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+ "http://www.w3.org/TR/html4/loose.dtd">
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+<html>
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+<head>
+
+<title> Postfix Basic Configuration </title>
+
+<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
+
+</head>
+
+<body>
+
+<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix Basic Configuration </h1>
+
+<hr>
+
+<h2> Introduction </h2>
+
+<p> Postfix has several hundred configuration parameters that are
+controlled via the main.cf file. Fortunately, all parameters have
+sensible default values. In many cases, you need to configure only
+two or three parameters before you can start to play with the mail
+system. Here's a quick introduction to the syntax: </p>
+
+<ul>
+
+<li> <p> <a href="#syntax">Postfix configuration files</a></p>
+
+</ul>
+
+<p> The text below assumes that you already have Postfix installed
+on the system, either by compiling the source code yourself (as
+described in the INSTALL file) or by installing an already compiled
+version. </p>
+
+<p> This document covers basic Postfix configuration. Information
+about how to configure Postfix for specific applications such as
+mailhub, firewall or dial-up client can be found in the
+STANDARD_CONFIGURATION_README file. But don't go there until you
+already have covered the material presented below. </p>
+
+<p> The first parameters of interest specify the machine's identity
+and role in the network. </p>
+
+<ul>
+
+<li> <p> <a href="#myorigin"> What domain name to use in outbound mail </a> </p>
+
+<li> <p> <a href="#mydestination"> What domains to receive mail for </a> </p>
+
+<li> <p> <a href="#relay_from"> What clients to relay mail from </a> </p>
+
+<li> <p> <a href="#relay_to"> What destinations to relay mail to </a> </p>
+
+<li> <p> <a href="#relayhost"> What delivery method: direct or
+indirect </a> </p>
+
+</ul>
+
+<p> The default values for many other configuration parameters are
+derived from just these. </p>
+
+<p> The next parameter of interest controls the amount of mail sent
+to the local postmaster: </p>
+
+<ul>
+
+<li> <p> <a href="#notify"> What trouble to report to the postmaster
+</a> </p>
+
+</ul>
+
+<p> Be sure to set the following correctly if you're behind a proxy or
+network address translator, and you are running a backup MX host
+for some other domain: </p>
+
+<ul>
+
+<li> <p> <a href="#proxy_interfaces"> Proxy/NAT external network
+addresses </a> </p>
+
+</ul>
+
+<p> Postfix daemon processes run in the background, and log problems
+and normal activity to the syslog daemon. Here are a few things
+that you need to be aware of: </p>
+
+<ul>
+
+<li> <p> <a href="#syslog_howto"> What you need to know about
+Postfix logging </a> </p>
+
+</ul>
+
+<p> If your machine has unusual security requirements you may
+want to run Postfix daemon processes inside a chroot environment. </p>
+
+<ul>
+
+<li> <p> <a href="#chroot_setup"> Running Postfix daemon processes
+chrooted </a> </p>
+
+</ul>
+<p> If you run Postfix on a virtual network interface, or if your
+machine runs other mailers on virtual interfaces, you'll have to
+look at the other parameters listed here as well: </p>
+
+<ul>
+
+<li> <p> <a href="#myhostname"> My own hostname </a> </p>
+
+<li> <p> <a href="#mydomain"> My own domain name </a> </p>
+
+<li> <p> <a href="#inet_interfaces"> My own network addresses </a> </p>
+
+</ul>
+
+<h2> <a name="syntax">Postfix configuration files</a></h2>
+
+<p> By default, Postfix configuration files are in /etc/postfix.
+The two most important files are main.cf and master.cf; these files
+must be owned by root. Giving someone else write permission to
+main.cf or master.cf (or to their parent directories) means giving
+root privileges to that person. </p>
+
+<p> In /etc/postfix/main.cf you will have to set up a minimal number
+of configuration parameters. Postfix configuration parameters
+resemble shell variables, with two important differences: the first
+one is that Postfix does not know about quotes like the UNIX shell
+does.</p>
+
+<p> You specify a configuration parameter as: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ parameter = value
+</pre>
+</blockquote>
+
+<p> and you use it by putting a "$" character in front of its name: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ other_parameter = $parameter
+</pre>
+</blockquote>
+
+<p> You can use $parameter before it is given a value (that is the
+second main difference with UNIX shell variables). The Postfix
+configuration language uses lazy evaluation, and does not look at
+a parameter value until it is needed at runtime. </p>
+
+<p> Postfix uses database files for access control, address rewriting
+and other purposes. The DATABASE_README file gives an introduction
+to how Postfix works with Berkeley DB, LDAP or SQL and other types.
+Here is a common example of how Postfix invokes a database: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ virtual_alias_maps = hash:/etc/postfix/virtual
+</pre>
+</blockquote>
+
+<p> Whenever you make a change to the main.cf or master.cf file,
+execute the following command as root in order to refresh a running
+mail system: </p>
+
+<blockquote>
+<pre>
+# postfix reload
+</pre>
+</blockquote>
+
+<h2> <a name="myorigin"> What domain name to use in outbound mail </a> </h2>
+
+<p> The myorigin parameter specifies the domain that appears in
+mail that is posted on this machine. The default is to use the
+local machine name, $myhostname, which defaults to the name of the
+machine. Unless you are running a really small site, you probably
+want to change that into $mydomain, which defaults to the parent
+domain of the machine name. </p>
+
+<p> For the sake of consistency between sender and recipient addresses,
+myorigin also specifies the domain name that is appended
+to an unqualified recipient address. </p>
+
+<p> Examples (specify only one of the following): </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ myorigin = $myhostname (default: send mail as "user@$myhostname")
+ myorigin = $mydomain (probably desirable: "user@$mydomain")
+</pre>
+</blockquote>
+
+<h2><a name="mydestination"> What domains to receive mail for </a>
+</h2>
+
+<p> The mydestination parameter specifies what domains this
+machine will deliver locally, instead of forwarding to another
+machine. The default is to receive mail for the machine itself.
+See the VIRTUAL_README file for how to configure Postfix for
+hosted domains. </p>
+
+<p> You can specify zero or more domain names, "/file/name" patterns
+and/or "type:table" lookup tables (such as hash:, btree:, nis:, ldap:,
+or mysql:), separated by whitespace and/or commas. A "/file/name"
+pattern is replaced by its contents; "type:table" requests that a
+table lookup is done and merely tests for existence: the lookup
+result is ignored. </p>
+
+<p> IMPORTANT: If your machine is a mail server for its entire
+domain, you must list $mydomain as well. </p>
+
+<p> Example 1: default setting. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mydestination = $myhostname localhost.$mydomain localhost
+</pre>
+</blockquote>
+
+<p> Example 2: domain-wide mail server. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mydestination = $myhostname localhost.$mydomain localhost $mydomain
+</pre>
+</blockquote>
+
+<p> Example 3: host with multiple DNS A records. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mydestination = $myhostname localhost.$mydomain localhost
+ www.$mydomain ftp.$mydomain
+</pre>
+</blockquote>
+
+<p> Caution: in order to avoid mail delivery loops, you must list all
+hostnames of the machine, including $myhostname, and localhost.$mydomain. </p>
+
+<h2> <a name="relay_from"> What clients to relay mail from </a> </h2>
+
+<p> By default, Postfix will forward mail from clients in authorized
+network blocks to any destination. Authorized networks are defined
+with the mynetworks configuration parameter. The current default is to
+authorize the local machine only. Prior to Postfix 3.0, the default
+was to authorize all clients in the IP subnetworks that the local
+machine is attached to. </p>
+
+<p> Postfix can also be configured to relay mail from "mobile"
+clients that send mail from outside an authorized network block.
+This is explained in the SASL_README and TLS_README documents. </p>
+
+<p> IMPORTANT: If your machine is connected to a wide area network
+then your default mynetworks setting may be too friendly. </p>
+
+<p> Examples (specify only one of the following): </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mynetworks_style = subnet (default: authorize subnetworks)
+ mynetworks_style = host (safe: authorize local machine only)
+ mynetworks = 127.0.0.0/8 (safe: authorize local machine only)
+ mynetworks = 127.0.0.0/8 168.100.189.2/32 (authorize local machine)
+</pre>
+</blockquote>
+
+<p> You can specify the trusted networks in the main.cf file, or
+you can let Postfix do the work for you. The default is to let
+Postfix do the work. The result depends on the mynetworks_style
+parameter value.
+
+<ul>
+
+<li> <p> Specify "mynetworks_style = host" when Postfix should
+forward mail from only the local machine. </p>
+
+<li> <p> Specify "mynetworks_style = subnet" (the default) when
+Postfix should forward mail from SMTP clients in the same IP
+subnetworks as the local machine. On Linux, this works correctly
+only with interfaces specified with the "ifconfig" command. </p>
+
+<li> <p> Specify "mynetworks_style = class" when Postfix should
+forward mail from SMTP clients in the same IP class A/B/C networks
+as the local machine. Don't do this with a dialup site - it would
+cause Postfix to "trust" your entire provider's network. Instead,
+specify an explicit mynetworks list by hand, as described below.
+</p>
+
+</ul>
+
+<p> Alternatively, you can specify the mynetworks list by hand,
+in which case Postfix ignores the mynetworks_style setting.
+To specify the list of trusted networks by hand, specify network
+blocks in CIDR (network/mask) notation, for example: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mynetworks = 168.100.189.0/28, 127.0.0.0/8
+</pre>
+</blockquote>
+
+<p> You can also specify the absolute pathname of a pattern file instead
+of listing the patterns in the main.cf file. </p>
+
+<h2> <a name="relay_to"> What destinations to relay mail to </a> </h2>
+
+<p> By default, Postfix will forward mail from strangers (clients outside
+authorized networks) to authorized remote destinations only.
+Authorized remote
+destinations are defined with the relay_domains configuration
+parameter. The default is to authorize all domains (and subdomains)
+of the domains listed with the mydestination parameter. </p>
+
+<p> Examples (specify only one of the following): </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ relay_domains = $mydestination (default)
+ relay_domains = (safe: never forward mail from strangers)
+ relay_domains = $mydomain (forward mail to my domain and subdomains)
+</pre>
+</blockquote>
+
+<h2> <a name="relayhost"> What delivery method: direct or
+indirect </a> </h2>
+
+<p> By default, Postfix tries to deliver mail directly to the
+Internet. Depending on your local conditions this may not be possible
+or desirable. For example, your system may be turned off outside
+office hours, it may be behind a firewall, or it may be connected
+via a provider who does not allow direct mail to the Internet. In
+those cases you need to configure Postfix to deliver mail indirectly
+via a relay host. </p>
+
+<p> Examples (specify only one of the following): </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ relayhost = (default: direct delivery to Internet)
+ relayhost = $mydomain (deliver via local mailhub)
+ relayhost = [mail.$mydomain] (deliver via local mailhub)
+ relayhost = [mail.isp.tld] (deliver via provider mailhub)
+</pre>
+</blockquote>
+
+<p> The form enclosed with <tt>[]</tt> eliminates DNS MX lookups.
+Don't worry if you don't know what that means. Just be sure to
+specify the <tt>[]</tt> around the mailhub hostname that your ISP
+gave to you, otherwise mail may be mis-delivered. </p>
+
+<p> The STANDARD_CONFIGURATION_README file has more hints and tips
+for firewalled and/or dial-up networks. </p>
+
+<h2> <a name="notify"> What trouble to report to the postmaster</a> </h2>
+
+<p> You should set up a postmaster alias in the aliases(5) table
+that directs mail to a human person. The postmaster address is
+required to exist, so that people can report mail delivery problems.
+While you're updating the aliases(5) table, be sure to direct mail
+for the super-user to a human person too. </p>
+
+<blockquote>
+<pre>
+/etc/aliases:
+ postmaster: you
+ root: you
+</pre>
+</blockquote>
+
+<p> Execute the command "newaliases" after changing the aliases
+file. Instead of /etc/aliases, your alias file may be located
+elsewhere. Use the command "postconf alias_maps" to find out.</p>
+
+<p> The Postfix system reports problems to the postmaster alias.
+You may not be interested in all types of trouble reports, so this
+reporting mechanism is configurable. The default is to report only
+serious problems (resource, software) to postmaster: </p>
+
+<p> Default setting: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ notify_classes = resource, software
+</pre>
+</blockquote>
+
+<p> The meaning of the classes is as follows: </p>
+
+<blockquote>
+
+<dl>
+
+<dt> bounce </dt> <dd> Inform the postmaster of undeliverable
+mail. Either send the postmaster a copy of undeliverable mail that
+is returned to the sender, or send a transcript of the SMTP session
+when Postfix rejected mail. For privacy reasons, the postmaster
+copy of undeliverable mail is truncated after the original message
+headers. This implies "2bounce" (see below). See also the
+luser_relay feature. The notification is sent to the address
+specified with the bounce_notice_recipient configuration parameter
+(default: postmaster). </dd>
+
+<dt> 2bounce </dt> <dd> When Postfix is unable to return undeliverable
+mail to the sender, send it to the postmaster instead (without
+truncating the message after the primary headers). The notification
+is sent to the address specified with the 2bounce_notice_recipient
+configuration parameter (default: postmaster). </dd>
+
+<dt> delay </dt> <dd> Inform the postmaster of delayed mail. In
+this case, the postmaster receives message headers only. The
+notification is sent to the address specified with the
+delay_notice_recipient configuration parameter (default: postmaster).
+</dd>
+
+<dt> policy </dt> <dd> Inform the postmaster of client requests
+that were rejected because of (UCE) policy restrictions. The
+postmaster receives a transcript of the SMTP session. The notification
+is sent to the address specified with the error_notice_recipient
+configuration parameter (default: postmaster). </dd>
+
+<dt> protocol </dt> <dd> Inform the postmaster of protocol errors
+(client or server side) or attempts by a client to execute
+unimplemented commands. The postmaster receives a transcript of
+the SMTP session. The notification is sent to the address specified
+with the error_notice_recipient configuration parameter (default:
+postmaster). </dd>
+
+<dt> resource </dt> <dd> Inform the postmaster of mail not delivered
+due to resource problems (for example, queue file write errors).
+The notification is sent to the address specified with the
+error_notice_recipient configuration parameter (default: postmaster).
+</dd>
+
+<dt> software </dt> <dd> Inform the postmaster of mail not delivered
+due to software problems. The notification is sent to the address
+specified with the error_notice_recipient configuration parameter
+(default: postmaster). </dd>
+
+</dl>
+
+</blockquote>
+
+<h2><a name="proxy_interfaces"> Proxy/NAT external network
+addresses</a> </h2>
+
+<p> Some mail servers are connected to the Internet via a network
+address translator (NAT) or proxy. This means that systems on the
+Internet connect to the address of the NAT or proxy, instead of
+connecting to the network address of the mail server. The NAT or
+proxy forwards the connection to the network address of the mail
+server, but Postfix does not know this. </p>
+
+<p> If you run a Postfix server behind a proxy or NAT, you need to
+configure the proxy_interfaces parameter and specify all the external
+proxy or NAT addresses that Postfix receives mail on. You may
+specify symbolic hostnames instead of network addresses. </p>
+
+<p> IMPORTANT: You must specify your proxy/NAT external addresses
+when your system is a backup MX host for other domains, otherwise
+mail delivery loops will happen when the primary MX host is down.
+</p>
+
+<p> Example: host behind NAT box running a backup MX host. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ proxy_interfaces = 1.2.3.4 (the proxy/NAT external network address)
+</pre>
+</blockquote>
+
+<h2> <a name="syslog_howto"> What you need to know about
+Postfix logging </a> </h2>
+
+<p> Postfix daemon processes run in the background, and log problems
+and normal activity to the syslog daemon. The syslogd process sorts
+events by class and severity, and appends them to logfiles. The
+logging classes, levels and logfile names are usually specified in
+/etc/syslog.conf. At the very least you need something like: </p>
+
+<blockquote>
+<pre>
+/etc/syslog.conf:
+ mail.err /dev/console
+ mail.debug /var/log/maillog
+</pre>
+</blockquote>
+
+<p> After changing the syslog.conf file, send a "HUP" signal to
+the syslogd process. </p>
+
+<p> IMPORTANT: many syslogd implementations will not create files.
+You must create files before (re)starting syslogd. </p>
+
+<p> IMPORTANT: on Linux you need to put a "-" character before the
+pathname, e.g., -/var/log/maillog, otherwise the syslogd process
+will use more system resources than Postfix. </p>
+
+<p> Hopefully, the number of problems will be small, but it is a good
+idea to run every night before the syslog files are rotated: </p>
+
+<blockquote>
+<pre>
+# postfix check
+# egrep '(reject|warning|error|fatal|panic):' /some/log/file
+</pre>
+</blockquote>
+
+<ul>
+
+<li> <p> The first line (postfix check) causes Postfix to report
+file permission/ownership discrepancies. </p>
+
+<li> <p> The second line looks for problem reports from the mail
+software, and reports how effective the relay and junk mail access
+blocks are. This may produce a lot of output. You will want to
+apply some postprocessing to eliminate uninteresting information.
+</p>
+
+</ul>
+
+<p> The <a href="DEBUG_README.html#logging"> DEBUG_README </a>
+document describes the meaning of the "warning" etc. labels in
+Postfix logging. </p>
+
+<h2> <a name="chroot_setup"> Running Postfix daemon processes
+chrooted </a> </h2>
+
+<p> Postfix daemon processes can be configured (via the master.cf
+file) to run in a chroot jail. The processes run at a fixed low
+privilege and with file system access limited to the Postfix queue
+directories (/var/spool/postfix). This provides a significant
+barrier against intrusion. The barrier is not impenetrable (chroot
+limits file system access only), but every little bit helps.</p>
+
+<p>With the exception of Postfix daemons that deliver mail locally
+and/or that execute non-Postfix commands, every Postfix daemon can
+run chrooted.</p>
+
+<p>Sites with high security requirements should consider to chroot
+all daemons that talk to the network: the smtp(8) and smtpd(8)
+processes, and perhaps also the lmtp(8) client. The author's own
+porcupine.org mail server runs all daemons chrooted that can be
+chrooted. </p>
+
+<p>The default /etc/postfix/master.cf file specifies that no Postfix
+daemon runs chrooted. In order to enable chroot operation, edit
+the file /etc/postfix/master.cf, and follow instructions in the
+file. When you're finished, execute "postfix reload" to make the
+change effective. </p>
+
+<p>Note that a chrooted daemon resolves all filenames relative to
+the Postfix queue directory (/var/spool/postfix). For successful
+use of a chroot jail, most UNIX systems require you to bring in
+some files or device nodes. The examples/chroot-setup directory in
+the source code distribution has a collection of scripts that help
+you set up Postfix chroot environments on different operating
+systems.</p>
+
+<p> Additionally, you almost certainly need to configure syslogd
+so that it listens on a socket inside the Postfix queue directory.
+Examples of syslogd command line options that achieve this for
+specific systems: </p>
+
+<p> FreeBSD: <tt>syslogd -l /var/spool/postfix/var/run/log</tt> </p>
+
+<p> Linux, OpenBSD: <tt>syslogd -a /var/spool/postfix/dev/log</tt> </p>
+
+<h2><a name="myhostname"> My own hostname </a> </h2>
+
+<p> The myhostname parameter specifies the fully-qualified domain
+name of the machine running the Postfix system. $myhostname
+appears as the default value in many other Postfix configuration
+parameters. </p>
+
+<p> By default, myhostname is set to the local machine name. If
+your local machine name is not in fully-qualified domain name form,
+or if you run Postfix on a virtual interface, you will have to
+specify the fully-qualified domain name that the mail system should
+use. </p>
+
+<p> Alternatively, if you specify mydomain in main.cf, then Postfix
+will use its value to generate a fully-qualified default value
+for the myhostname parameter. </p>
+
+<p> Examples (specify only one of the following): </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ myhostname = host.local.domain (machine name is not FQDN)
+ myhostname = host.virtual.domain (virtual interface)
+ myhostname = virtual.domain (virtual interface)
+</pre>
+</blockquote>
+
+<h2><a name="mydomain"> My own domain name</a> </h2>
+
+<p> The mydomain parameter specifies the parent domain of
+$myhostname. By default, it is derived from $myhostname
+by stripping off the first part (unless the result would be a
+top-level domain). </p>
+
+<p> Conversely, if you specify mydomain in main.cf, then Postfix
+will use its value to generate a fully-qualified default value
+for the myhostname parameter. </p>
+
+<p> Examples (specify only one of the following): </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mydomain = local.domain
+ mydomain = virtual.domain (virtual interface)
+</pre>
+</blockquote>
+
+<h2><a name="inet_interfaces">My own network addresses</a> </h2>
+
+<p>The inet_interfaces parameter specifies all network interface
+addresses that the Postfix system should listen on; mail addressed
+to "user@[network address]" will be delivered locally,
+as if it is addressed to a domain listed in $mydestination.</p>
+
+<p> You can override the inet_interfaces setting in the Postfix
+master.cf file by prepending an IP address to a server name. </p>
+
+<p> The default is to listen on all active interfaces. If you run
+mailers on virtual interfaces, you will have to specify what
+interfaces to listen on. </p>
+
+<p> IMPORTANT: If you run MTAs on virtual interfaces you must
+specify explicit inet_interfaces values for the MTA that receives
+mail for the machine itself: this MTA should never listen on the
+virtual interfaces or you would have a mailer loop when a virtual
+MTA is down. </p>
+
+<p> Example: default setting. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ inet_interfaces = all
+</pre>
+</blockquote>
+
+<p> Example: host running one or more virtual mailers. For
+each Postfix instance, specify only one of the following. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ inet_interfaces = virtual.host.tld (virtual Postfix)
+ inet_interfaces = $myhostname localhost... (non-virtual Postfix)
+</pre>
+</blockquote>
+
+<p> Note: you need to stop and start Postfix after changing this
+parameter. </p>
+
+</body>
+
+</html>