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NAME | DESCRIPTION | FILES | EXAMPLES | SEE ALSO | HISTORY | COLOPHON |
SMTPD.CONF(5) BSD File Formats Manual SMTPD.CONF(5)
smtpd.conf — Simple Mail Transfer Protocol daemon configuration file
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 (‘\’). Com‐
ments 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 com‐
menting 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 sur‐
rounded 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 speci‐
fied 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 for‐
ward 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 spec‐
ified, 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 user‐
name 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 for 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 fol‐
lowing protocols are available:
smtp Normal SMTP session with opportunistic
STARTTLS (the default).
smtp+tls Normal SMTP session with mandatory START‐
TLS.
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 ta‐
ble, 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.
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.
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 traf‐
fic is routed as efficiently as possible.
bounce warn-interval delay [, delay ...]
Send warning messages to the envelope sender when temporary
delivery failures cause a message to remain on 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 host caname, and use that file as the CA certifi‐
cate for that host. caname is the server's name, derived from
the default hostname or set using either /etc/mail/mailname or
using the hostname directive.
filter chain-name chain {filter-name [, ...]}
Register a chain of filters chain-name, consisting of the fil‐
ters listed from filter-name. Filters part of 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 but 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, else it will be run from “/usr/local/libexec/smtpd/”.
include "pathname"
Replace this directive with the content of the additional con‐
figuration file at the absolute pathname.
listen on interface [family] [options]
Listen on the interface for incoming connections, using the
same syntax as for 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 transac‐
tions after successful authentication. Users are
authenticated against either their own normal login
credentials or a credentials table authtable, the for‐
mat of which is described in table(5).
auth-optional [<authtable>]
Support SMTPAUTH optionally: clients need not authenti‐
cate, 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 associ‐
ated 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 lis‐
tener.
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 host‐
names. 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) exten‐
sion.
pki pkiname
For secure connections, use the certificate associated
with pkiname (declared in a pki directive) to prove a
mail server's identity.
port [port]
Listen on the given port instead of the default port
25.
proxy-v2
Support the PROXYv2 protocol, rewriting appropriately
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 ta‐
ble 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 exclu‐
sive 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 con‐
nection before being allowed to start an SMTP transac‐
tion. With the verify option, clients must also pro‐
vide a valid certificate to establish an SMTP session.
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 lis‐
tener.
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 dis‐
patcher 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 ta‐
ble domain.
[!] for domain regex domain | <domain>
Specify that session may address the regex or regex ta‐
ble domain.
[!] for rcpt-to recipient | <recipient>
Specify that session may address the string or list ta‐
ble recipient.
[!] for rcpt-to regex recipient | <recipient>
Specify that session may address the regex or regex ta‐
ble recipient.
[!] from any
Specify that session may originate from any source.
[!] from auth
Specify that session may originate from any authenti‐
cated 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 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:
[!] 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 transactions's MAIL FROM should match the
string or list table sender.
[!] mail-from regex sender | <sender>
Specify that transactions'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 com‐
mand 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 host pkiname, and use
that file to prove the identity of the mail server to clients.
pkiname is the server's name, derived from the default hostname
or set using either /etc/mail/mailname or using the hostname
directive. If a fallback certificate or SNI is wanted, the ‘*’
wildcard may be used as pkiname.
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 host pkiname.
pki pkiname dhe params
Specify the DHE parameters to use for DHE cipher suites with
host 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 exe‐
cuted with an absolute path, else 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 for‐
mat 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 contain‐
ing 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 con‐
taining the given static key-value pairs. The table must con‐
tain 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 sub‐
mitted, 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 exclama‐
tion mark:
!fcrdns forward-confirmed reverse DNS is invalid
Any conditions using a table may indicate that tables hold regex 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.
Descisions 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”
/etc/mail/smtpd.conf Default smtpd(8) configuration file.
/etc/mail/mailname If this file exists, the first line is used as
the server name. Otherwise, the server name
is derived from the local hostname returned by
gethostname(3), either directly if it is a
fully qualified domain name, or by retrieving
the associated canonical name through
getaddrinfo(3).
/var/run/smtpd.sock Unix domain socket for incoming SMTP connec‐
tions.
/var/spool/smtpd/ Spool directories for mail during processing.
The default smtpd.conf file which ships with OpenBSD listens on the
loopback network interface (lo0) and allows for mail from users and
daemons on the local machine, as well as permitting email to remote
servers. Some more complex configurations are given below.
This first example is the same as the default configuration, but all
outgoing mail is forwarded to a remote SMTP server. A secrets file is
needed to specify a username and password:
# touch /etc/mail/secrets
# chmod 640 /etc/mail/secrets
# chown root:_smtpd /etc/mail/secrets
# echo "bob username:password" > /etc/mail/secrets
smtpd.conf would look like this:
table aliases file:/etc/mail/aliases
table secrets file:/etc/mail/secrets
listen on lo0
action "local_mail" mbox alias <aliases>
action "outbound" relay host smtp+tls://bob@smtp.example.com \
auth <secrets>
match from local for local action "local_mail"
match from local for any action "outbound"
In this second example, the aim is to permit mail delivery and relaying
only for users that can authenticate (using their normal login creden‐
tials). An RSA certificate must be provided to prove the server's
identity. The mail server listens on all interfaces the default routes
point to. Mail with a local destination is sent to an external MDA.
First, the RSA certificate is created:
# openssl genrsa -out /etc/ssl/private/mail.example.com.key 4096
# openssl req -new -x509 -key /etc/ssl/private/mail.example.com.key \
-out /etc/ssl/mail.example.com.crt -days 365
# chmod 600 /etc/ssl/mail.example.com.crt
# chmod 600 /etc/ssl/private/mail.example.com.key
In the example above, a certificate valid for one year was created.
The configuration file would look like this:
pki mail.example.com cert "/etc/ssl/mail.example.com.crt"
pki mail.example.com key "/etc/ssl/private/mail.example.com.key"
table aliases file:/etc/mail/aliases
listen on lo0
listen on egress tls pki mail.example.com auth
action mda_with_aliases mda "/path/to/mda -f -" alias <aliases>
action mda_without_aliases mda "/path/to/mda -f -"
action "outbound" relay
match for local action mda_with_aliases
match from any for domain example.com action mda_without_aliases
match for any action "outbound"
match auth from any for any action "outbound"
For sites that wish to sign messages using DKIM, the following example
uses opensmtpd-filter-dkimsign for DKIM signing:
table aliases file:/etc/mail/aliases
filter "dkimsign" proc-exec "filter-dkimsign -d <domain> -s <selector> \
-k /etc/mail/dkim/private.key" user _dkimsign group _dkimsign
listen on socket filter "dkimsign"
listen on lo0 filter "dkimsign"
action "local_mail" mbox alias <aliases>
action "outbound" relay
match for local action "local_mail"
match for any action "outbound"
Alternatively, the opensmtpd-filter-rspamd package may be used to pro‐
vide integration with rspamd, a third-party daemon which provides mul‐
tiple antispam features as well as DKIM signing. As well as configur‐
ing rspamd itself, it requires use of the proc-exec keyword:
filter "rspamd" proc-exec "filter-rspamd"
Sites that accept non-local messages may be able to cut down on the
volume of spam received by rejecting forged messages that claim to be
from the local domain. The following example uses a list table
other-relays to specify the IP addresses of relays that may legiti‐
mately originate mail with the owner's domain as the sender.
table aliases file:/etc/mail/aliases
table other-relays file:/etc/mail/other-relays
listen on lo0
listen on egress
action "local_mail" mbox alias <aliases>
action "outbound" relay
match for local action "local_mail"
match for any action "outbound"
match !from src <other-relays> mail-from "@example.com" for any \
reject
match from any for domain example.com action "local_mail"
mailer.conf(5), table(5), makemap(8), smtpd(8)
smtpd(8) first appeared in OpenBSD 4.6.
This page is part of the OpenSMTPD (a FREE implementation of the
server-side SMTP protocol) project. Information about the project can
be found at https://www.opensmtpd.org/. If you have a bug report for
this manual page, see ⟨https://github.com/OpenSMTPD/OpenSMTPD/issues⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/OpenSMTPD/OpenSMTPD.git⟩ on 2020-08-13. (At that
time, the date of the most recent commit that was found in the reposi‐
tory was 2020-07-27.) If you discover any rendering problems in this
HTML version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or improvements to
the information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
BSD April 25, 2020 BSD