A.1. Postfix Parameter Reference

"2bounce" is one of several possible error classes. Each class of error can optionally generate an error notice. 2bounce_notice_recipient designates the recipient address for "2bounce" error notices.

Possible values:

email address

Default:

postmaster

Example:

2bounce_notice_recipient = postmaster

SMTP response code sent when a request is rejected because of an access map restriction.

Possible values:

reply code

Default:

554

Example:

access_map_reject_code = 554

List of alias databases used by the local delivery agent.

Possible values:

alias maps

Default: hash:/etc/aliases, nis

mail.aliases

Example:

alias_maps = hash:/etc/aliases, nis:mail.aliases

Restricts or allows local mail delivery to external files when expanded from an alias file.

Possible values:

explicit list

Default:

alias,forward

Example:

allow_mail_to_files = alias, forward

The percent hack is an old workaround that allowed sender-controlled routing of email messages. Nowadays, DNS and mail routing are much more reliable, but Postfix continues to support the hack. To turn off percent rewriting, set allow_percent_hack to no.

Possible values:

yes/no

Default:

yes

Example:

allow_percent_hack = yes

The commands postqueue and postdrop have options to use a different directory when reading the Postfix configuration file. Any nonstandard directories you plan to use must be listed in this parameter.

Possible values:

directory

Default:

(null)

Example:

alternate_config_directories = /usr/local/postfix/conf

Expands incomplete email addresses by appending the value from myorigin onto addresses that consist of a local part only. Changes user to user@host.example.com.

Possible values:

yes/no

Default:

yes

Example:

append_at_myorigin = yes

VERP is a technique used with mailing lists to handle bounced messages. It combines the list owner address and original recipient address with a special delimiter character. authorized_verp_clients contains a list of host and domain names and IP addresses of clients that are allowed to use the feature.

Possible values:

hosts/domains

Default:

$mynetworks

Example:

authorized_verp_clients = $mynetworks

Buffer size to use when reading Berkeley DB hash or btree tables.

Possible values:

bytes

Default:

131072

Example:

berkeley_db_read_buffer_size = 131072

biff is a small process that can notify local users when new mail has arrived. If you have no local users, you should turn off biff notifications since they may affect the performance of the mail server.

Possible values:

yes/no

Default:

yes

Example:

biff = yes

Limit on the amount of a message subject to body_checks filtering.

Possible values:

bytes

Default:

51200

Example:

body_checks_size_limit = 51200

Service the master daemon uses for maintaining log files with status information on messages that cannot be delivered. You normally do not need to change this parameter.

Possible values:

service

Default:

bounce

Example:

bounce_service_name = bounce

List of lookup tables used to map email addresses to their desired rewritten form.

Possible values:

lookup types

Default:

(null)

Example:

canonical_maps = hash:/etc/postfix/canonical_maps

Location of Postfix administrative command-line tools such as postcat and postqueue.

Possible values:

directory

Default:

/usr/sbin

Example:

command_directory = /usr/sbin

When the local delivery agent passes messages to a command, Postfix limits the amount of time the command can execute. command_time_limit indicates the time limit.

Possible values:

time unit

Default:

1000s

Example:

command_time_limit = 1000s

Transport to be used as a message filter. Postfix passes messages to the named transport.

Possible values:

transport

Default:

(null)

Example:

content_filter = myfilter

Amount of time Postfix daemons spend handling a request. When they exceed the specified time, they voluntarily die.

Possible values:

time unit

Default:

18000s

Example:

daemon_timeout = 18000s

For help with troubleshooting, Postfix can increase logging for particular hosts that you might be having problems with. debug_peer_list specifies a list of one or more hosts, domains, or regular expression patterns whose logging should be increased by the degree specified in debug_peer_level.

Possible values:

hosts/domains

Default:

(null)

Example:

debug_peer_list = example.com, mail.ora.com

Postfix allows you to set a limit on the number of simultaneous deliveries to any transport in master.cf. If you don't set an explicit limit for a transport, the value in default_destination_concurrency_limit is used. Note that concurrency limits are per destination as opposed to process limits, which are per transport.

Possible values:

count

Default:

20

Example:

default_destination_concurrency_limit = 20

Limit on the number of recipients for a transport when the queue manager preempts normal delivery with a higher priority transport.

Possible values:

count

Default:

1000

Example:

default_extra_recipient_limit = 1000

Process limits can be configured for any transport. If you don't set an explicit process limit for a transport, the value in default_process_limit is used. Note that process limits are per transport as opposed to concurrency limits, which are per destination.

Possible values:

count

Default:

100

Example:

default_process_limit = 100

Limit on the number of recipients the queue manager stores in memory for a particular transport.

Possible values:

count

Default:

10000

Example:

default_recipient_limit = 10000

VERP is a technique used with mailing lists to handle bounced messages. It combines the list owner address and original recipient address with a special delimiter character. The default_verp_delimiters parameter specifies which characters to use when constructing VERP return addresses.

Possible values:

characters

Default:

+=

Example:

default_verp_delimiters = +=

Service the master daemon uses for maintaining log files with status information on messages that cannot be delivered. You normally do not need to change this parameter.

Possible values:

service

Default:

defer

Example:

defer_service_name = defer

"delay" is one of several possible error classes. Each class of error can optionally generate an error notice. delay_notice_recipient designates the recipient address for "delay" error notices.

Possible values:

email address

Default:

postmaster

Example:

delay_notice_recipient = postmaster

Limit on the number of times Postfix tries to acquire an exclusive lock on a mailbox file.

Possible values:

count

Default:

20

Example:

deliver_lock_attempts = 20

Normally when Postfix determines where to deliver a message, it first looks up the DNS MX records for the destination domain. If disable_dns_lookups is set, Postfix does not check for MX records and delivers directly to the A record it finds for the destination domain.

Possible values:

yes/no

Default:

no

Example:

disable_dns_lookups = no

Normally Postfix converts 8-bit MIME format to 7-bit format when a remote system does not advertise 8-bit MIME support. Set disable_mime_output_conversion to yes to turn off the normal behavior.

Possible values:

yes/no

Default:

no

Example:

disable_mime_output_conversion = no

Normally Postfix allows the SMTP VRFY command. Set disable_vrfy_command to yes to disable it.

Possible values:

yes/no

Default:

no

Example:

disable_vrfy_command = no

A double bounce is produced when the original sender of a message cannot be notified that the message was not delivered. The double_bounce_sender parameter specifies the sender address Postfix uses for mail that should be discarded if it cannot be delivered. The specified address should not be used for anything else since all messages addressed to it are silently discarded.

Possible values:

email address

Default:

double-bounce

Example:

double_bounce_sender = double-bounce

The destination address for notifications when mail with a null sender (<>) cannot be delivered. For example, when a bounce notification, which uses a null sender, cannot be delivered, it is sent to the address specified in empty_address_recipient.

Possible values:

email address

Default:

MAILER-DAEMON

Example:

empty_address_recipient = MAILER-DAEMON

Service the master daemon uses to generate error reports when a message cannot be delivered. You normally do not need to change this parameter.

Possible values:

service

Default:

error

Example:

error_service_name = error

List of environment variables that are exported to external processes such as deliveries to the pipe service or external commands.

Possible values:

environment variables

Default:

TZ MAIL_CONFIG

Example:

export_environment = TZ, MAIL_CONFIG

List of IP addresses, hosts, or domains to receive messages when the normal destination is not found or is not reachable.

Possible values:

hosts/domains

Default:

(null)

Example:

fallback_relay = example.com

The fast flush service allows the queue manager to retry immediate delivery of messages for a particular domain upon request. The fast_flush_domains parameter specifies a list of IP addresses, hosts, and domains that are eligible for the fast flush service.

Possible values:

hosts/domains

Default:

$relay_domains

Example:

fast_flush_domains = $relay_domains

The fast flush service allows the queue manager to retry immediate delivery of messages for a particular domain upon request. The fast_flush_refresh_time parameter specifies a time interval for automatically flushing messages that have not otherwise had redelivery requested.

Possible values:

time unit

Default:

12h

Example:

fast_flush_refresh_time = 12h

Limit on the number of times Postfix tries to fork a process.

Possible values:

count

Default:

5

Example:

fork_attempts = 5

When assigning path names to the forward_path parameter, you can use macros such as $user that are expanded by Postfix to determine the path for the current message. The forward_expansion_filter parameter specifies a list of characters that should be allowed when expanding macros. Characters that are not permitted are replaced by underscores.

Possible values:

characters

Default:

(see example)

Example:

forward_expansion_filter = 1234567890!@%-_=+:,./abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ

Postfix creates a structure of subdirectories for each of its queues in order to organize queue files. The hash_queue_depth parameter specifies the number of subdirectory levels below the queue directories.

Possible values:

count

Default:

1

Example:

hash_queue_depth = 1

Limit on the number of tokens (every word and every @ or . is a token, as defined in RFC 2822) in header addresses to be rewritten by Postfix. Excess tokens are silently discarded.

Possible values:

count

Default:

10240

Example:

header_address_token_limit = 10240

Limit on the number of characters allowed in a message header. Excess text is silently discarded.

Possible values:

bytes

Default:

102400

Example:

header_size_limit = 102400

Postfix normally delivers messages to mailbox files in the mail spool. You can change the delivery to mailbox files relative to users' home directories by specifying a path with the home_mailbox parameter. Include a trailing slash to indicate maildir-style mailboxes.

Possible values:

pathname

Default:

(null)

Example:

home_mailbox = Mail/mbox

Normally when Postfix gets no response from a nameserver for an MX lookup, it tries again after some period of time. You can cause immediate lookups of A records by enabling ignore_mx_lookup_error.

Possible values:

yes/no

Default:

no

Example:

ignore_mx_lookup_error = no

Causes Postfix to pause for the specified time before accepting a new message. You would need to change this parameter only if you are experimenting with performance.

Possible values:

time unit

Default:

1s

Example:

in_flow_delay = 1s

Initial number of delivery processes for a particular destination.

Possible values:

count

Default:

5

Example:

initial_destination_concurrency = 5

Maximum idle time for internal communication channels. Once the maximum time has been reached, Postfix components disconnect voluntarily.

Possible values:

time unit

Default:

100s

Example:

ipc_idle = 100s

Limit on the length of any single line in a message. Lines that exceed the limit are broken up and reconstructed at delivery time.

Possible values:

count

Default:

2048

Example:

line_length_limit = 2048

Limit on the amount of time the LMTP client waits to complete a TCP connection. Set the parameter to 0 to disable timeouts.

Possible values:

time unit

Default:

0s

Example:

lmtp_connect_timeout = 0

Limit on the amount of time the LMTP client waits for a response from the server after sending the LMTP DATA command.

Possible values:

time unit

Default:

120s

Example:

lmtp_data_init_timeout = 120s

Limit on the amount of time the LMTP client waits for a response from the server after sending the LMTP LHLO command.

Possible values:

time unit

Default:

300s

Example:

lmtp_lhlo_timeout = 300s

Limit on the amount of time the LMTP client waits for a response from the server after sending the LMTP QUIT command.

Possible values:

time unit

Default:

300s

Example:

lmtp_quit_timeout = 300s

Limit on the amount of time the LMTP client waits for a response from the server after sending the LMTP RSET command.

Possible values:

time unit

Default:

300s

Example:

lmtp_rset_timeout = 300s

TCP port to use for LMTP connections if the lmtp service is not found in the services database.

Possible values:

port number

Default:

24

Example:

lmtp_tcp_port = 24

Limit on the number of delivery processes to the same local recipient.

Possible values:

count

Default:

2

Example:

local_destination_concurrency_limit = 2

List of lookup tables containing all email addresses that are local. It's used by the SMTP server to reject messages for nonexistent users.

Possible values:

lookup tables

Default: proxy:unix

passwd.byname $alias_maps

Example:

local_recipient_maps = unix:passwd.byname $alias_maps

Destination address that should receive all messages for unknown recipients.

Possible values:

email address

Default:

(null)

Example:

luser_relay = info

System username that owns Postfix queue files. It's also used for running Postfix daemon processes.

Possible values:

username

Default:

postfix

Example:

mail_owner = postfix

Directory where mailbox files are kept.

Possible values:

directory

Default:

(system dependent)

Example:

mail_spool_directory = /var/mail

An external command to use for final mailbox delivery. Commonly used for configuring an external local delivery agent such as procmail.

Possible values:

pathname

Default:

(null)

Example:

mailbox_command = /usr/local/bin/procmail

Locking methods Postfix should use when delivering mail to files.

Possible values:

explicit list

Default:

(system dependent)

Example:

mailbox_delivery_lock = fcntl, dotlock

Transport to use for final mailbox delivery.

Possible values:

transport

Default:

(null)

Example:

mailbox_transport = cyrus

Directory for Postfix manpages.

Possible values:

directory

Default:

(system dependent)

Example:

manpage_directory = /usr/local/man

Address masquerading hides the names of internal hosts by stripping internal hostnames off before messages are sent out from a gateway system. The masquerade_domains parameter specifies a list of domains that should be subject to address masquerading.

Possible values:

domains

Default:

(null)

Example:

masquerade_domains = example.com

Maximum idle time a Postfix daemon process (except the queue manager) waits for a new request.

Possible values:

time unit

Default:

100s

Example:

max_idle = 100s

Maximum time limit for Postfix to attempt redelivery of deferred messages. Each time a message is deferred, the queue manager increases the amount of time it waits to attempt delivery of that message again. The calculated increase of time is never allowed to exceed maximal_backoff_time.

Possible values:

time unit

Default:

4000s

Example:

maximal_backoff_time = 4000s

Limit on the size of any message your system will accept.

Possible values:

bytes

Default:

10240000

Example:

message_size_limit = 10240000

List of lookup tables containing patterns to match against each MIME header of incoming email messages. Each pattern is listed with the action to take if there is a match.

Possible values:

lookup tables

Default:

$header_checks

Example:

mime_header_checks = regexp:/etc/postfix/mime_header_checks

Minimum time limit on how often Postfix attempts redelivery of deferred messages. Each time a message is deferred, the queue manager increases the amount of time it waits to attempt delivery of that message again. The calculated time is never less than minimal_backoff_time.

Possible values:

time unit

Default:

1000s

Example:

minimal_backoff_time = 1000s

System's domain name.

Possible values:

domain

Default:

(system dependent)

Example:

mydomain = example.com

List of IP or network addresses that are allowed to relay messages through your mail server. Either mynetworks or mynetworks_style can be used to designate hosts permitted to relay. mynetworks has precedence over mynetworks_style.

Possible values:

net addresses

Default:

(system dependent)

Example:

mynetworks = 192.168.15.32/26

Domain portion to append to message email addresses that contain localparts only.

Possible values:

domain

Default:

$myhostname

Example:

myorigin = $myhostname

Full path to the Sendmail-compatibility newaliases command. newaliases is used to rebuild alias databases.

Possible values:

pathname

Default:

(system dependent)

Example:

newaliases_path = /usr/bin/newaliases

List of recognized error classes that cause a notification to be sent. Notification email addresses are configured in parameters named according to the class, class_notice_recipient.

Possible values:

explicit list

Default:

resource,software

Example:

notify_classes = resource, software

List of lookup map types where lookups should match the domain itself plus all of its subdomains.

Possible values:

yes/no

Default:

(see example)

Example:

parent_domain_matches_subdomains = debug_peer_list, fast_flush_domains, mynetworks, permit_mx_backup_networks, qmqpd_authorized_clients, relay_domains, smtpd_access_maps

Service the master daemon uses to retrieve locally injected messages. You normally do not need to change this parameter.

Possible values:

service

Default:

pickup

Example:

pickup_service_name = pickup

Directory for lock files used by the master daemon. The specified path is relative to the Postfix spool directory.

Possible values:

directory

Default:

pid

Example:

process_id_directory = pid

When a Postfix server is running on an internal network behind a proxy or NAT device, and it serves as the backup MX host for a domain, it's possible to get mail delivery loops when the primary MX host is down. The proxy_interfaces specifies a list of network interface addresses that receive mail via a proxy device. Postfix avoids mail loops with listed interfaces.

Possible values:

IP addresses

Default:

(null)

Example:

proxy_interfaces = 192.168.15.23

Minimum time between warnings that a particular destination is clogging up the active queue. A value of 0 disables the warnings.

Possible values:

time unit

Default:

300s

Example:

qmgr_clog_warn_time = 300s

Limit on the number of messages allowed in the active queue.

Possible values:

count

Default:

20000

Example:

qmgr_message_active_limit = 20000

Minimum number of recipients stored in memory for each message.

Possible values:

count

Default:

10

Example:

qmgr_message_recipient_minimum = 10

The QMQP service provides a centralized mail queue for a cluster of mail hosts. The qmqpd_error_delay specifies the length of time the QMQP server should pause before sending a negative reply to a client. The delay is meant to slow down misbehaving clients.

Possible values:

time unit

Default:

1s

Example:

qmqpd_error_delay = 1s

Directory for the Postfix queue.

Possible values:

directory

Default:

/var/spool/postfix

Example:

queue_directory = /var/spool/postfix

Amount of time between queue scans to check for deferred messages that are due for redelivery attempt.

Possible values:

time unit

Default:

1000s

Example:

queue_run_delay = 1000s

List of lookup tables used to map RBL domain names to responses when rejecting messages because of either reject_rbl or reject_rhsbl. If an RBL domain is not listed, the default_rbl_reply provides the response.

Possible values:

lookup tables

Default:

(null)

Example:

rbl_reply_maps = hash:/etc/postfix/rbl_reply

List of lookup tables used to map recipient email addresses to their desired rewritten form. Operates the same as canonical_maps but only for recipient addresses. recipient_canonical_maps has precedence over canonical_maps.

Possible values:

lookup tables

Default:

(null)

Example:

recipient_canonical_maps = hash:/etc/postfix/canonical

SMTP response code to send when a request is rejected because of a client restriction.

Possible values:

reply code

Default:

554

Example:

reject_code = 554

SMTP response code to send when a request is rejected due to a disallowed relay attempt.

Possible values:

reply code

Default:

554

Example:

relay_domains_reject_code = 554

Transport to use for delivering relayed messages.

Possible values:

transport

Default:

relay

Example:

relay_transport = relay

List of lookup tables that map moved addresses or domains to their new locations.

Possible values:

lookup tables

Default:

(null)

Example:

relocated_maps = hash:/etc/postfix/relocated

Specifies whether or not Postfix resolves addresses whose localparts contain user-specified routing. Set to yes to have Postfix quote localparts containing special symbols such as the @ character for strict adherence to RFC 822.

Possible values:

yes/no

Default:

yes

Example:

resolve_dequoted_address = yes

Directory for sample Postfix configuration files. The sample files give examples and document Postfix configuration parameters.

Possible values:

directory

Default:

/etc/postfix

Example:

sample_directory = /etc/postfix

Full path to the Sendmail-compatibility sendmail command. sendmail is used primarily for sending messages from a command line or from within scripts.

Possible values:

pathname

Default:

(system dependent)

Example:

sendmail_path = /usr/sbin/sendmail

Group ID used by Postfix for mail submission and queue management. Whatever group you use should be dedicated for Postfix use only.

Possible values:

group

Default:

postdrop

Example:

setgid_group = postdrop

Service used for reporting the Postfix mail queue status. You normally do not need to change this parameter.

Possible values:

service

Default:

showq

Example:

showq_service_name = showq

IP address of the interface the SMTP client should bind to when making connections to mail servers. Setting this parameter is necessary only on multihomed systems where you explicitly must use just one of the interfaces.

Possible values:

IP address

Default:

(null)

Example:

smtp_bind_address = 192.168.15.23

Limit on the amount of time the SMTP client waits for a response from the server after sending the SMTP . (a single dot) indicating the end of the message contents.

Possible values:

time unit

Default:

600s

Example:

smtp_data_done_timeout = 600s

Limit on the amount of time the SMTP client waits while sending the message contents. If the connection stalls for more than the specified value, the SMTP client terminates the connection.

Possible values:

time unit

Default:

180s

Example:

smtp_data_xfer_timeout = 180s

Limit on the number of recipients per message delivery going out via the SMTP client.

Possible values:

count

Default:

(see example)

Example:

smtp_destination_recipient_limit = $default_destination_recipient_limit

Limit on the amount of time the SMTP client waits for a response from the server after sending the SMTP HELO command.

Possible values:

time unit

Default:

300s

Example:

smtp_helo_timeout = 300s

Limit on the amount of time the SMTP client waits for a response from the server after sending the SMTP MAIL FROM command.

Possible values:

time unit

Default:

300s

Example:

smtp_mail_timeout = 300s

Certain older Cisco PIX firewalls contain a bug that causes them to interfere with SMTP delivery when the final period and CR/LF indicating the end of message content arrive in separate packets. Postfix can automatically detect the problem and adjust for it by waiting before sending the final period and CR/LF to give the socket send buffer a chance to empty out. The smtp_pix_workaround_delay_time parameter specifies how long Postfix waits for the socket send buffer to empty.

Possible values:

time unit

Default:

10s

Example:

smtp_pix_workaround_delay_time = 10s

Limit on the amount of time the SMTP client waits for a response from the server after sending the SMTP QUIT command.

Possible values:

time unit

Default:

300s

Example:

smtp_quit_timeout = 300s

Limit on the amount of time the SMTP client waits for a response from the server after sending the SMTP RCPT TO command.

Possible values:

time unit

Default:

300s

Example:

smtp_rcpt_timeout = 300s

When an SMTP server responds with 5xx reply code, Postfix can either bounce the message or move on to any additional mail exchangers for the destination domain to see if they are able to accept the message. The parameter smtp_skip_5xx_greeting specifies whether or not Postfix should react to the reply code or move on. A value of no causes Postfix to try additional mail exchangers.

Possible values:

yes/no

Default:

yes

Example:

smtp_skip_5xx_greeting = yes

Text that follows the 220 status code in the SMTP greeting banner. If you change this parameter, be sure to include $myhostname at the start of the text, according to RFC requirements.

Possible values:

template

Default:

(see example)

Example:

smtpd_banner = $myhostname ESMTP $mail_name

List of UBE restrictions to apply when a client sends the SMTP DATA command.

Possible values:

UBE restrictions

Default:

(null)

Example:

smtpd_data_restrictions = reject_unauth_pipelining

Length of time Postfix waits initially when a client causes an error. After the number of errors exceeds the value in smtpd_soft_error_limit, Postfix increases the delay by one second for every error.

Possible values:

time unit

Default:

1s

Example:

smtpd_error_sleep_time = 1s

List of characters that are allowed in macro expansion by the SMTP server.

Possible values:

characters

Default:

(see example)

Example:

smtpd_expansion_filter = 40!"#$%&'( )*+,-./0123456789:;<=>?@ ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

Specifies whether or not Postfix requires a client to start the SMTP conversation with the HELO/EHLO command.

Possible values:

yes/no

Default:

no

Example:

smtpd_helo_required = no

Limit on the number of lines in the SMTP server command history.

Possible values:

count

Default:

100

Example:

smtpd_history_flush_threshold = 100

List of SMTP commands that Postfix should accept but take no action on. Postfix always replies to these noop commands with a status of "250 Ok."

Possible values:

explicit list

Default:

(null)

Example:

smtpd_noop_commands = vrfy, expn

Limit on the number of recipients allowed in RCPT TO commands for each message. Postfix rejects RCPT TO commands once the limit is reached.

Possible values:

count

Default:

1000

Example:

smtpd_recipient_limit = 1000

List of administrator-defined restriction class names. Each defined class can be assigned to UBE parameters.

Possible values:

list

Default:

(null)

Example:

smtpd_restriction_classes = myrestriction_a, myrestriction_b

Number of errors after which Postfix should increase delays to one second for every error.

Possible values:

count

Default:

10

Example:

smtpd_soft_error_limit = 10

Specifies whether or not mail that would normally be bounced should be queued for redelivery attempts. Also converts any permanent rejection codes to temporary error codes. This parameter is useful for testing out configuration changes to make sure that no mail is permanently rejected.

Possible values:

yes/no

Default:

no

Example:

soft_bounce = no

Specifies whether or not Postfix should accept only 7-bit text in message headers as required by the RFC. By default, if mail arrives with 8-bit text in the message headers it is rejected.

Possible values:

yes/no

Default:

no

Example:

strict_7bit_headers = no

Specifies whether or not Postfix should reject messages that contain 8-bit text that is not properly MIME-encoded.

Possible values:

yes/no

Default:

no

Example:

strict_8bitmime_body = no

Specifies whether or not Postfix requires envelope addresses to be within angle brackets (<>) and without extraneous information as required by the RFC.

Possible values:

yes/no

Default:

no

Example:

strict_rfc821_envelopes = no

UUCP uses the bang character (!) for routing email messages. The swap_bangpath parameter specifies whether or not Postfix rewrites the bang as an at sign (@) for Internet email routing.

Possible values:

yes/no

Default:

yes

Example:

swap_bangpath = yes

Name to use with the process name in syslog records.

Possible values:

string

Default:

postfix

Example:

syslog_name = postfix

Time to wait before attempting to use a previously unavailable delivery transport.

Possible values:

time unit

Default:

60s

Example:

transport_retry_time = 60s

Header line to insert when no recipients are specified in any of the To: headers (e.g., To:, Resent-To:, Cc:).

Possible values:

string

Default:

(see example)

Example:

undisclosed_recipients_header = To: undisclosed-recipients:;

SMTP response code to send when a request is rejected due to the reject_unknown_client restriction.

Possible values:

reply code

Default:

450

Example:

unknown_client_reject_code = 450

SMTP response code to send when a request is rejected because it is addressed to a nonexistent local user.

Possible values:

reply code

Default:

550

Example:

unknown_local_recipient_reject_code = 550

SMTP response code to send when a request is rejected because it is addressed to a nonexistent user at one of your virtual alias domains.

Possible values:

reply code

Default:

550

Example:

unknown_virtual_alias_reject_code = 550

VERP is a technique used with mailing lists to handle bounced messages. It combines the list owner address and original recipient address with a special delimiter character. The verp_delimiter_filter parameter specifies which characters Postfix accepts as VERP delimiter characters.

Possible values:

characters

Default:

-=+

Example:

verp_delimiter_filter = -=+

List of lookup tables used to map virtual aliases to their destination email addresses.

Possible values:

lookup tables

Default:

(null)

Example:

virtual_alias_maps = hash:/etc/postfix/virtual_alias

Base directory for virtual mailbox files. All mailbox files are found relative to the base directory.

Possible values:

directory

Default:

(null)

Example:

virtual_mailbox_base = /usr/local/virtual_mail

Limit on the size of virtual mailbox files. For maildir-style mailboxes, it limits only individual file sizes, not the overall mailbox. The value here must not be smaller than message_size_limit.

Possible values:

bytes

Default:

51200000

Example:

virtual_mailbox_limit = 51200000

List of lookup tables used to map virtual mailbox addresses to their mailbox files. Mailbox file paths are relative to virtual_mailbox_base.

Possible values:

lookup tables

Default:

(null)

Example:

virtual_mailbox_maps = hash:/etc/postfix/virtual_mailbox

Default transport to use for delivering messages to virtual mailbox addresses.

Possible values:

transport

Default:

virtual

Example:

virtual_transport = virtual