Postfix manual - access(5)

    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.

    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.

    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)