Provided by: postfix_2.9.1-4_i386 bug

NAME

       ldap_table - Postfix LDAP client configuration

SYNOPSIS

       postmap -q "string" ldap:/etc/postfix/filename

       postmap -q - ldap:/etc/postfix/filename <inputfile

DESCRIPTION

       The  Postfix  mail system uses optional tables for address rewriting or
       mail routing. These tables are usually in dbm or db format.

       Alternatively, lookup tables can be specified as LDAP databases.

       In order to use LDAP lookups, define an LDAP source as a  lookup  table
       in main.cf, for example:

           alias_maps = ldap:/etc/postfix/ldap-aliases.cf

       The  file  /etc/postfix/ldap-aliases.cf  has  the  same  format  as the
       Postfix main.cf file, and can specify the parameters  described  below.
       An example is given at the end of this manual.

       This  configuration  method  is  available with Postfix version 2.1 and
       later.  See the  section  "BACKWARDS  COMPATIBILITY"  below  for  older
       Postfix versions.

       For  details  about  LDAP  SSL and STARTTLS, see the section on SSL and
       STARTTLS below.

BACKWARDS COMPATIBILITY

       For backwards compatibility with Postfix version 2.0 and earlier,  LDAP
       parameters  can  also  be defined in main.cf.  Specify as LDAP source a
       name that doesn't begin with a slash or a  dot.   The  LDAP  parameters
       will  then  be  accessible  as  the name you've given the source in its
       definition, an underscore, and the name of the parameter.  For example,
       if  the  map  is  specified  as  "ldap:ldapsource",  the  "server_host"
       parameter    below    would    be     defined     in     main.cf     as
       "ldapsource_server_host".

       Note: with this form, the passwords for the LDAP sources are written in
       main.cf, which is normally world-readable.  Support for this form  will
       be removed in a future Postfix version.

       For   backwards   compatibility   with   the   pre  2.2  LDAP  clients,
       result_filter can for now be used instead of  result_format,  when  the
       latter  parameter  is  not  also set.  The new name better reflects the
       function of the parameter. This compatibility interface may be  removed
       in a future release.

LIST MEMBERSHIP

       When  using  LDAP  to  store lists such as $mynetworks, $mydestination,
       $relay_domains,  $local_recipient_maps,  etc.,  it  is   important   to
       understand  that  the  table  must store each list member as a separate
       key. The table lookup verifies the *existence* of the key. See "Postfix
       lists versus tables" in the DATABASE_README document for a discussion.

       Do  NOT  create  tables  that  return  the  full  list  of  domains  in
       $mydestination or $relay_domains etc., or IP addresses in $mynetworks.

       DO create tables with each matching item as a key and with an arbitrary
       value. With LDAP databases it is not uncommon to return the key itself.

       For example, NEVER do this in a map defining $mydestination:

           query_filter = domain=*
           result_attribute = domain

       Do this instead:

           query_filter = domain=%s
           result_attribute = domain

GENERAL LDAP PARAMETERS

       In  the  text  below,  default  values are given in parentheses.  Note:
       don't use quotes in these variables; at least, not  until  the  Postfix
       configuration routines understand how to deal with quoted strings.

       server_host (default: localhost)
              The name of the host running the LDAP server, e.g.

                  server_host = ldap.example.com

              Depending  on the LDAP client library you're using, it should be
              possible to specify multiple  servers  here,  with  the  library
              trying  them  in order should the first one fail. It should also
              be possible to give each server in the  list  a  different  port
              (overriding server_port below), by naming them like

                  server_host = ldap.example.com:1444

              With OpenLDAP, a (list of) LDAP URLs can be used to specify both
              the hostname(s) and the port(s):

                  server_host = ldap://ldap.example.com:1444
                              ldap://ldap2.example.com:1444

              All LDAP URLs accepted by the OpenLDAP  library  are  supported,
              including  connections  over  UNIX  domain sockets, and LDAP SSL
              (the last one provided that OpenLDAP was compiled  with  support
              for SSL):

                  server_host = ldapi://%2Fsome%2Fpath
                              ldaps://ldap.example.com:636

       server_port (default: 389)
              The port the LDAP server listens on, e.g.

                  server_port = 778

       timeout (default: 10 seconds)
              The number of seconds a search can take before timing out, e.g.

                  timeout = 5

       search_base (No default; you must configure this)
              The RFC2253 base DN at which to conduct the search, e.g.

                  search_base = dc=your, dc=com

              With Postfix 2.2 and later this parameter supports the following
              '%' expansions:

              %%     This is replaced by a literal '%' character.

              %s     This is replaced by the input key.  RFC 2253  quoting  is
                     used  to  make  sure  that  the  input  key  does not add
                     unexpected metacharacters.

              %u     When the input key is an address of the form user@domain,
                     %u is replaced by the (RFC 2253) quoted local part of the
                     address.  Otherwise, %u is replaced by the entire  search
                     string.   If  the  localpart  is  empty,  the  search  is
                     suppressed and returns no results.

              %d     When the input key is an address of the form user@domain,
                     %d  is  replaced  by the (RFC 2253) quoted domain part of
                     the address.  Otherwise, the  search  is  suppressed  and
                     returns no results.

              %[SUD] For the search_base parameter, the upper-case equivalents
                     of the  above  expansions  behave  identically  to  their
                     lower-case    counter-parts.   With   the   result_format
                     parameter  (previously  called  result_filter   see   the
                     COMPATIBILITY  section  and  below),  they  expand to the
                     corresponding components of input  key  rather  than  the
                     result value.

              %[1-9] The   patterns  %1,  %2,  ...  %9  are  replaced  by  the
                     corresponding most significant  component  of  the  input
                     key's  domain. If the input key is user@mail.example.com,
                     then %1 is com, %2 is example and  %3  is  mail.  If  the
                     input  key  is unqualified or does not have enough domain
                     components to satisfy all  the  specified  patterns,  the
                     search is suppressed and returns no results.

       query_filter (default: mailacceptinggeneralid=%s)
              The  RFC2254  filter used to search the directory, where %s is a
              substitute for the address Postfix is trying to resolve, e.g.

                  query_filter = (&(mail=%s)(paid_up=true))

              This parameter supports the following '%' expansions:

              %%     This is replaced by a literal '%' character. (Postfix 2.2
                     and later).

              %s     This  is  replaced by the input key.  RFC 2254 quoting is
                     used to make  sure  that  the  input  key  does  not  add
                     unexpected metacharacters.

              %u     When the input key is an address of the form user@domain,
                     %u is replaced by the (RFC 2254) quoted local part of the
                     address.   Otherwise, %u is replaced by the entire search
                     string.   If  the  localpart  is  empty,  the  search  is
                     suppressed and returns no results.

              %d     When the input key is an address of the form user@domain,
                     %d is replaced by the (RFC 2254) quoted  domain  part  of
                     the  address.   Otherwise,  the  search is suppressed and
                     returns no results.

              %[SUD] The upper-case equivalents of the above expansions behave
                     in the query_filter parameter identically to their lower-
                     case  counter-parts.  With  the  result_format  parameter
                     (previously  called  result_filter  see the COMPATIBILITY
                     section and below),  they  expand  to  the  corresponding
                     components of input key rather than the result value.

                     The  above  %S,  %U  and %D expansions are available with
                     Postfix 2.2 and later.

              %[1-9] The  patterns  %1,  %2,  ...  %9  are  replaced  by   the
                     corresponding  most  significant  component  of the input
                     key's domain. If the input key is  user@mail.example.com,
                     then  %1  is  com,  %2  is example and %3 is mail. If the
                     input key is unqualified or does not have  enough  domain
                     components  to  satisfy  all  the specified patterns, the
                     search is suppressed and returns no results.

                     The above %1,  ...,  %9  expansions  are  available  with
                     Postfix 2.2 and later.

              The  "domain" parameter described below limits the input keys to
              addresses in matching domains. When the  "domain"  parameter  is
              non-empty,  LDAP  queries for unqualified addresses or addresses
              in non-matching domains are suppressed and return no results.

              NOTE: DO NOT put quotes around the query_filter parameter.

       result_format (default: %s)
              Called result_filter in Postfix releases prior to  2.2.   Format
              template  applied  to  result  attributes. Most commonly used to
              append (or prepend) text to the result. This parameter  supports
              the following '%' expansions:

              %%     This is replaced by a literal '%' character. (Postfix 2.2
                     and later).

              %s     This is replaced by the value of  the  result  attribute.
                     When result is empty it is skipped.

              %u     When the result attribute value is an address of the form
                     user@domain, %u is replaced by  the  local  part  of  the
                     address.  When  the  result  has an empty localpart it is
                     skipped.

              %d     When a result attribute value is an address of  the  form
                     user@domain,  %d  is  replaced  by the domain part of the
                     attribute value. When the result  is  unqualified  it  is
                     skipped.

              %[SUD1-9]
                     The  upper-case  and decimal digit expansions interpolate
                     the parts of the input key rather than the result.  Their
                     behavior    is   identical   to   that   described   with
                     query_filter, and in fact because the input key is  known
                     in  advance,  lookups  whose key does not contain all the
                     information  specified  in  the   result   template   are
                     suppressed and return no results.

                     The  above  %S,  %U,  %D  and  %1, ..., %9 expansions are
                     available with Postfix 2.2 and later.

              For example, using "result_format = smtp:[%s]" allows one to use
              a mailHost attribute as the basis of a transport(5) table. After
              applying the result format, multiple values are concatenated  as
              comma  separated  strings.  The  expansion_limit  and size_limit
              parameters explained below allow one to restrict the  number  of
              values  in  the result, which is especially useful for maps that
              should return a single value.

              The default value %s specifies that each attribute value  should
              be used as is.

              This  parameter  was  called  result_filter  in Postfix releases
              prior to 2.2. If no "result_format" is specified, the  value  of
              "result_filter"  will  be  used  instead before resorting to the
              default   value.   This   provides   compatibility   with    old
              configuration files.

              NOTE: DO NOT put quotes around the result format!

       domain (default: no domain list)
              This is a list of domain names, paths to files, or dictionaries.
              When specified, only fully qualified search keys  with  a  *non-
              empty*  localpart and a matching domain are eligible for lookup:
              'user' lookups, bare domain lookups and  "@domain"  lookups  are
              not  performed.  This can significantly reduce the query load on
              the LDAP server.

                  domain = postfix.org, hash:/etc/postfix/searchdomains

              It is best not to use LDAP to store  the  domains  eligible  for
              LDAP lookups.

              NOTE: DO NOT define this parameter for local(8) aliases.

              This feature is available in Postfix 1.0 and later.

       result_attribute (default: maildrop)
              The  attribute(s)  Postfix  will read from any directory entries
              returned by the lookup, to be resolved to an email address.

                  result_attribute = mailbox, maildrop

              Don't  rely  on  the  default  value   ("maildrop").   Set   the
              result_attribute  explicitly  in  all  ldap  table configuration
              files. This is particularly relevant when no result_attribute is
              applicable,  e.g.  cases  in  which leaf_result_attribute and/or
              terminal_result_attribute are used instead. The default value is
              harmless  if  "maildrop"  is  also  listed as a leaf or terminal
              result attribute, but it is best to not leave this to chance.

       special_result_attribute (default: empty)
              The attribute(s) of directory entries that can  contain  DNs  or
              RFC 2255 LDAP URLs. If found, a recursive search is performed to
              retrieve the entry referenced by the DN, or the entries  matched
              by the URL query.

                  special_result_attribute = memberdn

              DN  recursion  retrieves  the same result_attributes as the main
              query, including the special attributes for further recursion.

              URL processing retrieves only those attributes that are included
              in  both  the URL definition and as result attributes (ordinary,
              special, leaf or terminal) in the Postfix table definition.   If
              the  URL  lists  any  of  the table's special result attributes,
              these are retrieved and used recursively. A URL  that  does  not
              specify  any  attribute selection, is equivalent (RFC 2255) to a
              URL that selects all attributes,  in  which  case  the  selected
              attributes  will  be  the  full  set of result attributes in the
              Postfix table.

              If an LDAP URL attribute-descriptor or the corresponding Postfix
              LDAP  table  result  attribute (but not both) uses RFC 2255 sub-
              type options ("attr;option"), the attribute requested  from  the
              LDAP  server  will  include  the  sub-type  option. In all other
              cases, the URL attribute and  the  table  attribute  must  match
              exactly. Attributes with options in both the URL and the Postfix
              table are requested only when the options  are  identical.  LDAP
              attribute-descriptor  options  are  very  rarely used, most LDAP
              users will not need to concern themselves  with  this  level  of
              nuanced detail.

       terminal_result_attribute (default: empty)
              When one or more terminal result attributes are found in an LDAP
              entry, all other result attributes  are  ignored  and  only  the
              terminal  result  attributes  are  returned.  This is useful for
              delegating expansion of group members to a particular  host,  by
              using  an  optional  "maildrop"  attribute on selected groups to
              route the group to a specific host, where the group is expanded,
              possibly via mailing-list manager or other special processing.

                  result_attribute =
                  terminal_result_attribute = maildrop

              When   using   terminal   and/or  leaf  result  attributes,  the
              result_attribute is best set to an empty value when  it  is  not
              used, or else explicitly set to the desired value, even if it is
              the default value "maildrop".

              This feature is available with Postfix 2.4 or later.

       leaf_result_attribute (default: empty)
              When one or more special result attributes are found in  a  non-
              terminal  (see  above)  LDAP  entry,  leaf result attributes are
              excluded from the expansion of that entry. This is  useful  when
              expanding  groups  and  the desired mail address attribute(s) of
              the member objects obtained via DN or  URI  recursion  are  also
              present in the group object. To only return the attribute values
              from the leaf objects and not  the  containing  group,  add  the
              attribute   to  the  leaf_result_attribute  list,  and  not  the
              result_attribute list,  which  is  always  expanded.  Note,  the
              default  value  of "result_attribute" is not empty, you may want
              to set it explicitly empty when using "leaf_result_attribute" to
              expand  the  group  to  a list of member DN addresses. If groups
              have both member DN references AND attributes that hold multiple
              string valued rfc822 addresses, then the string attributes go in
              "result_attribute".  The attributes  that  represent  the  email
              addresses  of  objects  referenced  via a DN (or LDAP URI) go in
              "leaf_result_attribute".

                  result_attribute = memberaddr
                  special_result_attribute = memberdn
                  terminal_result_attribute = maildrop
                  leaf_result_attribute = mail

              When  using  terminal  and/or  leaf   result   attributes,   the
              result_attribute  is  best  set to an empty value when it is not
              used, or else explicitly set to the desired value, even if it is
              the default value "maildrop".

              This feature is available with Postfix 2.4 or later.

       scope (default: sub)
              The  LDAP search scope: sub, base, or one.  These translate into
              LDAP_SCOPE_SUBTREE, LDAP_SCOPE_BASE, and LDAP_SCOPE_ONELEVEL.

       bind (default: yes)
              Whether  or  how  to  bind  to  the  LDAP  server.  Newer   LDAP
              implementations don't require clients to bind, which saves time.
              Example:

                  # Don't bind
                  bind = no
                  # Use SIMPLE bind
                  bind = yes
                  # Use SASL bind
                  bind = sasl

              Postfix versions prior to 2.8 only support  "bind  =  no"  which
              means don't bind, and "bind = yes" which means do a SIMPLE bind.
              Postfix 2.8 and later also supports "bind = SASL" when  compiled
              with LDAP SASL support as described in LDAP_README, it also adds
              the synonyms "bind = none" and "bind = simple" for "bind  =  no"
              and  "bind  =  yes" respectively. See the SASL section below for
              additional parameters available with "bind = sasl".

              If you do need to bind, you might consider  configuring  Postfix
              to  connect  to the local machine on a port that's an SSL tunnel
              to your LDAP  server.  If  your  LDAP  server  doesn't  natively
              support  SSL, put a tunnel (wrapper, proxy, whatever you want to
              call it) on that system too. This should  prevent  the  password
              from traversing the network in the clear.

       bind_dn (default: empty)
              If  you  do  have  to  bind, do it with this distinguished name.
              Example:

                  bind_dn = uid=postfix, dc=your, dc=com
              With "bind = sasl" (see above) the DN may be optional  for  some
              SASL mechanisms, don't specify a DN if not needed.

       bind_pw (default: empty)
              The  password  for  the distinguished name above. If you have to
              use this, you probably want to make the map  configuration  file
              readable  only  by  the  Postfix  user.  When using the obsolete
              ldap:ldapsource syntax, with map parameters in  main.cf,  it  is
              not  possible  to  securely  store  the  bind  password. This is
              because main.cf needs  to  be  world  readable  to  allow  local
              accounts to submit mail via the sendmail command. Example:

                  bind_pw = postfixpw
              With  "bind = sasl" (see above) the password may be optional for
              some SASL mechanisms, don't specify a password if not needed.

       cache (IGNORED with a warning)

       cache_expiry (IGNORED with a warning)

       cache_size (IGNORED with a warning)
              The above parameters are NO LONGER SUPPORTED by Postfix.   Cache
              support has been dropped from OpenLDAP as of release 2.1.13.

       recursion_limit (default: 1000)
              A  limit  on  the  nesting  depth  of  DN and URL special result
              attribute evaluation. The limit  must  be  a  non-zero  positive
              number.

       expansion_limit (default: 0)
              A  limit  on  the total number of result elements returned (as a
              comma separated list) by a lookup against the map.  A setting of
              zero  disables the limit. Lookups fail with a temporary error if
              the limit is exceeded.  Setting the  limit  to  1  ensures  that
              lookups do not return multiple values.

       size_limit (default: $expansion_limit)
              A  limit  on  the  number of LDAP entries returned by any single
              LDAP search performed as part of the  lookup.  A  setting  of  0
              disables the limit.  Expansion of DN and URL references involves
              nested LDAP queries, each of which is  separately  subjected  to
              this limit.

              Note:  even  a  single  LDAP  entry can generate multiple lookup
              results, via  multiple  result  attributes  and/or  multi-valued
              result  attributes.  This  limit  caps  the  per search resource
              utilization on the LDAP server, not the  final  multiplicity  of
              the  lookup  result.  It  is  analogous  to  the  "-z" option of
              "ldapsearch".

       dereference (default: 0)
              When to dereference LDAP aliases. (Note that this has nothing do
              with  Postfix aliases.) The permitted values are those legal for
              the OpenLDAP/UM LDAP implementations:

              0      never

              1      when searching

              2      when locating the base object for the search

              3      always

              See ldap.h or the ldap_open(3) or ldapsearch(1)  man  pages  for
              more  information.  And if you're using an LDAP package that has
              other possible values, please bring it to the attention  of  the
              postfix-users@postfix.org mailing list.

       chase_referrals (default: 0)
              Sets  (or  clears)  LDAP_OPT_REFERRALS  (requires LDAP version 3
              support).

       version (default: 2)
              Specifies the LDAP protocol version to use.

       debuglevel (default: 0)
              What level to set for debugging in the OpenLDAP libraries.

LDAP SASL PARAMETERS

       If you're using the OpenLDAP  libraries  compiled  with  SASL  support,
       Postfix  2.8  and  later  built  with LDAP SASL support as described in
       LDAP_README can authenticate to LDAP servers via SASL.

       This enables authentication to the LDAP  server  via  mechanisms  other
       than  a  simple  password.  The  added flexibility has a cost: it is no
       longer practical to set an explicit timeout on the duration of an  LDAP
       bind  operation.  Under  adverse  conditions, whether a SASL bind times
       out, or if it does, the duration of the timeout is  determined  by  the
       LDAP and SASL libraries.

       It  is best to use tables that use SASL binds via proxymap(8), this way
       the requesting process can time-out the  proxymap  request.  This  also
       lets  you  tailer the process environment by overriding the proxymap(8)
       import_environment  setting  in   master.cf(5).   Special   environment
       settings  may  be needed to configure GSSAPI credential caches or other
       SASL mechanism specific options. The GSSAPI credentials used  for  LDAP
       lookups  may  need  to be different than say those used for the Postfix
       SMTP client to authenticate to remote servers.

       Using SASL mechanisms requires LDAP protocol  version  3,  the  default
       protocol  version  is  2  for  backwards  compatibility.  You  must set
       "version = 3" in addition to "bind = sasl".

       The following parameters are relevant to using LDAP with SASL

       sasl_mechs (default: empty)
              Space separated list of SASL mechanism(s) to try.

       sasl_realm (default: empty)
              SASL Realm to use, if applicable.

       sasl_authz_id (default: empty)
              The SASL authorization identity to assert, if applicable.

       sasl_minssf (default: 0)
              The minimum required sasl security factor required to  establish
              a connection.

LDAP SSL AND STARTTLS PARAMETERS

       If  you're  using  the  OpenLDAP  libraries  compiled with SSL support,
       Postfix can connect to LDAP SSL servers  and  can  issue  the  STARTTLS
       command.

       LDAP  SSL  service  can  be  requested  by  using a LDAP SSL URL in the
       server_host parameter:

           server_host = ldaps://ldap.example.com:636

       STARTTLS can be turned on with the start_tls parameter:

           start_tls = yes

       Both forms require LDAP  protocol  version  3,  which  has  to  be  set
       explicitly with:

           version = 3

       If  any  of  the  Postfix  programs  querying  the map is configured in
       master.cf to run chrooted, all the certificates and keys involved  have
       to  be  copied  to  the chroot jail. Of course, the private keys should
       only be readable by the user "postfix".

       The following parameters are relevant to LDAP SSL and STARTTLS:

       start_tls (default: no)
              Whether or not to issue STARTTLS upon connection to the  server.
              Don't  set  this  with  LDAP  SSL  (the  SSL  session  is  setup
              automatically when the TCP connection is opened).

       tls_ca_cert_dir (No default; set either this or tls_ca_cert_file)
              Directory containing X509 Certificate Authority certificates  in
              PEM  format  which are to be recognized by the client in SSL/TLS
              connections. The files each contain  one  CA  certificate.   The
              files  are  looked  up  by the CA subject name hash value, which
              must hence be available. If more than one  CA  certificate  with
              the  same name hash value exist, the extension must be different
              (e.g. 9d66eef0.0, 9d66eef0.1 etc). The search  is  performed  in
              the  ordering  of  the  extension  number,  regardless  of other
              properties of the certificates. Use the c_rehash  utility  (from
              the OpenSSL distribution) to create the necessary links.

       tls_ca_cert_file (No default; set either this or tls_ca_cert_dir)
              File  containing  the X509 Certificate Authority certificates in
              PEM format which are to be recognized by the client  in  SSL/TLS
              connections. This setting takes precedence over tls_ca_cert_dir.

       tls_cert (No default; you must set this)
              File  containing  client's  X509  certificate  to be used by the
              client in SSL/ TLS connections.

       tls_key (No default; you must set this)
              File containing the  private  key  corresponding  to  the  above
              tls_cert.

       tls_require_cert (default: no)
              Whether  or  not  to request server's X509 certificate and check
              its  validity  when  establishing  SSL/TLS   connections.    The
              supported values are no and yes.

              With  no, the server certificate trust chain is not checked, but
              with  OpenLDAP  prior  to  2.1.13,  the  name  in   the   server
              certificate must still match the LDAP server name. With OpenLDAP
              2.0.0 to 2.0.11 the server name  is  not  necessarily  what  you
              specified,  rather it is determined (by reverse lookup) from the
              IP address of the LDAP server connection. With OpenLDAP prior to
              2.0.13,  subjectAlternativeName  extensions  in  the LDAP server
              certificate are ignored: the server name must match the  subject
              CommonName.  The  no  setting  corresponds to the never value of
              TLS_REQCERT in LDAP client configuration files.

              Don't use TLS with OpenLDAP 2.0.x (and especially with x <=  11)
              if you can avoid it.

              With yes, the server certificate must be issued by a trusted CA,
              and not be expired. The LDAP server name must match one  of  the
              name(s) found in the certificate (see above for OpenLDAP library
              version dependent behavior). The yes setting corresponds to  the
              demand value of TLS_REQCERT in LDAP client configuration files.

              The  "try" and "never" values of TLS_REQCERT have no equivalents
              here. They are not available with OpenLDAP 2.0, and in any  case
              have  questionable  security  properties.  Either  you  want TLS
              verified LDAP connections, or you don't.

              The yes value only works correctly with Postfix 2.5  and  later,
              or with OpenLDAP 2.0. Earlier Postfix releases or later OpenLDAP
              releases don't work together with this setting. Support for LDAP
              over TLS was added to Postfix based on the OpenLDAP 2.0 API.

       tls_random_file (No default)
              Path of a file to obtain random bits from when /dev/[u]random is
              not available, to be used by the client in SSL/TLS connections.

       tls_cipher_suite (No default)
              Cipher suite to use in SSL/TLS negotiations.

EXAMPLE

       Here's a basic example for using LDAP  to  look  up  local(8)  aliases.
       Assume that in main.cf, you have:

           alias_maps = hash:/etc/aliases,
                   ldap:/etc/postfix/ldap-aliases.cf

       and in ldap:/etc/postfix/ldap-aliases.cf you have:

           server_host = ldap.example.com
           search_base = dc=example, dc=com

       Upon  receiving mail for a local address "ldapuser" that isn't found in
       the  /etc/aliases  database,  Postfix  will  search  the  LDAP   server
       listening  at  port 389 on ldap.example.com.  It will bind anonymously,
       search for any directory entries whose mailacceptinggeneralid attribute
       is "ldapuser", read the "maildrop" attributes of those found, and build
       a list of their maildrops, which will be treated as RFC822 addresses to
       which the message will be delivered.

SEE ALSO

       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters
       mysql_table(5), MySQL lookup tables
       pgsql_table(5), PostgreSQL lookup tables

README FILES

       Use  "postconf readme_directory" or "postconf html_directory" to locate
       this information.
       DATABASE_README, Postfix lookup table overview
       LDAP_README, Postfix LDAP client guide

LICENSE

       The Secure Mailer license must be distributed with this software.

AUTHOR(S)

       Carsten Hoeger,  Hery  Rakotoarisoa,  John  Hensley,  Keith  Stevenson,
       LaMont  Jones,  Liviu  Daia,  Manuel  Guesdon,  Mike Mattice, Prabhat K
       Singh, Sami  Haahtinen,  Samuel  Tardieu,  Victor  Duchovni,  and  many
       others.

                                                                 LDAP_TABLE(5)