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diff --git a/static/plan9-4e/man6/smtpd.6 b/static/plan9-4e/man6/smtpd.6 new file mode 100644 index 00000000..687426ce --- /dev/null +++ b/static/plan9-4e/man6/smtpd.6 @@ -0,0 +1,306 @@ +.TH SMTPD 6 +.SH NAME +smtpd \- SMTP listener configuration +.SH DESCRIPTION +The +SMTP +daemon +of +.IR mail (1) +implements the slave side of the SMTP protocol +to accept incoming mail on TCP port 25. +In general, +.IR smtpd 's +default parameters +are sufficient for internal systems +on protected networks, but external or +gateway systems require additional +security mechanisms. +The files +.BR /mail/lib/smtpd.conf , +containing configuration parameters, +and +.BR /mail/lib/blocked , +containing +banished addresses, provide the means to +exercise these facilities. +.SS Input Format +In both files input lines +consist of a verb followed by one or more +parameters. These tokens are separated by white space or +commas and all characters following a +.B # +are comments. A +.B # +cannot be escaped. Continuation lines are +not supported, but verbs that take multiple parameters +can be restated on many lines and the associated +parameters accumulate into a single set. +All token processing is case-insensitive. +.PP +Many parameters are +.IR addresses , +either numeric IP addresses in CIDR notation +or a +.I "sender address" +in UUCP-style format. +.PP +An IP address in CIDR notation has the form +.PP +.EX + aaa.bbb.ccc.ddd/mask +.EE +.PP +consisting of a four octet IP address, a slash, +and a +.I mask length +specifying the number of significant high-order bits. +The lower the mask length, the larger the +range of addresses covered by the CIDR address; +see RFC 1878 for a discussion of mask lengths. +Missing low-order octets are assumed to be zero. +If a mask length is not given, a mask length of +16, 24, or 32 is assumed for addresses containing +two, three, or four octets, respectively. These +mask lengths select a class B, class C or Class D +address block. Notice that this convention differs +from the standard treatment, where the default mask length +depends on the allocation class of the network +block containing the address. +.PP +.I "Sender addresses" +are specified in UUCP notation as +follows: +.PP +.EX + [domain!]...domain!user +.EE +.PP +It is seldom necessary to specify more than one domain. +When +.I domain +is missing or +.BR * , +the address selects the specified user in all domains. +A +.I domain +of the form +.BI *. domain +selects the domain and all of its sub-domains. +For example, +.B example.com!user +only matches the account +.I user +in domain +.BR example.com , +while +.B *.example.com!user +selects that account in +.B example.com +and all of its sub-domains. +When +.I user +is omitted or +.BR * , +the address selects all users in the specified domain. +Finally, when +.B * +is the last character of the user name it is a wild-card +matching all user names beginning with +.IR user . +This limited pattern matching capability should be used with care. +For safety, the sender addresses +.BR * , +.BR ! , +.BR *! , +.B !* +and +.B *!* +are ignored. +.SS /mail/lib/smtpd.conf +This file contains configuration options +and parameters describing the local domain. +Many of the options can also be specified on the command +line; command line options always override the values in +this file. +Configuration options are: +.PD0 +.TP 10 +.BI defaultdomain " domain" +The name of the local domain; it is appended to addresses +lacking a domain qualification. +This is identical to the +.B -h +command line option. +.TP 10 +.BR norelay \ [ on\f1|\fPoff ] +If +.I on +is specified, relaying is prohibited +from unauthorized networks to external domains. +Authorized networks and domains must be specified +by the +.B ournets +and +.B ourdomains +verbs described below. Setting this option on is equivalent to specifying the +.B -f +command line flag, but the list of +networks and domains can only be specified in +this file. +.TP 10 +.BR verifysenderdom \ [ on\f1|\fPoff ] +When +.IR on , +.I smtpd +verifies that the first domain of the sender's address +exists. The test is cursory; it checks only that +there is a DNS delegation for the domain. +Setting the option on is equivalent to specifying the +.B -r +command line option and +is useful for detecting some unreturnable +messages as well as messages with randomly +generated domain names. +.TP 10 +.BR saveblockedmsg \ [ on\f1|\fPoff ] +When +.IR on , +causes copies of blocked messages to be saved +in subdirectories of +.BR /mail/queue.dump . +Directories are named with the date and file names +are random numbers. +If this option is +.I off +blocked messages are discarded. +Setting this option on is equivalent to specifying the +.B -s +command line option. +.TP 10 +.BR ournets " \fIIP address\fP [, \fIIP address\fP, ..., \fIIP address\fP]" +This option specifies trusted +source networks that are allowed to relay mail to external domains. +These are usually the internal networks of the local domain, but they +can also include friendly +external networks. Addresses +are in CIDR notation. +.TP 10 +.BR ourdomains " \fIdomain\fP [, \fIdomain\fP, ..., \fIdomain\fP]" +This option specifies destination domains that are allowed +to receive relayed mail. These are usually the domains +served by a gateway system. +Domain specifications conform to the format +for sender addresses given above. +.PD +.PP +When the +.B norelay +option is enabled or the +.B -f +command line option given, +relaying is allowed only if the source IP address is in +.B ournets +or the destination domain is specified in +.BR ourdomains . +.SS Blocked Addresses +When +.B /mail/lib/blocked +exists and is readable, +.I smtpd +reads a list of banned addresses from it. +Messages received from these addresses are +rejected with a 5\fIxx\fP-series SMTP error code. +There is no option +to turn blocking on or off; if the file is accessible, +blocking is enabled on all +.I smtpd +sessions, including those from trusted networks. +.PP +The command line format and address specifications +conform to the notation described above. If the parameters +of the verb is sender addresses in UUCP format, the line +must begin with an +.B * +character; if the parameters are one or more IP addresses, +the +.B * +must precede the verb. Most +verbs cause messages to be rejected; verbs +of this class generally select different error +messages. The remaining verbs specify addresses that +are always accepted, in effect overriding blocked addresses. +The file is processed in order, so an override must +precede its associated blocked address. +Supported verbs are: +.PD0 +.TP 10 +.BR dial " \fIIP address\fP [,..., \fIIP address\fP]" +The parameters are IP addresses associated with +dial-up ports. The rejection message states +that connections from dial-up ports are not accepted. Copies +of messages are never saved. +.TP 10 +.BR block " \fIaddress\fP [, ... \fIaddress\fP]" +Messages from addresses +matching the parameters +are rejected with an error message saying +that spam is not accepted. The message is saved if +the option is enabled. +.TP 10 +.BR relay " \fIaddress\fP [, ... \fIaddress\fP]" +This verb is identical to +.BR block , +but the error message states that +the message is rejected because the sending +system is being used as a spam relay. +.TP +.BR deny " \fIaddress\fP [, ... \fIaddress\fP]" +The +.B deny +command rejects a message when the +sender address matches one of its parameters. +The rejection message asks the sender to +contact +.BR postmaster @ +.I hostdomain +for further information. +This verb is usually used to block +inadvertently abusive traffic, for example, +mail loops and stuck senders. Messages are +never saved. +.TP +.BR allow " \fIaddress\fP [, ... \fIaddress\fP]" +The +.B allow +verb negates the effect of subsequent blocking commands. +It is useful when a large range of addresses contains +a few legitimate addresses, for example, when +a mail server is in a Class C network block +of modem ports. Rather than enumerate the dial ports, it is +easier to block the entire Class C with a +.B dial +command, and precede it with an override for +the address of the mail server. Similarly, +it is possible to block mail from an entire +domain while accepting mail from a few friendly +senders in the domain. +The verb +.B accept +is a synonym for +.BR allow . +.PD +.PP +.IR Scanmail (8) +describes spam detection +software that works well with +the capabilities described here +and +.IR mail (1) +defines additional +.I smtpd +command line arguments applicable +to exposed systems. +.SH "SEE ALSO" +.IR mail (1), +.IR scanmail (8) |