postconf.proto   [plain text]

# This is the input file for automatically generating the postconf(5)
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%CLASS address-verification Address verification (Postfix 2.1 and later)

<p>
Sender/recipient address verification is implemented by sending
probe email messages that are not actually delivered. This feature
is requested via the reject_unverified_sender and
reject_unverified_recipient access restrictions.  The status of
verification probes is maintained by the address verification
service.  See the file ADDRESS_VERIFICATION_README for information
about how to configure and operate the Postfix sender/recipient
address verification service.
</p>

%CLASS smtpd-compatibility Compatibility controls

%CLASS resource-control Resource controls

%CLASS after-queue-filter After-queue content filter

<p>
As of version 1.0, Postfix can be configured to send new mail to
an external content filter AFTER the mail is queued. This content
filter is expected to inject mail back into a (Postfix or other)
MTA for further delivery.  See the FILTER_README document for
details.
</p>

%CLASS before-queue-filter Before-queue content filter

<p>
The Postfix SMTP server can be configured to send incoming mail to
a real-time SMTP-based content filter BEFORE mail is queued.  This
content filter is expected to inject mail back into Postfix.  See
the SMTPD_PROXY_README document for details on how to configure
and operate this feature.
</p>

%CLASS basic-config Basic configuration parameters

%CLASS smtpd-access-relay SMTP server access and relay control

%CLASS smtpd-sasl SMTP server SASL authentication

%CLASS unknown-recipients Rejecting mail for unknown recipients

%CLASS smtpd-reply-code SMTP server response codes

%CLASS other Other configuration parameters

%PARAM access_map_reject_code 554

<p>
The numerical Postfix SMTP server response code when a client
is rejected by an access(5) map restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM address_verify_default_transport $default_transport

<p>
Overrides the default_transport parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_local_transport $local_transport

<p>
Overrides the local_transport parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_map 

<p>
Optional lookup table for persistent address verification status
storage.  The table is maintained by the verify(8) service, and
is opened before the process releases privileges.
</p>

<p>
By default, the information is kept in volatile memory, and is lost
after "<b>postfix reload</b>" or "<b>postfix stop</b>".
</p>

<p>
Specify a location in a file system that will not fill up. If the
database becomes corrupted, the world comes to an end. To recover
delete the file and do "<b>postfix reload</b>".
</p>

<p>
Examples:
</p>

<pre>
address_verify_map = hash:/etc/postfix/verify
address_verify_map = btree:/etc/postfix/verify
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_negative_cache yes

<p>
Enable caching of failed address verification probe results.  When
this feature is enabled, the cache may pollute quickly with garbage.
When this feature is disabled, Postfix will generate an address
probe for every lookup.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_negative_expire_time 3d

<p>
The time after which a failed probe expires from the address
verification cache.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_negative_refresh_time 3h

<p>
The time after which a failed address verification probe needs to
be refreshed.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_poll_count 3

<p>
How many times to query the verify(8) service for the completion
of an address verification request in progress.
</p>

<p>
The default poll count is 3.
</p>

<p>
Specify 1 to implement a crude form of greylisting, that is, always
defer the first delivery request for a never seen before address.
</p>

<p>
Example:
</p>

<pre>
address_verify_poll_count = 1
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_poll_delay 3s

<p>
The delay between queries for the completion of an address
verification request in progress.
</p>

<p>
The default polling delay is 3 seconds.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_positive_expire_time 31d

<p>
The time after which a successful probe expires from the address
verification cache.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_positive_refresh_time 7d

<p>
The time after which a successful address verification probe needs
to be refreshed.  The address verification status is not updated
when the probe fails (optimistic caching).
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_relay_transport $relay_transport

<p>
Overrides the relay_transport parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_relayhost $relayhost

<p>
Overrides the relayhost parameter setting for address verification
probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_sender postmaster

<p> The sender address to use in address verification probes. To
avoid problems with address probes that are sent in response to
address probes, the Postfix SMTP server excludes the probe sender
address from all SMTPD access blocks. </p>

<p>
Specify an empty value (address_verify_sender =) or &lt;&gt; if you want
to use the null sender address. Beware, some sites reject mail from
&lt;&gt;, even though RFCs require that such addresses be accepted.
</p>

<p>
Examples:
</p>

<pre>
address_verify_sender = &lt;&gt;
address_verify_sender = postmaster@my.domain
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_transport_maps $transport_maps

<p>
Overrides the transport_maps parameter setting for address verification
probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM address_verify_virtual_transport $virtual_transport

<p>
Overrides the virtual_transport parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM alias_database see "postconf -d" output

<p>
The alias databases for local(8) delivery that are updated with
"<b>newaliases</b>" or with "<b>sendmail -bi</b>".
</p>

<p>
This is a separate configuration parameter because not all the
tables specified with $alias_maps have to be local files.
</p>

<p>
Examples:
</p>

<pre>
alias_database = hash:/etc/aliases
alias_database = hash:/etc/mail/aliases
</pre>

%PARAM alias_maps see "postconf -d" output

<p>
The alias databases that are used for local(8) delivery. See
aliases(5) for syntax details.
</p>

<p>
The default list is system dependent.  On systems with NIS, the
default is to search the local alias database, then the NIS alias
database.
</p>

<p>
If you change the alias database, run "<b>postalias /etc/aliases</b>"
(or wherever your system stores the mail alias file), or simply
run "<b>newaliases</b>" to build the necessary DBM or DB file.
</p>

<p>
Examples:
</p>

<pre>
alias_maps = hash:/etc/aliases, nis:mail.aliases
alias_maps = hash:/etc/aliases
</pre>

%PARAM allow_mail_to_commands alias, forward

<p>
Restrict local(8) mail delivery to external commands.  The default
is to disallow delivery to "|command" in :include:  files (see
aliases(5) for the text that defines this terminology).
</p>

<p>
Specify zero or more of: <b>alias</b>, <b>forward</b> or <b>include</b>,
in order to allow commands in aliases(5), .forward files or in
:include:  files, respectively.
</p>

<p>
Example:
</p>

<pre>
allow_mail_to_commands = alias,forward,include
</pre>

%PARAM allow_mail_to_files alias, forward

<p>
Restrict local(8) mail delivery to external files. The default is
to disallow "/file/name" destinations in :include:  files (see
aliases(5) for the text that defines this terminology).
</p>

<p>
Specify zero or more of: <b>alias</b>, <b>forward</b> or <b>include</b>,
in order to allow "/file/name" destinations in aliases(5), .forward
files and in :include:  files, respectively.
</p>

<p>
Example:
</p>

<pre>
allow_mail_to_files = alias,forward,include
</pre>

%PARAM allow_min_user no

<p>
Allow a recipient address to have `-' as the first character.  By
default, this is not allowed, to avoid accidents with software that
passes email addresses via the command line.
</p>

%PARAM allow_percent_hack yes

<p>
Enable the rewriting of the form "user%domain" to "user@domain".
This is enabled by default.
</p>

<p>
Example:
</p>

<pre>
allow_percent_hack = no
</pre>

%PARAM allow_untrusted_routing no

<p>
Forward mail with sender-specified routing (user[@%!]remote[@%!]site)
from untrusted clients to destinations matching $relay_domains.
</p>

<p>
By default, this feature is turned off.  This closes a nasty open
relay loophole where a backup MX host can be tricked into forwarding
junk mail to a primary MX host which then spams it out to the world.
</p>

<p>
This parameter also controls if non-local addresses with sender-specified
routing can match Postfix access tables. By default, such addresses
cannot match Postfix access tables, because the address is ambiguous.
</p>

%PARAM always_bcc 

<p>
Optional address that receives a "blind carbon copy" of each message
that is received by the Postfix mail system.
</p>

<p>
NOTE: if mail to the BCC address bounces it will be returned to
the sender.
</p>

%PARAM berkeley_db_create_buffer_size 16777216

<p>
The per-table I/O buffer size for programs that create Berkeley DB
hash or btree tables.  Specify a byte count.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM berkeley_db_read_buffer_size 131072

<p>
The per-table I/O buffer size for programs that read Berkeley DB
hash or btree tables.  Specify a byte count.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM best_mx_transport 

<p>
Where the Postfix SMTP client should deliver mail when it detects
a "mail loops back to myself" error condition. This happens when
the local MTA is the best SMTP mail exchanger for a destination
not listed in $mydestination, $inet_interfaces, $proxy_interfaces,
$virtual_alias_domains, or $virtual_mailbox_domains.  By default,
the Postfix SMTP client returns such mail as undeliverable.
</p>

<p>
Specify, for example, "best_mx_transport = local" to pass the mail
from the SMTP client to the local(8) delivery agent. You can specify
any message delivery "transport" or "transport:nexthop" that is
defined in the master.cf file. See the transport(5) manual page
for the syntax and meaning of "transport" or "transport:nexthop".
</p>

<p>
However, this feature is expensive because it ties up a Postfix
SMTP client process while the local(8) delivery agent is doing its
work. It is more efficient (for Postfix) to list all hosted domains
in a table or database.
</p>

%PARAM biff yes

<p>
Whether or not to use the local biff service.  This service sends
"new mail" notifications to users who have requested new mail
notification with the UNIX command "biff y".
</p>

<p>
For compatibility reasons this feature is on by default.  On systems
with lots of interactive users, the biff service can be a performance
drain.  Specify "biff = no" to disable.
</p>

%PARAM body_checks 

<p> Optional lookup tables for content inspection as specified in
the body_checks(5) manual page.  </p>

<p> Note: with Postfix versions before 2.0, these rules inspect
all content after the primary message headers. </p>

%PARAM body_checks_size_limit 51200

<p>
How much text in a message body segment (or attachment, if you
prefer to use that term) is subjected to body_checks inspection.
The amount of text is limited to avoid scanning huge attachments.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM bounce_queue_lifetime 5d

<p>
The maximal time a bounce message is queued before it is considered
undeliverable.  By default, this is the same as the queue life time
for regular mail.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).
</p>

<p>
Specify 0 when mail delivery should be tried only once.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM bounce_size_limit 50000

<p>
The maximal amount of original message text that is sent in a
non-delivery notification. Specify a byte count.
</p>

%PARAM canonical_maps 

<p>
Optional address mapping lookup tables for message headers and
envelopes. The mapping is applied to both sender and recipient
addresses, in both envelopes and in headers. This is typically used
to clean up dirty addresses from legacy mail systems, or to replace
login names by Firstname.Lastname.  The table format and lookups
are documented in canonical(5).
</p>

<p>
If you use this feature, run "<b>postmap /etc/postfix/canonical</b>" to
build the necessary DBM or DB file after every change. The changes
will become visible after a minute or so.  Use "<b>postfix reload</b>"
to eliminate the delay.
</p>

<p>
Examples:
</p>

<pre>
canonical_maps = dbm:/etc/postfix/canonical
canonical_maps = hash:/etc/postfix/canonical
</pre>

%PARAM command_directory see "postconf -d" output

<p>
The location of all postfix administrative commands.
</p>

%PARAM command_time_limit 1000s

<p>
Time limit for delivery to external commands. This limit is used
by the local(8) delivery agent, and is the default time limit for
delivery by the pipe(8) delivery agent.
</p>

<p>
Note: if you set this time limit to a large value you must update the
global ipc_timeout parameter as well.
</p>

%PARAM daemon_directory see "postconf -d" output

<p>
The directory with Postfix support programs and daemon programs.
These should not be invoked directly by humans. The directory must
be owned by root.
</p>

%PARAM daemon_timeout 18000s

<p> How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM debug_peer_level 2

<p> The increment in verbose logging level when a remote client or
server matches a pattern in the debug_peer_list parameter.  </p>

%PARAM debug_peer_list 

<p> Optional list of remote client or server hostname or network
address patterns that cause the verbose logging level to increase
by the amount specified in $debug_peer_level.  </p>

<p> Specify domain names, network/netmask patterns, "/file/name"
patterns or "type:table" lookup tables. The result from lookup
tables is ignored.  </p>

<p> Pattern matching of domain names is controlled by the
parent_domain_matches_subdomains parameter.  </p>

<p>
Examples:
</p>

<pre>
debug_peer_list = 127.0.0.1
debug_peer_list = some.domain
</pre>

%PARAM default_database_type see "postconf -d" output

<p>
The default database type for use in newaliases(1), postalias(1)
and postmap(1) commands. On many UNIX systems the default type is
either <b>dbm</b> or <b>hash</b>. The default setting is frozen
when the Postfix system is built.
</p>

<p>
Examples:
</p>

<pre>
default_database_type = hash
default_database_type = dbm
</pre>

%PARAM default_delivery_slot_cost 5

<p>
How often the Postfix queue manager's scheduler is allowed to
preempt delivery of one message with another.
</p>

<p>
Each transport maintains a so-called "available delivery slot counter"
for each message. One message can be preempted by another one when
the other message can be delivered using no more delivery slots
(i.e., invocations of delivery agents) than the current message
counter has accumulated (or will eventually accumulate - see about
slot loans below). This parameter controls how often is the counter
incremented - it happens after each default_delivery_slot_cost
recipients have been delivered.
</p>

<p>
The cost of 0 is used to disable the preempting scheduling completely.
The minimum value the scheduling algorithm can use is 2 - use it
if you want to maximize the message throughput rate. Although there
is no maximum, it doesn't make much sense to use values above say
50.
</p>

<p>
The only reason why the value of 2 is not the default is the way
this parameter affects the delivery of mailing-list mail. In the
worst case, their delivery can take somewhere between (cost+1/cost)
and (cost/cost-1) times more than if the preemptive scheduler was
disabled. The default value of 5 turns out to provide reasonable
message response times while making sure the mailing-list deliveries
are not extended by more than 20-25 percent even in the worst case.
</p>

<p>
Examples:
</p>

<pre>
default_delivery_slot_cost = 0
default_delivery_slot_cost = 2
</pre>

%PARAM default_destination_concurrency_limit 20

<p>
The default maximal number of parallel deliveries to the same
destination.  This is the default limit for delivery via the lmtp(8),
pipe(8), smtp(8) and virtual(8) delivery agents.
</p>

%PARAM default_destination_recipient_limit 50

<p>
The default maximal number of recipients per message delivery.
This is the default limit for delivery via the lmtp(8), pipe(8),
smtp(8) and virtual(8) delivery agents.
</p>

<p> Setting this parameter to a value of 1 changes the meaning of
the corresponding per-destination concurrency limit from concurrency
per domain into concurrency per recipient.  </p>

%PARAM default_extra_recipient_limit 1000

<p>
The default value for the extra per-transport limit imposed on the
number of in-memory recipients.  This extra recipient space is
reserved for the cases when the Postfix queue manager's scheduler
preempts one message with another and suddenly needs some extra
recipients slots for the chosen message in order to avoid performance
degradation.
</p>

%PARAM default_minimum_delivery_slots 3

<p>
How many recipients a message must have in order to invoke the
Postfix queue manager's scheduling algorithm at all.  Messages
which would never accumulate at least this many delivery slots
(subject to slot cost parameter as well) are never preempted.
</p>

%PARAM default_privs nobody

<p>
The default rights used by the local(8) delivery agent for delivery
to external file or command.  These rights are used when delivery
is requested from an aliases(5) file that is owned by <b>root</b>, or
when delivery is done on behalf of <b>root</b>. <b>DO NOT SPECIFY A
PRIVILEGED USER OR THE POSTFIX OWNER</b>.
</p>

%PARAM default_process_limit 100

<p>
The default maximal number of Postfix child processes that provide
a given service. This limit can be overruled for specific services
in the master.cf file.
</p>

%PARAM default_rbl_reply see "postconf -d" output

<p>
The default SMTP server response template for a request that is
rejected by an RBL-based restriction. This template can be overruled
by specific entries in the optional rbl_reply_maps lookup table.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p>
The template is subject to exactly one level of $name substitution:
</p>

<dl>

<dt><b>$client</b></dt>

<dd>The client hostname and IP address, formatted as name[address]. </dd>

<dt><b>$client_address</b></dt>

<dd>The client IP address. </dd>

<dt><b>$client_name</b></dt>

<dd>The client hostname or "<b>unknown</b>". </dd>

<dt><b>$helo_name</b></dt>

<dd>The hostname given in HELO or EHLO command or empty string. </dd>

<dt><b>$rbl_class</b></dt>

<dd>The blacklisted entity type: Client host, Helo command, Sender
address, or Recipient address. </dd>

<dt><b>$rbl_code</b></dt>

<dd>The numerical SMTP response code, as specified with the
maps_rbl_reject_code configuration parameter. </dd>

<dt><b>$rbl_domain</b></dt>

<dd>The RBL domain where $rbl_what is blacklisted. </dd>

<dt><b>$rbl_reason</b></dt>

<dd>The reason why $rbl_what is blacklisted, or an empty string. </dd>

<dt><b>$rbl_what</b></dt>

<dd>The entity that is blacklisted (an IP address, a hostname, a domain
name, or an email address whose domain was blacklisted). </dd>

<dt><b>$recipient</b></dt>

<dd>The recipient address or &lt;&gt; in case of the null address. </dd>

<dt><b>$recipient_domain</b></dt>

<dd>The recipient domain or empty string. </dd>

<dt><b>$recipient_name</b></dt>

<dd>The recipient address localpart or &lt;&gt; in case of null address. </dd>

<dt><b>$sender</b></dt>

<dd>The sender address or &lt;&gt; in case of the null address. </dd>

<dt><b>$sender_domain</b></dt>

<dd>The sender domain or empty string. </dd>

<dt><b>$sender_name</b></dt>

<dd>The sender address localpart or &lt;&gt; in case of the null address. </dd>

<dt><b>${name?text}</b></dt>

<dd>Expands to `text' if $name is not empty. </dd>

<dt><b>${name:text}</b></dt>

<dd>Expands to `text' if $name is empty. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

%PARAM smtpd_expansion_filter see "postconf -d" output

<p>
The smtpd_expansion_filter configuration parameter controls what
characters may appear in $name expansions.
</p>

%PARAM default_recipient_limit 10000

<p>
The default per-transport upper limit on the number of in-memory
recipients.  These limits take priority over the global
qmgr_message_recipient_limit after the message has been assigned
to the respective transports.  See also default_extra_recipient_limit
and qmgr_message_recipient_minimum.
</p>

%PARAM default_transport smtp

<p>
The default mail delivery transport for domains that do not match
$mydestination, $inet_interfaces, $proxy_interfaces,
$virtual_alias_domains, $virtual_mailbox_domains, or $relay_domains.
This information can be overruled with the transport(5) table.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in master.cf.
The <i>:nexthop</i> part is optional.  For more details see the
transport(5) manual page.
</p>

<p>
Example:
</p>

<pre>
default_transport = uucp:relayhostname
</pre>

%PARAM defer_code 450

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the "defer" restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM defer_transports 

<p>
The names of message delivery transports that should not be delivered
to unless someone issues "<b>sendmail -q</b>" or equivalent. Specify zero
or more names of mail delivery transports names that appear in the
first field of master.cf.
</p>

<p>
Example:
</p>

<pre>
defer_transports = smtp
</pre>

%PARAM deliver_lock_attempts 20

<p>
The maximal number of attempts to acquire an exclusive lock on a
mailbox file or bounce(8) logfile.
</p>

%PARAM deliver_lock_delay 1s

<p>
The time between attempts to acquire an exclusive lock on a mailbox
file or bounce(8) logfile.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM disable_vrfy_command no

<p>
Disable the SMTP VRFY command. This stops some techniques used to
harvest email addresses.
</p>

<p>
Example:
</p>

<pre>
disable_vrfy_command = no
</pre>

%PARAM double_bounce_sender double-bounce

<p> The sender address of postmaster notifications that are generated
by the mail system. All mail to this address is silently discarded,
in order to terminate mail bounce loops.  </p>

%PARAM duplicate_filter_limit 1000

<p> The maximal number of addresses remembered by the address
duplicate filter for aliases(5) or virtual(5) alias expansion, or
for showq(8) queue displays.  </p>

%PARAM enable_original_recipient yes

<p> Enable support for the X-Original-To message header. This header
is needed for multi-recipient mailboxes.  </p>

<p> When this parameter is set to yes, the cleanup(8) daemon performs
duplicate elimination on distinct pairs of (original recipient,
rewritten recipient), and generates non-empty original recipient
queue file records.  </p>

<p> When this parameter is set to no, the cleanup(8) daemon performs
duplicate elimination on the rewritten recipient address only, and
generates empty original recipient queue file records.  </p>

<p> This feature is available in Postfix 2.1 and later. With Postfix
2.0, support for the X-Original-To message header is always turned
on. Postfix versions before 2.0 have no support for the X-Original-To
message header.  </p>

%PARAM export_environment see "postconf -d" output

<p>
The list of environment variables that a Postfix process will export
to non-Postfix processes. The TZ variable is needed for sane
time keeping on System-V-ish systems.
</p>

<p>
Specify a list of names and/or name=value pairs, separated by
whitespace or comma.
</p>

<p>
Example:
</p>

<pre>
export_environment = TZ PATH=/bin:/usr/bin
</pre>

%PARAM fallback_relay 

<p>
Optional list of relay hosts for SMTP destinations that can't be
found or that are unreachable.  </p>

<p>
By default, mail is returned to the sender when a destination is
not found, and delivery is deferred if a destination is unreachable.
</p>

<p>
The fallback relays must be SMTP destinations. Specify a domain,
host, host:port, [host]:port, [address] or [address]:port; the form
[host] turns off MX lookups.  If you specify multiple SMTP
destinations, Postfix will try them in the specified order.
</p>

%PARAM fast_flush_domains $relay_domains

<p>
Optional list of destinations that are eligible for per-destination
logfiles with mail that is queued to those destinations.
</p>

<p>
By default, Postfix maintains "fast flush" logfiles only for
destinations that the Postfix SMTP server is willing to relay to
(i.e. the default is: "fast_flush_domains = $relay_domains"; see
the relay_domains parameter in the postconf(5) manual).
</p>

<p> Specify a list of hosts or domains, "/file/name" patterns or
"type:table" lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
"/file/name" pattern is replaced by its contents; a "type:table"
lookup table is matched when the domain or its parent domain appears
as lookup key.  </p>

<p>
Specify "fast_flush_domains =" to disable the feature altogether.
</p>

%PARAM fast_flush_purge_time 7d

<p>
The time after which an empty per-destination "fast flush" logfile
is deleted.
</p>

<p>
You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks.  The default time unit is days.
</p>

%PARAM fast_flush_refresh_time 12h

<p>
The time after which a non-empty but unread per-destination "fast
flush" logfile needs to be refreshed.  The contents of a logfile
are refreshed by requesting delivery of all messages listed in the
logfile.
</p>

<p>
You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks.  The default time unit is hours.
</p>

%PARAM fork_attempts 5

<p> The maximal number of attempts to fork() a child process.  </p>

%PARAM fork_delay 1s

<p> The delay between attempts to fork() a child process.  </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks).  The default time unit is s (seconds).  </p>

%PARAM forward_path see "postconf -d" output

<p> The local(8) delivery agent search list for finding a .forward
file with user-specified delivery methods. The first file that is
found is used.  </p>

<p>
The following expansions are done on forward_path before
the search actually happens:
</p>

<dl>

<dt><b>$user</b></dt>

<dd>The recipient's username. </dd>

<dt><b>$shell</b></dt>

<dd>The recipient's login shell pathname. </dd>

<dt><b>$home</b></dt>

<dd>The recipient's home directory. </dd>

<dt><b>$recipient</b></dt>

<dd>The full recipient address. </dd>

<dt><b>$extension</b></dt>

<dd>The optional recipient address extension. </dd>

<dt><b>$domain</b></dt>

<dd>The recipient domain. </dd>

<dt><b>$local</b></dt>

<dd>The entire recipient localpart. </dd>

<dt><b>$recipient_delimiter</b></dt>

<dd>The system-wide recipient address extension delimiter. </dd>

<dt><b>${name?value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> is non-empty. </dd>

<dt><b>${name:value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> is empty. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

<p>
Examples:
</p>

<pre>
forward_path = /var/forward/$user
forward_path =
    /var/forward/$user/.forward$recipient_delimiter$extension,
    /var/forward/$user/.forward
</pre>

%CLASS queue-hashing Queue directory hashing

<p>
Queue directory hashing is a performance feature. Splitting one
queue directory across multiple subdirectory levels can speed up
file access by reducing the number of files per directory.
</p>

<p>
Unfortunately, deeply hashing the incoming or deferred queue can
actually slow down the mail system (with a depth of 2, mailq with
an empty queue can take several seconds).
</p>

<p>
Hashing must NOT be used with a world-writable maildrop directory.
Hashing MUST be used for the defer logfile directory, to avoid poor
performance when handling lots of deferred mail.
</p>

%PARAM hash_queue_depth 1

<p>
The number of subdirectory levels for queue directories listed with
the hash_queue_names parameter.
</p>

<p>
After changing the hash_queue_names or hash_queue_depth parameter,
execute the command "<b>postfix reload</b>".
</p>

%PARAM hash_queue_names see "postconf -d" output

<p>
The names of queue directories that are split across multiple
subdirectory levels.
</p>

<p>
After changing the hash_queue_names or hash_queue_depth parameter,
execute the command "<b>postfix reload</b>".
</p>

%CLASS headerbody-checks Content inspection built-in features

<p>
The Postfix cleanup(8) server has a limited ability to inspect
message headers and body content for signs of trouble. This is not
meant to be a substitute for content filters that do complex
processing such attachment decoding and unzipping.
</p>

%PARAM header_checks 

<p>
Optional lookup tables for content inspection of primary non-MIME
message headers, as specified in the header_checks(5) manual page.
</p>

%PARAM header_size_limit 102400

<p>
The maximal amount of memory in bytes for storing a message header.
If a header is larger, the excess is discarded.  The limit is
enforced by the cleanup(8) server.
</p>

%PARAM home_mailbox 

<p>
Optional pathname of a mailbox file relative to a local(8) user's
home directory.
</p>

<p>
Specify a pathname ending "/" for qmail-style delivery.
</p>

<p>
The precedence of local(8) delivery features from high to low is:
aliases, .forward files, mailbox_transport, mailbox_command_maps,
mailbox_command, home_mailbox, mail_spool_directory, fallback_transport
and luser_relay.
</p>

<p>
Examples:
</p>

<pre>
home_mailbox = Mailbox
home_mailbox = Maildir/
</pre>

%PARAM hopcount_limit 50

<p>
The maximal number of Received:  message headers that is allowed
in the primary message headers. A message that exceeds the limit
is bounced, in order to stop a mailer loop.
</p>

%PARAM ignore_mx_lookup_error no

<p> Ignore DNS MX lookups that produce no response.  By default,
the Postfix SMTP client defers delivery and tries again after some
delay.  This behavior is required by the SMTP standard.  </p>

<p>
Specify "<b>ignore_mx_lookup_error = yes</b>" to force a DNS A record
lookup instead. This violates the SMTP standard and can result in
mis-delivery of mail.
</p>

%PARAM import_environment see "postconf -d" output

<p>
The list of environment parameters that a Postfix process will
import from a non-Postfix parent process. Examples of relevant
parameters:
</p>

<dl>

<dt><b>TZ</b></dt>

<dd>Needed for sane time keeping on most System-V-ish systems. </dd>

<dt><b>DISPLAY</b></dt>

<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>

<dt><b>XAUTHORITY</b></dt>

<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>

<dt><b>MAIL_CONFIG</b></dt>

<dd>Needed to make "<b>postfix -c</b>" work. </dd>

</dl>

<p> Specify a list of names and/or name=value pairs, separated by
whitespace or comma. The name=value form is supported with
Postfix 2.1 and later.  </p>

%PARAM in_flow_delay 1s

<p> Time to pause before accepting a new message, when the message
arrival rate exceeds the message delivery rate. This feature is
turned on by default (it's disabled on SCO UNIX due to an SCO bug).
</p>

<p>
With the default 100 SMTP server process limit, "<b>in_flow_delay
= 1s</b>" limits the mail inflow to 100 messages per second above the
number of messages delivered per second.
</p>

<p>
Specify 0 to disable the feature. Valid delays are 0..10.
</p>

%PARAM inet_interfaces all

<p>
The network interface addresses that this mail system receives mail
on.  By default, the software claims all active interfaces on the
machine. The parameter also controls delivery of mail to
user@[ip.address].
</p>

<p>
See also the proxy_interfaces parameter, for network addresses that
are forwarded to us by way of a proxy or address translator.
</p>

<p>
Note: you need to stop and start Postfix when this parameter changes.
</p>

%PARAM initial_destination_concurrency 5

<p>
The initial per-destination concurrency level for parallel delivery
to the same destination. This limit applies to delivery via smtp(8),
and via the pipe(8) and virtual(8) delivery agents.
</p>

<p>
Warning: with concurrency of 1, one bad message can be enough to
block all mail to a site.
</p>

%PARAM invalid_hostname_reject_code 501

<p>
The numerical Postfix SMTP server response code when the client
HELO or EHLO command parameter is rejected by the reject_invalid_hostname
restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM ipc_idle 100s

<p>
The time after which a client closes an idle internal communication
channel.  The purpose is to allow servers to terminate voluntarily
after they become idle. This is used, for example, by the address
resolving and rewriting clients.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM ipc_timeout 3600s

<p>
The time limit for sending or receiving information over an internal
communication channel.  The purpose is to break out of deadlock
situations. If the time limit is exceeded the software aborts with a
fatal error.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM ipc_ttl 1000s

<p>
The time after which a client closes an active internal communication
channel.  The purpose is to allow servers to terminate voluntarily
after reaching their client limit.  This is used, for example, by
the address resolving and rewriting clients.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM line_length_limit 2048

<p> Upon input, long lines are chopped up into pieces of at most
this length; upon delivery, long lines are reconstructed.  </p>

%PARAM lmtp_connect_timeout 0s

<p> The LMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit).  When no
connection can be made within the deadline, the LMTP client tries
the next address on the mail exchanger list.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
Example:
</p>

<pre>
lmtp_connect_timeout = 30s
</pre>

%PARAM lmtp_data_done_timeout 600s

<p> The LMTP client time limit for sending the LMTP ".", and for
receiving the server response.  When no response is received within
the deadline, a warning is logged that the mail may be delivered
multiple times.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_data_init_timeout 120s

<p>
The LMTP client time limit for sending the LMTP DATA command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_data_xfer_timeout 180s

<p>
The LMTP client time limit for sending the LMTP message content.
When the connection stalls for more than $lmtp_data_xfer_timeout
the LMTP client terminates the transfer.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_lhlo_timeout 300s

<p> The LMTP client time limit for receiving the LMTP greeting
banner.  When the server drops the connection without sending a
greeting banner, or when it sends no greeting banner within the
deadline, the LMTP client tries the next address on the mail
exchanger list.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_mail_timeout 300s

<p>
The LMTP client time limit for sending the MAIL FROM command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_quit_timeout 300s

<p>
The LMTP client time limit for sending the QUIT command, and for
receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_rcpt_timeout 300s

<p>
The LMTP client time limit for sending the RCPT TO command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_rset_timeout 120s

<p>
The LMTP client time limit for sending the RSET command, and for
receiving the server response. The LMTP client sends RSET in order
to find out if a cached connection is still alive.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM lmtp_send_xforward_command no

<p>
Send an XFORWARD command to the LMTP server when the LMTP LHLO
server response announces XFORWARD support.  This allows an lmtp(8)
delivery agent, used for content filter message injection, to
forward the name, address, protocol and HELO name of the original
client to the content filter and downstream queuing LMTP server.
Before you change the value to yes, it is best to make sure that
your content filter supports this command.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM lmtp_skip_quit_response no

<p>
Wait for the response to the LMTP QUIT command.
</p>

%PARAM lmtp_xforward_timeout 300s

<p>
The LMTP client time limit for sending the XFORWARD command, and
for receiving the server response.
</p>

<p>
In case of problems the client does NOT try the next address on
the mail exchanger list.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM local_command_shell 

<p>
Optional shell program for local(8) delivery to non-Postfix command.
By default, non-Postfix commands are executed directly; commands
are given to given to /bin/sh only when they contain shell meta
characters or shell built-in commands.  </p>

<p> "sendmail's restricted shell" (smrsh) is what most people will
use in order to restrict what programs can be run from e.g. .forward
files (smrsh is part of the Sendmail distribution).  </p>

<p> Note: when a shell program is specified, it is invoked even
when the command contains no shell built-in commands or meta
characters.  </p>

<p>
Example:
</p>

<pre>
local_command_shell = /some/where/smrsh -c
</pre>

%PARAM local_destination_concurrency_limit 2

<p> The maximal number of parallel deliveries via the local mail
delivery transport to the same recipient (when
"local_destination_recipient_limit = 1") or the maximal number of
parallel deliveries to the same local domain (when
"local_destination_recipient_limit &gt; 1"). This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the master.cf file. </p>

<p> A low limit of 2 is recommended, just in case someone has an
expensive shell command in a .forward file or in an alias (e.g.,
a mailing list manager).  You don't want to run lots of those at
the same time.  </p>

%PARAM local_destination_recipient_limit 1

<p> The maximal number of recipients per message delivery via the
local mail delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file. </p>

<p> Setting this parameter to a value &gt; 1 changes the meaning of
local_destination_concurrency_limit from concurrency per recipient
into concurrency per domain.  </p>

%PARAM local_recipient_maps proxy:unix:passwd.byname $alias_maps

<p> Lookup tables with all names or addresses of local recipients:
a recipient address is local when its domain matches $mydestination,
$inet_interfaces or $proxy_interfaces.  Specify @domain as a
wild-card for domains that do not have a valid recipient list.
Technically, tables listed with $local_recipient_maps are used as
lists: Postfix needs to know only if a lookup string is found or
not, but it does not use the result from table lookup.  </p>

<p>
If this parameter is non-empty (the default), then the Postfix SMTP server
will reject mail for unknown local users.
</p>

<p>
To turn off local recipient checking in the Postfix SMTP server,
specify "local_recipient_maps =" (i.e. empty).
</p>

<p>
The default setting assumes that you use the default Postfix local
delivery agent for local delivery. You need to update the
local_recipient_maps setting if:
</p>

<ul>

<li>You redefine the local delivery agent in master.cf.

<li> You redefine the "local_transport" setting in main.cf.

<li>You use the "luser_relay", "mailbox_transport", or "fallback_transport"
feature of the Postfix local(8) delivery agent.

</ul>

<p>
Details are described in the LOCAL_RECIPIENT_README file.
</p>

<p>
Beware: if the Postfix SMTP server runs chrooted, you need to access
the passwd file via the proxymap(8) service, in order to overcome
chroot access restrictions. The alternative, maintaining a copy of
the system password file in the chroot jail is not practical.
</p>

<p>
Examples:
</p>

<pre>
local_recipient_maps =
</pre>

%PARAM local_transport local:$myhostname

<p> The default mail delivery transport for domains that match
$mydestination, $inet_interfaces or $proxy_interfaces.  This
information can be overruled with the transport(5) table.  </p>

<p>
By default, local mail is delivered to the transport called "local",
which is just the name of a service that is defined the master.cf file.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in master.cf.
The <i>:nexthop</i> part is optional.  For more details see the
transport(5) manual page.
</p>

<p>
Beware: if you override the default local delivery agent then you
need to review the LOCAL_RECIPIENT_README document, otherwise the
SMTP server may reject mail for local recipients.
</p>

%PARAM luser_relay 

<p>
Optional catch-all destination for unknown local(8) recipients.
By default, mail for unknown recipients in domains that match
$mydestination, $inet_interfaces or $proxy_interfaces is returned
as undeliverable.
</p>

<p>
The following $name expansions are done on luser_relay:
</p>

<dl>

<dt><b>$domain</b></dt>

<dd>The recipient domain. </dd>

<dt><b>$extension</b></dt>

<dd>The recipient address extension. </dd>

<dt><b>$home</b></dt>

<dd>The recipient's home directory. </dd>

<dt><b>$local</b></dt>

<dd>The entire recipient address localpart. </dd>

<dt><b>$recipient</b></dt>

<dd>The full recipient address. </dd>

<dt><b>$recipient_delimiter</b></dt>

<dd>The system-wide recipient address extension delimiter. </dd>

<dt><b>$shell</b></dt>

<dd>The recipient's login shell. </dd>

<dt><b>$user</b></dt>

<dd>The recipient username. </dd>

<dt><b>${name?value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> has a non-empty value. </dd>

<dt><b>${name:value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> has an empty value. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

<p>
Note: luser_relay works only for the Postfix local(8) delivery agent.
</p>

<p>
NOTE: if you use this feature for accounts not in the UNIX password
file, then you must specify "<b>local_recipient_maps =</b>" (i.e. empty)
in the main.cf file, otherwise the Postfix SMTP server will reject mail
for non-UNIX accounts with "User unknown in local recipient table".
</p>

<p>
Examples:
</p>

<pre>
luser_relay = $user@other.host
luser_relay = $local@other.host
luser_relay = admin+$local
</pre>

%PARAM mail_name Postfix

<p>
The mail system name that is displayed in Received: headers, in
the SMTP greeting banner, and in bounced mail.
</p>

%PARAM mail_owner postfix

<p>
The UNIX system account that owns the Postfix queue and most Postfix
daemon processes.  Specify the name of a user account that does
not share a group with other accounts and that owns no other files
or processes on the system.  In particular, don't specify nobody
or daemon.  PLEASE USE A DEDICATED USER ID AND GROUP ID.
</p>

%PARAM mail_spool_directory see "postconf -d" output

<p>
The directory where local(8) UNIX-style mailboxes are kept. The
default setting depends on the system type. Specify a name ending
in / for maildir-style delivery.
</p>

<p>
Note: maildir delivery is done with the privileges of the recipient.
If you use the mail_spool_directory setting for maildir style
delivery, then you must create the top-level maildir directory in
advance. Postfix will not create it.
</p>

<p>
Examples:
</p>

<pre>
mail_spool_directory = /var/mail
mail_spool_directory = /var/spool/mail
</pre>

%PARAM mail_version see "postconf -d" output

<p>
The version of the mail system. Stable releases are named
<i>major</i>.<i>minor</i>.<i>patchlevel</i>. Experimental releases
also include the release date. The version string can be used in,
for example, the SMTP greeting banner.
</p>

%PARAM mailbox_command 

<p>
Optional external command that the local(8) delivery agent should
use for mailbox delivery.  The command is run with the user ID and
the primary group ID privileges of the recipient.  Exception:
command delivery for root executes with $default_privs privileges.
This is not a problem, because 1) mail for root should always be
aliased to a real user and 2) don't log in as root, use "su" instead.
</p>

<p>
The following environment variables are exported to the command:
</p>

<dl>

<dt><b>DOMAIN</b></dt>

<dd>The domain part of the recipient address. </dd>

<dt><b>EXTENSION</b></dt>

<dd>The optional address extension. </dd>

<dt><b>HOME</b></dt>

<dd>The recipient home directory. </dd>

<dt><b>LOCAL</b></dt>

<dd>The recipient address localpart. </dd>

<dt><b>LOGNAME</b></dt>

<dd>The recipient's username. </dd>

<dt><b>RECIPIENT</b></dt>

<dd>The full recipient address. </dd>

<dt><b>SENDER</b></dt>

<dd>The full sender address. </dd>

<dt><b>SHELL</b></dt>

<dd>The recipient's login shell. </dd>

<dt><b>USER</b></dt>

<dd>The recipient username. </dd>

</dl>

<p>
Unlike other Postfix configuration parameters, the mailbox_command
parameter is not subjected to $name substitutions. This is to make
it easier to specify shell syntax (see example below).
</p>

<p>
If you can, avoid shell meta characters because they will force
Postfix to run an expensive shell process. If you're delivering
via Procmail then running a shell won't make a noticeable difference
in the total cost.
</p>

<p>
Note: if you use the mailbox_command feature to deliver mail
system-wide, you must set up an alias that forwards mail for root
to a real user.
</p>

<p>
The precedence of local(8) delivery features from high to low is:
aliases, .forward files, mailbox_transport, mailbox_command_maps,
mailbox_command, home_mailbox, mail_spool_directory, fallback_transport
and luser_relay.
</p>

<p>
Examples:
</p>

<pre>
mailbox_command = /some/where/procmail
mailbox_command = /some/where/procmail -a "$EXTENSION"
mailbox_command = /some/where/maildrop -d "$USER"
        -f "$SENDER" "$EXTENSION"
</pre>

%PARAM mailbox_size_limit 51200000

<p> The maximal size of any local(8) individual mailbox or maildir
file, or zero (no limit).  In fact, this limits the size of any
file that is written to upon local delivery, including files written
by external commands that are executed by the local(8) delivery
agent.  </p>

<p>
This limit must not be smaller than the message size limit.
</p>

%PARAM maps_rbl_reject_code 554

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the reject_rbl_client, reject_rhsbl_client,
reject_rhsbl_sender or reject_rhsbl_recipient restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM masquerade_classes envelope_sender, header_sender, header_recipient

<p>
What addresses are subject to address masquerading.
</p>

<p>
By default, address masquerading is limited to envelope sender
addresses, and to header sender and header recipient addresses.
This allows you to use address masquerading on a mail gateway while
still being able to forward mail to users on individual machines.
</p>

<p>
Specify zero or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient
</p>

%PARAM masquerade_domains 

<p>
Optional list of domains whose subdomain structure will be stripped
off in email addresses.
</p>

<p>
The list is processed left to right, and processing stops at the
first match.  Thus,
</p>

<pre>
    masquerade_domains = foo.example.com example.com
</pre>

<p>
strips "user@any.thing.foo.example.com" to "user@foo.example.com",
but strips "user@any.thing.else.example.com" to "user@example.com".
</p>

<p>
A domain name prefixed with ! means do not masquerade this domain
or its subdomains. Thus,
</p>

<pre>
    masquerade_domains = !foo.example.com example.com
</pre>

<p>
does not change "user@any.thing.foo.example.com" or "user@foo.example.com",
but strips "user@any.thing.else.example.com" to "user@example.com".
</p>

<p>
Example:
</p>

<pre>
masquerade_domains = $mydomain
</pre>

%PARAM masquerade_exceptions 

<p>
Optional list of user names that are not subjected to address
masquerading, even when their address matches $masquerade_domains.
</p>

<p>
By default, address masquerading makes no exceptions.
</p>

<p>
Specify a list of user names, "/file/name" or "type:table" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. Specify "!name" to
exclude a name from the list. A "/file/name" pattern is replaced
by its contents; a "type:table" lookup table is matched when a name
matches a lookup key (the lookup result is ignored).  Continue long
lines by starting the next line with whitespace.  </p>

<p>
Examples:
</p>

<pre>
masquerade_exceptions = root, mailer-daemon
masquerade_exceptions = root
</pre>

%PARAM max_idle 100s

<p>
The maximum amount of time that an idle Postfix daemon process
waits for the next service request before exiting.  This parameter
is ignored by the Postfix queue manager.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM max_use 100

<p>
The maximal number of connection requests before a Postfix daemon
process terminates. This parameter is ignored by the Postfix queue
manager and by other long-lived Postfix daemon processes.
</p>

%PARAM maximal_backoff_time 4000s

<p>
The maximal time between attempts to deliver a deferred message.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM maximal_queue_lifetime 5d

<p>
The maximal time a message is queued before it is sent back as
undeliverable.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).
</p>

<p>
Specify 0 when mail delivery should be tried only once.
</p>

%PARAM message_size_limit 10240000

<p>
The maximal size in bytes of a message, including envelope information.
</p>

%PARAM minimal_backoff_time 1000s

<p>
The minimal time between attempts to deliver a deferred message.
This parameter also limits the time an unreachable destination is
kept in the short-term, in-memory, destination status cache.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM multi_recipient_bounce_reject_code 550

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the reject_multi_recipient_bounce
restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM mydestination $myhostname, localhost.$mydomain, localhost

<p> The list of domains that are delivered via the $local_transport
mail delivery transport. By default this is the Postfix local(8)
delivery agent which looks up all recipients in /etc/passwd and
/etc/aliases. The SMTP server validates recipient addresses with
$local_recipient_maps and rejects non-existent recipients. See also
the local domain class in the ADDRESS_CLASS_README file.
</p>

<p>
The default mydestination value specifies names for the local
machine only.  On a mail domain gateway, you should also include
$mydomain.
</p>

<p>
The $local_transport delivery method is also selected for mail
addressed to user@[the.net.work.address] of the mail system (the
IP addresses specified with the inet_interfaces and proxy_interfaces
parameters).
</p>

<p>
Warnings:
</p>

<ul>

<li><p>Do not specify the names of virtual domains - those domains
are specified elsewhere. See VIRTUAL_README for more information. </p>

<li><p>Do not specify the names of domains that this machine is
backup MX host for. See STANDARD_CONFIGURATION_README for how to
set up backup MX hosts. </p>

<li><p>By default, the Postfix SMTP server rejects mail for recipients
not listed with the local_recipient_maps parameter.  See the
postconf(5) manual for a description of the local_recipient_maps
and unknown_local_recipient_reject_code parameters. </p>

</ul>

<p>
Specify a list of host or domain names, "/file/name" or "type:table"
patterns, separated by commas and/or whitespace. A "/file/name"
pattern is replaced by its contents; a "type:table" lookup table
is matched when a name matches a lookup key (the lookup result is
ignored).  Continue long lines by starting the next line with
whitespace.  </p>

<p>
Examples:
</p>

<pre>
mydestination = $myhostname, localhost.$mydomain $mydomain
mydestination = $myhostname, localhost.$mydomain www.$mydomain, ftp.$mydomain
</pre>

%PARAM mydomain see "postconf -d" output

<p>
The internet domain name of this mail system.  The default is to
use $myhostname minus the first component.  $mydomain is used as
a default value for many other configuration parameters.
</p>

<p>
Example:
</p>

<pre>
mydomain = domain.tld
</pre>

%PARAM myhostname see "postconf -d" output

<p>
The internet hostname of this mail system. The default is to use
the fully-qualified domain name from gethostname(). $myhostname is
used as a default value for many other configuration parameters.
</p>

<p>
Example:
</p>

<pre>
myhostname = host.domain.tld
</pre>

%PARAM mynetworks see "postconf -d" output

<p>
The list of "trusted" SMTP clients that have more privileges than
"strangers".
</p>

<p>
In particular, "trusted" SMTP clients are allowed to relay mail
through Postfix.  See the smtpd_recipient_restrictions parameter
description in the postconf(5) manual.
</p>

<p>
You can specify the list of "trusted" network addresses by hand
or you can let Postfix do it for you (which is the default).
See the description of the mynetworks_style parameter for more
information.
</p>

<p>
Alternatively, you can specify the mynetworks list by hand, in
which case Postfix ignores the mynetworks_style setting.
</p>

<p>
Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address.  You can also specify "/file/name"
or "type:table" patterns.  A "/file/name" pattern is replaced by
its contents; a "type:table" lookup table is matched when a table
entry matches a lookup string (the lookup result is ignored).
Continue long lines by starting the next line with whitespace.
</p>

<p>
Examples:
</p>

<pre>
mynetworks = 168.100.189.0/28, 127.0.0.0/8
mynetworks = $config_directory/mynetworks
mynetworks = hash:/etc/postfix/network_table
</pre>

%PARAM myorigin $myhostname

<p>
The domain name that locally-posted mail appears to come
from, and that locally posted mail is delivered to. The default,
$myhostname, is adequate for small sites.  If you run a domain with
multiple machines, you should (1) change this to $mydomain and (2)
set up a domain-wide alias database that aliases each user to
user@that.users.mailhost.
</p>

<p>
Example:
</p>

<pre>
myorigin = $mydomain
</pre>

%PARAM notify_classes resource, software

<p>
The list of error classes that are reported to the postmaster. The
default is to report only the most serious problems. The paranoid
may wish to turn on the policy (UCE and mail relaying) and protocol
error (broken mail software) reports.
</p>

<p>
The error classes are:
</p>

<dl>

<dt><b>bounce</b> (also implies <b>2bounce</b>)</dt>

<dd>Send the postmaster copies of the headers of bounced mail, and
send transcripts of SMTP sessions when Postfix rejects mail. The
notification is sent to the address specified with the
bounce_notice_recipient configuration parameter (default: postmaster).
</dd>

<dt><b>2bounce</b></dt>

<dd>Send undeliverable bounced mail to the postmaster. The notification
is sent to the address specified with the 2bounce_notice_recipient
configuration parameter (default: postmaster). </dd>

<dt><b>delay</b></dt>

<dd>Send the postmaster copies of the headers of delayed mail. The
notification is sent to the address specified with the
delay_notice_recipient configuration parameter (default: postmaster).
</dd>

<dt><b>policy</b></dt>

<dd>Send the postmaster a transcript of the SMTP session when a
client request was rejected because of (UCE) policy. The notification
is sent to the address specified with the error_notice_recipient
configuration parameter (default: postmaster).  </dd>

<dt><b>protocol</b></dt>

<dd>Send the postmaster a transcript of the SMTP session in case
of client or server protocol errors. The notification is sent to
the address specified with the error_notice_recipient configuration
parameter (default: postmaster). </dd>

<dt><b>resource</b></dt>

<dd>Inform the postmaster of mail not delivered due to resource
problems.  The notification is sent to the address specified with
the error_notice_recipient configuration parameter (default:
postmaster). </dd>

<dt><b>software</b></dt>

<dd>Inform the postmaster of mail not delivered due to software
problems.  The notification is sent to the address specified with
the error_notice_recipient configuration parameter (default:
postmaster). </dd>

</dl>

<p>
Examples:
</p>

<pre>
notify_classes = bounce, delay, policy, protocol, resource, software
notify_classes = 2bounce, resource, software
</pre>

%PARAM parent_domain_matches_subdomains see "postconf -d" output

<p>
What Postfix features match subdomains of "domain.tld" automatically,
instead of requiring an explicit ".domain.tld" pattern.  This is
planned backwards compatibility:  eventually, all Postfix features
are expected to require explicit ".domain.tld" style patterns when
you really want to match subdomains.
</p>

%PARAM propagate_unmatched_extensions canonical, virtual

<p>
What address lookup tables copy an address extension from the lookup
key to the lookup result.
</p>

<p>
For example, with a virtual(5) mapping of "<i>joe@domain -&gt;
joe.user</i>", the address "<i>joe+foo@domain</i>" would rewrite
to "<i>joe.user+foo</i>".
</p>

<p>
Specify zero or more of <b>canonical</b>, <b>virtual</b>, <b>alias</b>,
<b>forward</b> or <b>include</b>. These cause address extension
propagation with canonical(5), virtual(5), and aliases(5) maps,
and with local(8) .forward and :include: file lookups, respectively.
</p>

<p>
Note: enabling this feature for types other than <b>canonical</b>
and <b>virtual</b> is likely to cause problems when mail is forwarded
to other sites, especially with mail that is sent to a mailing list
exploder address.
</p>

<p>
Examples:
</p>

<pre>
propagate_unmatched_extensions = canonical, virtual, alias,
        forward, include
propagate_unmatched_extensions = canonical, virtual
</pre>

%PARAM proxy_interfaces 

<p>
The network interface addresses that this mail system receives mail
on by way of a proxy or network address translation unit.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p> You must specify your "outside" proxy/NAT addresses when your
system is a backup MX host for other domains, otherwise mail delivery
loops will happen when the primary MX host is down.  </p>

<p>
Example:
</p>

<pre>
proxy_interfaces = 1.2.3.4
</pre>

%PARAM qmgr_message_active_limit 20000

<p>
The maximal number of messages in the active queue.
</p>

%PARAM qmgr_message_recipient_limit 20000

<p> The maximal number of recipients held in memory by the Postfix
queue manager, and the maximal size of the size of the short-term,
in-memory "dead" destination status cache.  </p>

%PARAM qmgr_message_recipient_minimum 10

<p>
The minimal number of in-memory recipients for any message. This
takes priority over any other in-memory recipient limits (i.e.,
the global qmgr_message_recipient_limit and the per transport
_recipient_limit) if necessary. The minimum value allowed for this
parameter is 1.
</p>

%PARAM qmqpd_authorized_clients 

<p>
What clients are allowed to connect to the QMQP server port.
</p>

<p>
By default, no client is allowed to use the service. This is
because the QMQP server will relay mail to any destination.
</p>

<p>
Specify a list of client patterns. A list pattern specifies a host
name, a domain name, an internet address, or a network/mask pattern,
where the mask specifies the number of bits in the network part.
When a pattern specifies a file name, its contents are substituted
for the file name; when a pattern is a "type:table" table specification,
table lookup is used instead.  </p>

<p>
Patterns are separated by whitespace and/or commas. In order to
reverse the result, precede a non-file name pattern with an
exclamation point (!).
</p>

<p>
Example:
</p>

<pre>
qmqpd_authorized_clients = !192.168.0.1, 192.168.0.0/24
</pre>

%PARAM qmqpd_error_delay 1s

<p>
How long the QMQP server will pause before sending a negative reply
to the client. The purpose is to slow down confused or malicious
clients.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM qmqpd_timeout 300s

<p>
The time limit for sending or receiving information over the network.
If a read or write operation blocks for more than $qmqpd_timeout
seconds the QMQP server gives up and disconnects.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM queue_minfree 0

<p>
The minimal amount of free space in bytes in the queue file system
that is needed to receive mail.  This is currently used by the SMTP
server to decide if it will accept any mail at all.
</p>

<p>
By default, the Postfix 2.1 SMTP server rejects MAIL FROM commands
when the amount of free space is less than 1.5*$message_size_limit.
To specify a higher minimum free space limit, specify a queue_minfree
value that is at least 1.5*$message_size_limit.
</p>

<p>
With Postfix versions 2.0 and earlier, a queue_minfree value of
zero means there is no minimum required amount of free space.
</p>

%PARAM queue_run_delay 1000s

<p>
The time between deferred queue scans by the queue manager.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM rbl_reply_maps 

<p>
Optional lookup tables with RBL response templates. The tables are
indexed by the RBL domain name. By default, Postfix uses the default
template as specified with the default_rbl_reply configuration
parameter. See there for a discussion of the syntax of RBL reply
templates.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM receive_override_options 

<p> Enable or disable recipient validation, built-in content
filtering, or address rewriting. Typically, these are specified in
master.cf as command-line arguments for the smtpd(8), qmqpd(8) or
pickup(8) daemons. </p>

<p> Specify zero or more of the following options.  The options
override main.cf settings and are either implemented by smtpd(8),
qmqpd(8), or pickup(8) themselves, or they are forwarded to the
cleanup server.  </p>

<dl>

<dt><b><a name="no_unknown_recipient_checks">no_unknown_recipient_checks</a></b></dt>

<dd>Do not try to reject unknown recipients (SMTP server only).
This is typically specified AFTER an external content filter.
</dd>

<dt><b><a name="no_address_mappings">no_address_mappings</a></b></dt>

<dd>Disable canonical address mapping, virtual alias map expansion,
address masquerading, and automatic BCC (blind carbon-copy)
recipients. This is typically specified BEFORE an external content
filter. </dd>

<dt><b><a name="no_header_body_checks">no_header_body_checks</a></b></dt>

<dd>Disable header/body_checks. This is typically specified AFTER
an external content filter. </dd>

</dl>

<p>
Note: when the "BEFORE content filter" receive_override_options
setting is specified in the main.cf file, specify the "AFTER content
filter" receive_override_options setting in master.cf (and vice
versa).
</p>

<p>
Examples:
</p>

<pre>
receive_override_options =
    no_unknown_recipient_checks, no_header_body_checks
receive_override_options = no_address_mappings
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM recipient_bcc_maps 

<p>
Optional BCC (blind carbon-copy) address lookup tables, indexed by
recipient address.  The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
The table search order is as follows:
</p>

<ul>

<li> Look up the "user+extension@domain.tld" address including the
optional address extension.

<li> Look up the "user@domain.tld" address without the optional
address extension.

<li> Look up the "user+extension" address local part when the
recipient domain equals $myorigin, $mydestination, $inet_interfaces
or $proxy_interfaces.

<li> Look up the "user" address local part when the recipient domain
equals $myorigin, $mydestination, $inet_interfaces or $proxy_interfaces.

<li> Look up the "@domain.tld" part.

</ul>

<p>
Specify the types and names of databases to use.  After change,
run "<b>postmap /etc/postfix/recipient_bcc</b>".
</p>

<p>
NOTE: if mail to the BCC address bounces it will be returned to
the sender.
</p>

<p>
Example:
</p>

<pre>
recipient_bcc_maps = hash:/etc/postfix/recipient_bcc
</pre>

%PARAM recipient_canonical_maps 

<p>
Optional address mapping lookup tables for envelope and header
recipient addresses.
The table format and lookups are documented in canonical(5).
</p>

<p>
Note: $recipient_canonical_maps is processed before $canonical_maps.
</p>

<p>
Example:
</p>

<pre>
recipient_canonical_maps = hash:/etc/postfix/recipient_canonical
</pre>

%PARAM recipient_delimiter 

<p>
The separator between user names and address extensions (user+foo).
See canonical(5), local(8), relocated(5) and virtual(5) for the
effects this has on aliases, canonical, virtual, relocated and
on .forward file lookups.  Basically, the software tries user+foo
and .forward+foo before trying user and .forward.
</p>

<p>
Example:
</p>

<pre>
recipient_delimiter = +
</pre>

%PARAM reject_code 554

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the "<b>reject</b>" restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM relay_domains $mydestination

<p> What destination domains (and subdomains thereof) this system
will relay mail to. Subdomain matching is controlled with the
parent_domain_matches_subdomains parameter. For details about how
the relay_domains value is used, see the description of the
permit_auth_destination and reject_unauth_destination SMTP recipient
restrictions.  </p>

<p> Domains that match $relay_domains are delivered with the
$relay_transport mail delivery transport. The SMTP server validates
recipient addresses with $relay_recipient_maps and rejects non-existent
recipients. See also the relay domains address class in the
ADDRESS_CLASS_README file.  </p>

<p> NOTE: Postfix will not automatically forward mail for domains
that list this system as their primary or backup MX host. See the
permit_mx_backup restriction in the postconf(5) manual page.  </p>

<p> Specify a list of host or domain names, "/file/name" patterns
or "type:table" lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
"/file/name" pattern is replaced by its contents; a "type:table"
lookup table is matched when a (parent) domain appears as lookup
key.  </p>

%PARAM relay_domains_reject_code 554

<p>
The numerical Postfix SMTP server response code when a client
request is rejected by the reject_unauth_destination recipient
restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM relay_recipient_maps 

<p> Optional lookup tables with all valid addresses in the domains
that match $relay_domains. Specify @domain as a wild-card for
domains that do not have a valid recipient list. Technically, tables
listed with $relay_recipient_maps are used as lists: Postfix needs
to know only if a lookup string is found or not, but it does not
use the result from table lookup.  </p>

<p>
If this parameter is non-empty, then the Postfix SMTP server will reject
mail to unknown relay users. This feature is off by default.
</p>

<p>
See also the relay domains address class in the ADDRESS_CLASS_README
file.
</p>

<p>
Example:
</p>

<pre>
relay_recipient_maps = hash:/etc/postfix/relay_recipients
</pre>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM relayhost 

<p>
The default host to send non-local mail to when no entry is matched
in the optional transport(5) table. When no relayhost is given,
mail is routed directly to the destination.
</p>

<p>
On an intranet, specify the organizational domain name. If your
internal DNS uses no MX records, specify the name of the intranet
gateway host instead.
</p>

<p>
In the case of SMTP, specify a domain name, hostname, hostname:port,
[hostname]:port, [hostaddress] or [hostaddress]:port. The form
[hostname] turns off MX lookups.
</p>

<p>
If you're connected via UUCP, see the UUCP_README file for useful
information.
</p>

<p>
Examples:
</p>

<pre>
relayhost = $mydomain
relayhost = [gateway.my.domain]
relayhost = uucphost
relayhost = [an.ip.add.ress]
</pre>

%PARAM relocated_maps 

<p>
Optional lookup tables with new contact information for users or
domains that no longer exist.  The table format and lookups are
documented in relocated(5).
</p>

<p>
If you use this feature, run "<b>postmap /etc/postfix/relocated</b>" to
build the necessary DBM or DB file after change, then "<b>postfix
reload</b>" to make the changes visible.
</p>

<p>
Examples:
</p>

<pre>
relocated_maps = dbm:/etc/postfix/relocated
relocated_maps = hash:/etc/postfix/relocated
</pre>

%PARAM require_home_directory no

<p>
Whether or not a local(8) recipient's home directory must exist
before mail delivery is attempted. By default this test is disabled.
It can be useful for environments that import home directories to
the mail server (NOT RECOMMENDED).
</p>

%PARAM resolve_dequoted_address yes

<p> Resolve a recipient address safely instead of correctly, by
looking inside quotes.  </p>

<p> By default, the Postfix address resolver does not quote the
address localpart as per RFC 822, so that additional @ or % or !
operators remain visible. This behavior is safe but it is also
technically incorrect.  </p>

<p> If you specify "resolve_dequoted_address = no", then the Postfix
resolver will not know about additional @ etc. operators in the
address localpart. This opens opportunities for obscure mail relay
attacks with user@domain@domain addresses when Postfix provides
backup MX service for Sendmail systems.  </p>

%PARAM resolve_null_domain no

<p> Resolve an address that ends in the "@" null domain as if the
local hostname were specified, instead of rejecting the address as
invalid.  </p>

<p> This feature is available in Postfix version 2.1 and later.
Earlier versions always resolve the null domain as the local
hostname.  </p>

<p> The Postfix SMTP server uses this feature to reject mail from
or to addresses that end in the "@" null domain, and from addresses
that rewrite into a form that ends in the "@" null domain.  </p>

%PARAM sender_bcc_maps

<p> Optional BCC (blind carbon-copy) address lookup tables, indexed
by sender address.  The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.  </p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
The table search order is as follows:
</p>

<ul>

<li> Look up the "user+extension@domain.tld" address including the
optional address extension.

<li> Look up the "user@domain.tld" address without the optional
address extension.

<li> Look up the "user+extension" address local part when the
sender domain equals $myorigin, $mydestination, $inet_interfaces
or $proxy_interfaces.

<li> Look up the "user" address local part when the sender domain
equals $myorigin, $mydestination, $inet_interfaces or $proxy_interfaces.

<li> Look up the "@domain.tld" part.

</ul>

<p>
Specify the types and names of databases to use.  After change,
run "<b>postmap /etc/postfix/sender_bcc</b>".
</p>

<p>
NOTE: if mail to the BCC address bounces it will be returned to
the sender.
</p>

<p>
Example:
</p>

<pre>
sender_bcc_maps = hash:/etc/postfix/sender_bcc
</pre>

%PARAM sender_canonical_maps 

<p>
Optional address mapping lookup tables for envelope and header
sender addresses.
The table format and lookups are documented in canonical(5).
</p>

<p>
Example: you want to rewrite the SENDER address "user@ugly.domain"
to "user@pretty.domain", while still being able to send mail to
the RECIPIENT address "user@ugly.domain".
</p>

<p>
Note: $sender_canonical_maps is processed before $canonical_maps.
</p>

<p>
Example:
</p>

<pre>
sender_canonical_maps = hash:/etc/postfix/sender_canonical
</pre>

%PARAM smtp_always_send_ehlo yes

<p>
Always send EHLO at the start of an SMTP session.
</p>

<p>
With "smtp_always_send_ehlo = no", Postfix sends EHLO only when
the word "ESMTP" appears in the server greeting banner (example:
220 spike.porcupine.org ESMTP Postfix).
</p>

%PARAM smtp_bind_address 

<p>
An optional numerical network address that the SMTP client should
bind to when making a connection.
</p>

<p>
This can be specified in the main.cf file for all SMTP clients, or
it can be specified in the master.cf file for a specific client,
for example:
</p>

<pre>
  /etc/postfix/master.cf:
        smtp ... smtp -o smtp_bind_address=11.22.33.44
</pre>

%PARAM smtp_connect_timeout 30s

<p>
The SMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit).
</p>

<p>
When no connection can be made within the deadline, the SMTP client
tries the next address on the mail exchanger list. Specify 0 to
disable the time limit (i.e. use whatever timeout is implemented by
the operating system).
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_data_done_timeout 600s

<p>
The SMTP client time limit for sending the SMTP ".", and for receiving
the server response.
</p>

<p>
When no response is received within the deadline, a warning is
logged that the mail may be delivered multiple times.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_data_init_timeout 120s

<p>
The SMTP client time limit for sending the SMTP DATA command, and for
receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_data_xfer_timeout 180s

<p>
The SMTP client time limit for sending the SMTP message content.
When the connection makes no progress for more than $smtp_data_xfer_timeout
seconds the SMTP client terminates the transfer.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_defer_if_no_mx_address_found no

<p>
Defer mail delivery when no MX record resolves to an IP address.
</p>

<p>
The default (no) is to return the mail as undeliverable. With older
Postfix versions the default was to keep trying to deliver the mail
until someone fixed the MX record or until the mail was too old.
</p>

<p>
Note: Postfix always ignores MX records with equal or worse preference
than the local MTA itself.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM lmtp_destination_concurrency_limit $default_destination_concurrency_limit

<p> The maximal number of parallel deliveries to the same destination
via the lmtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the master.cf file.  </p>

%PARAM lmtp_destination_recipient_limit $default_destination_recipient_limit

<p> The maximal number of recipients per delivery via the lmtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
lmtp_destination_concurrency_limit from concurrency per domain into
concurrency per recipient.  </p>

%PARAM relay_destination_concurrency_limit $default_destination_concurrency_limit

<p> The maximal number of parallel deliveries to the same destination
via the relay message delivery transport. This limit is enforced
by the queue manager. The message delivery transport name is the
first field in the entry in the master.cf file.  </p>

<p> This feature is available in Postfix version 2.0 and later. </p>

%PARAM relay_destination_recipient_limit $default_destination_recipient_limit

<p> The maximal number of recipients per delivery via the relay
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
relay_destination_concurrency_limit from concurrency per domain
into concurrency per recipient.  </p>

<p> This feature is available in Postfix version 2.0 and later. </p>

%PARAM smtp_destination_concurrency_limit $default_destination_concurrency_limit

<p> The maximal number of parallel deliveries to the same destination
via the smtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the master.cf file.  </p>

%PARAM smtp_destination_recipient_limit $default_destination_recipient_limit

<p> The maximal number of recipients per delivery via the smtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
smtp_destination_concurrency_limit from concurrency per domain
into concurrency per recipient.  </p>

%PARAM virtual_destination_concurrency_limit $default_destination_concurrency_limit

<p> The maximal number of parallel deliveries to the same destination
via the virtual message delivery transport. This limit is enforced
by the queue manager. The message delivery transport name is the
first field in the entry in the master.cf file.  </p>

%PARAM virtual_destination_recipient_limit $default_destination_recipient_limit

<p> The maximal number of recipients per delivery via the virtual
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
virtual_destination_concurrency_limit from concurrency per domain
into concurrency per recipient.  </p>

%PARAM smtp_helo_name $myhostname

<p>
The hostname to send in the SMTP EHLO or HELO command.
</p>

<p>
The default value is the machine hostname.  Specify a hostname or
[ip.add.re.ss].
</p>

<p>
This information can be specified in the main.cf file for all SMTP
clients, or it can be specified in the master.cf file for a specific
client, for example:
</p>

<pre>
  /etc/postfix/master.cf:
        mysmtp ... smtp -o smtp_helo_name=foo.bar.com
</pre>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM smtp_helo_timeout 300s

<p>
The SMTP client time limit for sending the HELO or EHLO command,
and for receiving the initial server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_host_lookup dns

<p>
What mechanisms when the SMTP client uses to look up a host's IP
address.  This parameter is ignored when DNS lookups are disabled.
</p>

<p>
Specify one of the following:
</p>

<dl>

<dt><b>dns</b></dt>

<dd>Hosts can be found in the DNS (preferred).  </dd>

<dt><b>native</b></dt>

<dd>Use the native naming service only (nsswitch.conf, or equivalent
mechanism).  </dd>

<dt><b>dns, native</b></dt>

<dd>Use the native service for hosts not found in the DNS.  </dd>

</dl>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtp_line_length_limit 990

<p>
The maximal length of message header and body lines that Postfix
will send via SMTP.  Longer lines are broken by inserting
"&lt;CR&gt;&lt;LF&gt;&lt;SPACE&gt;". This minimizes the damage to
MIME formatted mail.
</p>

<p>
By default, the line length is limited to 990 characters, because
some server implementations cannot receive mail with long lines.
</p>

%PARAM smtp_mail_timeout 300s

<p>
The SMTP client time limit for sending the MAIL FROM command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_mx_address_limit 0

<p>
The maximal number of MX (mail exchanger) IP addresses that can
result from mail exchanger lookups, or zero (no limit).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtp_mx_session_limit 2

<p> The maximal number of SMTP sessions per delivery request before
giving up or delivering to a fall-back relay host, or zero (no
limit). This restriction ignores IP addresses that fail to complete
the SMTP initial handshake.  </p>

<p> This feature is available in Postfix 2.1 and later.  </p>

%PARAM smtp_never_send_ehlo no

<p> Never send EHLO at the start of an SMTP session. See also the
smtp_always_send_ehlo parameter.  </p>

%PARAM smtp_pix_workaround_threshold_time 500s

<p>
How long a message must be queued before the PIX firewall
"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug workaround is turned
on.
</p>

<p>
By default, the workaround is turned off for mail that is queued
for less than 500 seconds. In other words, the workaround is normally
turned off for the first delivery attempt.
</p>

<p>
Specify 0 to enable the PIX firewall
"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug workaround upon the
first delivery attempt.
</p>

%PARAM smtp_quit_timeout 300s

<p>
The SMTP client time limit for sending the QUIT command, and for
receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_quote_rfc821_envelope yes

<p>
Quote addresses in SMTP MAIL FROM and RCPT TO commands as required
by RFC 821. This includes putting quotes around an address localpart
that ends in ".".
</p>

<p>
The default is to comply with RFC 821. If you have to send mail to
a broken SMTP server, configure a special SMTP client in master.cf:
</p>

<pre>
    /etc/postfix/master.cf:
        broken-smtp . . . smtp -o smtp_quote_rfc821_envelope=no
</pre>

<p>
and route mail for the destination in question to the "broken-smtp"
message delivery with a transport(5) table.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtp_rcpt_timeout 300s

<p>
The SMTP client time limit for sending the SMTP RCPT TO command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM smtp_sasl_auth_enable no

<p>
Enable SASL authentication in the Postfix SMTP client.  By default,
the Postfix SMTP client uses no authentication.
</p>

<p>
Example:
</p>

<pre>
smtp_sasl_auth_enable = yes
</pre>

%PARAM smtp_sasl_password_maps 

<p>
Optional SMTP client lookup tables with one username:password entry
per remote hostname or domain.  If a remote host or domain has no
username:password entry, then the Postfix SMTP client will not
attempt to authenticate to the remote host.
</p>

<p>
The Postfix SMTP client opens the lookup table before going to
chroot jail, so you can leave the password file in /etc/postfix.
</p>

%PARAM smtp_sasl_security_options noplaintext, noanonymous

<p>
What authentication mechanisms the Postfix SMTP client is allowed
to use. The list of available authentication mechanisms is system
dependent.
</p>

<p>
Specify zero or more of the following:
</p>

<dl>

<dt><b>noplaintext</b></dt>

<dd>Disallow methods that use plaintext passwords. </dd>

<dt><b>noactive</b></dt>

<dd>Disallow methods subject to active (non-dictionary) attack.
</dd>

<dt><b>nodictionary</b></dt>

<dd>Disallow methods subject to passive (dictionary) attack. </dd>

<dt><b>noanonymous</b></dt>

<dd>Disallow methods that allow anonymous authentication. </dd>

<dt><b>mutual_auth</b></dt>

<dd>Only allow methods that provide mutual authentication (not
available with SASL version 1). </dd>

</dl>

<p>
Example:
</p>

<pre>
smtp_sasl_security_options = noplaintext
</pre>

%PARAM smtp_send_xforward_command no

<p>
Send the non-standard XFORWARD command when the Postfix SMTP server EHLO
response announces XFORWARD support.
</p>

<p>
This allows an "smtp" delivery agent, used for injecting mail into
a content filter, to forward the name, address, protocol and HELO
name of the original client to the content filter and downstream
queuing SMTP server. This can produce more useful logging than
localhost[127.0.0.1] etc.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtp_skip_4xx_greeting yes

<p>
Skip SMTP servers that greet with a 4XX status code (go away, try
again later).
</p>

<p>
By default, Postfix moves on the next mail exchanger. Specify
"smtp_skip_4xx_greeting = no" if Postfix should defer delivery
immediately.
</p>

<p> This feature is available in Postfix version 2.0 and earlier.
Later Postfix versions always skip SMTP servers that greet with a
4XX status code. </p>

%PARAM smtp_skip_5xx_greeting yes

<p>
Skip SMTP servers that greet with a 5XX status code (go away, do
not try again later).
</p>

<p> By default, the Postfix SMTP client moves on the next mail
exchanger. Specify "smtp_skip_5xx_greeting = no" if Postfix should
bounce the mail immediately. The default setting is incorrect, but
it is what a lot of people expect to happen.  </p>

%PARAM smtp_skip_quit_response yes

<p>
Do not wait for the response to the SMTP QUIT command.
</p>

%PARAM smtp_xforward_timeout 300s

<p>
The SMTP client time limit for sending the XFORWARD command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM authorized_verp_clients $mynetworks

<p> What SMTP clients are allowed to specify the XVERP command.
This command requests that mail be delivered one recipient at a
time with a per recipient return address.  </p>

<p> By default, only trusted clients are allowed to specify XVERP.
</p>

<p> This parameter was introduced with Postfix version 1.1.  Postfix
version 2.1 renamed this parameter to smtpd_authorized_verp_clients
and changed the default to none. </p>

<p> Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "type:table" patterns.  A "/file/name"
pattern is replaced by its contents; a "type:table" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace. </p>

%PARAM smtpd_authorized_verp_clients $authorized_verp_clients

<p> What SMTP clients are allowed to specify the XVERP command.
This command requests that mail be delivered one recipient at a
time with a per recipient return address.  </p>

<p> By default, no clients are allowed to specify XVERP.  </p>

<p> This parameter was renamed with Postfix 2.1. The default value
is backwards compatible with Postfix 2.0.  </p>

<p> Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "type:table" patterns.  A "/file/name"
pattern is replaced by its contents; a "type:table" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace.  </p>

%PARAM smtpd_authorized_xclient_hosts 

<p>
What SMTP clients are allowed to use the XCLIENT feature.  This
command overrides SMTP client information that is used for access
control. Typical use is for SMTP-based content filters, fetchmail-like
programs, or SMTP server access rule testing. See the XCLIENT_README
document for details.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
By default, no clients are allowed to specify XCLIENT.
</p>

<p>
Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "type:table" patterns.  A "/file/name"
pattern is replaced by its contents; a "type:table" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace.  </p>

%PARAM smtpd_authorized_xforward_hosts 

<p>
What SMTP clients are allowed to use the XFORWARD feature.  This
command forwards information that is used to improve logging after
SMTP-based content filters. See the XFORWARD_README document for
details.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
By default, no clients are allowed to specify XFORWARD.
</p>

<p>
Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "type:table" patterns.  A "/file/name"
pattern is replaced by its contents; a "type:table" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace.  </p>

%PARAM smtpd_banner $myhostname ESMTP $mail_name

<p>
The text that follows the 220 status code in the SMTP greeting
banner. Some people like to see the mail version advertised. By
default, Postfix shows no version.
</p>

<p>
You MUST specify $myhostname at the start of the text. This is
required by the SMTP protocol.
</p>

<p>
Example:
</p>

<pre>
smtpd_banner = $myhostname ESMTP $mail_name ($mail_version)
</pre>

%PARAM smtpd_client_connection_count_limit 50

<p>
How many simultaneous connections any SMTP client is allowed to
make to the SMTP service.  By default, the limit is set it to half
the default process limit value.
</p>

<p>
To disable this feature, specify a limit of 0.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is not part of the stable Postfix 2.1 release.
</p>

%PARAM smtpd_client_connection_limit_exceptions $mynetworks

<p>
Clients that are excluded from connection count or connection rate
restrictions.
</p>

<p>
By default, clients in trusted networks are excluded. Specify a
list of network blocks, hostnames or .domain names (the initial
dot causes the domain to match any name below it).
</p>

<p>
This feature is not part of the stable Postfix 2.1 release.
</p>

%PARAM smtpd_client_connection_rate_limit 0

<p>
The maximal number of connection attempts any client is allowed to
make to this service per time unit.  The time unit is specified
with the anvil_rate_time_unit configuration parameter, and defaults
to one minute.
</p>

<p>
By default, a client can make as many connections per time unit as
Postfix can accept.
</p>

<p>
To disable this feature, specify a limit of 0.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is not part of the stable Postfix 2.1 release.
</p>

<p>
Example:
</p>

<pre>
smtpd_client_connection_rate_limit = 1000
</pre>

%PARAM smtpd_client_restrictions 

<p>
Optional SMTP server access restrictions in the context of a client
SMTP connection request.
</p>

<p>
The default is to allow all connection requests.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to client hostname or
client network address information.
</p>

<dl>

<dt><b><a name="check_client_access">check_client_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access database for the client hostname,
parent domains, client IP address, or networks obtained by stripping
least significant octets. See the access(5) manual page for details. </dd>

<dt><b><a name="permit_mynetworks">permit_mynetworks</a></b></dt>

<dd>Permit the request when the client IP address matches any
network listed in  $mynetworks. </dd>

<dt><b><a name="permit_tls_all_clientcerts">permit_tls_all_clientcerts</a></b></dt>

<dd> Permit the request when the remote SMTP client certificate is
verified successfully.  This option must be used only if a special
CA issues the certificates and only this CA is listed as trusted
CA, otherwise all clients with a recognized certificate would be
allowed to relay.  </dd>

<dt><b><a name="permit_tls_clientcerts">permit_tls_clientcerts</a></b></dt>

<dd>Permit the request when the remote SMTP client certificate is
verified successfully, and the certificate fingerprint is listed
in $relay_clientcerts. </dd>
<dt><b><a name="reject_rbl_client">reject_rbl_client <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the reversed client network address is
listed with the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i>
(Postfix version 2.1 and later only).  If no "<i>=d.d.d.d</i>" is
specified, reject the request when the reversed client network
address is listed with any A record under <i>rbl_domain</i>. <br>
The maps_rbl_reject_code parameter specifies the response code for
rejected requests (default:  554), the default_rbl_reply  parameter
specifies the default server reply, and the rbl_reply_maps  parameter
specifies tables with server replies indexed by <i>rbl_domain</i>.
This feature is available in Postfix 2.0 and later.  </dd>

<dt><b><a name="reject_rhsbl_client">reject_rhsbl_client <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the client hostname is listed with the
A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix version
2.1 and later only).  If no "<i>=d.d.d.d</i>" is specified, reject
the request when the reversed client network address is listed with
any A record under <i>rbl_domain</i>. See the reject_rbl_client
description above for additional RBL related configuration parameters.
This feature is available in Postfix 2.0 and later.  </dd>

<dt><b><a name="reject_unknown_client">reject_unknown_client</a></b></dt>

<dd>Reject the request when the client IP address has no PTR (address
to name) record in the DNS, or when the PTR record does not have
a matching A (name to address) record. <br> The unknown_client_reject_code
parameter specifies the response code for rejected requests (default:
450). The reply is always 450 in case the hostname lookup failed
due to a temporary problem. </dd>

</dl>

<p>
In addition, you can use any of the following <a name="generic">
generic</a> restrictions.  These restrictions are applicable in
any SMTP command context.
</p>

<dl>

<dt><b><a name="check_policy_service">check_policy_service <i>servername</i></a></b></dt>

<dd>Query the specified policy server. See the SMTPD_POLICY_README
document for details. This feature is available in Postfix 2.1
and later. </dd>

<dt><b><a name="defer">defer</a></b></dt>

<dd>Defer the request. The client is told to try again later. This
restriction is useful at the end of a restriction list, to make
the default policy explicit. <br> The defer_code parameter specifies
the SMTP server reply code (default: 450).</dd>

<dt><b><a name="defer_if_permit">defer_if_permit</a></b></dt>

<dd>Defer the request if some later restriction would result in an
explicit or implicit PERMIT action.  This is useful when a blacklisting
feature fails due to a temporary problem.  This feature is available
in Postfix 2.1 and later.  </dd>

<dt><b><a name="defer_if_reject">defer_if_reject</a></b></dt>

<dd>Defer the request if some later restriction would result in a
REJECT action.  This is useful when a whitelisting feature fails
due to a temporary problem.  This feature is available in Postfix
2.1 and later.  </dd>

<dt><b><a name="permit">permit</a></b></dt>

<dd>Permit the request. This restriction is useful at the end of
a restriction list, to make the default policy explicit.</dd>

<dt><b><a name="reject_multi_recipient_bounce">reject_multi_recipient_bounce</a></b></dt>

<dd>Reject the request when the envelope sender is the null address,
and the message has multiple envelope recipients. Although this
usage is technically allowed, it seems to have no legitimate
application. <br> The multi_recipient_bounce_reject_code parameter
specifies the response code for rejected requests (default: 550).
This feature is available in Postfix 2.1 and later. </dd>

<dt><b><a name="reject_unauth_pipelining">reject_unauth_pipelining</a></b></dt>

<dd>Reject the request when the client sends SMTP commands ahead
of time where it is not allowed, or when the client sends SMTP
commands ahead of time without knowing that Postfix actually supports
SMTP command pipelining. This stops mail from bulk mail software
that improperly uses SMTP command pipelining in order to speed up
deliveries.</dd>

<dt><b><a name="reject">reject</a></b></dt>

<dd>Reject the request. This restriction is useful at the end of
a restriction list, to make the default policy explicit.  The
reject_code configuration parameter specifies the response code to
rejected requests (default: 554).</dd>

<dt><b><a name="warn_if_reject">warn_if_reject</a></b></dt>

<dd>Change the meaning of the next restriction, so that it logs
a warning instead of rejecting a request (look for logfile records
that contain "reject_warning"). This is useful for testing new
restrictions in a "live" environment without risking unnecessary
loss of mail. </dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li> SMTP command specific restrictions that are described under
the smtpd_helo_restrictions, smtpd_sender_restrictions or
smtpd_recipient_restrictions parameters. When helo, sender or
recipient restrictions are listed under smtpd_client_restrictions,
they have effect only with "smtpd_delay_reject = yes", so that
$smtpd_client_restrictions is evaluated at the time of the RCPT TO
command.

</ul>

<p>
Example:
</p>

<pre>
smtpd_client_restrictions = permit_mynetworks, reject_unknown_client
</pre>

%CLASS smtpd-tarpit Tarpit features

<p>
When a remote SMTP client makes errors, the Postfix SMTP server
can insert delays before responding. This can help to slow down
run-away software.  The behavior is controlled by an error counter
that counts the number of errors within an SMTP session that a
client makes without delivering mail.
</p>

<ul>

<li><p>When the error counter is less than $smtpd_soft_error_limit the
Postfix SMTP server replies immediately (Postfix 2.0 and earlier
delay their 4xx or 5xx error response). </p>

<li><p>When the error counter reaches $smtpd_soft_error_limit, the Postfix
SMTP server delays all its responses. </p>

<li><p>When the error counter reaches $smtpd_hard_error_limit the Postfix
SMTP server breaks the connection. </p>

</ul>

%PARAM smtpd_error_sleep_time 1s

<p>With Postfix 2.1 and later: the SMTP server response delay after
a client has made more than $smtpd_soft_error_limit errors, and
fewer than $smtpd_hard_error_limit errors, without delivering mail.
</p>

<p>With Postfix 2.0 and earlier: the SMTP server delay before
sending a reject (4xx or 5xx) response, when the client has made
fewer than $smtpd_soft_error_limit errors without delivering
mail. </p>

%PARAM smtpd_soft_error_limit 10

<p>
The number of errors a remote SMTP client is allowed to make without
delivering mail before the Postfix SMTP server slows down all its
responses.
</p>

<ul>

<li><p>With Postfix version 2.1 and later, the Postfix SMTP server
delays all responses by $smtpd_error_sleep_time seconds. </p>

<li><p>With Postfix versions 2.0 and earlier, the Postfix SMTP
server delays all responses by (number of errors) seconds. </p>

</ul>

%PARAM smtpd_hard_error_limit 20

<p>
The maximal number of errors a remote SMTP client is allowed to
make without delivering mail. The Postfix SMTP server disconnects
when the limit is exceeded.
</p>

%PARAM smtpd_junk_command_limit 100

<p>
The number of junk commands (NOOP, VRFY, ETRN or RSET) that a remote
SMTP client can send before the Postfix SMTP server starts to
increment the error counter with each junk command.  The junk
command count is reset after mail is delivered.  See also the
smtpd_error_sleep_time and smtpd_soft_error_limit configuration
parameters.
</p>

%PARAM smtpd_recipient_overshoot_limit 1000

<p> The number of recipients that a remote SMTP client can send in
excess of the limit specified with $smtpd_recipient_limit, before
the Postfix SMTP server increments the per-session error count
for each excess recipient.  </p>

%PARAM smtpd_etrn_restrictions 

<p>
Optional SMTP server access restrictions in the context of a client
ETRN request.
</p>

<p>
The Postfix ETRN implementation accepts only destinations that are
eligible for the Postfix "fast flush" service. See the ETRN_README
file for details.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the domain name information
received with the ETRN command.
</p>

<dl>

<dt><b><a name="check_etrn_access">check_etrn_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access database for the ETRN domain name
or its parent domains. See the access(5) manual page for details.
</dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li><a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under smtpd_client_restrictions.

<li>SMTP command specific restrictions described under
smtpd_client_restrictions and smtpd_helo_restrictions.

</ul>

<p>
Example:
</p>

<pre>
smtpd_etrn_restrictions = permit_mynetworks, reject
</pre>

%PARAM smtpd_expansion_filter see "postconf -d" output

<p>
What characters are allowed in $name expansions of RBL reply
templates. Characters not in the allowed set are replaced by "_".
Use C like escapes to specify special characters such as whitespace.
</p>

<p>
This parameter is not subjected to $parameter expansion.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM smtpd_helo_required no

<p>
Require that a remote SMTP client introduces itself at the beginning
of an SMTP session with the HELO or EHLO command.
</p>

<p>
Example:
</p>

<pre>
smtpd_helo_required = yes
</pre>

%PARAM smtpd_helo_restrictions 

<p>
Optional restrictions that the Postfix SMTP server applies in the
context of the SMTP HELO command.
</p>

<p>
The default is to permit everything.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the hostname information
received with the HELO or EHLO command.
</p>

<dl>

<dt><b><a name="check_helo_access">check_helo_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the HELO or EHLO
hostname or parent domains, and execute the corresponding action.
</dd>

<dt><b><a name="check_helo_mx_access">check_helo_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the MX hosts for
the HELO or EHLO hostname, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="check_helo_ns_access">check_helo_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the DNS servers
for the HELO or EHLO hostname, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,        
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="reject_invalid_hostname">reject_invalid_hostname</a></b></dt>

<dd>Reject the request when the HELO or EHLO hostname syntax is
invalid. <br> The invalid_hostname_reject_code specifies the response
code to rejected requests (default: 501).</dd>

<dt><b><a name="reject_non_fqdn_hostname">reject_non_fqdn_hostname</a></b></dt>

<dd>Reject the request when the HELO or EHLO hostname is not in
fully-qualified domain form, as required by the RFC. <br> The
non_fqdn_reject_code parameter specifies the response code to
rejected requests (default: 504).</dd>

<dt><b><a name="reject_unknown_hostname">reject_unknown_hostname</a></b></dt>

<dd>Reject the request when the HELO or EHLO hostname has no DNS
A or MX record. <br> The unknown_hostname_reject_code specifies
the response code to rejected requests (default: 450).</dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li> <a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under smtpd_client_restrictions.

<li> Client hostname or network address specific restrictions
described under smtpd_client_restrictions.

<li> SMTP command specific restrictions described under
smtpd_sender_restrictions or smtpd_recipient_restrictions.  When
sender or recipient restrictions are listed under smtpd_helo_restrictions,
they have effect only with "smtpd_delay_reject = yes", so that
$smtpd_helo_restrictions is evaluated at the time of the RCPT TO
command.

</ul>

<p>
Examples:
</p>

<pre>
smtpd_helo_restrictions = permit_mynetworks, reject_invalid_hostname
smtpd_helo_restrictions = permit_mynetworks, reject_unknown_hostname
</pre>

%PARAM smtpd_history_flush_threshold 100

<p>
The maximal number of lines in the Postfix SMTP server command history
before it is flushed upon receipt of EHLO, RSET, or end of DATA.
</p>

%PARAM smtpd_noop_commands 

<p>
List of commands that the Postfix SMTP server replies to with "250
Ok", without doing any syntax checks and without changing state.
This list overrides any commands built into the Postfix SMTP server.
</p>

%PARAM smtpd_proxy_ehlo $myhostname

<p>
How the Postfix SMTP server announces itself to the proxy filter.
By default, the Postfix hostname is used.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%CLASS smtpd-proxy SMTP Proxy filter

<p>
As of Postfix version 2.1, the SMTP server can forward all incoming
mail to a content filtering proxy server that inspects all mail
BEFORE it is stored in the Postfix mail queue.
</p>

<p>
WARNING: the proxy filter must reply within a fixed deadline or
else the remote SMTP client times out and mail duplication happens.
This becomes a problem as mail load increases so that fewer and
fewer CPU cycles remain available to mead the fixed deadline.
</p>

%PARAM smtpd_proxy_filter 

<p> The hostname and TCP port of the mail filtering proxy server.
The proxy receives all mail from the Postfix SMTP server, and is
supposed to give the result to another Postfix SMTP server process.
</p>

<p> Specify host:port. The host can be specified as an IP address
or as a symbolic name; no MX lookups are done. When no host or
host:  are specified, the local machine is assumed.  </p>

<p> This feature is available in Postfix 2.1 and later.  </p>

%PARAM smtpd_proxy_timeout 100s

<p>
The time limit for connecting to a proxy filter and for sending or
receiving information.  When a connection fails the client gets a
generic error message while more detailed information is logged to
the maillog file.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_recipient_limit 1000

<p>
The maximal number of recipients that the Postfix SMTP server
accepts per message delivery request.
</p>

%PARAM smtpd_recipient_restrictions permit_mynetworks, reject_unauth_destination

<p>
The access restrictions that the Postfix SMTP server applies in
the context of the RCPT TO command.
</p>

<p>
By default, the Postfix SMTP server accepts:
</p>

<ul>

<li> Mail from clients whose IP address matches $mynetworks, or:

<li> Mail to remote destinations that match $relay_domains, except
for addresses that contain sender-specified routing
(user@elsewhere@domain), or:

<li> Mail to local destinations that match $inet_interfaces
or $proxy_interfaces, $mydestination, $virtual_alias_domains, or
$virtual_mailbox_domains.

</ul>

<p>
IMPORTANT: If you change this parameter setting, you must specify
at least one of the following restrictions. Otherwise Postfix will
refuse to receive mail:
</p>

<pre>
    reject, defer, defer_if_permit, reject_unauth_destination
</pre>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the recipient address
that is received with the RCPT TO command.
</p>

<dl>

<dt><b><a name="check_recipient_access">check_recipient_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the resolved RCPT
TO address, domain, parent domains, or localpart@, and execute the
corresponding action.  </dd>

<dt><b><a name="check_recipient_mx_access">check_recipient_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the MX hosts for
the RCPT TO address, and execute the corresponding action.  Note:
a result of "OK" is not allowed for safety reasons. Instead, use
DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later. </dd>

<dt><b><a name="check_recipient_ns_access">check_recipient_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the DNS servers
for the RCPT TO address, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="permit_auth_destination">permit_auth_destination</a></b></dt>

<dd>Permit the request when one of the following is true:

<ul>

<li> Postfix is mail forwarder: the resolved RCPT TO address matches
$relay_domains or a subdomain thereof, and the address contains no
sender-specified routing (user@elsewhere@domain),

<li> Postfix is the final destination: the resolved RCPT TO address
matches $mydestination, $inet_interfaces, $proxy_interfaces,
$virtual_alias_domains, or $virtual_mailbox_domains, and the address
contains no sender-specified routing (user@elsewhere@domain).

</ul></dd>

<dt><b><a name="permit_mx_backup">permit_mx_backup</a></b></dt>

<dd>Permit the request when the local mail system is MX host for
the RCPT TO address. This includes the case that the local mail
system is the final destination. However, the SMTP server will not
forward mail with addresses that have sender-specified routing
information (example: user@elsewhere@domain).  Use the optional
permit_mx_backup_networks parameter to require that the primary
MX hosts match a list of network blocks. <br> NOTE: prior to
Postfix version 2.0, use of permit_mx_backup is not recommended;
mail may be rejected in case of a temporary DNS lookup problem. </dd>

<dt><b><a name="reject_non_fqdn_recipient">reject_non_fqdn_recipient</a></b></dt>

<dd>Reject the request when the RCPT TO address is not in
fully-qualified domain form, as required by the RFC. <br> The
non_fqdn_reject_code parameter specifies the response code to
rejected requests (default: 504). </dd>

<dt><b><a name="reject_rhsbl_recipient">reject_rhsbl_recipient <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the RCPT TO domain is listed with the
A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix version
2.1 and later only).  If no "<i>=d.d.d.d</i>" is specified, reject
the request when the reversed client network address is listed with
any A record under <i>rbl_domain</i>. <br> The maps_rbl_reject_code
parameter specifies the response code for rejected requests (default:
554); the default_rbl_reply parameter specifies the default server
reply; and the rbl_reply_maps parameter specifies tables with server
replies indexed by <i>rbl_domain</i>.  This feature is available
in Postfix 2.0 and later.</dd>

<dt><b><a name="reject_unauth_destination">reject_unauth_destination</a></b></dt>

<dd>Reject the request unless one of the following is true:

<ul>

<li> Postfix is mail forwarder: the resolved RCPT TO address matches
$relay_domains or a subdomain thereof, and contains no sender-specified
routing (user@elsewhere@domain),

<li> Postfix is the final destination: the resolved RCPT TO address
matches $mydestination, $inet_interfaces, $proxy_interfaces,
$virtual_alias_domains, or $virtual_mailbox_domains, and contains
no sender-specified routing (user@elsewhere@domain).

</ul> The relay_domains_reject_code parameter specifies the response
code for rejected requests (default: 554). </dd>

<dt><b><a name="reject_unknown_recipient_domain">reject_unknown_recipient_domain</a></b></dt>

<dd>Reject the request when the RCPT TO address has no DNS A or MX
record and Postfix is not final destination for the recipient
address. <br> The unknown_address_reject_code parameter specifies
the response code for rejected requests (default: 450).  The response
is always 450 in case of a temporary DNS error.</dd>

<dt><b><a name="reject_unlisted_recipient">reject_unlisted_recipient</a></b> (Postfix 2.0 name: check_recipient_maps)</dt>

<dd> Reject the request when the RCPT TO address is not listed in
the list of valid recipients for its domain class. See the
smtpd_reject_unlisted_recipient parameter description for details.
This feature is available in Postfix 2.1 and later.</dd>

<dt><b><a name="reject_unverified_recipient">reject_unverified_recipient</a></b></dt>

<dd>Reject the request when mail to the RCPT TO address is known
to bounce, or when the recipient address destination is not reachable.
Address verification information is managed by the verify(8) server;
see the ADDRESS_VERIFICATION_README file for details.  <br> The
unverified_recipient_reject_code parameter specifies the response
when an address is known to bounce (default: 450, change into 550
when you are confident that it is safe to do so). Postfix replies
with 450 when an address probe failed due to a temporary problem.
This feature is available in Postfix 2.1 and later.  </dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li><a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under smtpd_client_restrictions.

<li>SMTP command specific restrictions described under
smtpd_client_restrictions, smtpd_helo_restrictions and
smtpd_sender_restrictions.

</ul>

<p>
Example:
</p>

<pre>
smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination
</pre>

%CLASS sasl-auth SASL Authentication

<p>
Postfix SASL support (RFC 2554) can be used to authenticate remote
SMTP clients to the Postfix SMTP server, and to authenticate the
Postfix SMTP client to a remote SMTP server.
See the SASL_README document for details.
</p>

%PARAM smtpd_sasl_auth_enable no

<p>
Enable SASL authentication in the Postfix SMTP server. By default,
the Postfix SMTP server does not use authentication.
</p>

<p>
If a remote SMTP client is authenticated, the permit_sasl_authenticated
access restriction can be used to permit relay access, like this:
</p>

<pre>
    smtpd_recipient_restrictions =
        permit_mynetworks, permit_sasl_authenticated, ...
</pre>

<p> To reject all SMTP connections from unauthenticated clients,
specify "smtpd_delay_reject = yes" (which is the default) and use:
</p>

<pre>
    smtpd_client_restrictions = permit_sasl_authenticated, reject
</pre>

<p>
See the SASL_README file for SASL configuration and operation details.
</p>

%PARAM smtpd_sasl_exceptions_networks 

<p>
What SMTP clients Postfix will not offer AUTH support to.
</p>

<p>
Some clients (Netscape 4 at least) have a bug that causes them to
require a login and password whenever AUTH is offered, whether it's
necessary or not. To work around this, specify, for example,
$mynetworks to prevent Postfix from offering AUTH to local clients.
</p>

<p>
Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also "/file/name" or
"type:table" patterns.  A "/file/name" pattern is replaced by its
contents; a "type:table" lookup table is matched when a table entry
matches a lookup string (the lookup result is ignored).  Continue
long lines by starting the next line with whitespace.  </p>

<p>
Example:
</p>

<pre>
smtpd_sasl_exceptions_networks = $mynetworks
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_sasl_local_domain 

<p>
The name of the local SASL authentication realm.
</p>

<p>
By default, the local authentication realm name is the null string.
</p>

<p>
Examples:
</p>

<pre>
smtpd_sasl_local_domain = $mydomain
smtpd_sasl_local_domain = $myhostname
</pre>

%PARAM smtpd_sasl_security_options noanonymous

<p>
Restrict what authentication mechanisms the Postfix SMTP server
will offer to the client.  The list of available authentication
mechanisms is system dependent.
</p>

<p>
Specify zero or more of the following:
</p>

<dl>

<dt><b>noplaintext</b></dt>

<dd>Disallow methods that use plaintext passwords. </dd>

<dt><b>noactive</b></dt>

<dd>Disallow methods subject to active (non-dictionary) attack. </dd>

<dt><b>nodictionary</b></dt>

<dd>Disallow methods subject to passive (dictionary) attack. </dd>

<dt><b>noanonymous</b></dt>

<dd>Disallow methods that allow anonymous authentication. </dd>

<dt><b>mutual_auth</b></dt>

<dd>Only allow methods that provide mutual authentication (not available
with SASL version 1). </dd>

</dl>

<p>
By default, the Postfix SMTP server accepts plaintext passwords but
not anonymous logins.
</p>

<p>
Warning: it appears that clients try authentication methods in the
order as advertised by the server (e.g., PLAIN ANONYMOUS CRAM-MD5)
which means that if you disable plaintext passwords, clients will
log in anonymously, even when they should be able to use CRAM-MD5.
So, if you disable plaintext logins, disable anonymous logins too.
Postfix treats anonymous login as no authentication.
</p>

<p>
Example:
</p>

<pre>
smtpd_sasl_security_options = noanonymous, noplaintext
</pre>

%PARAM smtpd_sender_login_maps 

<p>
Optional lookup table with the SASL login names that own sender
(MAIL FROM) addresses.
</p>

<p>
Specify zero or more "type:table" lookup tables. With lookups from
indexed files such as DB or DBM, or from networked tables such as
NIS, LDAP or SQL, the following search operations are done with a
sender address of <i>user@domain</i>:  </p>

<dl>

<dt> 1) <i>user@domain</i> </dt>

<dd>This table lookup is always done and has the highest precedence. </dd>

<dt> 2) <i>user</i> </dt>

<dd>This table lookup is done only when the <i>domain</i> part of the
sender address matches $myorigin, $mydestination, $inet_interfaces
or $proxy_interfaces. </dd>

<dt> 3) <i>@domain</i> </dt>

<dd>This table lookup is done last and has the lowest precedence. </dd>

</dl>

<p>
In all cases the result of table lookup must be either "not found"
or a list of SASL login names separated by comma and/or whitespace.
</p>

%PARAM smtpd_sender_restrictions 

<p>
Optional restrictions that the Postfix SMTP server applies in the
context of the MAIL FROM command.
</p>

<p>
The default is to permit everything.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the sender address
received with the MAIL FROM command.
</p>

<dl>

<dt><b><a name="check_sender_access">check_sender_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the MAIL FROM
address, domain, parent domains, or localpart@, and execute the
corresponding action. </dd>

<dt><b><a name="check_sender_mx_access">check_sender_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the MX hosts for
the MAIL FROM address, and execute the corresponding action.  Note:
a result of "OK" is not allowed for safety reasons. Instead, use
DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later. </dd>

<dt><b><a name="check_sender_ns_access">check_sender_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access(5) database for the DNS servers
for the MAIL FROM address, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="reject_authenticated_sender_login_mismatch">reject_authenticated_sender_login_mismatch</a></b></dt>

<dd>Enforces the reject_sender_login_mismatch restriction for
authenticated clients only. This feature is available in
Postfix version 2.1 and later. </dd>

<dt><b><a name="reject_non_fqdn_sender">reject_non_fqdn_sender</a></b></dt>

<dd>Reject the request when the MAIL FROM address is not in
fully-qualified domain form, as required by the RFC. <br> The
non_fqdn_reject_code parameter specifies the response code to
rejected requests (default: 504). </dd>

<dt><b><a name="reject_rhsbl_sender">reject_rhsbl_sender <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the MAIL FROM domain is listed with
the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix
version 2.1 and later only).  If no "<i>=d.d.d.d</i>" is specified,
reject the request when the reversed client network address is
listed with any A record under <i>rbl_domain</i>. <br> The
maps_rbl_reject_code parameter specifies the response code for
rejected requests (default:  554); the default_rbl_reply parameter
specifies the default server reply; and the rbl_reply_maps parameter
specifies tables with server replies indexed by <i>rbl_domain</i>.
This feature is available in Postfix 2.0 and later.</dd>

<dt><b><a name="reject_sender_login_mismatch">reject_sender_login_mismatch</a></b></dt>

<dd>Reject the request when $smtpd_sender_login_maps specifies an
owner for the MAIL FROM address, but the client is not (SASL) logged
in as that MAIL FROM address owner; or when the client is (SASL)
logged in, but the client login name doesn't own the MAIL FROM
address according to $smtpd_sender_login_maps.</dd>

<dt><b><a name="reject_unauthenticated_sender_login_mismatch">reject_unauthenticated_sender_login_mismatch</a></b></dt>

<dd>Enforces the reject_sender_login_mismatch restriction for
unauthenticated clients only. This feature is available in
Postfix version 2.1 and later. </dd>

<dt><b><a name="reject_unknown_sender_domain">reject_unknown_sender_domain</a></b></dt>

<dd>Reject the request when the MAIL FROM address has no DNS A or
MX record and Postfix is not final destination for the sender
address. <br> The unknown_address_reject_code parameter specifies
the response code for rejected requests (default: 450).  The response
is always 450 in case of a temporary DNS error. </dd>

<dt><b><a name="reject_unlisted_sender">reject_unlisted_sender</a></b></dt>

<dd>Reject the request when the MAIL FROM address is not listed in
the list of valid recipients for its domain class. See the
smtpd_reject_unlisted_sender parameter description for details.
This feature is available in Postfix 2.1 and later.</dd>

<dt><b><a name="reject_unverified_sender">reject_unverified_sender</a></b></dt>

<dd>Reject the request when mail to the MAIL FROM address is known to
bounce, or when the sender address destination is not reachable.
Address verification information is managed by the verify(8) server;
see the ADDRESS_VERIFICATION_README file for details. <br> The
unverified_sender_reject_code parameter specifies the response when
an address is known to bounce (default: 450, change into 550 when
you are confident that it is safe to do so). Postfix replies with
450 when an address probe failed due to a temporary problem.  This
feature is available in Postfix 2.1 and later.  </dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li> <a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under smtpd_client_restrictions.

<li> SMTP command specific restrictions described under
smtpd_client_restrictions and smtpd_helo_restrictions.

<li> SMTP command specific restrictions described under
smtpd_recipient_restrictions. When recipient restrictions are listed
under smtpd_sender_restrictions, they have effect only with
"smtpd_delay_reject = yes", so that $smtpd_sender_restrictions is
evaluated at the time of the RCPT TO command.

</ul>

<p>
Examples:
</p>

<pre>
smtpd_sender_restrictions = reject_unknown_sender_domain
smtpd_sender_restrictions = reject_unknown_sender_domain,
    check_sender_access hash:/etc/postfix/access
</pre>

%PARAM smtpd_timeout 300s

<p>
The time limit for sending a Postfix SMTP server response and for
receiving a remote SMTP client request.
</p>

<p>
Note: if you set SMTP time limits to very large values you may have
to update the global ipc_timeout parameter.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM soft_bounce no

<p>
Safety net to keep mail queued that would otherwise be returned to
the sender.  This parameter disables locally-generated bounces,
and prevents the Postfix SMTP server from rejecting mail permanently,
by changing 5xx reply codes into 4xx.  However, soft_bounce is no
cure for address rewriting mistakes or mail routing mistakes.
</p>

<p>
Example:
</p>

<pre>
soft_bounce = yes
</pre>

%PARAM stale_lock_time 500s

<p>
The time after which a stale exclusive mailbox lockfile is removed.
This is used for delivery to file or mailbox.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM strict_rfc821_envelopes no

<p>
Require that addresses received in SMTP MAIL FROM and RCPT TO
commands are enclosed with &lt;&gt;, and that those addresses do
not contain RFC 822 style comments or phrases.  This stops mail
from poorly written software.
</p>

<p>
By default, the Postfix SMTP server accepts RFC 822 syntax in MAIL
FROM and RCPT TO addresses.
</p>

%PARAM swap_bangpath yes

<p>
Enable the rewriting of "site!user" into "user@site".  This is
necessary if your machine is connected to UUCP networks.  It is
enabled by default.
</p>

<p>
Example:
</p>

<pre>
swap_bangpath = no
</pre>

%PARAM syslog_facility mail

<p>
The syslog facility of Postfix logging. Specify a facility as
defined in syslog.conf(5). The default facility is "mail".
</p>

<p>
Warning: a non-default syslog_facility setting takes effect only
after a Postfix process has completed initialization.  Errors during
process initialization will be logged with the default facility.
Examples are errors while parsing the command line arguments, and
errors while accessing the Postfix main.cf configuration file.
</p>

%PARAM syslog_name postfix

<p>
The mail system name that is prepended to the process name in syslog
records, so that "smtpd" becomes, for example, "postfix/smtpd".
</p>

<p>
Warning: a non-default syslog_name setting takes effect only after
a Postfix process has completed initialization. Errors during
process initialization will be logged with the default name. Examples
are errors while parsing the command line arguments, and errors
while accessing the Postfix main.cf configuration file.
</p>

%PARAM transport_maps 

<p>
Optional lookup tables with mappings from recipient address to
(message delivery transport, next-hop destination).  See transport(5)
for details.
</p>

<p>
Specify zero or more "type:table" lookup tables.  If you use this
feature with local files, run "<b>postmap /etc/postfix/transport</b>"
after making a change.  </p>

<p>
Examples:
</p>

<pre>
transport_maps = dbm:/etc/postfix/transport
transport_maps = hash:/etc/postfix/transport
</pre>

%PARAM transport_retry_time 60s

<p>
The time between attempts by the Postfix queue manager to contact
a malfunctioning message delivery transport.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM trigger_timeout 10s

<p>
The time limit for sending a trigger to a Postfix daemon (for
example, the pickup(8) or qmgr(8) daemon). This time limit prevents
programs from getting stuck when the mail system is under heavy
load.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM unknown_address_reject_code 450

<p>
The numerical Postfix SMTP server response code when a sender or
recipient address is rejected by the reject_unknown_sender_domain
or reject_unknown_recipient_domain restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM unknown_client_reject_code 450

<p>
The numerical Postfix SMTP server response code when a client
without valid address &lt;=&gt; name mapping is rejected by the
reject_unknown_client restriction. The SMTP server always replies
with 450 when the mapping failed due to a temporary error condition.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM unknown_hostname_reject_code 450

<p>
The numerical Postfix SMTP server response code when the hostname
specified with the HELO or EHLO command is rejected by the
reject_unknown_hostname restriction.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

%PARAM unknown_local_recipient_reject_code 550

<p>
The numerical Postfix SMTP server response code when a recipient
address is local, and $local_recipient_maps specifies a list of
lookup tables that does not match the recipient.  A recipient
address is local when its domain matches $mydestination,
$proxy_interfaces or $inet_interfaces.
</p>

<p>
The default setting is 550 (reject mail) but it is safer to initially
use 450 (try again later) so you have time to find out if your
local_recipient_maps settings are OK.
</p>

<p>
Example:
</p>

<pre>
unknown_local_recipient_reject_code = 450
</pre>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM unverified_recipient_reject_code 450

<p>
The numerical Postfix SMTP server response when a recipient address
is rejected by the reject_unverified_recipient restriction.
</p>

<p>
Unlike elsewhere in Postfix, you can specify 250 in order to
accept the address anyway.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM unverified_sender_reject_code 450

<p>
The numerical Postfix SMTP server response code when a recipient
address is rejected by the reject_unverified_sender restriction.
</p>

<p>
Unlike elsewhere in Postfix, you can specify 250 in order to
accept the address anyway.
</p>

<p>
Do not change this unless you have a complete understanding of RFC 821.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM virtual_alias_domains $virtual_alias_maps

<p> Optional list of names of virtual alias domains, that is,
domains for which all addresses are aliased to addresses in other
local or remote domains. The SMTP server validates recipient
addresses with $virtual_alias_maps and rejects non-existent
recipients. See also the virtual alias domain class in the
ADDRESS_CLASS_README file </p>

<p>
This feature is available in Postfix 2.0 and later. The default
value is backwards compatible with Postfix 1.1.
</p>

<p>
The default value is $virtual_alias_maps so that you can keep all
information about virtual alias domains in one place.  If you have
many users, it is better to separate information that changes more
frequently (virtual address -&gt; local or remote address mapping)
from information that changes less frequently (the list of virtual
domain names).
</p>

<p> Specify a list of host or domain names, "/file/name" or
"type:table" patterns, separated by commas and/or whitespace. A
"/file/name" pattern is replaced by its contents; a "type:table"
lookup table is matched when a table entry matches a lookup string
(the lookup result is ignored).  Continue long lines by starting
the next line with whitespace.  </p>

<p>
See also the VIRTUAL_README and ADDRESS_CLASS_README documents
for further information.
</p>

<p>
Example:
</p>

<pre>
virtual_alias_domains = virtual1.tld virtual2.tld
</pre>

%PARAM virtual_alias_expansion_limit 1000

<p>
The maximal number of addresses that virtual alias expansion produces
from each original recipient.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM virtual_alias_maps $virtual_maps

<p>
Optional lookup tables that alias specific mail addresses or domains
to other local or remote address.  The table format and lookups
are documented in virtual(5).
</p>

<p>
This feature is available in Postfix 2.0 and later. The default
value is backwards compatible with Postfix 1.1.
</p>

<p>
If you use this feature with indexed files, run "<b>postmap
/etc/postfix/virtual</b>" after changing the file.
</p>

<p>
Examples:
</p>

<pre>
virtual_alias_maps = dbm:/etc/postfix/virtual
virtual_alias_maps = hash:/etc/postfix/virtual
</pre>

%PARAM virtual_alias_recursion_limit 1000

<p>
The maximal nesting depth of virtual alias expansion.  Currently
the recursion limit is applied only to the left branch of the
expansion graph, so the depth of the tree can in the worst case
reach the sum of the expansion and recursion limits.  This may
change in the future.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%CLASS trouble-shooting Trouble shooting

<p>
The DEBUG_README document describes how to debug parts of the
Postfix mail system. The methods vary from making the software log
a lot of detail, to running some daemon processes under control of
a call tracer or debugger.
</p>

%PARAM debugger_command 

<p>
The external command to execute when a Postfix daemon program is
invoked with the -D option.
</p>

<p>
Use "command .. &amp; sleep 5" so that the debugger can attach before
the process marches on. If you use an X-based debugger, be sure to
set up your XAUTHORITY environment variable before starting Postfix.
</p>

<p>
Example:
</p>

<pre>
debugger_command =
    PATH=/usr/bin:/usr/X11R6/bin
    xxgdb $daemon_directory/$process_name $process_id &amp; sleep 5
</pre>

%PARAM 2bounce_notice_recipient postmaster

<p> The recipient of undeliverable mail that cannot be returned to
the sender.  This feature is enabled with the notify_classes
parameter.  </p>

%PARAM address_verify_service_name verify

<p>
The name of the verify(8) address verification service. This service
maintains the status of sender and/or recipient address verification
probes, and generates probes on request by other Postfix processes.
</p>

%PARAM alternate_config_directories 

<p>
A list of non-default Postfix configuration directories that may
be specified with "-c config_directory" on the command line, or
via the MAIL_CONFIG environment parameter.
</p>

<p>
This list must be specified in the default Postfix configuration
directory, and is used by set-gid Postfix commands such as postqueue(1)
and postdrop(1).
</p>

%PARAM append_at_myorigin yes

<p>
Append the string "@$myorigin" to mail addresses without domain
information.
</p>

<p>
This feature is enabled by default and must not be turned off.
Postfix does not support domain-less addresses.
</p>

%PARAM append_dot_mydomain yes

<p>
Append the string ".$mydomain" to addresses that have no ".domain"
information.
</p>

<p>
This feature is enabled by default. If disabled, users will not be
able to send mail to "user@partialdomainname" but will have to
specify full domain names instead.
</p>

%PARAM application_event_drain_time 100s

<p>
How long the postkick(1) command waits for a request to enter the
server's input buffer before giving up.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM backwards_bounce_logfile_compatibility yes

<p>
Produce additional bounce(8) logfile records that can be read by
older Postfix versions. The current and more extensible "name =
value" format is needed in order to implement more sophisticated
functionality.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM bounce_notice_recipient postmaster

<p>
The recipient of postmaster notifications with the message headers
of mail that Postfix did not deliver and of SMTP conversation
transcripts of mail that Postfix did not receive.  This feature is
enabled with the notify_classes parameter.  </p>

%PARAM bounce_service_name bounce

<p>
The name of the bounce(8) service. This service maintains a record
of failed delivery attempts and generates non-delivery notifications.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM broken_sasl_auth_clients no

<p>
Enable inter-operability with SMTP clients that implement an obsolete
version of the AUTH command (RFC 2554). Examples of such clients
are MicroSoft Outlook Express version 4 and MicroSoft Exchange
version 5.0.
</p>

<p>
Specify "<b>broken_sasl_auth_clients = yes</b>" to have Postfix advertise
AUTH support in a non-standard way.
</p>

%PARAM cleanup_service_name cleanup

<p>
The name of the cleanup(8) service. This service rewrites addresses
into the standard form, and performs canonical(5) address mapping
and virtual(5) aliasing.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM anvil_status_update_time 600s

<p>
How frequently the anvil(8) connection and rate limiting server
logs peak usage information.
</p>

<p>
This feature is implemented by the anvil(8) service which is not
part of the stable Postfix 2.1 release.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM enable_errors_to no

<p> Report mail delivery errors to the address specified with the
non-standard Errors-To: message header, instead of the envelope
sender address.  This support is disabled by default with Postfix
2.1 and later, and is always turned on with older Postfix versions.
</p>

%PARAM extract_recipient_limit 10240

<p>
The maximal number of recipient addresses that Postfix will extract
from message headers when mail is submitted with "sendmail -t".
</p>

<p>
This feature was removed in Postfix 2.1.
</p>

%PARAM anvil_rate_time_unit 60s

<p>
The time unit over which client connection rates and other rates
are calculated.
</p>

<p>
This feature is implemented by the anvil(8) service which is not
part of the stable Postfix 2.1 release.
</p>

<p>
The default interval is relatively short. Because of the high
frequency of updates, the anvil(8) server uses volatile memory
only. Thus, information is lost whenever the process terminates.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM command_expansion_filter see "postconf -d" output

<p>
Restrict the characters that the local(8) delivery agent allows in
$name expansions of $mailbox_command.  Characters outside the
allowed set are replaced by underscores.
</p>

%PARAM content_filter 

<p>
The name of a mail delivery transport that filters mail after
it is queued.
</p>

<p>
This parameter uses the same syntax as the right-hand side of a
Postfix transport(5) table. This setting has a lower precedence
than a content filter that is specified with an access(5) table or
in a header_checks(5) or body_checks(5) table.
</p>

%PARAM default_delivery_slot_discount 50

<p>
The default value for transport-specific _delivery_slot_discount
settings.
</p>

<p>
This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
transport_delivery_slot_discount percent of the required amount
plus transport_delivery_slot_loan still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.
</p>

%PARAM default_delivery_slot_loan 3

<p>
The default value for transport-specific _delivery_slot_loan
settings.
</p>

<p>
This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
transport_delivery_slot_discount percent of the required amount
plus transport_delivery_slot_loan still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.
</p>

%CLASS verp VERP Support

<p>
With VERP style delivery, each recipient of a message receives a
customized copy of the message with his/her own recipient address
encoded in the envelope sender address.  The VERP_README file
describes configuration and operation details of Postfix support
for variable envelope return path addresses.  VERP style delivery
is requested with the SMTP XVERP command or with the "<b>sendmail
-V</b>" command-line option and is available in Postfix version 
1.1 and later.
</p>

%PARAM default_verp_delimiters +=

<p> The two default VERP delimiter characters. These are used when
no explicit delimiters are specified with the SMTP XVERP command
or with the "<b>sendmail -V</b>" command-line option. Specify
characters that are allowed by the verp_delimiter_filter setting.
</p>

<p>
This feature is available in Postfix 1.1 and later.
</p>

%PARAM defer_service_name defer

<p>
The name of the defer(8) service. This service maintains a record
of failed delivery attempts and generates non-delivery notifications.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM delay_notice_recipient postmaster

<p>
The recipient of postmaster notifications with the message headers
of mail that cannot be delivered within $delay_warning_time time
units.  </p>

<p>
This feature is enabled with the delay_warning_time parameter.
</p>

%PARAM delay_warning_time 0h

<p>
The time after which the sender receives the message headers of
mail that is still queued.
</p>

<p>
To enable this feature, specify a non-zero integral value.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).
</p>

%PARAM disable_dns_lookups no

<p>
Disable DNS lookups in the Postfix SMTP and LMTP clients. When
disabled, hosts are looked up with the gethostbyname() system
library routine which normally also looks in /etc/hosts.
</p>

<p>
DNS lookups are enabled by default.
</p>

%CLASS mime MIME Processing

<p>
MIME processing is available in Postfix as of version 2.0.  Older
Postfix versions do not recognize MIME headers inside the message
body.
</p>

%PARAM disable_mime_input_processing no

<p>
Turn off MIME processing while receiving mail. This means that no
special treatment is given to Content-Type: message headers, and
that all text after the initial message headers is considered to
be part of the message body.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p>
Mime input processing is enabled by default, and is needed in order
to recognize MIME headers in message content.
</p>

%PARAM disable_mime_output_conversion no

<p>
Disable the conversion of 8BITMIME format to 7BIT format.  Mime
output conversion is needed when the destination does not advertise
8BITMIME support.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM disable_verp_bounces no

<p>
Disable sending one bounce report per recipient.
</p>

<p>
The default, one per recipient, is what ezmlm needs.
</p>

<p>
This feature is available in Postfix 1.1 and later.
</p>

%PARAM dont_remove 0

<p>
Don't remove queue files and save them to the "saved" mail queue.
This is a debugging aid.  To inspect the envelope information and
content of a Postfix queue file, use the postcat(1) command.
</p>

%PARAM empty_address_recipient MAILER-DAEMON

<p>
The recipient of mail addressed to the null address.  Postfix does
not accept such addresses in SMTP commands, but they may still be
created locally as the result of configuration or software error.
</p>

%PARAM error_notice_recipient postmaster

<p> The recipient of postmaster notifications about mail delivery
problems that are caused by policy, resource, software or protocol
errors.  These notifications are enabled with the notify_classes
parameter.  </p>

%PARAM error_service_name error

<p>
The name of the error(8) pseudo delivery agent. This service always
returns mail as undeliverable.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM expand_owner_alias no

<p>
When delivering to an alias "aliasname" that has an "owner-aliasname"
companion alias, set the envelope sender address to the expansion
of the "owner-aliasname" alias. Normally, Postfix sets the envelope
sender address to the name of the "owner-aliasname" alias.
</p>

%PARAM fallback_transport 

<p>
Optional message delivery transport that the local(8) delivery
agent should use for names that are not found in the aliases(5)
database or in the UNIX passwd database.
</p>

%PARAM fault_injection_code 0

<p>
Force specific internal tests to fail, to test the handling of
errors that are difficult to reproduce otherwise.
</p>

%PARAM flush_service_name flush

<p>
The name of the flush(8) service. This service maintains per-destination
logfiles with the queue file names of mail that is queued for those
destinations.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM forward_expansion_filter see "postconf -d" output

<p>
Restrict the characters that the local(8) delivery agent allows in
$name expansions of $forward_path.  Characters outside the
allowed set are replaced by underscores.
</p>

<p>
Characters outside the allowed set are replaced by underscores.
</p>

%PARAM header_address_token_limit 10240

<p>
The maximal number of address tokens are allowed in an address
message header. Information that exceeds the limit is discarded.
The limit is enforced by the cleanup(8) server.
</p>

%PARAM helpful_warnings yes

<p>
Log warnings about problematic configuration settings, and provide
helpful suggestions.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM lmtp_cache_connection yes

<p>
Keep Postfix LMTP client connections open for up to $max_idle
seconds. When the LMTP client receives a request for the same
connection the connection is reused.
</p>

<p>
The effectiveness of cached connections will be determined by the
number of LMTP servers in use, and the concurrency limit specified
for the LMTP client. Cached connections are closed under any of
the following conditions:
</p>

<ul>

<li> The LMTP client idle time limit is reached.  This limit is
specified with the Postfix max_idle configuration parameter.

<li> A delivery request specifies a different destination than the
one currently cached.

<li> The per-process limit on the number of delivery requests is
reached.  This limit is specified with the Postfix max_use
configuration parameter.

<li> Upon the onset of another delivery request, the LMTP server
associated with the current session does not respond to the RSET
command.

</ul>

<p>
Most of these limitations will be removed after Postfix implements
a connection cache that is shared among multiple LMTP client
programs.
</p>

%PARAM lmtp_sasl_auth_enable no

<p>
Enable SASL authentication in the Postfix LMTP client.
</p>

%PARAM lmtp_sasl_password_maps 

<p>
Optional LMTP client lookup tables with one username:password entry
per host or domain.  If a remote host or domain has no username:password
entry, then the Postfix LMTP client will not attempt to authenticate
to the remote host.
</p>

%PARAM lmtp_sasl_security_options noplaintext, noanonymous

<p>
What authentication mechanisms the Postfix LMTP client is allowed
to use. The list of available authentication mechanisms is system
dependent.
</p>

<dl>

<dt><b>noplaintext</b></dt>

<dd>Disallow authentication methods that use plaintext passwords. </dd>

<dt><b>noactive</b></dt>

<dd>Disallow authentication methods that are vulnerable to non-dictionary
active attacks. </dd>

<dt><b>nodictionary</b></dt>

<dd>Disallow authentication methods that are vulnerable to passive
dictionary attack. </dd>

<dt><b>noanonymous</b></dt>

<dd>Disallow anonymous logins. </dd>

</dl>

<p>
Example:
</p>

<pre>
lmtp_sasl_security_options = noplaintext
</pre>

%PARAM lmtp_tcp_port 24

<p>
The default TCP port that the Postfix LMTP client connects to.
</p>

%PARAM mail_release_date see "postconf -d" output

<p>
The Postfix release date, in "YYYYMMDD" format.
</p>

%PARAM mailbox_command_maps 

<p>
Optional lookup tables with per-recipient external commands to use
for local(8) mailbox delivery.  Behavior is as with mailbox_command.
</p>

<p>
The precedence of local(8) delivery features from high to low is:
aliases, .forward files, mailbox_transport, mailbox_command_maps,
mailbox_command, home_mailbox, mail_spool_directory, fallback_transport
and luser_relay.
</p>

%PARAM mailbox_delivery_lock see "postconf -d" output

<p>
How to lock a UNIX-style local(8) mailbox before attempting delivery.
For a list of available file locking methods, use the "<b>postconf
-l</b>" command.
</p>

<p>
This setting is ignored with <b>maildir</b> style delivery,
because such deliveries are safe without explicit locks.
</p>

<p>
Note: The <b>dotlock</b> method requires that the recipient UID or
GID has write access to the parent directory of the mailbox file.
</p>

<p>
Note: the default setting of this parameter is system dependent.
</p>

%PARAM mailbox_transport 

<p>
Optional message delivery transport that the local(8) delivery
agent should use for mailbox delivery to all local recipients,
whether or not they are found in the UNIX passwd database.
</p>

<p>
The precedence of local(8) delivery features from high to low is:
aliases, .forward files, mailbox_transport, mailbox_command_maps,
mailbox_command, home_mailbox, mail_spool_directory, fallback_transport
and luser_relay.
</p>

%PARAM mailq_path see "postconf -d" output

<p>
Sendmail compatibility feature that specifies where the Postfix
mailq(1) command is installed. This command can be used to
list the Postfix mail queue.
</p>

%PARAM manpage_directory see "postconf -d" output

<p>
Where the Postfix manual pages are installed.
</p>

%PARAM maps_rbl_domains 

<p>
Obsolete feature: use the reject_rbl_client feature instead.
</p>

%PARAM mime_boundary_length_limit 2048

<p>
The maximal length of MIME multipart boundary strings. The MIME
processor is unable to distinguish between boundary strings that
do not differ in the first $mime_boundary_length_limit characters.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM mime_header_checks $header_checks

<p>
Optional lookup tables for content inspection of MIME related
message headers, as described in the header_checks(5) manual page.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM mime_nesting_limit 100

<p>
The maximal nesting level of multipart mail that the MIME processor
will handle. Postfix refuses mail that is nested deeper.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM mynetworks_style subnet

<p>
The method to generate the default value for the mynetworks parameter.
This is the list of trusted networks for relay access control etc.
</p>

<ul>

<li><p>Specify "mynetworks_style = host" when Postfix should
"trust" only the local machine. </p>

<li><p>Specify "mynetworks_style = subnet" when Postfix
should "trust" SMTP clients in the same IP subnetworks as the local
machine.  On Linux, this works correctly only with interfaces
specified with the "ifconfig" command. </p>

<li><p>Specify "mynetworks_style = class" when Postfix should
"trust" SMTP clients in the same IP class A/B/C networks as the
local machine.  Don't do this with a dialup site - it would cause
Postfix to "trust" your entire provider's network.  Instead, specify
an explicit mynetworks list by hand, as described with the mynetworks
configuration parameter. </p>

</ul>

%PARAM nested_header_checks $header_checks

<p>
Optional lookup tables for content inspection of non-MIME message
headers in attached messages, as described in the header_checks(5)
manual page.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM newaliases_path see "postconf -d" output

<p>
Sendmail compatibility feature that specifies the location of the
newaliases(1) command. This command can be used to rebuild the
local(8) aliases(5) database.
</p>

%PARAM non_fqdn_reject_code 504

<p>
The numerical Postfix SMTP server reply code when a client request
is rejected by the reject_non_fqdn_hostname, reject_non_fqdn_sender
or reject_non_fqdn_recipient restriction.
</p>

%PARAM owner_request_special yes

<p>
Give special treatment to owner-listname and listname-request
address localparts: don't don't split such addresses when the
recipient_delimiter is set to "-".  This feature is useful for
mailing lists.
</p>

%PARAM permit_mx_backup_networks 

<p>
Restrict the use of the permit_mx_backup SMTP access feature to
only domains whose primary MX hosts match the listed networks.
</p>

%PARAM pickup_service_name pickup

<p>
The name of the pickup(8) service. This service picks up local mail
submissions from the Postfix maildrop queue.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM prepend_delivered_header command, file, forward

<p>
The message delivery contexts where the Postfix local(8) delivery
agent prepends a Delivered-To:  message header.
</p>

<p>
By default, the Postfix local delivery agent prepends a Delivered-To:
header when forwarding mail and when delivering to file (mailbox)
and command. Turning off the Delivered-To: header when forwarding
mail is not recommended.
</p>

<p>
Specify zero or more of <b>forward</b>, <b>file</b>, or <b>command</b>.
</p>

<p>
Example:
</p>

<pre>
prepend_delivered_header = forward
</pre>

%PARAM process_name read-only

<p>
The process name of a Postfix command or daemon process.
</p>

%PARAM process_id read-only

<p>
The process ID of a Postfix command or daemon process.
</p>

%PARAM process_id_directory pid

<p>
The location of Postfix PID files relative to $queue_directory.
This is a read-only parameter.
</p>

%PARAM proxy_read_maps see "postconf -d" output

<p>
The lookup tables that the proxymap(8) server is allowed to access.
Table references that don't begin with proxy: are ignored.  The
proxymap(8) table accesses are read-only.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM qmgr_clog_warn_time 300s

<p>
The minimal delay between warnings that a specific destination is
clogging up the Postfix active queue. Specify 0 to disable.
</p>

<p>
This feature is enabled with the helpful_warnings parameter.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM qmgr_fudge_factor 100

<p>
Obsolete feature: the percentage of delivery resources that a busy
mail system will use up for delivery of a large mailing  list
message.
</p>

<p>
This feature exists only in the oqmgr(8) old queue manager. The
current queue manager solves the problem in a better way.
</p>

%PARAM queue_directory see "postconf -d" output

<p>
The location of the Postfix top-level queue directory. This is the
root directory of Postfix daemon processes that run chrooted.
</p>

%PARAM queue_file_attribute_count_limit 100

<p>
The maximal number of (name=value) attributes that may be stored
in a Postfix queue file. The limit is enforced by the cleanup(8)
server.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM queue_service_name qmgr

<p>
The name of the qmgr(8) service. This service manages the Postfix
queue and schedules delivery requests.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM html_directory see "postconf -d" output

<p>
The location of Postfix HTML files that describe how to build,
configure or operate a specific Postfix subsystem or feature.
</p>

%PARAM readme_directory see "postconf -d" output

<p>
The location of Postfix README files that describe how to build,
configure or operate a specific Postfix subsystem or feature.
</p>

%PARAM relay_transport relay

<p>
The default mail delivery transport and next-hop information for
domains that match the $relay_domains parameter value. This
information can be overruled with the transport(5) table.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in master.cf.
The <i>:nexthop</i> part is optional.  For more details see the
transport(5) manual page.
</p>

<p>
See also the relay domains address class in the ADDRESS_CLASS_README
file.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM rewrite_service_name rewrite

<p>
The name of the address rewriting service. This service rewrites
addresses to standard form and resolves them to a (delivery method,
next-hop host, recipient) triple.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM sample_directory /etc/postfix

<p>
The name of the directory with example Postfix configuration files.
</p>

%PARAM sender_based_routing no

<p>
This parameter should not be used.
</p>

%PARAM sendmail_path see "postconf -d" output

<p>
A Sendmail compatibility feature that specifies the location of
the Postfix sendmail(1) command. This command can be used to
submit mail into the Postfix queue.
</p>

%PARAM service_throttle_time 60s

<p>
How long the Postfix master(8) waits before forking a server that
appears to be malfunctioning.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

%PARAM setgid_group postdrop

<p>
The group ownership of set-gid Postfix commands and of group-writable
Postfix directories. When this parameter value is changed you need
to re-run "<b>post-install set-permissions</b>".
</p>

%PARAM show_user_unknown_table_name yes

<p>
Display the name of the recipient table in the "User unknown"
responses.  The extra detail makes trouble shooting easier but also
reveals information that is nobody elses business.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM showq_service_name showq

<p>
The name of the showq(8) service. This service produces mail queue
status reports.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM smtp_pix_workaround_delay_time 10s

<p>
How long the Postfix SMTP client pauses before sending
".&lt;CR&gt;&lt;LF&gt;" in order to work around the PIX firewall
"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug.
</p>

<p>
Choosing a too short time makes this workaround ineffective when
sending large messages over slow network connections.
</p>

%PARAM smtp_randomize_addresses yes

<p>
Randomize the order of equal-preference MX host addresses.  This
is a performance feature of the Postfix SMTP client.
</p>

%PARAM smtp_rset_timeout 120s

<p> The SMTP client time limit for sending the RSET command, and
for receiving the server response.  </p>

<p> This feature is available in Postfix 2.1 and later.  </p>

%PARAM smtpd_data_restrictions 

<p>
Optional access restrictions that the Postfix SMTP server applies
in the context of the SMTP DATA command.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are valid in this context:
</p>

<ul>

<li><a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under smtpd_client_restrictions.

<li>SMTP command specific restrictions described under
smtpd_client_restrictions, smtpd_helo_restrictions,
smtpd_sender_restrictions or smtpd_recipient_restrictions.

</ul>

<p>
Examples:
</p>

<pre>
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_data_restrictions = reject_multi_recipient_bounce
</pre>

%PARAM smtpd_delay_reject yes

<p>
Wait until the RCPT TO command before evaluating
$smtpd_client_restrictions, $smtpd_helo_restrictions and
$smtpd_sender_restrictions, or wait until the ETRN command before
evaluating $smtpd_client_restrictions and $smtpd_helo_restrictions.
</p>

<p>
This feature is turned on by default because some clients apparently
mis-behave when the Postfix SMTP server rejects commands before
RCPT TO.
</p>

<p>
The default setting has one major benefit: it allows Postfix to log
recipient address information when rejecting a client name/address
or sender address, so that it is possible to find out whose mail
is being rejected.
</p>

%PARAM smtpd_null_access_lookup_key &lt;&gt;

<p>
The lookup key to be used in SMTP access(5) tables instead of the
null sender address.
</p>

%CLASS smtpd-policy SMTP server policy delegation

<p>
The Postfix SMTP server has a number of built-in mechanisms to
block or accept mail at specific SMTP protocol stages. As of version
2.1 Postfix can be configured to delegate policy decisions to an
external server that runs outside Postfix. See the file
SMTPD_POLICY_README for more information.
</p>

%PARAM smtpd_policy_service_max_idle 300s

<p>
The time after which an idle SMTPD policy service connection is
closed.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_policy_service_max_ttl 1000s

<p>
The time after which an active SMTPD policy service connection is
closed.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_policy_service_timeout 100s

<p>
The time limit for connecting to, writing to or receiving from a
delegated SMTPD policy server.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_reject_unlisted_recipient yes

<p>
Request that the Postfix SMTP server rejects mail for unknown
recipient addresses, even when no explicit reject_unlisted_recipient
access restriction is specified. This prevents the Postfix queue
from filling up with undeliverable MAILER-DAEMON messages.
</p>

<ul>

<li> The recipient domain matches $mydestination, $inet_interfaces
or $proxy_interfaces, but the recipient is not listed in
$local_recipient_maps, and $local_recipient_maps is not null.

<li> The recipient domain matches $virtual_alias_domains but the
recipient is not listed in $virtual_alias_maps.

<li> The recipient domain matches $virtual_mailbox_domains but the
recipient is not listed in $virtual_mailbox_maps, and $virtual_mailbox_maps
is not null.

<li> The recipient domain matches $relay_domains but the recipient
is not listed in $relay_recipient_maps, and $relay_recipient_maps
is not null.

</ul>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_reject_unlisted_sender no

<p> Request that the Postfix SMTP server rejects mail from unknown
sender addresses, even when no explicit reject_unlisted_sender
access restriction is specified. This can slow down an explosion
of forged mail from worms or viruses.  </p>

<ul>

<li> The sender domain matches $mydestination, $inet_interfaces or
$proxy_interfaces, but the recipient is not listed in
$local_recipient_maps, and $local_recipient_maps is not null.

<li> The sender domain matches $virtual_alias_domains but the recipient
is not listed in $virtual_alias_maps.

<li> The sender domain matches $virtual_mailbox_domains but the
recipient is not listed in $virtual_mailbox_maps, and $virtual_mailbox_maps
is not null.

<li> The sender domain matches $relay_domains but the recipient is
not listed in $relay_recipient_maps, and $relay_recipient_maps is
not null.

</ul>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM smtpd_restriction_classes 

<p>
User-defined aliases for groups of access restrictions. The aliases
can be specified in smtpd_recipient_restrictions etc., and on the
right-hand side of a Postfix access(5) table.
</p>

<p>
One major application is for implementing per-recipient UCE control.
See the RESTRICTION_CLASS_README document for other examples.
</p>

%PARAM smtpd_sasl_application_name smtpd

<p>
The application name used for SASL server initialization. This
controls the name of the SASL configuration file. The default value
is <b>smtpd</b>, corresponding to a SASL configuration file named
<b>smtpd.conf</b>.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM strict_7bit_headers no

<p>
Reject mail with 8-bit text in message headers. This blocks mail
from poorly written applications.
</p>

<p>
This feature should not be enabled on a general purpose mail server,
because it is likely to reject legitimate email.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM strict_8bitmime no

<p>
Enable both strict_7bit_headers and strict_8bitmime_body.
</p>

<p>
This feature should not be enabled on a general purpose mail server,
because it is likely to reject legitimate email.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM strict_8bitmime_body no

<p>
Reject 8-bit message body text without 8-bit MIME content encoding
information.  This blocks mail from poorly written applications.
</p>

<p>
Unfortunately, this also rejects majordomo approval requests when
the included request contains valid 8-bit MIME mail, and it rejects
bounces from mailers that do not MIME encapsulate 8-bit content
(for example, bounces from qmail or from old versions of Postfix).
</p>

<p>
This feature should not be enabled on a general purpose mail server,
because it is likely to reject legitimate email.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM strict_mime_encoding_domain no

<p>
Reject mail with invalid Content-Transfer-Encoding: information
for the message/* or multipart/* MIME content types.  This blocks
mail from poorly written software.
</p>

<p>
This feature should not be enabled on a general purpose mail server,
because it will reject mail after a single violation.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM sun_mailtool_compatibility no

<p>
Obsolete SUN mailtool compatibility feature. Instead, use
"<b>mailbox_delivery_lock = dotlock</b>".
</p>

%PARAM trace_service_name trace

<p>
The name of the trace(8) service. This service maintains a record
of mail deliveries and produces a mail delivery report when verbose
delivery is requested with "<b>sendmail -v</b>".
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

%PARAM undisclosed_recipients_header To: undisclosed-recipients:;

<p>
Message header that the Postfix cleanup(8) server inserts when a
message contains no To: or Cc: message header.  </p>

%PARAM unknown_relay_recipient_reject_code 550

<p>
The numerical Postfix SMTP server reply code when a recipient
address matches $relay_domains, and relay_recipient_maps specifies
a list of lookup tables that does not match the recipient address.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM unknown_virtual_alias_reject_code 550

<p>
The SMTP server reply code when a recipient address matches
$virtual_alias_domains, and $virtual_alias_maps specifies a list
of lookup tables that does not match the recipient address.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM unknown_virtual_mailbox_reject_code 550

<p>
The SMTP server reply code when a recipient address matches
$virtual_mailbox_domains, and $virtual_mailbox_maps specifies a list
of lookup tables that does not match the recipient address.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM verp_delimiter_filter -=+

<p>
The characters Postfix accepts as VERP delimiter characters on the
Postfix sendmail(1) command line and in SMTP commands.
</p>

<p>
This feature is available in Postfix 1.1 and later.
</p>

%PARAM virtual_gid_maps 

<p>
Lookup tables with the per-recipient group ID for virtual(8) mailbox
delivery.
</p>

<p>
In a lookup table, specify a left-hand side of "@domain.tld" to
match any user in the specified domain that does not have a specific
"user@domain.tld" entry.
</p>

<p>
When a recipient address has an optional address extension
(user+foo@domain.tld), the virtual(8) delivery agent looks up
the full address first, and when the lookup fails, it looks up the
unextended address (user@domain.tld).
</p>

<p>
Note 1: for security reasons, the virtual(8) delivery agent disallows
regular expression substitution of $1 etc. in regular expression
lookup tables, because that would open a security hole.
</p>

<p>
Note 2: for security reasons, the virtual(8) delivery agent does
not allow table lookup through the proxymap(8) service, because
that would open a security hole.
</p>

%PARAM virtual_mailbox_base 

<p>
A prefix that the virtual(8) delivery agent prepends to all pathname
results from $virtual_mailbox_maps table lookups.  This is a safety
measure to ensure that an out of control map doesn't litter the
file system with mailboxes.  While virtual_mailbox_base could be
set to "/", this setting isn't recommended.
</p>

<p>
Example:
</p>

<pre>
virtual_mailbox_base = /var/mail
</pre>

%PARAM virtual_mailbox_domains $virtual_mailbox_maps

<p> The list of domains that are delivered via the $virtual_transport
mail delivery transport.  By default this is the Postfix virtual(8)
delivery agent.  The SMTP server validates recipient addresses with
$virtual_mailbox_maps and rejects mail for non-existent recipients.
See also the virtual mailbox domain class in the ADDRESS_CLASS_README
file.  </p>

<p> This parameter expects the same syntax as the mydestination
configuration parameter.  </p>

<p>
This feature is available in Postfix 2.0 and later. The default
value is backwards compatible with Postfix 1.1.
</p>

%PARAM virtual_mailbox_limit 51200000

<p>
The maximal size in bytes of an individual mailbox or maildir file,
or zero (no limit).
</p>

%PARAM virtual_mailbox_lock see "postconf -d" output

<p>
How to lock a UNIX-style virtual(8) mailbox before attempting
delivery.  For a list of available file locking methods, use the
"<b>postconf -l</b>" command.
</p>

<p>
This setting is ignored with <b>maildir</b> style delivery, because
such deliveries are safe without application-level locks.
</p>

<p>
Note 1: The <b>dotlock</b> method requires that the recipient UID
or GID has write access to the parent directory of the recipient's
mailbox file.
</p>

<p>
Note 2: the default setting of this parameter is system dependent.
</p>

%PARAM virtual_mailbox_maps 

<p>
Optional lookup tables with all valid addresses in the domains that
match $virtual_mailbox_domains.
</p>

<p>
In a lookup table, specify a left-hand side of "@domain.tld" to
match any user in the specified domain that does not have a specific
"user@domain.tld" entry.
</p>

<p>
The virtual(8) delivery agent uses this table to look up the
per-recipient mailbox or maildir pathname.  If the lookup result
ends in a slash ("/"), maildir-style delivery is carried out,
otherwise the path is assumed to specify a UNIX-style mailbox file.
Note that $virtual_mailbox_base is unconditionally prepended to
this path.
</p>

<p>
When a recipient address has an optional address extension
(user+foo@domain.tld), the virtual(8) delivery agent looks up
the full address first, and when the lookup fails, it looks up the
unextended address (user@domain.tld).
</p>

<p>
Note 1: for security reasons, the virtual(8) delivery agent disallows
regular expression substitution of $1 etc. in regular expression
lookup tables, because that would open a security hole.
</p>

<p>
Note 2: for security reasons, the virtual(8) delivery agent disallows
table lookup through the proxymap(8) server, because that would
open a security hole.
</p>

%PARAM virtual_minimum_uid 100

<p>
The minimum user ID value that the virtual(8) delivery agent accepts
as a result from <b>$virtual_uid_maps</b> table lookup.  Returned
values less than this will be rejected, and the message will be
deferred.
</p>

%PARAM virtual_transport virtual

<p>
The default mail delivery transport for domains that match the
$virtual_mailbox_domains parameter value. This information can
be overruled with the transport(5) table.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in master.cf.
The <i>:nexthop</i> part is optional.  For more details see the
transport(5) manual page.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

%PARAM virtual_uid_maps 

<p>
Lookup tables with the per-recipient user ID that the virtual(8)
delivery agent uses while writing to the recipient's mailbox.
</p>

<p>
In a lookup table, specify a left-hand side of "@domain.tld"
to match any user in the specified domain that does not have a
specific "user@domain.tld" entry.
</p>

<p>
When a recipient address has an optional address extension
(user+foo@domain.tld), the virtual(8) delivery agent looks up
the full address first, and when the lookup fails, it looks up the
unextended address (user@domain.tld).
</p>

<p>
Note 1: for security reasons, the virtual(8) delivery agent disallows
regular expression substitution of $1 etc. in regular expression
lookup tables, because that would open a security hole.
</p>

<p>
Note 2: for security reasons, the virtual(8) delivery agent does
not allow table lookup through the proxymap(8) service, because
that would open a security hole.
</p>

%PARAM config_directory see "postconf -d" output

<p> The default location of the Postfix main.cf and master.cf
configuration files. This can be overruled via the following
mechanisms: </p>

<ul>

<li> <p> The MAIL_CONFIG environment variable (daemon processes
and commands). </p>

<li> <p> The "-c" command-line option (commands only). </p>

</ul>

<p> With Postfix command that run with set-gid privileges, a
config_directory override requires either root privileges, or it
requires that the directory is listed with the alternate_config_directories
parameter in the default main.cf file.  </p>

%PARAM virtual_maps

<p> Optional lookup tables with a) names of domains for which all
addresses are aliased to addresses in other local or remote domains,
and b) addresses that are aliased to addresses in other local or
remote domains.  Available before Postfix version 2.0. With Postfix 2.1
and later, this is replaced by separate controls: virtual_alias_domains
and virtual_alias_maps. </p>

%PARAM smtpd_tls_cert_file

<p> File with the Postfix SMTP server RSA certificate in PEM format.
This file may also contain the server private key. </p>

<p> Both RSA and DSA certificates are supported.  When both types
are present, the cipher used determines which certificate will be
presented to the client.  For Netscape and OpenSSL clients without
special cipher choices the RSA certificate is preferred. </p>

<p> In order to verify a certificate, the CA certificate (in case
of a certificate chain, all CA certificates) must be available.
You should add these certificates to the server certificate, the
server certificate first, then the issuing CA(s).  </p>

<p> Example: the certificate for "server.dom.ain" was issued by
"intermediate CA" which itself has a certificate of "root CA".
Create the server.pem file with "cat server_cert.pem intermediate_CA.pem
root_CA.pem &gt; server.pem". </p>

<p> If you want to accept certificates issued by these CAs yourself,
you can also add the CA certificates to the smtpd_tls_CAfile, in
which case it is not necessary to have them in the smtpd_tls_dcert_file
or smtpd_tls_cert_file. </p>

<p> A certificate supplied here must be usable as SSL server
certificate and hence pass the "openssl verify -purpose sslserver
..." test. </p>

<p> Example: </p>

<pre>
smtpd_tls_cert_file = /etc/postfix/server.pem
</pre>

%PARAM smtpd_tls_key_file $smtpd_tls_cert_file

<p> File with the Postfix SMTP server RSA private key in PEM format.
This file may be combined with the server certificate file specified
with $smtpd_tls_cert_file. </p>

<p> The private key must not be encrypted. In other words, the key
must be accessible without password. </p>

%PARAM smtpd_tls_dcert_file

<p> File with the Postfix SMTP server DSA certificate in PEM format.
This file may also contain the server private key. <p>

<p> See the discussion under smtpd_tls_cert_file for more details.
</p>

<p> Example: </p>

<pre>
smtpd_tls_dcert_file = /etc/postfix/server-dsa.pem
</pre>

%PARAM smtpd_tls_dkey_file $smtpd_tls_dcert_file

<p> File with the Postfix SMTP server DSA private key in PEM format.
This file may be combined with the server certificate file specified
with $smtpd_tls_dcert_file. </p>

<p> The private key must not be encrypted. In other words, the key
must be accessible without password. </p>

%PARAM smtpd_tls_CAfile

<p> The file with the certificate of the certification authority
(CA) that issued the Postfix SMTP server certificate.  This is
needed only when the CA certificate is not already present in the
server certificate file.  This file may also contain the CA
certificates of other trusted CAs.  You must use this file for the
list of trusted CAs if you want to use chroot-mode. </p>

<p> Example: </p>

<pre>
smtpd_tls_CAfile = /etc/postfix/CAcert.pem
</pre>

%PARAM smtpd_tls_CApath

<p> Directory with PEM format certificate authority certificates
that the Postfix SMTP server offers to remote SMTP clients for the
purpose of client certificate verification.  Do not forget to create
the necessary "hash" links with, for example, "$OPENSSL_HOME/bin/c_rehash
/etc/postfix/certs".  </p>

<p> To use this option in chroot mode, this directory (or a copy)
must be inside the chroot jail. Please note that in this case the
CA certificates are not offered to the client, so that e.g.  Netscape
clients might not offer certificates issued by them.  Use of this
feature is therefore not recommended. </p>

<p> Example: </p>

<pre>
smtpd_tls_CApath = /etc/postfix/certs
</pre>

%PARAM smtpd_tls_loglevel 0

<p> Enable additional Postfix SMTP server logging of TLS activity.
Each logging level also includes the information that is logged at
a lower logging level.  </p>

<dl compact>

<dt> </dt> <dd> 0 Disable logging of TLS activity. </dd>

<dt> </dt> <dd> 1 Log TLS handshake and certificate information. </dd>

<dt> </dt> <dd> 2 Log levels during TLS negotiation. </dd>

<dt> </dt> <dd> 3 Log hexadecimal and ASCII dump of TLS negotiation
process.  </dd>

<dt> </dt> <dd> 4 Also log hexadecimal and ASCII dump of complete
transmission after STARTTLS. </dd>

</dl>

<p> Use "smtpd_tls_loglevel = 3" only in case of problems. Use of
loglevel 4 is strongly discouraged. </p>

%PARAM smtpd_tls_received_header no

<p> Request that the Postfix SMTP server produces Received:  message
headers that include information about the protocol and cipher used,
as well as the client CommonName and client certificate issuer
CommonName.  This is disabled by default, as the information may
be modified in transit through other mail servers.  Only information
that was recorded by the final destination can be trusted. </p>

%PARAM smtpd_use_tls no

<p> Enable TLS support in the Postfix SMTP server. </p>

<p> Note: when invoked via "sendmail -bs", Postfix will never offer
STARTTLS due to insufficient privileges to access the server private
key. This is intended behavior. </p>

%PARAM smtpd_enforce_tls no

<p> Require that remote SMTP clients use TLS encryption.  According
to RFC 2487 this MUST NOT be applied in case of a publicly-referenced
SMTP server.  This option is off by default and should only rarely
be used. </p>

<p> This option implies "smtpd_use_tls = yes". </p>

<p> Note: when invoked via "sendmail -bs", Postfix will never offer
STARTTLS due to insufficient privileges to access the server private  
key. This is intended behavior. </p>

%PARAM smtpd_tls_wrappermode no

<p> Run the Postfix SMTP server in the non-standard "wrapper" mode,
instead of using the STARTTLS command. </p>

<p> If you want to support this service, enable a special port in
master.cf, and specify "-o smtpd_tls_wrappermode=yes" on the SMTP
server's command line. Port 465 (smtps) was once chosen for this
purpose. </p>

%PARAM smtpd_tls_ask_ccert no

<p> Ask a remote SMTP client for a client certificate. This
information is needed for certificate based mail relaying with,
for example, the permit_tls_clientcerts feature. </p>

<p> Some clients such as Netscape will either complain if no
certificate is available (for the list of CAs in /etc/postfix/certs)
or will offer multiple client certificates to choose from. This
may be annoying, so this option is "off" by default. </p>

%PARAM smtpd_tls_req_ccert no

<p> When TLS encryption is enforced, require a remote SMTP client
certificate in order to allow TLS connections to proceed.  This
option implies "smtpd_tls_ask_ccert = yes". </p>

<p> When TLS encryption is optional, remote SMTP clients can bypass
the restriction by simply not using STARTTLS at all. For this reason
a TLS connection will be handled as if only "smtpd_tls_ask_ccert
= yes" is specified.  </p>

%PARAM smtpd_tls_ccert_verifydepth 5

<p> The verification depth for remote SMTP client certificates. A
depth of 1 is sufficient if the issuing CA is listed in a local CA
file.  The default value should also suffice for longer chains (the
root CA issues special CA which then issues the actual certificate...).
</p>

%PARAM smtpd_tls_auth_only no

<p> When TLS encryption is optional in the Postfix SMTP server, do
not announce or accept SASL authentication over un-encrypted
connections. </p>

%PARAM smtpd_tls_session_cache_database

<p> Name of the SDBM file (type sdbm:) containing the optional
Postfix SMTP server TLS session cache. SDBM is required in order
to support concurrent updates.  The file is created if it does not
exist.  </p>

<p> Example: </p>

<pre>
smtpd_tls_session_cache_database = sdbm:/etc/postfix/smtpd_scache
</pre>

%PARAM smtpd_tls_session_cache_timeout 3600s

<p> The expiration time of Postfix SMTP server TLS session cache
information.  A cache cleanup is performed periodically every
$smtpd_tls_session_cache_timeout seconds.  </p>

%PARAM relay_clientcerts

<p> The list of remote SMTP client certificates for which the
Postfix SMTP server will allow access with the permit_tls_clientcerts
feature.  This feature does not use certificate names, because
Postfix list manipulation routines treat whitespace and some other
characters as special.  Instead we use certificate fingerprints as
they are difficult to fake but easy to use for lookup. </p>

<p> Postfix lookup tables are in the form of (key, value) pairs.
Since we only need the key, the value can be chosen freely, e.g.
the name of the user or host:
D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80 lutzpc.at.home </p>

<p> Example: </p>

<pre>
relay_clientcerts = hash:/etc/postfix/relay_clientcerts
</pre>

%PARAM smtpd_tls_cipherlist

<p> Controls the Postfix SMTP server TLS cipher selection scheme.
For details, see the OpenSSL documentation. Note: do not use ""
quotes around the parameter value. </p>

%PARAM smtpd_tls_dh1024_param_file

<p> File with DH parameters that the Postfix SMTP server should
use with EDH ciphers. </p>

<p> Instead of using the exact same parameter sets as distributed
with other TLS packages, it is more secure to generate your own
set of parameters with something like the following command:  </p>

<pre>
openssl gendh -out /etc/postfix/dh_1024.pem -2 -rand /var/run/egd-pool 1024
</pre>

<p> Your actual source for entropy may differ. Some systems have
/dev/random; on other system you may consider using the "Entropy
Gathering Daemon EGD", available at http://www.lothar.com/tech/crypto/.
</p>

<p> Example: </p>

<pre>
smtpd_tls_dh1024_param_file = /etc/postfix/dh_1024.pem
</pre>

%PARAM smtpd_tls_dh512_param_file

<p> File with DH parameters that the Postfix SMTP server should
use with EDH ciphers. </p>

<p> See also the discussion under the smtpd_tls_dh1024_param_file
configuration parameter.  </p>

<p> Example: </p>

<pre>
smtpd_tls_dh512_param_file = /etc/postfix/dh_512.pem
</pre>

%PARAM smtpd_starttls_timeout 300s

<p> The time limit for Postfix SMTP server write and read operations
during TLS startup and shutdown handshake procedures. </p>

%PARAM smtp_tls_cert_file

<p> File with the Postfix SMTP client RSA certificate in PEM format.
This file may also contain the client private key, and these may
be the same as the server certificate and key file. </p>

<p> In order to verify certificates, the CA certificate (in case
of a certificate chain, all CA certificates) must be available.
You should add these certificates to the server certificate, the
server certificate first, then the issuing CA(s). </p>

<p> Example: the certificate for "client.dom.ain" was issued by
"intermediate CA" which itself has a certificate of "root CA".
Create the client.pem file with "cat client_cert.pem intermediate_CA.pem
root_CA.pem &gt; client.pem". </p>

<p> If you want to accept remote SMTP server certificates issued
by these CAs yourself, you can also add the CA certificates to the
smtp_tls_CAfile, in which case it is not necessary to have them in
the smtp_tls_cert_file or smtp_tls_dcert_file. </p>

<p> A certificate supplied here must be usable as SSL client certificate and
hence pass the "openssl verify -purpose sslclient ..." test. </p>

<p> Example: </p>

<pre>
smtp_tls_cert_file = /etc/postfix/client.pem
</pre>

%PARAM smtp_tls_key_file $smtp_tls_cert_file

<p> File with the Postfix SMTP client RSA private key in PEM format.
This file may be combined with the client certificate file specified
with $smtp_tls_cert_file. </p>

<p> The private key must not be encrypted. In other words, the key
must be accessible without password. </p>

<p> Example: </p>

<pre>
smtp_tls_key_file = $smtp_tls_cert_file
</pre>

%PARAM smtp_tls_CAfile

<p> The file with the certificate of the certification authority
(CA) that issued the Postfix SMTP client certificate.  This is
needed only when the CA certificate is not already present in the
client certificate file.  </p>

<p> Example: </p>

<pre>
smtp_tls_CAfile = /etc/postfix/CAcert.pem
</pre>

%PARAM smtp_tls_CApath

<p> Directory with PEM format certificate authority certificates
that the Postfix SMTP client uses to verify a remote SMTP server
certificate.  Don't forget to create the necessary "hash" links
with, for example, "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs".
</p>

<p> To use this option in chroot mode, this directory (or a copy) 
must be inside the chroot jail. </p>

<p> Example: </p>

<pre>
smtp_tls_CApath = /etc/postfix/certs
</pre>

%PARAM smtp_tls_loglevel 0

<p> Enable additional Postfix SMTP client logging of TLS activity.
Each logging level also includes the information that is logged at
a lower logging level.  </p>

<dl compact>

<dt> </dt> <dd> 0 Disable logging of TLS activity. </dd>

<dt> </dt> <dd> 1 Log TLS handshake and certificate information. </dd>

<dt> </dt> <dd> 2 Log levels during TLS negotiation. </dd>

<dt> </dt> <dd> 3 Log hexadecimal and ASCII dump of TLS negotiation
process.  </dd>

<dt> </dt> <dd> 4 Log hexadecimal and ASCII dump of complete
transmission after STARTTLS. </dd>

</dl>

<p> Use "smtp_tls_loglevel = 3" only in case of problems. Use of
loglevel 4 is strongly discouraged. </p>

%PARAM smtp_tls_session_cache_database

<p> Name of the SDBM file (type sdbm:) containing the optional
Postfix SMTP client TLS session cache. SDBM is required in order
to support concurrent updates. The file is created if it does not
exist.  </p>

<p> Example: </p>

<pre>
smtp_tls_session_cache_database = sdbm:/etc/postfix/smtp_scache
</pre>

%PARAM smtp_tls_session_cache_timeout 3600s

<p> The expiration time of Postfix SMTP client TLS session cache
information.  A cache cleanup is performed periodically every
$smtp_tls_session_cache_timeout seconds.  </p>

%PARAM smtp_use_tls no

<p> Always use TLS when a remote SMTP server announces STARTTLS
support.  Beware: some remote SMTP servers offer STARTTLS even if
it is not configured.  If the TLS handshake fails, and no other
server is available, delivery is deferred and mail stays in the
queue.  If this is a concern for you, use the smtp_tls_per_site
feature instead.  </p>

%PARAM smtp_enforce_tls no

<p> Require that remote SMTP servers use TLS encryption.  This also
requires that the remote SMTP server hostname matches the information
in the remote server certificate, and that the remote SMTP server
certificate was issued by a CA that is trusted by the Postfix SMTP
client. If the certificate doesn't verify or the hostname doesn't
match, delivery is deferred and mail stays in the queue.  </p>

<p> The hostname used in the check is performed against all names
provided as dNSNames in the SubjectAlternativeName.  If no dNSNames
are specified, the CommonName is checked.  The behavior may be
changed with the smtp_tls_enforce_peername option.  </p>

<p> This option is useful only if you are definitely sure that you
will only connect to servers that support RFC 2487 _and_ that
provide valid server certificates.  It is relatively safe to use
for local clients that only send email to one mailhub with the
necessary STARTTLS support.  </p>

%PARAM smtp_tls_enforce_peername yes

<p> When TLS encryption is enforced, require that the remote SMTP
server hostname matches the information in the remote SMTP server
certificate.  As of RFC 2487 the requirements for hostname checking
for MTA clients are not set. </p>

<p> This option can be set to "no" to disable strict peer name
checking. This setting has no effect on sessions that are controlled
via the smtp_tls_per_site table.  </p>

<p> Disabling the hostname verification can make sense in closed
environment where special CAs are created.  If not used carefully,
this option opens the danger of a "man-in-the-middle" attack (the
CommonName of this attacker will be logged). </p>

%PARAM smtp_tls_per_site

<p> Optional lookup tables with the Postfix SMTP client TLS usage
policy by next-hop domain name and by remote SMTP server hostname.
</p>

<p> Table format:  domain names or server hostnames are specified
on the left-hand side; no wildcards are allowed.  On the right hand
side specify one of the following keywords:  </p>

<dl>

<dt> NONE </dt> <dd>Don't use TLS at all. </dd>

<dt> MAY </dt> <dd>Try to use STARTTLS if offered,
otherwise use the un-encrypted connection. </dd>

<dt> MUST </dt> <dd>Require usage of STARTTLS, require that the
remote SMTP server hostname matches the information in the remote
SMTP server certificate, and require that the remote SMTP server
certificate was issued by a trusted CA. </dd>

<dt> MUST_NOPEERMATCH </dt> <dd>Require usage of STARTTLS, but do
not require that the remote SMTP server hostname matches the
information in the remote SMTP server certificate, or that the
server certificate was issued by a trusted CA. </dd>

</dl>

<p> Special hint for enforcement mode:  since no secure DNS lookup
mechanism is available, the recommended setup is:  specify local
transport(5) table entries for sensitive domains with explicit
smtp:[mailhost] destinations (since you can assure security of this
table unlike DNS), then specify MUST for these mail hosts in the
smtp_tls_per_site table. </p>

%PARAM smtp_tls_scert_verifydepth 5

<p> The verification depth for remote SMTP server certificates. A
depth of 1 is sufficient, if the certificate is directly issued by
a CA listed in the CA files.  The default value (5) should suffice
for longer chains (the root CA issues special CA which then issues
the actual certificate...). </p>

%PARAM smtp_tls_note_starttls_offer no

<p> Log the hostname of a remote SMTP server that offers STARTTLS,
when TLS is not already enabled for that server. </p>

<p> The logfile record looks like:  </p>

<pre>
postfix/smtp[pid]:  Host offered STARTTLS: [name.of.host]
</pre>

%PARAM smtp_tls_cipherlist

<p> Controls the Postfix SMTP client TLS cipher selection scheme.
For details, see the OpenSSL documentation. Note: do not use ""
quotes around the parameter value. </p>

%PARAM smtp_starttls_timeout 300s

<p> Time limit for Postfix SMTP client write and read operations
during TLS startup and shutdown handshake procedures. </p>

%PARAM smtp_tls_dkey_file $smtp_tls_dcert_file

<p> File with the Postfix SMTP client DSA private key in PEM format.
The private key must not be encrypted. In other words, the key must
be accessible without password. </p>

<p> This file may be combined with the server certificate file
specified with $smtp_tls_cert_file. </p>

%PARAM smtp_tls_dcert_file

<p> File with the Postfix SMTP client DSA certificate in PEM format.
This file may also contain the server private key. </p>

<p> See the discussion under smtp_tls_cert_file for more details.
</p>

<p> Example: </p>

<pre>
smtp_tls_dcert_file = /etc/postfix/client-dsa.pem
</pre>

%PARAM tls_random_exchange_name ${config_directory}/prng_exch

<p> Name of the pseudo random number generator (PRNG) seed file
that is maintained by tlsmgr(8), and that is read by the smtp(8)
and smtpd(8) processes upon startup. The file length is fixed at
1024 bytes, and is created by tlsmgr(8) when it does not exist.
</p>

<p> Since this file is changed by Postfix, it should probably be
kept in the /var file system, instead of under $config_directory.
The location should not be inside the chroot jail. </p>

%PARAM tls_random_source

<p> The external entropy source for the in-memory tlsmgr(8) pseudo
random number generator (PRNG) pool. Be sure to specify a non-blocking
source.  If this source is not a regular file, the entropy source
type must be prepended:  egd:/path/to/egd_socket for a source with
EGD compatible socket interface, or dev:/path/to/device for a
device file.  </p>

%PARAM tls_random_bytes 32

<p> The number of bytes that tlsmgr(8) reads from $tls_random_source
when (re)seeding the in-memory pseudo random number generator (PRNG)
pool. The default of 32 bytes (256 bits) is good enough for 128bit
symmetric keys.  If using EGD, a maximum of 255 bytes is read. </p>

%PARAM tls_random_reseed_period 3600s

<p> The maximal time between attempts by tlsmgr(8) to re-seed the
in-memory pseudo random number generator (PRNG) pool from external
sources.  The actual time between re-seeding attempts is calculated
using the PRNG, and is between 0 and the time specified.  </p>

%PARAM tls_random_prng_update_period 60s

<p> The maximal time between attempts by tlsmgr(8) to rewrite the
pseudo random number generator (PRNG) seed file specified with
$tls_random_exchange_name. This file is read by smtpd(8) and smtpd(8)
processes in order to seed their PRNGs.  The actual time between
rewriting attempts is calculated using the PRNG, and is between 0
and the time specified.  </p>

%PARAM tls_daemon_random_source

<p> Optional external source of entropy that can be read by smtpd(8)
and smtpd(8) processes in order to initialize their PRNGs. Be sure
to specify a non-blocking source.  The entropy source type must be
prepended to the source name:  egd:/path/to/egd_socket for a source
with EGD compatible socket interface, or dev:/path/to/device for
a device file.  </p>

<p> Examples: </p>

<pre>
tls_daemon_random_source = dev:/dev/urandom
tls_daemon_random_source = egd:/var/run/egd-pool
</pre>

%PARAM tls_daemon_random_bytes 32

<p> The amount of data that smtpd(8) and smtpd(8) processes read
from the entropy source specified with $tls_daemon_random_source.
The default of 32 bytes (equivalent to 256 bits) is sufficient to
generate a 128bit (or 168bit) session key. </p>

<p> Usage of this option may drain EGD (consider the case of 50
smtp(8) processes starting up with a full queue and "postfix start",
which will request 1600 bytes of entropy). This is however not