ACCESS(5) ACCESS(5)
NAME
access - Postfix SMTP server access table
SYNOPSIS
postmap /etc/postfix/access
postmap -q "string" /etc/postfix/access
postmap -q - /etc/postfix/access <inputfile
DESCRIPTION
This document describes access control on remote SMTP
client information: host names, network addresses, and
envelope sender or recipient addresses; it is implemented
by the Postfix SMTP server. See header_checks(5) or
body_checks(5) for access control on the content of email
messages.
Normally, the access(5) table is specified as a text file
that serves as input to the postmap(1) command. The
result, an indexed file in dbm or db format, is used for
fast searching by the mail system. Execute the command
"postmap /etc/postfix/access" to rebuild an indexed file
after changing the corresponding text file.
When the table is provided via other means such as NIS,
LDAP or SQL, the same lookups are done as for ordinary
indexed files.
Alternatively, the table can be provided as a regular-
expression map where patterns are given as regular expres-
sions, or lookups can be directed to TCP-based server. In
those cases, the lookups are done in a slightly different
way as described below under "REGULAR EXPRESSION TABLES"
or "TCP-BASED TABLES".
CASE FOLDING
The search string is folded to lowercase before database
lookup. As of Postfix 2.3, the search string is not case
folded with database types such as regexp: or pcre: whose
lookup fields can match both upper and lower case.
TABLE FORMAT
The input format for the postmap(1) command is as follows:
pattern action
When pattern matches a mail address, domain or host
address, perform the corresponding action.
blank lines and comments
Empty lines and whitespace-only lines are ignored,
as are lines whose first non-whitespace character
is a `#'.
multi-line text
A logical line starts with non-whitespace text. A
line that starts with whitespace continues a logi-
cal line.
EMAIL ADDRESS PATTERNS
With lookups from indexed files such as DB or DBM, or from
networked tables such as NIS, LDAP or SQL, patterns are
tried in the order as listed below:
user@domain
Matches the specified mail address.
domain.tld
Matches domain.tld as the domain part of an email
address.
The pattern domain.tld also matches subdomains, but
only when the string smtpd_access_maps is listed in
the Postfix parent_domain_matches_subdomains con-
figuration setting.
.domain.tld
Matches subdomains of domain.tld, but only when the
string smtpd_access_maps is not listed in the Post-
fix parent_domain_matches_subdomains configuration
setting.
user@ Matches all mail addresses with the specified user
part.
Note: lookup of the null sender address is not possible
with some types of lookup table. By default, Postfix uses
<> as the lookup key for such addresses. The value is
specified with the smtpd_null_access_lookup_key parameter
in the Postfix main.cf file.
EMAIL ADDRESS EXTENSION
When a mail address localpart contains the optional recip-
ient delimiter (e.g., user+foo@domain), the lookup order
becomes: user+foo@domain, user@domain, domain, user+foo@,
and user@.
HOST NAME/ADDRESS PATTERNS
With lookups from indexed files such as DB or DBM, or from
networked tables such as NIS, LDAP or SQL, the following
lookup patterns are examined in the order as listed:
domain.tld
Matches domain.tld.
The pattern domain.tld also matches subdomains, but
only when the string smtpd_access_maps is listed in
the Postfix parent_domain_matches_subdomains con-
figuration setting.
.domain.tld
Matches subdomains of domain.tld, but only when the
string smtpd_access_maps is not listed in the Post-
fix parent_domain_matches_subdomains configuration
setting.
net.work.addr.ess
net.work.addr
net.work
net Matches the specified IPv4 host address or subnet-
work. An IPv4 host address is a sequence of four
decimal octets separated by ".".
Subnetworks are matched by repeatedly truncating
the last ".octet" from the remote IPv4 host address
string until a match is found in the access table,
or until further truncation is not possible.
NOTE 1: The access map lookup key must be in canon-
ical form: do not specify unnecessary null charac-
ters, and do not enclose network address informa-
tion with "[]" characters.
NOTE 2: use the cidr lookup table type to specify
network/netmask patterns. See cidr_table(5) for
details.
net:work:addr:ess
net:work:addr
net:work
net Matches the specified IPv6 host address or subnet-
work. An IPv6 host address is a sequence of three
to eight hexadecimal octet pairs separated by ":".
Subnetworks are matched by repeatedly truncating
the last ":octetpair" from the remote IPv6 host
address string until a match is found in the access
table, or until further truncation is not possible.
NOTE 1: the truncation and comparison are done with
the string representation of the IPv6 host address.
Thus, not all the ":" subnetworks will be tried.
NOTE 2: The access map lookup key must be in canon-
ical form: do not specify unnecessary null charac-
ters, and do not enclose network address informa-
tion with "[]" characters.
NOTE 3: use the cidr lookup table type to specify
network/netmask patterns. See cidr_table(5) for
details.
IPv6 support is available in Postfix 2.2 and later.
ACCEPT ACTIONS
OK Accept the address etc. that matches the pattern.
all-numerical
An all-numerical result is treated as OK. This for-
mat is generated by address-based relay authoriza-
tion schemes such as pop-before-smtp.
For other accept actions, see "OTHER ACTIONS" below.
REJECT ACTIONS
Postfix version 2.3 and later support enhanced status
codes as defined in RFC 3463. When no code is specified
at the beginning of the text below, Postfix inserts a
default enhanced status code of "5.7.1" in the case of
reject actions, and "4.7.1" in the case of defer actions.
See "ENHANCED STATUS CODES" below.
4NN text
5NN text
Reject the address etc. that matches the pattern,
and respond with the numerical three-digit code and
text. 4NN means "try again later", while 5NN means
"do not try again".
The following responses have special meaning for
the Postfix SMTP server:
421 text (Postfix 2.3 and later)
521 text (Postfix 2.6 and later)
After responding with the numerical three-
digit code and text, disconnect immediately
from the SMTP client. This frees up SMTP
server resources so that they can be made
available to another SMTP client.
Note: The "521" response should be used only
with botnets and other malware where inter-
operability is of no concern. The "send 521
and disconnect" behavior is NOT defined in
the SMTP standard.
REJECT optional text...
Reject the address etc. that matches the pattern.
Reply with "$access_map_reject_code optional
text..." when the optional text is specified, oth-
erwise reply with a generic error response message.
DEFER optional text...
Reject the address etc. that matches the pattern.
Reply with "$access_map_defer_code optional
text..." when the optional text is specified, oth-
erwise reply with a generic error response message.
This feature is available in Postfix 2.6 and later.
DEFER_IF_REJECT optional text...
Defer the request if some later restriction would
result in a REJECT action. Reply with
"$access_map_defer_code 4.7.1 optional text..."
when the optional text is specified, otherwise
reply with a generic error response message.
Prior to Postfix 2.6, the SMTP reply code is 450.
This feature is available in Postfix 2.1 and later.
DEFER_IF_PERMIT optional text...
Defer the request if some later restriction would
result in a an explicit or implicit PERMIT action.
Reply with "$access_map_defer_code 4.7.1 optional
text..." when the optional text is specified, oth-
erwise reply with a generic error response message.
Prior to Postfix 2.6, the SMTP reply code is 450.
This feature is available in Postfix 2.1 and later.
For other reject actions, see "OTHER ACTIONS" below.
OTHER ACTIONS
restriction...
Apply the named UCE restriction(s) (permit, reject,
reject_unauth_destination, and so on).
BCC user@domain
Send one copy of the message to the specified
recipient.
If multiple BCC actions are specified within the
same SMTP MAIL transaction, only the last action
will be used.
This feature is not part of the stable Postfix
release.
DISCARD optional text...
Claim successful delivery and silently discard the
message. Log the optional text if specified, oth-
erwise log a generic message.
Note: this action currently affects all recipients
of the message. To discard only one recipient
without discarding the entire message, use the
transport(5) table to direct mail to the discard(8)
service.
This feature is available in Postfix 2.0 and later.
DUNNO Pretend that the lookup key was not found. This
prevents Postfix from trying substrings of the
lookup key (such as a subdomain name, or a network
address subnetwork).
This feature is available in Postfix 2.0 and later.
FILTER transport:destination
After the message is queued, send the entire mes-
sage through the specified external content filter.
The transport name specifies the first field of a
mail delivery agent definition in master.cf; the
syntax of the next-hop destination is described in
the manual page of the corresponding delivery
agent. More information about external content
filters is in the Postfix FILTER_README file.
Note 1: do not use $number regular expression sub-
stitutions for transport or destination unless you
know that the information has a trusted origin.
Note 2: this action overrides the main.cf con-
tent_filter setting, and affects all recipients of
the message. In the case that multiple FILTER
actions fire, only the last one is executed.
Note 3: the purpose of the FILTER command is to
override message routing. To override the recipi-
ent's transport but not the next-hop destination,
specify an empty filter destination (Postfix 2.7
and later), or specify a transport:destination that
delivers through a different Postfix instance
(Postfix 2.6 and earlier). Other options are using
the recipient-dependent transport_maps or the sen-
der-dependent sender_dependent_default_transport-
_maps features.
This feature is available in Postfix 2.0 and later.
HOLD optional text...
Place the message on the hold queue, where it will
sit until someone either deletes it or releases it
for delivery. Log the optional text if specified,
otherwise log a generic message.
Mail that is placed on hold can be examined with
the postcat(1) command, and can be destroyed or
released with the postsuper(1) command.
Note: use "postsuper -r" to release mail that was
kept on hold for a significant fraction of $maxi-
mal_queue_lifetime or $bounce_queue_lifetime, or
longer. Use "postsuper -H" only for mail that will
not expire within a few delivery attempts.
Note: this action currently affects all recipients
of the message.
This feature is available in Postfix 2.0 and later.
PREPEND headername: headervalue
Prepend the specified message header to the mes-
sage. When more than one PREPEND action executes,
the first prepended header appears before the sec-
ond etc. prepended header.
Note: this action must execute before the message
content is received; it cannot execute in the con-
text of smtpd_end_of_data_restrictions.
This feature is available in Postfix 2.1 and later.
REDIRECT user@domain
After the message is queued, send the message to
the specified address instead of the intended
recipient(s).
Note: this action overrides the FILTER action, and
currently affects all recipients of the message.
This feature is available in Postfix 2.1 and later.
WARN optional text...
Log a warning with the optional text, together with
client information and if available, with helo,
sender, recipient and protocol information.
This feature is available in Postfix 2.1 and later.
ENHANCED STATUS CODES
Postfix version 2.3 and later support enhanced status
codes as defined in RFC 3463. When an enhanced status
code is specified in an access table, it is subject to
modification. The following transformations are needed
when the same access table is used for client, helo,
sender, or recipient access restrictions; they happen
regardless of whether Postfix replies to a MAIL FROM, RCPT
TO or other SMTP command.
o When a sender address matches a REJECT action, the
Postfix SMTP server will transform a recipient DSN
status (e.g., 4.1.1-4.1.6) into the corresponding
sender DSN status, and vice versa.
o When non-address information matches a REJECT
action (such as the HELO command argument or the
client hostname/address), the Postfix SMTP server
will transform a sender or recipient DSN status
into a generic non-address DSN status (e.g.,
4.0.0).
REGULAR EXPRESSION TABLES
This section describes how the table lookups change when
the table is given in the form of regular expressions. For
a description of regular expression lookup table syntax,
see regexp_table(5) or pcre_table(5).
Each pattern is a regular expression that is applied to
the entire string being looked up. Depending on the appli-
cation, that string is an entire client hostname, an
entire client IP address, or an entire mail address. Thus,
no parent domain or parent network search is done,
user@domain mail addresses are not broken up into their
user@ and domain constituent parts, nor is user+foo broken
up into user and foo.
Patterns are applied in the order as specified in the ta-
ble, until a pattern is found that matches the search
string.
Actions are the same as with indexed file lookups, with
the additional feature that parenthesized substrings from
the pattern can be interpolated as $1, $2 and so on.
TCP-BASED TABLES
This section describes how the table lookups change when
lookups are directed to a TCP-based server. For a descrip-
tion of the TCP client/server lookup protocol, see tcp_ta-
ble(5). This feature is not available up to and including
Postfix version 2.4.
Each lookup operation uses the entire query string once.
Depending on the application, that string is an entire
client hostname, an entire client IP address, or an entire
mail address. Thus, no parent domain or parent network
search is done, user@domain mail addresses are not broken
up into their user@ and domain constituent parts, nor is
user+foo broken up into user and foo.
Actions are the same as with indexed file lookups.
EXAMPLE
The following example uses an indexed file, so that the
order of table entries does not matter. The example per-
mits access by the client at address 1.2.3.4 but rejects
all other clients in 1.2.3.0/24. Instead of hash lookup
tables, some systems use dbm. Use the command "postconf
-m" to find out what lookup tables Postfix supports on
your system.
/etc/postfix/main.cf:
smtpd_client_restrictions =
check_client_access hash:/etc/postfix/access
/etc/postfix/access:
1.2.3 REJECT
1.2.3.4 OK
Execute the command "postmap /etc/postfix/access" after
editing the file.
BUGS
The table format does not understand quoting conventions.
SEE ALSO
postmap(1), Postfix lookup table manager
smtpd(8), SMTP server
postconf(5), configuration parameters
transport(5), transport:nexthop syntax
README FILES
SMTPD_ACCESS_README, built-in SMTP server access control
DATABASE_README, Postfix lookup table overview
LICENSE
The Secure Mailer license must be distributed with this
software.
AUTHOR(S)
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
ACCESS(5)