файл конфигурации демона Simple Mail Transfer Protocol (Simple Mail Transfer Protocol daemon configuration file)
Имя (Name)
smtpd.conf — Simple Mail Transfer Protocol daemon configuration
file
Описание (Description)
smtpd.conf is the configuration file for the mail daemon smtpd(8).
When mail arrives, each 'RCPT TO:' command generates a mail
envelope. If an envelope matches any of a pre-designated set of
criteria (using the match directive), the message is accepted for
delivery. A copy of the message, as well as its associated
envelopes, is saved in the mail queue and later dispatched
according to an associated set of actions (using the action
directive). If an envelope does not match any options, it is
rejected. The match rules are evaluated sequentially, with the
first match winning.
The format of the configuration file is fairly flexible. The
current line can be extended over multiple lines using a backslash
('\'). Comments can be put anywhere in the file using a hash mark
('#'), and extend to the end of the current line. Care should be
taken when commenting out multi-line text: the comment is effective
until the end of the entire block. Argument names not beginning
with a letter, digit, or underscore, as well as reserved words
(such as listen, match, and port), must be quoted. Arguments
containing whitespace should be surrounded by double quotes (").
Macros can be defined that are later expanded in context. Macro
names must start with a letter, digit, or underscore, and may
contain any of those characters, but may not be reserved words.
Macros are not expanded inside quotes. For example:
lan_addr = "192.168.0.1"
listen on $lan_addr
listen on $lan_addr tls auth
The syntax of smtpd.conf is described below.
action name method [options]
When the queue runner processes an envelope from the mail
queue, it carries out the action name, selected by the
match ... action directive when the message was received.
The action directive provides configuration data for
delivery attempts. Required lookups are performed at the
time of each delivery attempt. Consequently, changing an
action directive or the files it references and restarting
the smtpd(8) daemon causes the changes to take effect for
subsequent delivery attempts for the respective dispatcher
name, even for messages that were already stuck in the
queue prior to the configuration changes.
The delivery method parameter may be one of the following:
expand-only
Only accept the message if a delivery method was
specified in an aliases or .forward file.
forward-only
Only accept the message if the recipient results in
a remote address after the processing of aliases or
forward file.
lmtp destination [rcpt-to]
Deliver the message to an LMTP server at
destination. The location may be expressed as
host:port or as a UNIX socket.
Optionally, rcpt-to might be specified to use the
recipient email address (after expansion) instead
of the local user in the LMTP session as RCPT TO.
maildir [pathname [junk]]
Deliver the message to the maildir in pathname if
specified, or by default to ~/Maildir.
The pathname may contain format specifiers that are
expanded before use (see FORMAT SPECIFIERS).
If the junk argument is provided, the message will
be moved to the 'Junk' folder if it contains a
positive 'X-Spam' header. This folder will be
created under pathname if it does not yet exist.
mbox Deliver the message to the user's mbox with
mail.local(8).
mda command
Delegate the delivery to a command that receives
the message on its standard input.
The command may contain format specifiers that are
expanded before use (see FORMAT SPECIFIERS).
relay Relay the message to another SMTP server.
The local delivery methods support additional options:
alias <table>
Use the mapping table for aliases(5) expansion.
ttl n{s|m|h|d}
Specify how long a message may remain in the queue.
user username
Specify the username for performing the delivery,
to be looked up with getpwnam(3).
This is used for virtual hosting where a single
username is in charge of handling delivery for all
virtual users.
This option is not usable with the mbox delivery
method.
userbase <table>
Use the mapping table for user lookups instead of
the getpwnam(3) function.
The userbase does not apply to the user option.
virtual <table>
Use the mapping table for virtual expansion. The
aliasing table format is described in table(5).
wrapper name
Use the wrapper specified in mda wrapper.
The relay delivery methods also support additional options:
backup Operate as a backup mail exchanger delivering
messages to any mail exchanger with higher
priority.
backup mx name
Operate as a backup mail exchanger delivering
messages to any mail exchanger with higher priority
than mail exchanger identified as name.
helo heloname
Advertise heloname as the hostname to other mail
exchangers during the HELO phase.
helo-src <table>
Use the mapping table to look up a hostname
matching the source address, to advertise during
the HELO phase.
domain <domains>
Do not perform MX lookups but look up destination
domain in domains and use matching relay url as
relay host.
host relay-url
Do not perform MX lookups but relay messages to the
relay host described by relay-url. The format for
relay-url is [proto://[label@]]host[:port]. The
following protocols are available:
smtp Normal SMTP session with opportunistic
STARTTLS (the default).
smtp+tls Normal SMTP session with mandatory
STARTTLS.
smtp+notls Plain text SMTP session without TLS.
lmtp LMTP session. port is required.
smtps SMTP session with forced TLS on
connection, default port is 465.
Unless noted, port defaults to 25.
The label corresponds to an entry in a credentials
table, as documented in table(5). It is used with
the 'smtp+tls' and 'smtps' protocols for
authentication. Server certificates for those
protocols are verified by default.
pki pkiname
For secure connections, use the certificate
associated with pkiname (declared in a pki
directive) to prove the client's identity to the
remote mail server.
srs When relaying a mail resulting from a forward, use
the Sender Rewriting Scheme to rewrite sender
address.
tls [no-verify]
Require TLS to be used when relaying, using
mandatory STARTTLS by default. When used with a
smarthost, the protocol must not be
'smtp+notls://'. If no-verify is specified, do not
require a valid certificate.
protocols protostr
Define the protocol versions to be used for TLS
sessions. Refer to the
tls_config_parse_protocols(3) manpage for the
format of protostr.
ciphers cipherstr
Define the list of ciphers that may be used for TLS
sessions. Refer to the tls_config_set_ciphers(3)
manpage for the format of cipherstr.
auth <table>
Use the mapping table for connecting to relay-url
using credentials. This option is usable only with
host option. The credential table format is
described in table(5).
mail-from mailaddr
Use mailaddr as the MAIL FROM address within the
SMTP transaction.
src sourceaddr | <sourceaddr>
Use the string or list table sourceaddr for the
source IP address, which is useful on machines with
multiple interfaces. If the list contains more
than one address, all of them are used in such a
way that traffic is routed as efficiently as
possible.
admd authservid
The Administrative Management Domain this mail server
belongs to. The authservid will be forwarded to filters
using it to identify or mark authentication-results
headers. If omitted it defaults to the server name.
bounce warn-interval delay [, delay ...]
Send warning messages to the envelope sender when temporary
delivery failures cause a message to remain in the queue
for longer than delay. Each delay parameter consists of a
positive decimal integer and a unit s, m, h, or d. At most
four delay parameters can be specified. The default is
"bounce warn-interval 4h", sending a single warning after
four hours.
ca caname cert cafile
Associate the Certificate Authority (CA) certificate file
cafile with ca entry caname. The ca entry can be
referenced in listener rules and relay actions.
filter chain-name chain {filter-name [, ...]}
Register a chain of filters chain-name, consisting of the
filters listed in filter-name. Filters in a filter chain
are executed in order of declaration for each phase that
they are registered for. A filter chain may be used in
place of a filter for any directive except filter chains
themselves.
filter filter-name phase phase-name match conditions decision
Register a filter filter-name. A decision about what to do
with the mail is taken at phase phase-name when matching
conditions. Phases, matching conditions, and decisions are
described in MAIL FILTERING, below.
filter filter-name proc proc-name
Register "proc" filter filter-name backed by the proc-name
process.
filter filter-name proc-exec command
Register and execute "proc" filter filter-name from
command. If command starts with a slash it is executed
with an absolute path, otherwise it will be run from
'/usr/local/libexec/smtpd/'.
include "pathname"
Replace this directive with the content of the additional
configuration file at the absolute pathname.
listen on interface [family] [options]
Listen on the interface for incoming connections, using the
same syntax as ifconfig(8). The interface parameter may
also be an interface group, an IP address, or a domain
name. Listening can optionally be restricted to a specific
address family, which can be either inet4 or inet6.
The options are as follows:
auth [<authtable>]
Support SMTPAUTH: clients may only start SMTP
transactions after successful authentication.
Users are authenticated against either their own
normal login credentials or a credentials table
authtable, the format of which is described in
table(5).
auth-optional [<authtable>]
Support SMTPAUTH optionally: clients need not
authenticate, but may do so. This allows a listen
on directive to both accept incoming mail from
untrusted senders and permit outgoing mail from
authenticated users (using match auth). It can be
used in situations where it is not possible to
listen on a separate port (usually the submission
port, 587) for users to authenticate.
ca caname
For secure connections, use the CA certificate
associated with caname (declared in a ca directive)
as the CA certificate when verifying client
certificates.
filter name
Apply filter name on connections handled by this
listener.
hostname hostname
Use hostname in the greeting banner instead of the
default server name.
hostnames <names>
Override the server name for specific addresses.
The names table contains a mapping of IP addresses
to hostnames. If the address on which the
connection arrives appears in the mapping, the
associated hostname is used.
mask-src
Omit the from part when prepending 'Received'
headers.
no-dsn Disable the DSN (Delivery Status Notification)
extension.
pki pkiname
For secure connections, use the certificate
associated with pkiname (declared in a pki
directive) to prove a mail server's identity. This
option can be used multiple times to provide
alternate certificates for SNI.
port [port]
Listen on the given port instead of the default
port 25.
proxy-v2
Support the PROXYv2 protocol, appropriately
rewriting the source address received from proxy.
received-auth
In 'Received' headers, report whether the session
was authenticated and by which local user.
senders <users> [masquerade]
Look up the authenticated user in the users mapping
table to find the email addresses that user is
allowed to submit mail as. In addition, if the
masquerade option is provided, the From header is
rewritten to match the sender provided in the SMTP
session.
smtps Support SMTPS, by default on port 465. Mutually
exclusive with tls.
tag tag
Clients connecting to the listener are tagged with
the given tag.
tls Support STARTTLS, by default on port 25. Mutually
exclusive with smtps.
tls-require [verify]
Like tls, but force clients to establish a secure
connection before being allowed to start an SMTP
transaction. With the verify option, clients must
also provide a valid certificate to establish an
SMTP session.
protocols protostr
Define the protocol versions to be used for TLS
sessions. Refer to the
tls_config_parse_protocols(3) manpage for the
format of protostr.
ciphers cipherstr
Define the list of ciphers that may be used for TLS
sessions. Refer to the tls_config_set_ciphers(3)
manpage for the format of cipherstr.
listen on socket [options]
Listen for incoming SMTP connections on the Unix domain
socket /var/run/smtpd.sock. This is done by default, even
if the directive is absent.
The options are as follows:
filter name
Apply filter name on connections handled by this
listener.
mask-src
Omit the from part when prepending 'Received'
headers.
tag tag
Clients connecting to the listener are tagged with
the given tag.
match options action name
If at least one mail envelope matches the options of one
match action directive, receive the incoming message, put a
copy into each matching envelope, and atomically save the
envelopes to the mail spool for later processing by the
respective dispatcher name.
The following matching options are supported and can all be
negated:
[!] for any
Specify that session may address any destination.
[!] for local
Specify that session may address any local domain.
This is the default, and may be omitted.
[!] for domain domain | <domain>
Specify that session may address the string or list
table domain.
[!] for domain regex domain | <domain>
Specify that session may address the regex or regex
table domain.
[!] for rcpt-to recipient | <recipient>
Specify that session may address the string or list
table recipient.
[!] for rcpt-to regex recipient | <recipient>
Specify that session may address the regex or regex
table recipient.
[!] from any
Specify that session may originate from any source.
[!] from auth
Specify that session may originate from any
authenticated user, no matter the source IP
address.
[!] from auth user | <user>
Specify that session may originate from
authenticated user or user list user, no matter the
source IP address.
[!] from auth regex user | <user>
Specify that session may originate from
authenticated regex or regex list user, no matter
the source IP address.
[!] from local
Specify that session may only originate from a
local IP address, or from the local enqueuer. This
is the default, and may be omitted.
[!] from mail-from sender | <sender>
Specify that session may originate from sender or
sender list sender, no matter the source IP
address.
[!] from mail-from regex sender | <sender>
Specify that session may originate from regex or
regex list sender, no matter the source IP address.
[!] from rdns
Specify that session may only originate from an IP
address that resolves to a reverse DNS.
[!] from rdns hostname | <hostname>
Specify that session may only originate from an IP
address that resolves to a reverse DNS matching
string or list string hostname.
[!] from rdns regex hostname | <hostname>
Specify that session may only originate from an IP
address that resolves to a reverse DNS matching
regex or list regex hostname.
[!] from socket
Specify that session may only originate from the
local enqueuer.
[!] from src address | <address>
Specify that session may only originate from string
or list table address which can be a specific
address or a subnet expressed in CIDR-notation.
[!] from src regex address | <address>
Specify that session may only originate from regex
or regex table address which can be a specific
address or a subnet expressed in CIDR-notation.
In addition, the following transaction options may be
matched:
[!] auth
Matches transactions which have been authenticated.
[!] auth username | <username>
Matches transactions which have been authenticated
for user or user list username.
[!] auth regex username | <username>
Matches transactions which have been authenticated
for regex or regex list username.
[!] helo helo-name | <helo-name>
Specify that session's HELO / EHLO should match the
string or list table helo-name.
[!] helo regex helo-name | <helo-name>
Specify that session's HELO / EHLO should match the
regex or regex table helo-name.
[!] mail-from sender | <sender>
Specify that transaction's MAIL FROM should match
the string or list table sender.
[!] mail-from regex sender | <sender>
Specify that transaction's MAIL FROM should match
the regex or regex table sender.
[!] rcpt-to recipient | <recipient>
Specify that transaction's RCPT TO should match the
string or list table recipient.
[!] rcpt-to regex recipient | <recipient>
Specify that transaction's RCPT TO should match the
regex or regex table recipient.
[!] tag tag
Matches transactions tagged with the given tag.
[!] tag regex tag
Matches transactions tagged with the given tag
regex.
[!] tls
Specify that transaction should take place in a TLS
channel.
match options reject
Reject the incoming message during the SMTP dialogue. The
same options are supported as for the match action
directive.
mda wrapper name command
Associate command with the mail delivery agent wrapper
named name. When a local delivery specifies a wrapper, the
command associated with the wrapper will be executed
instead. The command may contain format specifiers (see
FORMAT SPECIFIERS).
mta max-deferred number
When delivery to a given host is suspended due to temporary
failures, cache at most number envelopes for that host such
that they can be delivered as soon as another delivery
succeeds to that host. The default is 100.
pki pkiname cert certfile
Associate certificate file certfile with pki entry pkiname.
The pki entry defines a keypair configuration that can be
referenced in listener rules and relay actions.
A certificate chain may be created by appending one or many
certificates, including a Certificate Authority
certificate, to certfile. The creation of certificates is
documented in starttls(8).
pki pkiname key keyfile
Associate the key located in keyfile with pki entry
pkiname.
pki pkiname dhe params
Specify the DHE parameters to use for DHE cipher suites
with pki entry pkiname. Valid parameter values are none,
legacy, and auto. For legacy, a fixed key length of 1024
bits is used, whereas for auto, the key length is
determined automatically. The default is none, which
disables DHE cipher suites.
proc proc-name command
Register an external process named proc-name from command.
Such processes may be used to share the same instance
between multiple filters. If command starts with a slash
it is executed with an absolute path, otherwise it will be
run from '/usr/local/libexec/smtpd/'.
queue compression
Store queue files in a compressed format. This may be
useful to save disk space.
queue encryption [key]
Encrypt queue files with EVP_aes_256_gcm(3). If no key is
specified, it is read with getpass(3). If the string stdin
or a single dash ('-') is given instead of a key, the key
is read from the standard input.
queue ttl delay
Set the default expiration time for temporarily
undeliverable messages, given as a positive decimal integer
followed by a unit s, m, h, or d. The default is four days
(4d).
smtp ciphers control
Set the control string for SSL_CTX_set_cipher_list(3). The
default is "HIGH:!aNULL:!MD5".
smtp limit max-mails count
Limit the number of messages to count for each session.
The default is 100.
smtp limit max-rcpt count
Limit the number of recipients to count for each
transaction. The default is 1000.
smtp max-message-size size
Reject messages larger than size, given as a positive
number of bytes or as a string to be parsed with
scan_scaled(3). The default is "35M".
smtp sub-addr-delim character
When resolving the local part of a local email address,
ignore the ASCII character and all characters following it.
The default is '+'.
srs key secret
Set the secret key to use for SRS, the Sender Rewriting
Scheme.
srs key backup secret
Set a backup secret key to use as a fallback for SRS. This
can be used to implement SRS key rotation.
srs ttl delay
Set the time-to-live delay for SRS envelopes. After this
delay, a bounce reply to the SRS address will be discarded
to limit risks of forged addresses. The default is four
days (4d).
table name [type:]pathname
Tables provide additional configuration information for
smtpd(8) in the form of lists or key-value mappings. The
format of the entries depends on what the table is used
for. Refer to table(5) for the exhaustive documentation.
Each table is identified by an arbitrary, unique name.
If the type is db, information is stored in a file created
with makemap(8); if it is file or omitted, information is
stored in a plain text file using the format described in
table(5). The pathname to the file must be absolute.
table name {value [, ...]}
Instead of using a separate file, declare a list table
containing the given static values. The table must contain
at least one value and may declare multiple values as a
comma-separated (whitespace optional) list.
table name {key=value [, ...]}
Instead of using a separate file, declare a mapping table
containing the given static key-value pairs. The table
must contain at least one key-value pair and may declare
multiple pairs as a comma-separated (whitespace optional)
list.
MAIL FILTERING
In a regular workflow, smtpd(8) may accept or reject a message
based only on the content of envelopes. Its decisions are about
the handling of the message, not about the handling of an active
session.
Filtering extends the decision making process by allowing smtpd(8)
to stop at each phase of an SMTP session, check that conditions are
met, then decide if a session is allowed to move forward.
With filtering, a session may be interrupted at any phase before an
envelope is complete. A message may also be rejected after being
submitted, regardless of whether the envelope was accepted or not.
The following phases are currently supported:
connect upon connection, before a banner is displayed
helo after HELO command is submitted
ehlo after EHLO command is submitted
mail-from after MAIL FROM command is submitted
rcpt-to after RCPT TO command is submitted
data after DATA command is submitted
commit after message is fully is submitted
At each phase, various conditions may be matched. The fcrdns,
rdns, and src data are available in all phases, but other data must
have been already submitted before they are available.
fcrdns forward-confirmed reverse DNS is
valid
rdns session has a reverse DNS
rdns <table> session has a reverse DNS in table
src <table> source address is in table
helo <table> helo name is in table
auth session is authenticated
auth <table> session username is in table
mail-from <table> sender address is in table
rcpt-to <table> recipient address is in table
These conditions may all be negated by prefixing them with an
exclamation mark:
!fcrdns forward-confirmed reverse DNS is
invalid
Any conditions using a table may indicate that the table contains
regular expressions by prefixing the table name with the keyword
regex.
helo regex <table> helo name matches a regex in table
Finally, a number of decisions may be taken:
bypass the session or transaction bypasses
filters
disconnect message the session is disconnected with
message
junk the session or transaction is
junked, i.e., an 'X-Spam: yes'
header is added to any messages
reject message the command is rejected with message
rewrite value the command parameter is rewritten
with value
Decisions that involve a message require that the message be RFC
valid, meaning that they should either start with a 4xx or 5xx
status code. Decisions can be taken at any phase, though junking
can only happen before a message is committed.
FORMAT SPECIFIERS
Some configuration directives support expansion of their parameters
at runtime. Such directives (for example action maildir, action
mda) may use format specifiers which are expanded before delivery
or relaying. The following formats are currently supported:
%{sender} sender email address, may be empty
string
%{sender.user} user part of the sender email address,
may be empty
%{sender.domain} domain part of the sender email address,
may be empty
%{rcpt} recipient email address
%{rcpt.user} user part of the recipient email address
%{rcpt.domain} domain part of the recipient email
address
%{dest} recipient email address after expansion
%{dest.user} user part after expansion
%{dest.domain} domain part after expansion
%{user.username} local user
%{user.directory} home directory of the local user
%{mbox.from} name used in mbox From separator lines
%{mda} mda command, only available for mda
wrappers
Expansion formats also support partial expansion using the optional
bracket notations with substring offset. For example, with
recipient domain 'example.org':
%{rcpt.domain[0]} expands to 'e'
%{rcpt.domain[1]} expands to 'x'
%{rcpt.domain[8:]} expands to 'org'
%{rcpt.domain[-3:]} expands to 'org'
%{rcpt.domain[0:6]} expands to 'example'
%{rcpt.domain[0:-4]} expands to 'example'
In addition, modifiers may be applied to the token. For example,
with recipient 'User+Tag@Example.org':
%{rcpt:lowercase} expands to 'user+tag@example.org'
%{rcpt:uppercase} expands to 'USER+TAG@EXAMPLE.ORG'
%{rcpt:strip} expands to 'User@Example.org'
%{rcpt:lowercase|strip} expands to 'user@example.org'
For security concerns, expanded values are sanitized and
potentially dangerous characters are replaced with ':'. In
situations where they are desirable, the 'raw' modifier may be
applied. For example, with recipient 'user+t?g@example.org':
%{rcpt} expands to 'user+t:g@example.org'
%{rcpt:raw} expands to 'user+t?g@example.org'
