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<html> <head> </head> <body> <pre>
SMTPD(8) SMTPD(8)
<b>NAME</b>
smtpd - Postfix SMTP server
<b>SYNOPSIS</b>
<b>smtpd</b> [generic Postfix daemon options]
<b>DESCRIPTION</b>
The SMTP server accepts network connection requests and
performs zero or more SMTP transactions per connection.
Each received message is piped through the <a href="cleanup.8.html"><b>cleanup</b>(8)</a> dae-
mon, and is placed into the <b>incoming</b> queue as one single
queue file. For this mode of operation, the program
expects to be run from the <a href="master.8.html"><b>master</b>(8)</a> process manager.
Alternatively, the SMTP server takes an established con-
nection on standard input and deposits messages directly
into the <b>maildrop</b> queue. In this so-called stand-alone
mode, the SMTP server can accept mail even while the mail
system is not running.
The SMTP server implements a variety of policies for con-
nection requests, and for parameters given to <b>HELO,</b> <b>ETRN,</b>
<b>MAIL</b> <b>FROM,</b> <b>VRFY</b> and <b>RCPT</b> <b>TO</b> commands. They are detailed
below and in the <b>main.cf</b> configuration file.
<b>SECURITY</b>
The SMTP server is moderately security-sensitive. It talks
to SMTP clients and to DNS servers on the network. The
SMTP server can be run chrooted at fixed low privilege.
<b>STANDARDS</b>
<a href="http://www.faqs.org/rfcs/rfc821.html">RFC 821</a> (SMTP protocol)
<a href="http://www.faqs.org/rfcs/rfc1123.html">RFC 1123</a> (Host requirements)
<a href="http://www.faqs.org/rfcs/rfc1652.html">RFC 1652</a> (8bit-MIME transport)
<a href="http://www.faqs.org/rfcs/rfc1869.html">RFC 1869</a> (SMTP service extensions)
<a href="http://www.faqs.org/rfcs/rfc1870.html">RFC 1870</a> (Message Size Declaration)
<a href="http://www.faqs.org/rfcs/rfc1985.html">RFC 1985</a> (ETRN command)
<a href="http://www.faqs.org/rfcs/rfc2554.html">RFC 2554</a> (AUTH command)
<a href="http://www.faqs.org/rfcs/rfc2821.html">RFC 2821</a> (SMTP protocol)
<a href="http://www.faqs.org/rfcs/rfc2920.html">RFC 2920</a> (SMTP Pipelining)
<b>DIAGNOSTICS</b>
Problems and transactions are logged to <b>syslogd</b>(8).
Depending on the setting of the <b>notify</b><i>_</i><b>classes</b> parameter,
the postmaster is notified of bounces, protocol problems,
policy violations, and of other trouble.
<b>CONFIGURATION</b> <b>PARAMETERS</b>
The following <b>main.cf</b> parameters are especially relevant
to this program. See the Postfix <b>main.cf</b> file for syntax
details and for default values. Use the <b>postfix</b> <b>reload</b>
command after a configuration change.
<b>Compatibility</b> <b>controls</b>
<b>strict</b><i>_</i><b>rfc821</b><i>_</i><b>envelopes</b>
Disallow non-<a href="http://www.faqs.org/rfcs/rfc821.html">RFC 821</a> style addresses in SMTP com-
mands. For example, the RFC822-style address forms
with comments that Sendmail allows.
<b>broken</b><i>_</i><b>sasl</b><i>_</i><b>auth</b><i>_</i><b>clients</b>
Support older Microsoft clients that mis-implement
the AUTH protocol, and that expect an EHLO response
of "250 AUTH=list" instead of "250 AUTH list".
<b>smtpd</b><i>_</i><b>noop</b><i>_</i><b>commands</b>
List of commands that are treated as NOOP (no oper-
ation) commands, without any parameter syntax
checking and without any state change. This list
overrides built-in command definitions.
<b>Content</b> <b>inspection</b> <b>controls</b>
<b>content</b><i>_</i><b>filter</b>
The name of a mail delivery transport that filters
mail and that either bounces mail or re-injects the
result back into Postfix. This parameter uses the
same syntax as the right-hand side of a Postfix
transport table.
<b>Authentication</b> <b>controls</b>
<b>enable</b><i>_</i><b>sasl</b><i>_</i><b>authentication</b>
Enable per-session authentication as per <a href="http://www.faqs.org/rfcs/rfc2554.html">RFC 2554</a>
(SASL). This functionality is available only when
explicitly selected at program build time and
explicitly enabled at runtime.
<b>smtpd</b><i>_</i><b>sasl</b><i>_</i><b>local</b><i>_</i><b>domain</b>
The name of the local authentication realm.
<b>smtpd</b><i>_</i><b>sasl</b><i>_</i><b>security</b><i>_</i><b>options</b>
Zero or more of the following.
<b>noplaintext</b>
Disallow authentication methods that use
plaintext passwords.
<b>noactive</b>
Disallow authentication methods that are
vulnerable to non-dictionary active attacks.
<b>nodictionary</b>
Disallow authentication methods that are
vulnerable to passive dictionary attack.
<b>noanonymous</b>
Disallow anonymous logins.
<b>smtpd</b><i>_</i><b>sender</b><i>_</i><b>login</b><i>_</i><b>maps</b>
Maps that specify the SASL login name that owns a
MAIL FROM sender address. Used by the
<b>reject</b><i>_</i><b>sender</b><i>_</i><b>login</b><i>_</i><b>mismatch</b> sender anti-spoofing
restriction.
<b>Miscellaneous</b>
<b>always</b><i>_</i><b>bcc</b>
Address to send a copy of each message that enters
the system.
<b>authorized</b><i>_</i><b>verp</b><i>_</i><b>clients</b>
Hostnames, domain names and/or addresses of clients
that are authorized to use the XVERP extension.
<b>debug</b><i>_</i><b>peer</b><i>_</i><b>level</b>
Increment in verbose logging level when a remote
host matches a pattern in the <b>debug</b><i>_</i><b>peer</b><i>_</i><b>list</b>
parameter.
<b>debug</b><i>_</i><b>peer</b><i>_</i><b>list</b>
List of domain or network patterns. When a remote
host matches a pattern, increase the verbose log-
ging level by the amount specified in the
<b>debug</b><i>_</i><b>peer</b><i>_</i><b>level</b> parameter.
<b>default</b><i>_</i><b>verp</b><i>_</i><b>delimiters</b>
The default VERP delimiter characters that are used
when the XVERP command is specified without
explicit delimiters.
<b>error</b><i>_</i><b>notice</b><i>_</i><b>recipient</b>
Recipient of protocol/policy/resource/software
error notices.
<b>hopcount</b><i>_</i><b>limit</b>
Limit the number of <b>Received:</b> message headers.
<b>notify</b><i>_</i><b>classes</b>
List of error classes. Of special interest are:
<b>policy</b> When a client violates any policy, mail a
transcript of the entire SMTP session to the
postmaster.
<b>protocol</b>
When a client violates the SMTP protocol or
issues an unimplemented command, mail a
transcript of the entire SMTP session to the
postmaster.
<b>smtpd</b><i>_</i><b>banner</b>
Text that follows the <b>220</b> status code in the SMTP
greeting banner.
<b>smtpd</b><i>_</i><b>expansion</b><i>_</i><b>filter</b>
Controls what characters are allowed in $name
expansion of rbl template responses and other text.
<b>smtpd</b><i>_</i><b>recipient</b><i>_</i><b>limit</b>
Restrict the number of recipients that the SMTP
server accepts per message delivery.
<b>smtpd</b><i>_</i><b>timeout</b>
Limit the time to send a server response and to
receive a client request.
<b>soft</b><i>_</i><b>bounce</b>
Change hard (5xx) reject responses into soft (4xx)
reject responses. This can be useful for testing
purposes.
<b>verp</b><i>_</i><b>delimiter</b><i>_</i><b>filter</b>
The characters that Postfix accepts as VERP delim-
iter characters.
<b>Known</b> <b>versus</b> <b>unknown</b> <b>recipients</b>
<b>show</b><i>_</i><b>user</b><i>_</i><b>unknown</b><i>_</i><b>table</b><i>_</i><b>name</b>
Whether or not to reveal the table name in the
"User unknown" responses. The extra detail makes
trouble shooting easier but also reveals informa-
tion that is nobody elses business.
<b>unknown</b><i>_</i><b>local</b><i>_</i><b>recipient</b><i>_</i><b>reject</b><i>_</i><b>code</b>
The response code when a client specifies a recipi-
ent whose domain matches <b>$mydestination</b> or
<b>$inet</b><i>_</i><b>interfaces</b>, while <b>$local</b><i>_</i><b>recipient</b><i>_</i><b>maps</b> is
non-empty and does not list the recipient address
or address local-part.
<b>unknown</b><i>_</i><b>relay</b><i>_</i><b>recipient</b><i>_</i><b>reject</b><i>_</i><b>code</b>
The response code when a client specifies a recipi-
ent whose domain matches <b>$relay</b><i>_</i><b>domains</b>, while
<b>$relay</b><i>_</i><b>recipient</b><i>_</i><b>maps</b> is non-empty and does not
list the recipient address.
<b>unknown</b><i>_</i><b>virtual</b><i>_</i><b>alias</b><i>_</i><b>reject</b><i>_</i><b>code</b>
The response code when a client specifies a recipi-
ent whose domain matches <b>$virtual</b><i>_</i><b>alias</b><i>_</i><b>domains</b>,
while the recipient is not listed in <b>$vir-</b>
<b>tual</b><i>_</i><b>alias</b><i>_</i><b>maps</b>.
<b>unknown</b><i>_</i><b>virtual</b><i>_</i><b>mailbox</b><i>_</i><b>reject</b><i>_</i><b>code</b>
The response code when a client specifies a recipi-
ent whose domain matches <b>$virtual</b><i>_</i><b>mailbox</b><i>_</i><b>domains</b>,
while the recipient is not listed in <b>$virtual</b><i>_</i><b>mail-</b>
<b>box</b><i>_</i><b>maps</b>.
<b>Resource</b> <b>controls</b>
<b>line</b><i>_</i><b>length</b><i>_</i><b>limit</b>
Limit the amount of memory in bytes used for the
handling of partial input lines.
<b>message</b><i>_</i><b>size</b><i>_</i><b>limit</b>
Limit the total size in bytes of a message, includ-
ing on-disk storage for envelope information.
<b>queue</b><i>_</i><b>minfree</b>
Minimal amount of free space in bytes in the queue
file system for the SMTP server to accept any mail
at all.
<b>smtpd</b><i>_</i><b>history</b><i>_</i><b>flush</b><i>_</i><b>threshold</b>
Flush the command history to postmaster after
receipt of RSET etc. only if the number of history
lines exceeds the given threshold.
<b>Tarpitting</b>
<b>smtpd</b><i>_</i><b>error</b><i>_</i><b>sleep</b><i>_</i><b>time</b>
Time to wait in seconds before sending a 4xx or 5xx
server error response.
<b>smtpd</b><i>_</i><b>soft</b><i>_</i><b>error</b><i>_</i><b>limit</b>
When an SMTP client has made this number of errors,
wait <i>error_count</i> seconds before responding to any
client request.
<b>smtpd</b><i>_</i><b>hard</b><i>_</i><b>error</b><i>_</i><b>limit</b>
Disconnect after a client has made this number of
errors.
<b>smtpd</b><i>_</i><b>junk</b><i>_</i><b>command</b><i>_</i><b>limit</b>
Limit the number of times a client can issue a junk
command such as NOOP, VRFY, ETRN or RSET in one
SMTP session before it is penalized with tarpit
delays.
<b>UCE</b> <b>control</b> <b>restrictions</b>
<b>parent</b><i>_</i><b>domain</b><i>_</i><b>matches</b><i>_</i><b>subdomains</b>
List of Postfix features that use <i>domain.tld</i> pat-
terns to match <i>sub.domain.tld</i> (as opposed to
requiring <i>.domain.tld</i> patterns).
<b>smtpd</b><i>_</i><b>client</b><i>_</i><b>restrictions</b>
Restrict what clients may connect to this mail sys-
tem.
<b>smtpd</b><i>_</i><b>helo</b><i>_</i><b>required</b>
Require that clients introduce themselves at the
beginning of an SMTP session.
<b>smtpd</b><i>_</i><b>helo</b><i>_</i><b>restrictions</b>
Restrict what client hostnames are allowed in <b>HELO</b>
and <b>EHLO</b> commands.
<b>smtpd</b><i>_</i><b>sender</b><i>_</i><b>restrictions</b>
Restrict what sender addresses are allowed in <b>MAIL</b>
<b>FROM</b> commands.
<b>smtpd</b><i>_</i><b>recipient</b><i>_</i><b>restrictions</b>
Restrict what recipient addresses are allowed in
<b>RCPT</b> <b>TO</b> commands.
<b>smtpd</b><i>_</i><b>etrn</b><i>_</i><b>restrictions</b>
Restrict what domain names can be used in <b>ETRN</b> com-
mands, and what clients may issue <b>ETRN</b> commands.
<b>smtpd</b><i>_</i><b>data</b><i>_</i><b>restrictions</b>
Restrictions on the <b>DATA</b> command. Currently, the
only restriction that makes sense here is
<b>reject</b><i>_</i><b>unauth</b><i>_</i><b>pipelining</b>.
<b>allow</b><i>_</i><b>untrusted</b><i>_</i><b>routing</b>
Allow untrusted clients to specify addresses with
sender-specified routing. Enabling this opens up
nasty relay loopholes involving trusted backup MX
hosts.
<b>smtpd</b><i>_</i><b>restriction</b><i>_</i><b>classes</b>
Declares the name of zero or more parameters that
contain a list of UCE restrictions. The names of
these parameters can then be used instead of the
restriction lists that they represent.
<b>smtpd</b><i>_</i><b>null</b><i>_</i><b>access</b><i>_</i><b>lookup</b><i>_</i><b>key</b>
The lookup key to be used in SMTPD access tables
instead of the null sender address. A null sender
address cannot be looked up.
<b>maps</b><i>_</i><b>rbl</b><i>_</i><b>domains</b> (deprecated)
List of DNS domains that publish the addresses of
blacklisted hosts. This is used with the deprecated
<b>reject</b><i>_</i><b>maps</b><i>_</i><b>rbl</b> restriction.
<b>permit</b><i>_</i><b>mx</b><i>_</i><b>backup</b><i>_</i><b>networks</b>
Only domains whose primary MX hosts match the
listed networks are eligible for the <b>per-</b>
<b>mit</b><i>_</i><b>mx</b><i>_</i><b>backup</b> feature.
<b>relay</b><i>_</i><b>domains</b>
Restrict what domains this mail system will relay
mail to. The domains are routed to the delivery
agent specified with the <b>relay</b><i>_</i><b>transport</b> setting.
<b>UCE</b> <b>control</b> <b>responses</b>
<b>access</b><i>_</i><b>map</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a client violates an access
database restriction.
<b>default</b><i>_</i><b>rbl</b><i>_</i><b>reply</b>
Default template reply when a request is RBL black-
listed. This template is used by the <b>reject</b><i>_</i><b>rbl</b><i>_</i><b>*</b>
and <b>reject</b><i>_</i><b>rhsbl</b><i>_</i><b>*</b> restrictions. See also:
<b>rbl</b><i>_</i><b>reply</b><i>_</i><b>maps</b> and <b>smtpd</b><i>_</i><b>expansion</b><i>_</i><b>filter</b>.
<b>defer</b><i>_</i><b>code</b>
Response code when a client request is rejected by
the <b>defer</b> restriction.
<b>invalid</b><i>_</i><b>hostname</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a client violates the
<b>reject</b><i>_</i><b>invalid</b><i>_</i><b>hostname</b> restriction.
<b>maps</b><i>_</i><b>rbl</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a request is RBL blacklisted.
<b>rbl</b><i>_</i><b>reply</b><i>_</i><b>maps</b>
Table with template responses for RBL blacklisted
requests, indexed by RBL domain name. These tem-
plates are used by the <b>reject</b><i>_</i><b>rbl</b><i>_</i><b>*</b> and
<b>reject</b><i>_</i><b>rhsbl</b><i>_</i><b>*</b> restrictions. See also:
<b>default</b><i>_</i><b>rbl</b><i>_</i><b>reply</b> and <b>smtpd</b><i>_</i><b>expansion</b><i>_</i><b>filter</b>.
<b>reject</b><i>_</i><b>code</b>
Response code when the client matches a <b>reject</b>
restriction.
<b>relay</b><i>_</i><b>domains</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a client attempts to violate the
mail relay policy.
<b>unknown</b><i>_</i><b>address</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a client violates the
<b>reject</b><i>_</i><b>unknown</b><i>_</i><b>address</b> restriction.
<b>unknown</b><i>_</i><b>client</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a client without address to name
mapping violates the <b>reject</b><i>_</i><b>unknown</b><i>_</i><b>client</b> restric-
tion.
<b>unknown</b><i>_</i><b>hostname</b><i>_</i><b>reject</b><i>_</i><b>code</b>
Response code when a client violates the
<b>reject</b><i>_</i><b>unknown</b><i>_</i><b>hostname</b> restriction.
<b>SEE</b> <b>ALSO</b>
<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a> address resolver
<a href="cleanup.8.html">cleanup(8)</a> message canonicalization
<a href="master.8.html">master(8)</a> process manager
syslogd(8) system logging
<b>LICENSE</b>
The Secure Mailer license must be distributed with this
software.
<b>AUTHOR(S)</b>
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
SMTPD(8)
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