Postfix manual - ldap_table(5)

    LDAP_TABLE(5)                                                    LDAP_TABLE(5)

    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  parame-
           ters  described  below.  An example is given at the end of
           this manual.

           This configuration method is available with  Postfix  ver-
           sion  2.1  and later.  See the section "BACKWARDS COMPATI-
           BILITY" 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 accessi-
           ble as the name you've given the source in its definition,
           an underscore, and the name of the parameter.   For  exam-
           ple,  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_for-
           mat, 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  dis-
           cussion.

           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 $mydestina-
           tion:

               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  parenthe-
           ses.  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 tim-
                  ing 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 param-
                         eter  (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  speci-
                         fied  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  '%'  expan-
                  sions:

                  %%     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 param-
                         eter   identically   to   their   lower-case
                         counter-parts. With the result_format param-
                         eter  (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 speci-
                         fied patterns, the search is suppressed  and
                         returns no results.

                         The  above %1, ..., %9 expansions are avail-
                         able 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_fil-
                         ter, 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  expan-
                         sions  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 direc-
                  tory 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  termi-
                  nal_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 con-
                  tain DNs or RFC 2255 LDAP URLs. If found, a  recur-
                  sive search is performed to retrieve the entry ref-
                  erenced 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 ter-
                  minal) 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 corre-
                  sponding 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 expan-
                  sion 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 expan-
                  sion 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 avail-
                  able with "bind = sasl".

                  If you do need to bind, you might consider  config-
                  uring  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 distin-
                  guished 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 syn-
                  tax, with map parameters in main.cf, it is not pos-
                  sible  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 com-
                  mand. 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.  Expan-
                  sion 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  multi-
                  ple  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 sup-
           port as described in LDAP_README can authenticate to  LDAP
           servers via SASL.

           This  enables authentication to the LDAP server via mecha-
           nisms 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 prox-
           ymap(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_environ-
           ment setting in master.cf(5). Special environment settings
           may be needed to configure  GSSAPI  credential  caches  or
           other  SASL mechanism specific options. The GSSAPI creden-
           tials 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 compati-
           bility. 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 config-
           ured  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 connec-
                  tion 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 recog-
                  nized 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 cer-
                  tificates  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 con-
                  figuration 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.exam-
           ple.com.  It will bind anonymously, search for any  direc-
           tory  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  deliv-
           ered.

    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
           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)