Provided by: postfix_3.1.0-3_amd64 bug

NAME

       smtp - Postfix SMTP+LMTP client

SYNOPSIS

       smtp [generic Postfix daemon options]

DESCRIPTION

       The  Postfix  SMTP+LMTP  client  implements  the SMTP and LMTP mail delivery protocols. It
       processes message delivery requests from the queue manager. Each request specifies a queue
       file,  a  sender address, a domain or host to deliver to, and recipient information.  This
       program expects to be run from the master(8) process manager.

       The SMTP+LMTP client updates the queue file  and  marks  recipients  as  finished,  or  it
       informs  the  queue  manager that delivery should be tried again at a later time. Delivery
       status reports are sent to the bounce(8), defer(8) or trace(8) daemon as appropriate.

       The SMTP+LMTP client looks up a list of mail exchanger addresses for the destination host,
       sorts  the list by preference, and connects to each listed address until it finds a server
       that responds.

       When a server is not reachable, or when mail delivery fails due  to  a  recoverable  error
       condition, the SMTP+LMTP client will try to deliver the mail to an alternate host.

       After a successful mail transaction, a connection may be saved to the scache(8) connection
       cache server, so that it may be used by any SMTP+LMTP client for a subsequent transaction.

       By default, connection caching is enabled temporarily for destinations that  have  a  high
       volume  of  mail  in  the  active queue. Connection caching can be enabled permanently for
       specific destinations.

SMTP DESTINATION SYNTAX

       SMTP destinations have the following form:

       domainname

       domainname:port
              Look up the mail exchangers for the specified domain, and connect to the  specified
              port (default: smtp).

       [hostname]

       [hostname]:port
              Look  up  the  address(es) of the specified host, and connect to the specified port
              (default: smtp).

       [address]

       [address]:port
              Connect to the host at the specified address, and connect  to  the  specified  port
              (default: smtp). An IPv6 address must be formatted as [ipv6:address].

LMTP DESTINATION SYNTAX

       LMTP destinations have the following form:

       unix:pathname
              Connect to the local UNIX-domain server that is bound to the specified pathname. If
              the process runs chrooted, an absolute pathname  is  interpreted  relative  to  the
              Postfix queue directory.

       inet:hostname

       inet:hostname:port

       inet:[address]

       inet:[address]:port
              Connect to the specified TCP port on the specified local or remote host. If no port
              is specified, connect to the port defined as  lmtp  in  services(4).   If  no  such
              service  is  found, the lmtp_tcp_port configuration parameter (default value of 24)
              will be used.  An IPv6 address must be formatted as [ipv6:address].

SECURITY

       The SMTP+LMTP client is moderately security-sensitive. It talks to SMTP  or  LMTP  servers
       and  to  DNS servers on the network. The SMTP+LMTP client can be run chrooted at fixed low
       privilege.

STANDARDS

       RFC 821 (SMTP protocol)
       RFC 822 (ARPA Internet Text Messages)
       RFC 1651 (SMTP service extensions)
       RFC 1652 (8bit-MIME transport)
       RFC 1870 (Message Size Declaration)
       RFC 2033 (LMTP protocol)
       RFC 2034 (SMTP Enhanced Error Codes)
       RFC 2045 (MIME: Format of Internet Message Bodies)
       RFC 2046 (MIME: Media Types)
       RFC 2554 (AUTH command)
       RFC 2821 (SMTP protocol)
       RFC 2920 (SMTP Pipelining)
       RFC 3207 (STARTTLS command)
       RFC 3461 (SMTP DSN Extension)
       RFC 3463 (Enhanced Status Codes)
       RFC 4954 (AUTH command)
       RFC 5321 (SMTP protocol)
       RFC 6531 (Internationalized SMTP)
       RFC 6533 (Internationalized Delivery Status Notifications)
       RFC 7672 (SMTP security via opportunistic DANE TLS)

DIAGNOSTICS

       Problems and transactions are logged to syslogd(8).  Corrupted message files are marked so
       that the queue manager can move them to the corrupt queue for further inspection.

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

BUGS

       SMTP and LMTP connection caching does not work with TLS. The  necessary  support  for  TLS
       object  passivation  and  re-activation  does not exist without closing the session, which
       defeats the purpose.

       SMTP and LMTP  connection  caching  assumes  that  SASL  credentials  are  valid  for  all
       destinations that map onto the same IP address and TCP port.

CONFIGURATION PARAMETERS

       Before  Postfix  version 2.3, the LMTP client is a separate program that implements only a
       subset of the functionality available  with  SMTP:  there  is  no  support  for  TLS,  and
       connections  are  cached  in-process,  making  it  ineffective when the client is used for
       multiple domains.

       Most smtp_xxx configuration  parameters  have  an  lmtp_xxx  "mirror"  parameter  for  the
       equivalent  LMTP  feature. This document describes only those LMTP-related parameters that
       aren't simply "mirror" parameters.

       Changes to main.cf are picked up automatically,  as  smtp(8)  processes  run  for  only  a
       limited amount of time. Use the command "postfix reload" to speed up a change.

       The  text  below  provides  only  a  parameter  summary.  See postconf(5) for more details
       including examples.

COMPATIBILITY CONTROLS

       ignore_mx_lookup_error (no)
              Ignore DNS MX lookups that produce no response.

       smtp_always_send_ehlo (yes)
              Always send EHLO at the start of an SMTP session.

       smtp_never_send_ehlo (no)
              Never send EHLO at the start of an SMTP session.

       smtp_defer_if_no_mx_address_found (no)
              Defer mail delivery when no MX record resolves to an IP address.

       smtp_line_length_limit (998)
              The maximal length of message header and body lines  that  Postfix  will  send  via
              SMTP.

       smtp_pix_workaround_delay_time (10s)
              How long the Postfix SMTP client pauses before sending ".<CR><LF>" in order to work
              around the PIX firewall "<CR><LF>.<CR><LF>" bug.

       smtp_pix_workaround_threshold_time (500s)
              How long a message must be queued before the Postfix SMTP client turns on  the  PIX
              firewall  "<CR><LF>.<CR><LF>"  bug  workaround  for delivery through firewalls with
              "smtp fixup" mode turned on.

       smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
              A list that specifies zero or more workarounds for CISCO PIX firewall bugs.

       smtp_pix_workaround_maps (empty)
              Lookup tables, indexed by the remote  SMTP  server  address,  with  per-destination
              workarounds for CISCO PIX firewall bugs.

       smtp_quote_rfc821_envelope (yes)
              Quote  addresses  in Postfix SMTP client MAIL FROM and RCPT TO commands as required
              by RFC 5321.

       smtp_reply_filter (empty)
              A mechanism to transform replies from remote SMTP servers one line at a time.

       smtp_skip_5xx_greeting (yes)
              Skip remote SMTP servers that greet with a 5XX status code.

       smtp_skip_quit_response (yes)
              Do not wait for the response to the SMTP QUIT command.

       Available in Postfix version 2.0 and earlier:

       smtp_skip_4xx_greeting (yes)
              Skip SMTP servers that greet with a 4XX status code (go away, try again later).

       Available in Postfix version 2.2 and later:

       smtp_discard_ehlo_keyword_address_maps (empty)
              Lookup tables, indexed by the remote SMTP server  address,  with  case  insensitive
              lists  of  EHLO  keywords  (pipelining, starttls, auth, etc.) that the Postfix SMTP
              client will ignore in the EHLO response from a remote SMTP server.

       smtp_discard_ehlo_keywords (empty)
              A case insensitive list of EHLO keywords (pipelining, starttls,  auth,  etc.)  that
              the Postfix SMTP client will ignore in the EHLO response from a remote SMTP server.

       smtp_generic_maps (empty)
              Optional  lookup  tables that perform address rewriting in the Postfix SMTP client,
              typically to transform a locally valid address into a globally valid  address  when
              sending mail across the Internet.

       Available in Postfix version 2.2.9 and later:

       smtp_cname_overrides_servername (version dependent)
              When  the  remote  SMTP  servername is a DNS CNAME, replace the servername with the
              result from CNAME expansion for the purpose of logging, SASL password  lookup,  TLS
              policy decisions, or TLS certificate verification.

       Available in Postfix version 2.3 and later:

       lmtp_discard_lhlo_keyword_address_maps (empty)
              Lookup  tables,  indexed  by  the remote LMTP server address, with case insensitive
              lists of LHLO keywords (pipelining, starttls, auth, etc.)  that  the  Postfix  LMTP
              client will ignore in the LHLO response from a remote LMTP server.

       lmtp_discard_lhlo_keywords (empty)
              A  case  insensitive  list of LHLO keywords (pipelining, starttls, auth, etc.) that
              the Postfix LMTP client will ignore in the LHLO response from a remote LMTP server.

       Available in Postfix version 2.4.4 and later:

       send_cyrus_sasl_authzid (no)
              When authenticating to a remote SMTP or LMTP server with the default setting  "no",
              send  no  SASL  authoriZation  ID  (authzid);  send only the SASL authentiCation ID
              (authcid) plus the authcid's password.

       Available in Postfix version 2.5 and later:

       smtp_header_checks (empty)
              Restricted header_checks(5) tables for the Postfix SMTP client.

       smtp_mime_header_checks (empty)
              Restricted mime_header_checks(5) tables for the Postfix SMTP client.

       smtp_nested_header_checks (empty)
              Restricted nested_header_checks(5) tables for the Postfix SMTP client.

       smtp_body_checks (empty)
              Restricted body_checks(5) tables for the Postfix SMTP client.

       Available in Postfix version 2.6 and later:

       tcp_windowsize (0)
              An optional workaround for routers that break TCP window scaling.

       Available in Postfix version 2.8 and later:

       smtp_dns_resolver_options (empty)
              DNS Resolver options for the Postfix SMTP client.

       Available in Postfix version 2.9 and later:

       smtp_per_record_deadline (no)
              Change the behavior of the smtp_*_timeout time limits, from a time limit  per  read
              or write system call, to a time limit to send or receive a complete record (an SMTP
              command line, SMTP response line,  SMTP  message  content  line,  or  TLS  protocol
              message).

       smtp_send_dummy_mail_auth (no)
              Whether  or  not  to  append  the  "AUTH=<>"  option  to  the  MAIL FROM command in
              SASL-authenticated SMTP sessions.

       Available in Postfix version 2.11 and later:

       smtp_dns_support_level (empty)
              Level of DNS support in the Postfix SMTP client.

       Available in Postfix version 3.0 and later:

       smtp_delivery_status_filter ($default_delivery_status_filter)
              Optional filter for the smtp(8) delivery agent to change the delivery  status  code
              or explanatory text of successful or unsuccessful deliveries.

       smtp_dns_reply_filter (empty)
              Optional filter for Postfix SMTP client DNS lookup results.

MIME PROCESSING CONTROLS

       Available in Postfix version 2.0 and later:

       disable_mime_output_conversion (no)
              Disable the conversion of 8BITMIME format to 7BIT format.

       mime_boundary_length_limit (2048)
              The maximal length of MIME multipart boundary strings.

       mime_nesting_limit (100)
              The maximal recursion level that the MIME processor will handle.

EXTERNAL CONTENT INSPECTION CONTROLS

       Available in Postfix version 2.1 and later:

       smtp_send_xforward_command (no)
              Send  the  non-standard XFORWARD command when the Postfix SMTP server EHLO response
              announces XFORWARD support.

SASL AUTHENTICATION CONTROLS

       smtp_sasl_auth_enable (no)
              Enable SASL authentication in the Postfix SMTP client.

       smtp_sasl_password_maps (empty)
              Optional Postfix SMTP client lookup tables with  one  username:password  entry  per
              sender, remote hostname or next-hop domain.

       smtp_sasl_security_options (noplaintext, noanonymous)
              Postfix  SMTP client SASL security options; as of Postfix 2.3 the list of available
              features  depends  on  the  SASL  client  implementation  that  is  selected   with
              smtp_sasl_type.

       Available in Postfix version 2.2 and later:

       smtp_sasl_mechanism_filter (empty)
              If  non-empty,  a  Postfix  SMTP client filter for the remote SMTP server's list of
              offered SASL mechanisms.

       Available in Postfix version 2.3 and later:

       smtp_sender_dependent_authentication (no)
              Enable  sender-dependent  authentication  in  the  Postfix  SMTP  client;  this  is
              available  only  with  SASL authentication, and disables SMTP connection caching to
              ensure that mail from different senders will use the appropriate credentials.

       smtp_sasl_path (empty)
              Implementation-specific information that the Postfix SMTP client passes through  to
              the SASL plug-in implementation that is selected with smtp_sasl_type.

       smtp_sasl_type (cyrus)
              The SASL plug-in type that the Postfix SMTP client should use for authentication.

       Available in Postfix version 2.5 and later:

       smtp_sasl_auth_cache_name (empty)
              An  optional  table  to prevent repeated SASL authentication failures with the same
              remote SMTP server hostname, username and password.

       smtp_sasl_auth_cache_time (90d)
              The maximal age of an smtp_sasl_auth_cache_name entry before it is removed.

       smtp_sasl_auth_soft_bounce (yes)
              When a remote SMTP server rejects a SASL authentication request with  a  535  reply
              code, defer mail delivery instead of returning mail as undeliverable.

       Available in Postfix version 2.9 and later:

       smtp_send_dummy_mail_auth (no)
              Whether  or  not  to  append  the  "AUTH=<>"  option  to  the  MAIL FROM command in
              SASL-authenticated SMTP sessions.

STARTTLS SUPPORT CONTROLS

       Detailed information about STARTTLS configuration may be found in the TLS_README document.

       smtp_tls_security_level (empty)
              The default SMTP TLS security level for the Postfix SMTP client; when  a  non-empty
              value   is   specified,   this  overrides  the  obsolete  parameters  smtp_use_tls,
              smtp_enforce_tls, and smtp_tls_enforce_peername.

       smtp_sasl_tls_security_options ($smtp_sasl_security_options)
              The SASL authentication security options that the Postfix SMTP client uses for  TLS
              encrypted SMTP sessions.

       smtp_starttls_timeout (300s)
              Time limit for Postfix SMTP client write and read operations during TLS startup and
              shutdown handshake procedures.

       smtp_tls_CAfile (empty)
              A file containing CA certificates of root CAs trusted to sign  either  remote  SMTP
              server certificates or intermediate CA certificates.

       smtp_tls_CApath (empty)
              Directory  with  PEM  format  Certification Authority certificates that the Postfix
              SMTP client uses to verify a remote SMTP server certificate.

       smtp_tls_cert_file (empty)
              File with the Postfix SMTP client RSA certificate in PEM format.

       smtp_tls_mandatory_ciphers (medium)
              The minimum TLS cipher grade that the Postfix SMTP client will use  with  mandatory
              TLS encryption.

       smtp_tls_exclude_ciphers (empty)
              List of ciphers or cipher types to exclude from the Postfix SMTP client cipher list
              at all TLS security levels.

       smtp_tls_mandatory_exclude_ciphers (empty)
              Additional list of ciphers or cipher types to exclude from the Postfix SMTP  client
              cipher list at mandatory TLS security levels.

       smtp_tls_dcert_file (empty)
              File with the Postfix SMTP client DSA certificate in PEM format.

       smtp_tls_dkey_file ($smtp_tls_dcert_file)
              File with the Postfix SMTP client DSA private key in PEM format.

       smtp_tls_key_file ($smtp_tls_cert_file)
              File with the Postfix SMTP client RSA private key in PEM format.

       smtp_tls_loglevel (0)
              Enable additional Postfix SMTP client logging of TLS activity.

       smtp_tls_note_starttls_offer (no)
              Log  the  hostname  of  a  remote SMTP server that offers STARTTLS, when TLS is not
              already enabled for that server.

       smtp_tls_policy_maps (empty)
              Optional lookup tables with the Postfix SMTP client TLS security policy by next-hop
              destination;  when  a  non-empty  value  is  specified, this overrides the obsolete
              smtp_tls_per_site parameter.

       smtp_tls_mandatory_protocols (!SSLv2, !SSLv3)
              List of SSL/TLS protocols that the Postfix SMTP client will use with mandatory  TLS
              encryption.

       smtp_tls_scert_verifydepth (9)
              The verification depth for remote SMTP server certificates.

       smtp_tls_secure_cert_match (nexthop, dot-nexthop)
              How  the  Postfix  SMTP  client  verifies  the  server certificate peername for the
              "secure" TLS security level.

       smtp_tls_session_cache_database (empty)
              Name of the file containing the optional Postfix SMTP client TLS session cache.

       smtp_tls_session_cache_timeout (3600s)
              The expiration time of Postfix SMTP client TLS session cache information.

       smtp_tls_verify_cert_match (hostname)
              How the Postfix SMTP client  verifies  the  server  certificate  peername  for  the
              "verify" TLS security level.

       tls_daemon_random_bytes (32)
              The number of pseudo-random bytes that an smtp(8) or smtpd(8) process requests from
              the tlsmgr(8) server in order to seed its internal pseudo random  number  generator
              (PRNG).

       tls_high_cipherlist (see 'postconf -d' output)
              The OpenSSL cipherlist for "high" grade ciphers.

       tls_medium_cipherlist (see 'postconf -d' output)
              The OpenSSL cipherlist for "medium" or higher grade ciphers.

       tls_low_cipherlist (see 'postconf -d' output)
              The OpenSSL cipherlist for "low" or higher grade ciphers.

       tls_export_cipherlist (see 'postconf -d' output)
              The OpenSSL cipherlist for "export" or higher grade ciphers.

       tls_null_cipherlist (eNULL:!aNULL)
              The OpenSSL cipherlist for "NULL" grade ciphers that provide authentication without
              encryption.

       Available in Postfix version 2.4 and later:

       smtp_sasl_tls_verified_security_options ($smtp_sasl_tls_security_options)
              The SASL authentication security options that the Postfix SMTP client uses for  TLS
              encrypted SMTP sessions with a verified server certificate.

       Available in Postfix version 2.5 and later:

       smtp_tls_fingerprint_cert_match (empty)
              List   of   acceptable   remote   SMTP  server  certificate  fingerprints  for  the
              "fingerprint" TLS security level (smtp_tls_security_level = fingerprint).

       smtp_tls_fingerprint_digest (md5)
              The message digest algorithm used  to  construct  remote  SMTP  server  certificate
              fingerprints.

       Available in Postfix version 2.6 and later:

       smtp_tls_protocols (!SSLv2, !SSLv3)
              List  of  TLS  protocols  that the Postfix SMTP client will exclude or include with
              opportunistic TLS encryption.

       smtp_tls_ciphers (medium)
              The  minimum  TLS  cipher  grade  that  the  Postfix  SMTP  client  will  use  with
              opportunistic TLS encryption.

       smtp_tls_eccert_file (empty)
              File with the Postfix SMTP client ECDSA certificate in PEM format.

       smtp_tls_eckey_file ($smtp_tls_eccert_file)
              File with the Postfix SMTP client ECDSA private key in PEM format.

       Available in Postfix version 2.7 and later:

       smtp_tls_block_early_mail_reply (no)
              Try  to  detect  a  mail  hijacking  attack  based  on a TLS protocol vulnerability
              (CVE-2009-3555), where an  attacker  prepends  malicious  HELO,  MAIL,  RCPT,  DATA
              commands to a Postfix SMTP client TLS session.

       Available in Postfix version 2.8 and later:

       tls_disable_workarounds (see 'postconf -d' output)
              List or bit-mask of OpenSSL bug work-arounds to disable.

       Available in Postfix version 2.11 and later:

       smtp_tls_trust_anchor_file (empty)
              Zero or more PEM-format files with trust-anchor certificates and/or public keys.

       smtp_tls_force_insecure_host_tlsa_lookup (no)
              Lookup  the associated DANE TLSA RRset even when a hostname is not an alias and its
              address records lie in an unsigned zone.

       tls_dane_trust_anchor_digest_enable (yes)
              RFC 6698 trust-anchor digest support in the Postfix TLS library.

       tlsmgr_service_name (tlsmgr)
              The name of the tlsmgr(8) service entry in master.cf.

       Available in Postfix version 3.0 and later:

       smtp_tls_wrappermode (no)
              Request that the Postfix SMTP client  connects  using  the  legacy  SMTPS  protocol
              instead of using the STARTTLS command.

       Available in Postfix version 3.1 and later:

       smtp_tls_dane_insecure_mx_policy (dane)
              The TLS policy for MX hosts with "secure" TLSA records when the nexthop destination
              security level is dane, but the MX record was found via an "insecure" MX lookup.

OBSOLETE STARTTLS CONTROLS

       The following configuration parameters  exist  for  compatibility  with  Postfix  versions
       before 2.3. Support for these will be removed in a future release.

       smtp_use_tls (no)
              Opportunistic  mode:  use TLS when a remote SMTP server announces STARTTLS support,
              otherwise send the mail in the clear.

       smtp_enforce_tls (no)
              Enforcement mode: require that remote SMTP servers use TLS  encryption,  and  never
              send mail in the clear.

       smtp_tls_enforce_peername (yes)
              With mandatory TLS encryption, require that the remote SMTP server hostname matches
              the information in the remote SMTP server certificate.

       smtp_tls_per_site (empty)
              Optional lookup tables with the Postfix SMTP client TLS usage  policy  by  next-hop
              destination and by remote SMTP server hostname.

       smtp_tls_cipherlist (empty)
              Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS cipher list.

RESOURCE AND RATE CONTROLS

       smtp_destination_concurrency_limit ($default_destination_concurrency_limit)
              The  maximal  number  of  parallel  deliveries to the same destination via the smtp
              message delivery transport.

       smtp_destination_recipient_limit ($default_destination_recipient_limit)
              The maximal number  of  recipients  per  message  for  the  smtp  message  delivery
              transport.

       smtp_connect_timeout (30s)
              The  Postfix  SMTP  client time limit for completing a TCP connection, or zero (use
              the operating system built-in time limit).

       smtp_helo_timeout (300s)
              The Postfix SMTP client time limit for sending the HELO or EHLO  command,  and  for
              receiving the initial remote SMTP server response.

       lmtp_lhlo_timeout (300s)
              The  Postfix LMTP client time limit for sending the LHLO command, and for receiving
              the initial remote LMTP server response.

       smtp_xforward_timeout (300s)
              The Postfix SMTP client time limit  for  sending  the  XFORWARD  command,  and  for
              receiving the remote SMTP server response.

       smtp_mail_timeout (300s)
              The  Postfix  SMTP  client  time  limit  for sending the MAIL FROM command, and for
              receiving the remote SMTP server response.

       smtp_rcpt_timeout (300s)
              The Postfix SMTP client time limit for sending the SMTP RCPT TO  command,  and  for
              receiving the remote SMTP server response.

       smtp_data_init_timeout (120s)
              The  Postfix  SMTP  client  time  limit  for sending the SMTP DATA command, and for
              receiving the remote SMTP server response.

       smtp_data_xfer_timeout (180s)
              The Postfix SMTP client time limit for sending the SMTP message content.

       smtp_data_done_timeout (600s)
              The Postfix SMTP client time limit for sending the SMTP ".", and for receiving  the
              remote SMTP server response.

       smtp_quit_timeout (300s)
              The  Postfix SMTP client time limit for sending the QUIT command, and for receiving
              the remote SMTP server response.

       Available in Postfix version 2.1 and later:

       smtp_mx_address_limit (5)
              The maximal number of MX (mail exchanger) IP addresses that can result from Postfix
              SMTP client mail exchanger lookups, or zero (no limit).

       smtp_mx_session_limit (2)
              The  maximal  number  of SMTP sessions per delivery request before the Postfix SMTP
              client gives up or delivers to a fall-back relay host, or zero (no limit).

       smtp_rset_timeout (20s)
              The Postfix SMTP client time limit for sending the RSET command, and for  receiving
              the remote SMTP server response.

       Available in Postfix version 2.2 and earlier:

       lmtp_cache_connection (yes)
              Keep Postfix LMTP client connections open for up to $max_idle seconds.

       Available in Postfix version 2.2 and later:

       smtp_connection_cache_destinations (empty)
              Permanently enable SMTP connection caching for the specified destinations.

       smtp_connection_cache_on_demand (yes)
              Temporarily enable SMTP connection caching while a destination has a high volume of
              mail in the active queue.

       smtp_connection_reuse_time_limit (300s)
              The amount of time during which Postfix will use an SMTP connection repeatedly.

       smtp_connection_cache_time_limit (2s)
              When SMTP connection caching is enabled, the amount of time  that  an  unused  SMTP
              client socket is kept open before it is closed.

       Available in Postfix version 2.3 and later:

       connection_cache_protocol_timeout (5s)
              Time limit for connection cache connect, send or receive operations.

       Available in Postfix version 2.9 and later:

       smtp_per_record_deadline (no)
              Change  the  behavior of the smtp_*_timeout time limits, from a time limit per read
              or write system call, to a time limit to send or receive a complete record (an SMTP
              command  line,  SMTP  response  line,  SMTP  message  content line, or TLS protocol
              message).

       Available in Postfix version 2.11 and later:

       smtp_connection_reuse_count_limit (0)
              When SMTP connection caching is enabled, the number of times that an  SMTP  session
              may be reused before it is closed, or zero (no limit).

SMTPUTF8 CONTROLS

       Preliminary SMTPUTF8 support is introduced with Postfix 3.0.

       smtputf8_enable (yes)
              Enable preliminary SMTPUTF8 support for the protocols described in RFC 6531..6533.

       smtputf8_autodetect_classes (sendmail, verify)
              Detect  that  a  message  requires  SMTPUTF8  support for the specified mail origin
              classes.

TROUBLE SHOOTING CONTROLS

       debug_peer_level (2)
              The increment in verbose logging level when a remote client  or  server  matches  a
              pattern in the debug_peer_list parameter.

       debug_peer_list (empty)
              Optional  list of remote client or server hostname or network address patterns that
              cause  the  verbose  logging  level  to  increase  by  the  amount   specified   in
              $debug_peer_level.

       error_notice_recipient (postmaster)
              The  recipient  of  postmaster  notifications about mail delivery problems that are
              caused by policy, resource, software or protocol errors.

       internal_mail_filter_classes (empty)
              What categories of Postfix-generated  mail  are  subject  to  before-queue  content
              inspection by non_smtpd_milters, header_checks and body_checks.

       notify_classes (resource, software)
              The list of error classes that are reported to the postmaster.

MISCELLANEOUS CONTROLS

       best_mx_transport (empty)
              Where  the  Postfix  SMTP  client should deliver mail when it detects a "mail loops
              back to myself" error condition.

       config_directory (see 'postconf -d' output)
              The default location of the Postfix main.cf and master.cf configuration files.

       daemon_timeout (18000s)
              How much time a Postfix daemon process may take to handle a request  before  it  is
              terminated by a built-in watchdog timer.

       delay_logging_resolution_limit (2)
              The  maximal number of digits after the decimal point when logging sub-second delay
              values.

       disable_dns_lookups (no)
              Disable DNS lookups in the Postfix SMTP and LMTP clients.

       inet_interfaces (all)
              The network interface addresses that this mail system receives mail on.

       inet_protocols (all)
              The Internet protocols Postfix  will  attempt  to  use  when  making  or  accepting
              connections.

       ipc_timeout (3600s)
              The  time limit for sending or receiving information over an internal communication
              channel.

       lmtp_assume_final (no)
              When a remote LMTP server announces no DSN support, assume that the server performs
              final  delivery,  and  send  "delivered"  delivery  status notifications instead of
              "relayed".

       lmtp_tcp_port (24)
              The default TCP port that the Postfix LMTP client connects to.

       max_idle (100s)
              The maximum amount of time that  an  idle  Postfix  daemon  process  waits  for  an
              incoming connection before terminating voluntarily.

       max_use (100)
              The  maximal  number  of  incoming  connections  that a Postfix daemon process will
              service before terminating voluntarily.

       process_id (read-only)
              The process ID of a Postfix command or daemon process.

       process_name (read-only)
              The process name of a Postfix command or daemon process.

       proxy_interfaces (empty)
              The network interface addresses that this mail system receives mail on by way of  a
              proxy or network address translation unit.

       smtp_address_preference (any)
              The  address  type  ("ipv6", "ipv4" or "any") that the Postfix SMTP client will try
              first, when a destination has IPv6 and IPv4 addresses with equal MX preference.

       smtp_bind_address (empty)
              An optional numerical network address that the Postfix SMTP client should  bind  to
              when making an IPv4 connection.

       smtp_bind_address6 (empty)
              An  optional  numerical network address that the Postfix SMTP client should bind to
              when making an IPv6 connection.

       smtp_helo_name ($myhostname)
              The hostname to send in the SMTP HELO or EHLO command.

       lmtp_lhlo_name ($myhostname)
              The hostname to send in the LMTP LHLO command.

       smtp_host_lookup (dns)
              What mechanisms the Postfix SMTP client uses to look up a host's IP address.

       smtp_randomize_addresses (yes)
              Randomize the order of equal-preference MX host addresses.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
              The mail system name that is prepended to the process name in  syslog  records,  so
              that "smtpd" becomes, for example, "postfix/smtpd".

       Available with Postfix 2.2 and earlier:

       fallback_relay (empty)
              Optional  list of relay hosts for SMTP destinations that can't be found or that are
              unreachable.

       Available with Postfix 2.3 and later:

       smtp_fallback_relay ($fallback_relay)
              Optional list of relay hosts for SMTP destinations that can't be found or that  are
              unreachable.

       Available with Postfix 3.0 and later:

       smtp_address_verify_target (rcpt)
              In  the  context  of  email  address  verification,  the  SMTP  protocol stage that
              determines whether an email address is deliverable.

       Available with Postfix 3.1 and later:

       lmtp_fallback_relay (empty)
              Optional list of relay hosts for LMTP destinations that can't be found or that  are
              unreachable.

SEE ALSO

       generic(5), output address rewriting
       header_checks(5), message header content inspection
       body_checks(5), body parts content inspection
       qmgr(8), queue manager
       bounce(8), delivery status reports
       scache(8), connection cache server
       postconf(5), configuration parameters
       master(5), generic daemon options
       master(8), process manager
       tlsmgr(8), TLS session and PRNG management
       syslogd(8), system logging

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       SASL_README, Postfix SASL howto
       TLS_README, Postfix STARTTLS howto

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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

       Command pipelining in cooperation with:
       Jon Ribbens
       Oaktree Internet Solutions Ltd.,
       Internet House,
       Canal Basin,
       Coventry,
       CV1 4LY, United Kingdom.

       SASL support originally by:
       Till Franke
       SuSE Rhein/Main AG
       65760 Eschborn, Germany

       TLS support originally by:
       Lutz Jaenicke
       BTU Cottbus
       Allgemeine Elektrotechnik
       Universitaetsplatz 3-4
       D-03044 Cottbus, Germany

       Revised TLS and SMTP connection cache support by:
       Victor Duchovni
       Morgan Stanley

                                                                                   SMTP(8postfix)