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ACCESS(5) File Formats Manual 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 expressions, 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:



  

  
When pattern matches a mail address, domain or host address,
      perform the corresponding action.

  

  
Empty lines and whitespace-only lines are ignored, as are lines whose
      first non-whitespace character is a `#'.

  

  
A logical line starts with non-whitespace text. A line that starts with
      whitespace continues a logical 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:



  

  
Matches the specified mail address.

  

  
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 configuration setting (note that
        this is the default for some versions of Postfix). Otherwise, specify
        .domain.tld (note the initial dot) in order to match
      subdomains.

  

  

  
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 recipient
    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:



  

  
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 configuration setting.
        Otherwise, specify .domain.tld (note the initial dot) in order to
        match subdomains.

  

  

  

  

  

  

  

  

  
Matches the specified IPv4 host address or subnetwork. 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 canonical form:
        do not specify unnecessary null characters, and do not enclose network
        address information with "[]" characters.

    
NOTE 2: use the cidr lookup table type to specify
        network/netmask patterns. See cidr_table(5) for details.

  

  

  

  

  

  

  

  

  
Matches the specified IPv6 host address or subnetwork. 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 canonical form:
        do not specify unnecessary null characters, and do not enclose network
        address information 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





  

  
Accept the address etc. that matches the pattern.

  

  
An all-numerical result is treated as OK. This format is generated by
      address-based relay authorization schemes such as pop-before-smtp.








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 interoperability is of no concern. The "send 521
      and disconnect" behavior is NOT defined in the SMTP standard.







  

  
Reject the address etc. that matches the pattern. Reply with
      "$access_map_reject_code optional text..." when
      the optional text is specified, otherwise reply with a generic error
      response message.

  

  
Reject the address etc. that matches the pattern. Reply with
      "$access_map_defer_code optional text..." when the
      optional text is specified, otherwise reply with a generic error response
      message.
    
This feature is available in Postfix 2.6 and later.

  

  

  
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 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, 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.

  








OTHER ACTIONS





  

  
Apply the named UCE restriction(s) (permit, reject,
      reject_unauth_destination, and so on).

  

  
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.

  

  

  
Claim successful delivery and silently discard the message. Log the
      optional text if specified, otherwise 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.

  

  

  
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.

  

  

  
After the message is queued, send the entire message through the specified
      external content filter. The transport:destination syntax is
      described in the transport(5) manual page. More information about
      external content filters is in the Postfix FILTER_README file.
    
Note: this action overrides the content_filter setting,
        and currently affects all recipients of the message.

    
This feature is available in Postfix 2.0 and later.

  

  

  
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
        $maximal_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 the specified message header to the message. When more than one
      PREPEND action executes, the first prepended header appears before the
      second etc. prepended header.
    
Note: this action must execute before the message content is
        received; it cannot execute in the context of
        smtpd_end_of_data_restrictions.

    
This feature is available in Postfix 2.1 and later.

  

  

  
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.

  

  

  
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.


    
  
  • 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.
    • 
  
  • 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 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.


Patterns are applied in the order as specified in the table, 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 description of the TCP
    client/server lookup protocol, see tcp_table(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 permits 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




Use "postconf readme_directory" or
    "postconf html_directory" to locate this information.


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