.TH SMTP 8 .ad .fi .SH NAME smtp \- Postfix remote delivery via SMTP .SH SYNOPSIS .na .nf \fBsmtp\fR [generic Postfix daemon options] .SH DESCRIPTION .ad .fi The SMTP client 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 \fBmaster\fR(8) process manager. The SMTP 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 problem reports are sent to the \fBbounce\fR(8) or \fBdefer\fR(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. When the domain or host is specified as a comma/whitespace separated list, the SMTP client repeats the above process for all destinations 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. .SH SECURITY .na .nf .ad .fi 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. .SH STANDARDS .na .nf 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) .SH DIAGNOSTICS .ad .fi Problems and transactions are logged to \fBsyslogd\fR(8). Corrupted message files are marked so that the queue manager can move them to the \fBcorrupt\fR queue for further inspection. Depending on the setting of the \fBnotify_classes\fR parameter, the postmaster is notified of bounces, protocol problems, and of other trouble. .SH BUGS .ad .fi .SH CONFIGURATION PARAMETERS .na .nf .ad .fi The following \fBmain.cf\fR parameters are especially relevant to this program. See the Postfix \fBmain.cf\fR file for syntax details and for default values. Use the \fBpostfix reload\fR command after a configuration change. .SH Miscellaneous .ad .fi .IP \fBbest_mx_transport\fR 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). .IP \fBdebug_peer_level\fR Verbose logging level increment for hosts that match a pattern in the \fBdebug_peer_list\fR parameter. .IP \fBdebug_peer_list\fR List of domain or network patterns. When a remote host matches a pattern, increase the verbose logging level by the amount specified in the \fBdebug_peer_level\fR parameter. .IP \fBdisable_dns_lookups\fR Disable DNS lookups. This means that mail must be forwarded via a smart relay host. .IP \fBerror_notice_recipient\fR Recipient of protocol/policy/resource/software error notices. .IP \fBfallback_relay\fR Hosts to hand off mail to if a message destination is not found or if a destination is unreachable. .IP \fBignore_mx_lookup_error\fR When a name server fails to respond to an MX query, search for an A record instead deferring mail delivery. .IP \fBinet_interfaces\fR 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 \fBproxy_interfaces\fR parameter. .IP \fBnotify_classes\fR When this parameter includes the \fBprotocol\fR class, send mail to the postmaster with transcripts of SMTP sessions with protocol errors. .IP \fBproxy_interfaces\fR 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 \fBinet_interfaces\fR parameter. .IP \fBsmtp_always_send_ehlo\fR Always send EHLO at the start of a connection. .IP \fBsmtp_never_send_ehlo\fR Never send EHLO at the start of a connection. .IP \fBsmtp_bind_address\fR Numerical source network address to bind to when making a connection. .IP \fBsmtp_line_length_limit\fR Length limit for SMTP message content lines. Zero means no limit. Some SMTP servers misbehave on long lines. .IP \fBsmtp_helo_name\fR The hostname to be used in HELO and EHLO commands. .IP \fBsmtp_skip_4xx_greeting\fR Skip servers that greet us with a 4xx status code. .IP \fBsmtp_skip_5xx_greeting\fR Skip servers that greet us with a 5xx status code. .IP \fBsmtp_skip_quit_response\fR Do not wait for the server response after sending QUIT. .IP \fBsmtp_pix_workaround_delay_time\fR The time to pause before sending .<CR><LF>, while working around the CISCO PIX firewall <CR><LF>.<CR><LF> bug. .IP \fBsmtp_pix_workaround_threshold_time\fR The time a message must be queued before the CISCO PIX firewall <CR><LF>.<CR><LF> bug workaround is turned on. .SH "MIME Conversion" .IP \fBdisable_mime_output_conversion\fR Disable the conversion of 8BITMIME format to 7BIT format when the remote system does not advertise 8BITMIME support. .IP \fBmime_boundary_length_limit\fR 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 \fB$mime_boundary_length_limit\fR characters. .IP \fBmime_nesting_limit\fR The maximal nesting level of multipart mail that the MIME processor can handle. Refuse mail that is nested deeper, when converting from 8BITMIME format to 7BIT format. .SH "Authentication controls" .IP \fBsmtp_sasl_auth_enable\fR Enable per-session authentication as per RFC 2554 (SASL). By default, Postfix is built without SASL support. .IP \fBsmtp_sasl_password_maps\fR Lookup tables with per-host or domain \fIname\fR:\fIpassword\fR entries. No entry for a host means no attempt to authenticate. .IP \fBsmtp_sasl_security_options\fR Zero or more of the following. .RS .IP \fBnoplaintext\fR Disallow authentication methods that use plaintext passwords. .IP \fBnoactive\fR Disallow authentication methods that are vulnerable to non-dictionary active attacks. .IP \fBnodictionary\fR Disallow authentication methods that are vulnerable to passive dictionary attack. .IP \fBnoanonymous\fR Disallow anonymous logins. .RE .SH "Resource controls" .ad .fi .IP \fBsmtp_destination_concurrency_limit\fR Limit the number of parallel deliveries to the same destination. The default limit is taken from the \fBdefault_destination_concurrency_limit\fR parameter. .IP \fBsmtp_destination_recipient_limit\fR Limit the number of recipients per message delivery. The default limit is taken from the \fBdefault_destination_recipient_limit\fR parameter. .SH "Timeout controls" .ad .fi .PP The default time unit is seconds; an explicit time unit can be specified by appending a one-letter suffix to the value: s (seconds), m (minutes), h (hours), d (days) or w (weeks). .IP \fBsmtp_connect_timeout\fR 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. .IP \fBsmtp_helo_timeout\fR 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. .IP \fBsmtp_helo_timeout\fR Timeout for sending the \fBHELO\fR command, and for receiving the server response. .IP \fBsmtp_mail_timeout\fR Timeout for sending the \fBMAIL FROM\fR command, and for receiving the server response. .IP \fBsmtp_rcpt_timeout\fR Timeout for sending the \fBRCPT TO\fR command, and for receiving the server response. .IP \fBsmtp_data_init_timeout\fR Timeout for sending the \fBDATA\fR command, and for receiving the server response. .IP \fBsmtp_data_xfer_timeout\fR Timeout for sending the message content. .IP \fBsmtp_data_done_timeout\fR Timeout for sending the "\fB.\fR" command, and for receiving the server response. When no response is received, a warning is logged that the mail may be delivered multiple times. .IP \fBsmtp_quit_timeout\fR Timeout for sending the \fBQUIT\fR command, and for receiving the server response. .SH SEE ALSO .na .nf bounce(8) non-delivery status reports master(8) process manager qmgr(8) queue manager syslogd(8) system logging .SH LICENSE .na .nf .ad .fi The Secure Mailer license must be distributed with this software. .SH AUTHOR(S) .na .nf Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA