SMTP(8) SMTP(8) [1mNAME[0m smtp - Postfix remote delivery via SMTP [1mSYNOPSIS[0m [1msmtp [22m[generic Postfix daemon options] [1mDESCRIPTION[0m The SMTP client processes message delivery requests from the queue man- ager. 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 [1mmaster[22m(8) process manager. The SMTP client updates the queue file and marks recipients as fin- ished, or it informs the queue manager that delivery should be tried again at a later time. Delivery problem reports are sent to the [1mbounce[22m(8) or [1mdefer[22m(8) daemon as appropriate. The SMTP 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. Once the SMTP client has received the server greeting banner, no error will cause it to proceed to the next address on the mail exchanger list. Instead, the message is either bounced, or its delivery is deferred until later. [1mSECURITY[0m The SMTP client is moderately security-sensitive. It talks to SMTP servers and to DNS servers on the network. The SMTP client can be run chrooted at fixed low privilege. [1mSTANDARDS[0m 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 2045 (MIME: Format of Internet Message Bodies) RFC 2046 (MIME: Media Types) RFC 2554 (AUTH command) RFC 2821 (SMTP protocol) RFC 2920 (SMTP Pipelining) [1mDIAGNOSTICS[0m Problems and transactions are logged to [1msyslogd[22m(8). Corrupted message files are marked so that the queue manager can move them to the [1mcorrupt[0m queue for further inspection. Depending on the setting of the [1mnotify_classes [22mparameter, the postmas- ter is notified of bounces, protocol problems, and of other trouble. [1mBUGS[0m [1mCONFIGURATION PARAMETERS[0m The following [1mmain.cf [22mparameters are especially relevant to this pro- gram. See the Postfix [1mmain.cf [22mfile for syntax details and for default values. Use the [1mpostfix reload [22mcommand after a configuration change. [1mMiscellaneous[0m [1mbest_mx_transport[0m Name of the delivery transport to use when the local machine is the most-preferred mail exchanger (by default, a mailer loop is reported, and the message is bounced). [1mdebug_peer_level[0m Verbose logging level increment for hosts that match a pattern in the [1mdebug_peer_list [22mparameter. [1mdebug_peer_list[0m List of domain or network patterns. When a remote host matches a pattern, increase the verbose logging level by the amount speci- fied in the [1mdebug_peer_level [22mparameter. [1mdisable_dns_lookups[0m Disable DNS lookups. This means that mail must be forwarded via a smart relay host. [1msmtp_host_lookup[0m What host lookup mechanism the SMTP client should use. Specify [1mdns [22m(use DNS lookup) and/or [1mnative [22m(use the native naming ser- vice which also uses /etc/hosts). This setting is ignored when DNS lookups are disabled. [1merror_notice_recipient[0m Recipient of protocol/policy/resource/software error notices. [1mfallback_relay[0m Hosts to hand off mail to if a message destination is not found or if a destination is unreachable. [1mignore_mx_lookup_error[0m When a name server fails to respond to an MX query, search for an A record, instead of deferring mail delivery. [1minet_interfaces[0m The network interface addresses that this mail system receives mail on. When any of those addresses appears in the list of mail exchangers for a remote destination, the list is truncated to avoid mail delivery loops. See also the [1mproxy_interfaces [22mparam- eter. [1mnotify_classes[0m When this parameter includes the [1mprotocol [22mclass, send mail to the postmaster with transcripts of SMTP sessions with protocol errors. [1mproxy_interfaces[0m Network interfaces that this mail system receives mail on by way of a proxy or network address translator. When any of those addresses appears in the list of mail exchangers for a remote destination, the list is truncated to avoid mail delivery loops. See also the [1minet_interfaces [22mparameter. [1msmtp_always_send_ehlo[0m Always send EHLO at the start of a connection. [1msmtp_never_send_ehlo[0m Never send EHLO at the start of a connection. [1msmtp_bind_address[0m Numerical source network address to bind to when making a con- nection. [1msmtp_defer_if_no_mx_address_found[0m If no, bounce mail when no MX host resolves to an address (Post- fix always ignores MX hosts with equal or worse preference than the local MTA). If yes, keep trying until a suitable MX host resolves or until the mail is too old. [1msmtp_line_length_limit[0m Length limit for SMTP message content lines. Zero means no limit. Some SMTP servers misbehave on long lines. [1msmtp_helo_name[0m The hostname to be used in HELO and EHLO commands. [1msmtp_quote_rfc821_envelope[0m Whether or not to quote MAIL FROM and RCPT TO addresses as per the rules laid out in RFC 821. [1msmtp_skip_4xx_greeting[0m Skip servers that greet us with a 4xx status code. [1msmtp_skip_5xx_greeting[0m Skip servers that greet us with a 5xx status code. [1msmtp_skip_quit_response[0m Do not wait for the server response after sending QUIT. [1msmtp_pix_workaround_delay_time[0m The time to pause before sending .<CR><LF>, while working around the CISCO PIX firewall <CR><LF>.<CR><LF> bug. [1msmtp_pix_workaround_threshold_time[0m The time a message must be queued before the CISCO PIX firewall <CR><LF>.<CR><LF> bug workaround is turned on. [1mMIME Conversion[0m [1mdisable_mime_output_conversion[0m Disable the conversion of 8BITMIME format to 7BIT format when the remote system does not advertise 8BITMIME support. [1mmime_boundary_length_limit[0m The amount of space that will be allocated for MIME multipart boundary strings. The MIME processor is unable to distinguish between boundary strings that do not differ in the first [1m$mime_boundary_length_limit [22mcharacters. [1mmime_nesting_limit[0m The maximal nesting level of multipart mail that the MIME pro- cessor can handle. Refuse mail that is nested deeper, when con- verting from 8BITMIME format to 7BIT format. [1msmtp_send_xforward_command[0m If the SMTP server announces XFORWARD support, send the name, address, protocol and HELO name of the original client. This can be used to forward client information through a content filter to a downstream queuing SMTP server. [1mAuthentication controls[0m [1msmtp_sasl_auth_enable[0m Enable per-session authentication as per RFC 2554 (SASL). By default, Postfix is built without SASL support. [1msmtp_sasl_password_maps[0m Lookup tables with per-host or domain [4mname[24m:[4mpassword[24m entries. No entry for a host means no attempt to authenticate. [1msmtp_sasl_security_options[0m Zero or more of the following. [1mnoplaintext[0m Disallow authentication methods that use plaintext pass- words. [1mnoactive[0m Disallow authentication methods that are vulnerable to non-dictionary active attacks. [1mnodictionary[0m Disallow authentication methods that are vulnerable to passive dictionary attack. [1mnoanonymous[0m Disallow anonymous logins. [1mResource controls[0m [1msmtp_sasl_path[0m The path where SASL will look for plugins. This is a colon sepa- rated list of directories where the SASL plugins shared objects are located. The default value is the null string, which will use the path defined in the SASL library. [1msmtp_destination_concurrency_limit[0m Limit the number of parallel deliveries to the same destination. The default limit is taken from the [1mdefault_destination_concur-[0m [1mrency_limit [22mparameter. NB: This limit is enforced by the queue manager. [1msmtp_destination_recipient_limit[0m Limit the number of recipients per message delivery. The default limit is taken from the [1mdefault_destination_recipi-[0m [1ment_limit [22mparameter. [1msmtp_mx_address_limit[0m An upper bound on the total number of MX (mail exchanger) IP addresses that can result from mail exchanger lookups. Specify zero to disable the limit. Note: by default, equal preference MX addresses are sorted into random order. [1msmtp_mx_session_limit[0m An upper bound on the number of SMTP sessions per delivery request before giving up or delivering to a fall-back relay host (ignoring IP addresses that fail to complete the SMTP initial handshake). Specify zero to disable the limit. [1mTimeout controls[0m The default time unit is seconds; an explicit time unit can be speci- fied by appending a one-letter suffix to the value: s (seconds), m (minutes), h (hours), d (days) or w (weeks). [1msmtp_connect_timeout[0m Timeout for completing a TCP connection. When no connection can be made within the deadline, the SMTP client tries the next address on the mail exchanger list. [1msmtp_helo_timeout[0m Timeout for receiving the SMTP greeting banner. When the server drops the connection without sending a greeting banner, or when it sends no greeting banner within the deadline, the SMTP client tries the next address on the mail exchanger list. [1msmtp_helo_timeout[0m Timeout for sending the [1mHELO [22mcommand, and for receiving the server response. [1msmtp_xforward_timeout[0m Timeout for sending the [1mXFORWARD [22mcommand, and for receiving the server response. [1msmtp_mail_timeout[0m Timeout for sending the [1mMAIL FROM [22mcommand, and for receiving the server response. [1msmtp_rcpt_timeout[0m Timeout for sending the [1mRCPT TO [22mcommand, and for receiving the server response. [1msmtp_data_init_timeout[0m Timeout for sending the [1mDATA [22mcommand, and for receiving the server response. [1msmtp_data_xfer_timeout[0m Timeout for sending the message content. [1msmtp_data_done_timeout[0m Timeout for sending the "[1m.[22m" command, and for receiving the server response. When no response is received, a warning is logged that the mail may be delivered multiple times. [1msmtp_rset_timeout[0m Timeout for sending the [1mRSET [22mcommand. [1msmtp_quit_timeout[0m Timeout for sending the [1mQUIT [22mcommand, and for receiving the server response. [1mSEE ALSO[0m bounce(8) non-delivery status reports master(8) process manager qmgr(8) queue manager syslogd(8) system logging [1mLICENSE[0m The Secure Mailer license must be distributed with this software. [1mAUTHOR(S)[0m Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA SMTP(8)