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 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 external commands cannot handle more than one recipient
per delivery 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 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=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 delivery 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), according 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 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 $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 $sender command-line macro, and
when generating a From_ or Return-Path: message header.
If the null sender replacement text is a non-empty string
then it is affected by the q flag for address quoting
in command-line arguments.
The null sender replacement text may be empty; this form
is recommended for content filters that feed mail back into
Postfix. The empty sender address is not affected by the
q flag for address quoting in command-line arguments.
Caution: a null sender address is easily mis-parsed by
naive software. For example, when the pipe(8) daemon
executes a command such as:
command -f$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. without interpretation of
shell meta characters by a shell command interpreter.
In the command argument vector, the following macros are recognized
and replaced with corresponding 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 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 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.
${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 authentication.
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-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 conventions 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).
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.
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.
