260 lines
5.4 KiB
Text
260 lines
5.4 KiB
Text
.TH SMTP 8
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.SH NAME
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smtp, smtpd \- mail transport
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.SH SYNOPSIS
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.in +0.5i
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.ti -0.5i
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.B upas/smtp
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[
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.B -aAdfips
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] [
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.B -b
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.I busted-mx
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] ... [
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.B -g
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.I gateway
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] [
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.B -h
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.I host
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] [
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.B -u
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.I user
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] [
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.BI . domain
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]
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.I destaddr
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.I sender
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.I rcpt-list
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.in -0.5i
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.PP
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.in +0.5i
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.ti -0.5i
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.B upas/smtpd
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[
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.B -adDfrg
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] [
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.B -c
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.I certfile
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] [
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.B -h
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.I mydom
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] [
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.B -k
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.I evilipaddr
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] [
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.B -m
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.I mailer
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] [
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.B -n
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.I netdir
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]
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.in -0.5i
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.SH DESCRIPTION
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.I Smtp
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sends the mail message from standard input
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to the users
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.I rcpt-list
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on the host at network address
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.I address
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using the Simple Mail Transfer Protocol.
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The options are:
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.TF -
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.PD
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.TP
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.B -a
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if the server supports PLAIN or LOGIN authentication,
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authenticate to the server using a password from
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.IR factotum (4).
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See RFCs 3207 and 2554.
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This option implies
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.BR -s .
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.TP
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.B -A
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autistic server: don't wait for an SMTP greeting banner
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but immediately send a
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.L NOOP
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command to provoke the server into responding.
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.TP
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.B -b
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ignore
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.I busted-mx
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when trying MX hosts.
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May be repeated.
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.TP
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.B -d
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turn on debugging to standard error.
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.TP
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.B -f
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just filter the converted message to standard
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output rather than sending it.
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.TP
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.B -g
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makes
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.I gateway
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the system to pass the message to if
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.I smtp
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can't find an address nor MX entry for the destination system.
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.TP
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.B -h
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use
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.I host
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as the local system name;
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it may be fully-qualified or not. If not
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specified, it will default to the contents of
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.BR /dev/sysname .
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.TP
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.B -i
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under
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.BR -a ,
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authenticate even if we can't start TLS.
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.TP
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.B -p
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ping: just verify that the users named in the
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.I rcpt-list
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are valid users at
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.IR destaddr ;
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don't send any mail.
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.TP
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.B -s
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if the server supports the ESMTP extension to use TLS encryption, turn it on for
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this session. See RFC3207 for details.
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.TP
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.B -u
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specify a user name to be used in authentication. The default name is
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the current login id.
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.PD
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.PP
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Finally if
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.I .domain
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is given, it is appended to the end of any unqualified system names
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in the envelope or header.
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.
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.PP
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.I Smtpd
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receives a message using the Simple Mail Transfer Protocol.
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Standard input and output are the protocol connection.
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SMTP authentication by
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.I login
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and
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.I cram-md5
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protocols is supported; authenticated connections are permitted to relay.
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.PP
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The options are:
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.TF -
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.PD
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.TP
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.B -a
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requires that all clients authenticate to be able to send mail.
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.TP
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.B -c
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specifies a certificate to use for TLS. Without this
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option, the capability to start TLS will not be advertised.
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.TP
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.B -d
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turns on debugging output,
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with each connection's output going to a uniquely-named file in
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.BR /sys/log/smtpdb .
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.TP
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.B -D
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sleeps for 15 seconds usually at the start of the SMTP dialogue;
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this deters some spammers.
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Connections from Class A networks frequented by spammers will incur
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a longer delay.
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.TP
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.B -f
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prevents relaying from non-trusted networks.
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It also tags messages from non-trusted sites when they deliver mail
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from an address in a domain we believe we represent.
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.TP
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.B -g
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turns on grey/white list processing. All mail is rejected (with a
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retry code) unless the sender's IP address is on the whitelist,
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.BR /mail/grey/whitelist ,
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an append only file.
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Addresses can be added to the whitelist by the administrator. However,
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the usual way for addresses to be added is by
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.I smtpd
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itself.
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Whenever a message is received and the sender's address isn't on the whitelist,
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.I smtpd
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first looks for the file
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.BI /mail\%/grey\%/tmp\%/\| local\% /\| remote\% /\| recipient\fP,
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where
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.I local
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and
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.I remote
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are IP addresses of the local and remote systems, respectively.
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If it exists and was created more than a few minutes go,
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the remote address is added to the whitelist.
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If not, the file is created and the mail is rejected with a `try again' code.
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The expectation is that spammers will not retry for more than a few minutes
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and that others will.
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.TP
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.B -h
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specifies the receiving domain. If this flag is not specified, the
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receiving domain is inferred from the host name.
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.TP
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.B -k
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causes connections from the host at
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the IP address,
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.IR evilipaddr ,
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to be dropped at program startup. Multiple addresses
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can be specified with several
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.B -k
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options. This option should be used carefully;
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it is intended to lessen the effects of denial of
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service attacks or broken mailers which continually
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connect. The connections are not logged and the
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remote system is not notified via the protocol.
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.TP
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.B -m
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set the
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.I mailer
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to which
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.I smtpd
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passes a received message.
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The default is
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.BR /bin/upas/send .
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.TP
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.B -n
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specifies the name of the network directory assigned to the incoming connection.
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This is used to determine the peer IP address. If this flag is not
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specified, the peer address is determined using standard input.
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.TP
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.B -p
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permits clients to authenticate using protocols which transfer
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the password in the clear, e.g.
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.I login
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protocol. This should only be used if the connection has
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previously encrypted using e.g.
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.IR tlssrv (8).
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.TP
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.B -r
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turns on forward DNS validation of non-trusted sender address.
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.TP
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.B -s
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causes copies of blocked messages to be saved in a sub-directory of
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.BR /mail/queue.dump .
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.PP
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.I Smtpd
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is normally run by a network listener such as
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.IR listen (8).
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Most of the command line options are more conveniently
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specified in the smtpd configuration file stored in
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.BR /mail/lib/smtpd.conf .
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.SH SOURCE
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.TP
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.B /sys/src/cmd/upas/smtp
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.SH "SEE ALSO"
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.IR aliasmail (8),
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.IR faces (1),
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.IR filter (1),
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.IR mail (1),
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.IR marshal (1),
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.IR mlmgr (1),
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.IR nedmail (1),
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.IR qer (8),
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.IR rewrite (6),
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.IR send (8),
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.IR tlssrv (8),
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.IR upasfs (4)
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