON; 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 ${user} expands
into as many command-line arguments as there are recipi‐
ents.
This information is modified by the u flag for case fold‐
ing.
STANDARDS
RFC 3463 (Enhanced status codes)
DIAGNOSTICS
Command exit status codes are expected to follow the conventions
defined in <sysexits.h>. Exit status 0 means normal successful comple‐
tion.
Postfix version 2.3 and later support RFC 3463-style enhanced status
codes. If a command terminates with a non-zero exit status, and the
command output begins with an enhanced status code, this status code
takes precedence over the non-zero exit status.
Problems and transactions are logged to syslogd(8). Corrupted message
files are marked so that the queue manager can move them to the corrupt
queue for further inspection.
SECURITY
This program needs a dual personality 1) to access the private Postfix
queue and IPC mechanisms, and 2) to execute external commands as the
specified user. It is therefore security sensitive.
CONFIGURATION PARAMETERS
Changes to main.cf are picked up automatically as pipe(8) processes run
for only a limited amount of time. Use the command "postfix reload" to
speed up a change.
The text below provides only a parameter summary. See postconf(5) for
more details including examples.
RESOURCE AND RATE CONTROLS
In the text below, transport is the first field in a master.cf entry.
transport_destination_concurrency_limit ($default_destination_concur‐
rency_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 ($default_destination_recipi‐
ent_limit)
Limit the number of recipients per message delivery, for deliv‐
ery via the named transport. The limit is enforced by the Post‐
fix queue manager.
transport_time_limit ($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.
MISCELLANEOUS CONTROLS
config_directory (see 'postconf -d' output)
The default location of the Postfix main.cf and master.cf con‐
figuration 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 log‐
ging 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 the next service request before exiting.
max_use (100)
The maximal number of connection requests before a Postfix dae‐
mon process terminates.
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 directory.
recipient_delimiter (empty)
The separator between user names and address extensions
(user+foo).
syslog_facility (mail)
The syslog facility of Postfix logging.
syslog_name (postfix)
The mail system name that is prepended to the process name in
syslog records, so that "smtpd" becomes, for example, "post‐
fix/smtpd".
SEE ALSOqmgr(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)
