3 smtp, smtpd \- mail transport
54 sends the mail message from standard input
57 on the host at network address
59 using the Simple Mail Transfer Protocol.
65 if the server supports PLAIN or LOGIN authentication,
66 authenticate to the server using a password from
68 See RFCs 3207 and 2554.
73 autistic server: don't wait for an SMTP greeting banner
74 but immediately send a
76 command to provoke the server into responding.
85 turn on debugging to standard error.
88 just filter the converted message to standard
89 output rather than sending it.
94 the system to pass the message to if
96 can't find an address nor MX entry for the destination system.
101 as the local system name;
102 it may be fully-qualified or not. If not
103 specified, it will default to the contents of
109 authenticate even if we can't start TLS.
112 ping: just verify that the users named in the
119 if the server supports the ESMTP extension to use TLS encryption, turn it on for
120 this session. See RFC3207 for details.
123 preemtively establish TLS connection before SMTP handshake (SMTPS).
126 specify a user name to be used in authentication. The default name is
127 the current login id.
132 is given, it is appended to the end of any unqualified system names
133 in the envelope or header.
137 receives a message using the Simple Mail Transfer Protocol.
138 Standard input and output are the protocol connection.
139 SMTP authentication by
143 protocols is supported; authenticated connections are permitted to relay.
150 requires that all clients authenticate to be able to send mail.
153 specifies a certificate to use for TLS. Without this
154 option, the capability to start TLS will not be advertised.
157 turns on debugging output,
158 with each connection's output going to a uniquely-named file in
159 .BR /sys/log/smtpdb .
162 sleeps for 15 seconds usually at the start of the SMTP dialogue;
163 this deters some spammers.
164 Connections from Class A networks frequented by spammers will incur
168 prevents relaying from non-trusted networks.
169 It also tags messages from non-trusted sites when they deliver mail
170 from an address in a domain we believe we represent.
173 turns on grey/white list processing. All mail is rejected (with a
174 retry code) unless the sender's IP address is on the whitelist,
175 .BR /mail/grey/whitelist ,
177 Addresses can be added to the whitelist by the administrator. However,
178 the usual way for addresses to be added is by
181 Whenever a message is received and the sender's address isn't on the whitelist,
183 first looks for the file
184 .BI /mail\%/grey\%/tmp\%/\| local\% /\| remote\% /\| recipient\fP,
189 are IP addresses of the local and remote systems, respectively.
190 If it exists and was created more than a few minutes go,
191 the remote address is added to the whitelist.
192 If not, the file is created and the mail is rejected with a `try again' code.
193 The expectation is that spammers will not retry for more than a few minutes
194 and that others will.
197 specifies the receiving domain. If this flag is not specified, the
198 receiving domain is inferred from the host name.
201 causes connections from the host at
204 to be dropped at program startup. Multiple addresses
205 can be specified with several
207 options. This option should be used carefully;
208 it is intended to lessen the effects of denial of
209 service attacks or broken mailers which continually
210 connect. The connections are not logged and the
211 remote system is not notified via the protocol.
218 passes a received message.
223 specifies the name of the network directory assigned to the incoming connection.
224 This is used to determine the peer IP address. If this flag is not
225 specified, the peer address is determined using standard input.
228 permits clients to authenticate using protocols which transfer
229 the password in the clear, e.g.
231 protocol. This should only be used if the connection has
232 previously encrypted using e.g.
236 turns on forward DNS validation of non-trusted sender address.
239 causes copies of blocked messages to be saved in a sub-directory of
240 .BR /mail/queue.dump .
243 is normally run by a network listener such as
245 Most of the command line options are more conveniently
246 specified in the smtpd configuration file stored in
247 .BR /mail/lib/smtpd.conf .
250 .B /sys/src/cmd/upas/smtp