SMTPD(8)                                                 SMTPD(8)

NAME
       smtpd - Postfix SMTP server

SYNOPSIS
       smtpd [generic Postfix daemon options]

DESCRIPTION
       The  SMTP  server  accepts network connection requests and
       performs zero or more SMTP  transactions  per  connection.
       Each received message is piped through the cleanup(8) dae-
       mon, and is placed into the incoming queue as  one  single
       queue  file.   For  this  mode  of  operation, the program
       expects to be run from the master(8) process manager.

       Alternatively, the SMTP server takes an  established  con-
       nection  on  standard input and deposits messages directly
       into the maildrop queue.  In  this  so-called  stand-alone
       mode,  the SMTP server can accept mail even while the mail
       system is not running.

       The SMTP server implements a variety of policies for  con-
       nection  requests, and for parameters given to HELO, ETRN,
       MAIL FROM, VRFY and RCPT TO commands.  They  are  detailed
       below and in the main.cf configuration file.

SECURITY
       The SMTP server is moderately security-sensitive. It talks
       to SMTP clients and to DNS servers  on  the  network.  The
       SMTP server can be run chrooted at fixed low privilege.

STANDARDS
       RFC 821 (SMTP protocol)
       RFC 1123 (Host requirements)
       RFC 1652 (8bit-MIME transport)
       RFC 1869 (SMTP service extensions)
       RFC 1854 (SMTP Pipelining)
       RFC 1870 (Message Size Declaration)
       RFC 1985 (ETRN command)
       RFC 2554 (AUTH command)
       RFC 2821 (SMTP protocol)

DIAGNOSTICS
       Problems and transactions are logged to syslogd(8).

       Depending  on the setting of the notify_classes parameter,
       the postmaster is notified of bounces, protocol  problems,
       policy violations, and of other trouble.

CONFIGURATION PARAMETERS
       The  following  main.cf parameters are especially relevant
       to this program. See the Postfix main.cf file  for  syntax
       details  and  for  default  values. Use the postfix reload
       command after a configuration change.

Compatibility controls
       strict_rfc821_envelopes
              Disallow non-RFC 821 style addresses in  SMTP  com-
              mands.  For example, the RFC822-style address forms
              with comments that Sendmail allows.

       broken_sasl_auth_clients
              Support older Microsoft clients that  mis-implement
              the AUTH protocol, and that expect an EHLO response
              of "250 AUTH=list" instead of "250 AUTH list".

       smtpd_noop_commands
              List of commands that are treated as NOOP (no oper-
              ation)   commands,  without  any  parameter  syntax
              checking and without any state change.   This  list
              overrides built-in command definitions.

Content inspection controls
       content_filter
              The  name of a mail delivery transport that filters
              mail and that either bounces mail or re-injects the
              result  back into Postfix.  This parameter uses the
              same syntax as the right-hand  side  of  a  Postfix
              transport table.

Authentication controls
       enable_sasl_authentication
              Enable  per-session  authentication as per RFC 2554
              (SASL).  This functionality is available only  when
              explicitly  selected  at  program  build  time  and
              explicitly enabled at runtime.

       smtpd_sasl_local_domain
              The name of the local authentication realm.

       smtpd_sasl_security_options
              Zero or more of the following.

              noplaintext
                     Disallow  authentication  methods  that  use
                     plaintext passwords.

              noactive
                     Disallow  authentication  methods  that  are
                     vulnerable to non-dictionary active attacks.

              nodictionary
                     Disallow  authentication  methods  that  are
                     vulnerable to passive dictionary attack.

              noanonymous
                     Disallow anonymous logins.

       smtpd_sender_login_maps
              Maps that specify the SASL login name that  owns  a
              MAIL    FROM    sender   address.   Used   by   the
              reject_sender_login_mismatch  sender  anti-spoofing
              restriction.

Miscellaneous
       always_bcc
              Address  to send a copy of each message that enters
              the system.

       command_directory
              Location  of  Postfix  support  commands  (default:
              $program_directory).

       debug_peer_level
              Increment  in  verbose  logging level when a remote
              host  matches  a  pattern  in  the  debug_peer_list
              parameter.

       debug_peer_list
              List  of  domain or network patterns. When a remote
              host matches a pattern, increase the  verbose  log-
              ging   level   by   the  amount  specified  in  the
              debug_peer_level parameter.

       default_verp_delimiters
              The default VERP delimiter characters that are used
              when   the   XVERP  command  is  specified  without
              explicit delimiters.

       error_notice_recipient
              Recipient   of    protocol/policy/resource/software
              error notices.

       hopcount_limit
              Limit the number of Received: message headers.

       local_recipient_maps
              List  of  maps  with  user  names that are local to
              $myorigin or $inet_interfaces. If this parameter is
              defined,  then  the  SMTP  server  rejects mail for
              unknown local users.

       notify_classes
              List of error classes. Of special interest are:

              policy When a client violates any  policy,  mail  a
                     transcript of the entire SMTP session to the
                     postmaster.

              protocol
                     When a client violates the SMTP protocol  or
                     issues  an  unimplemented  command,  mail  a
                     transcript of the entire SMTP session to the
                     postmaster.

       smtpd_banner
              Text  that  follows the 220 status code in the SMTP
              greeting banner.

       smtpd_recipient_limit
              Restrict the number of  recipients  that  the  SMTP
              server accepts per message delivery.

       smtpd_timeout
              Limit  the  time  to  send a server response and to
              receive a client request.

       soft_bounce
              Change hard (5xx) reject responses into soft  (4xx)
              reject  responses.   This can be useful for testing
              purposes.

       verp_delimiter_filter
              The characters that Postfix accepts as VERP  delim-
              iter characters.

Resource controls
       line_length_limit
              Limit  the  amount  of memory in bytes used for the
              handling of partial input lines.

       message_size_limit
              Limit the total size in bytes of a message, includ-
              ing on-disk storage for envelope information.

       queue_minfree
              Minimal  amount of free space in bytes in the queue
              file system for the SMTP server to accept any  mail
              at all.

       smtpd_history_flush_threshold
              Flush  the  command  history  to  postmaster  after
              receipt of RSET etc.  only if the number of history
              lines exceeds the given threshold.

Tarpitting
       smtpd_error_sleep_time
              Time to wait in seconds before sending a 4xx or 5xx
              server error response.

       smtpd_soft_error_limit
              When an SMTP client has made this number of errors,
              wait  error_count  seconds before responding to any
              client request.

       smtpd_hard_error_limit
              Disconnect after a client has made this  number  of
              errors.

       smtpd_junk_command_limit
              Limit the number of times a client can issue a junk
              command such as NOOP, VRFY, ETRN  or  RSET  in  one
              SMTP  session  before  it  is penalized with tarpit
              delays.

UCE control restrictions
       parent_domain_matches_subdomains
              List of Postfix features that use  domain.tld  pat-
              terns   to  match  sub.domain.tld  (as  opposed  to
              requiring .domain.tld patterns).

       smtpd_client_restrictions
              Restrict what clients may connect to this mail sys-
              tem.

       smtpd_helo_required
              Require  that  clients  introduce themselves at the
              beginning of an SMTP session.

       smtpd_helo_restrictions
              Restrict what client hostnames are allowed in  HELO
              and EHLO commands.

       smtpd_sender_restrictions
              Restrict  what sender addresses are allowed in MAIL
              FROM commands.

       smtpd_recipient_restrictions
              Restrict what recipient addresses  are  allowed  in
              RCPT TO commands.

       smtpd_etrn_restrictions
              Restrict what domain names can be used in ETRN com-
              mands, and what clients may issue ETRN commands.

       allow_untrusted_routing
              Allow untrusted clients to specify  addresses  with
              sender-specified  routing.   Enabling this opens up
              nasty relay loopholes involving trusted  backup  MX
              hosts.

       smtpd_restriction_classes
              Declares  the  name of zero or more parameters that
              contain a list of UCE restrictions.  The  names  of
              these  parameters  can  then be used instead of the
              restriction lists that they represent.

       smtpd_null_access_lookup_key
              The lookup key to be used in  SMTPD  access  tables
              instead  of  the null sender address. A null sender
              address cannot be looked up.

       maps_rbl_domains
              List of DNS domains that publish the  addresses  of
              blacklisted hosts.

       permit_mx_backup_networks
              Only  domains  whose  primary  MX  hosts  match the
              listed  networks  are   eligible   for   the   per-
              mit_mx_backup feature.

       relay_domains
              Restrict  what domains or networks this mail system
              will relay mail from or to.

UCE control responses
       access_map_reject_code
              Server response when a client  violates  an  access
              database restriction.

       invalid_hostname_reject_code
              Server   response   when   a  client  violates  the
              reject_invalid_hostname restriction.

       maps_rbl_reject_code
              Server  response  when  a   client   violates   the
              maps_rbl_domains restriction.

       reject_code
              Response  code  when  the  client  matches a reject
              restriction.

       relay_domains_reject_code
              Server response when a client attempts  to  violate
              the mail relay policy.

       unknown_address_reject_code
              Server   response   when   a  client  violates  the
              reject_unknown_address restriction.

       unknown_client_reject_code
              Server response when a client  without  address  to
              name  mapping  violates  the reject_unknown_clients
              restriction.

       unknown_hostname_reject_code
              Server  response  when  a   client   violates   the
              reject_unknown_hostname restriction.

SEE ALSO
       cleanup(8) message canonicalization
       master(8) process manager
       syslogd(8) system logging

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

                                                         SMTPD(8)