Adding upstream version 3.4.23.upstream/3.4.23upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 631 insertions, 0 deletions

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+PPoossttffiixx SSttaannddaarrdd CCoonnffiigguurraattiioonn EExxaammpplleess
+
+-------------------------------------------------------------------------------
+
+PPuurrppoossee ooff tthhiiss ddooccuummeenntt
+
+This document presents a number of typical Postfix configurations. This
+document should be reviewed after you have followed the basic configuration
+steps as described in the BASIC_CONFIGURATION_README document. In particular,
+do not proceed here if you don't already have Postfix working for local mail
+submission and for local mail delivery.
+
+The first part of this document presents standard configurations that each
+solve one specific problem.
+
+  * Postfix on a stand-alone Internet host
+  * Postfix on a null client
+  * Postfix on a local network
+  * Postfix email firewall/gateway
+
+The second part of this document presents additional configurations for hosts
+in specific environments.
+
+  * Delivering some but not all accounts locally
+  * Running Postfix behind a firewall
+  * Configuring Postfix as primary or backup MX host for a remote site
+  * Postfix on a dialup machine
+  * Postfix on hosts without a real Internet hostname
+
+PPoossttffiixx oonn aa ssttaanndd--aalloonnee IInntteerrnneett hhoosstt
+
+Postfix should work out of the box without change on a stand-alone machine that
+has direct Internet access. At least, that is how Postfix installs when you
+download the Postfix source code via http://www.postfix.org/.
+
+You can use the command "ppoossttccoonnff --nn" to find out what settings are overruled
+by your main.cf. Besides a few pathname settings, few parameters should be set
+on a stand-alone box, beyond what is covered in the BASIC_CONFIGURATION_README
+document:
+
+    /etc/postfix/main.cf:
+        # Optional: send mail as user@domainname instead of user@hostname.
+        #myorigin = $mydomain
+
+        # Optional: specify NAT/proxy external address.
+        #proxy_interfaces = 1.2.3.4
+
+        # Alternative 1: don't relay mail from other hosts.
+        mynetworks_style = host
+        relay_domains =
+
+        # Alternative 2: relay mail from local clients only.
+        # mynetworks = 192.168.1.0/28
+        # relay_domains =
+
+See also the section "Postfix on hosts without a real Internet hostname" if
+this is applicable to your configuration.
+
+PPoossttffiixx oonn aa nnuullll cclliieenntt
+
+A null client is a machine that can only send mail. It receives no mail from
+the network, and it does not deliver any mail locally. A null client typically
+uses POP, IMAP or NFS for mailbox access.
+
+In this example we assume that the Internet domain name is "example.com" and
+that the machine is named "hostname.example.com". As usual, the examples show
+only parameters that are not left at their default settings.
+
+    1 /etc/postfix/main.cf:
+    2     myhostname = hostname.example.com
+    3     myorigin = $mydomain
+    4     relayhost = $mydomain
+    5     inet_interfaces = loopback-only
+    6     mydestination =
+
+Translation:
+
+  * Line 2: Set myhostname to hostname.example.com, in case the machine name
+    isn't set to a fully-qualified domain name (use the command "postconf -
+    d myhostname" to find out what the machine name is).
+
+  * Line 2: The myhostname value also provides the default value for the
+    mydomain parameter (here, "mydomain = example.com").
+
+  * Line 3: Send mail as "user@example.com" (instead of
+    "user@hostname.example.com"), so that nothing ever has a reason to send
+    mail to "user@hostname.example.com".
+
+  * Line 4: Forward all mail to the mail server that is responsible for the
+    "example.com" domain. This prevents mail from getting stuck on the null
+    client if it is turned off while some remote destination is unreachable.
+    Specify a real hostname here if your "example.com" domain has no MX record.
+
+  * Line 5: Do not accept mail from the network.
+
+  * Line 6: Disable local mail delivery. All mail goes to the mail server as
+    specified in line 4.
+
+PPoossttffiixx oonn aa llooccaall nneettwwoorrkk
+
+This section describes a local area network environment of one main server and
+multiple other systems that send and receive email. As usual we assume that the
+Internet domain name is "example.com". All systems are configured to send mail
+as "user@example.com", and all systems receive mail for
+"user@hostname.example.com". The main server also receives mail for
+"user@example.com". We call this machine by the name of mailhost.example.com.
+
+A drawback of sending mail as "user@example.com" is that mail for "root" and
+other system accounts is also sent to the central mailhost. See the section
+"Delivering some but not all accounts locally" below for possible solutions.
+
+As usual, the examples show only parameters that are not left at their default
+settings.
+
+First we present the non-mailhost configuration, because it is the simpler one.
+This machine sends mail as "user@example.com" and is final destination for
+"user@hostname.example.com".
+
+    1 /etc/postfix/main.cf:
+    2     myorigin = $mydomain
+    3     mynetworks = 127.0.0.0/8 10.0.0.0/24
+    4     relay_domains =
+    5     # Optional: forward all non-local mail to mailhost
+    6     #relayhost = $mydomain
+
+Translation:
+
+  * Line 2: Send mail as "user@example.com".
+
+  * Line 3: Specify the trusted networks.
+
+  * Line 4: This host does not relay mail from untrusted networks.
+
+  * Line 6: This is needed if no direct Internet access is available. See also
+    below, "Postfix behind a firewall".
+
+Next we present the mailhost configuration. This machine sends mail as
+"user@example.com" and is final destination for "user@hostname.example.com" as
+well as "user@example.com".
+
+     1 DNS:
+     2     example.com    IN    MX  10 mailhost.example.com.
+     3
+     4 /etc/postfix/main.cf:
+     5     myorigin = $mydomain
+     6     mydestination = $myhostname localhost.$mydomain localhost $mydomain
+     7     mynetworks = 127.0.0.0/8 10.0.0.0/24
+     8     relay_domains =
+     9     # Optional: forward all non-local mail to firewall
+    10     #relayhost = [firewall.example.com]
+
+Translation:
+
+  * Line 2: Send mail for the domain "example.com" to the machine
+    mailhost.example.com. Remember to specify the "." at the end of the line.
+
+  * Line 5: Send mail as "user@example.com".
+
+  * Line 6: This host is the final mail destination for the "example.com"
+    domain, in addition to the names of the machine itself.
+
+  * Line 7: Specify the trusted networks.
+
+  * Line 8: This host does not relay mail from untrusted networks.
+
+  * Line 10: This is needed only when the mailhost has to forward non-local
+    mail via a mail server on a firewall. The [] forces Postfix to do no MX
+    record lookups.
+
+In an environment like this, users access their mailbox in one or more of the
+following ways:
+
+  * Mailbox access via NFS or equivalent.
+
+  * Mailbox access via POP or IMAP.
+
+  * Mailbox on the user's preferred machine.
+
+In the latter case, each user has an alias on the mailhost that forwards mail
+to her preferred machine:
+
+    /etc/aliases:
+        joe:    joe@joes.preferred.machine
+        jane:   jane@janes.preferred.machine
+
+On some systems the alias database is not in /etc/aliases. To find out the
+location for your system, execute the command "ppoossttccoonnff aalliiaass__mmaappss".
+
+Execute the command "nneewwaalliiaasseess" whenever you change the aliases file.
+
+PPoossttffiixx eemmaaiill ffiirreewwaallll//ggaatteewwaayy
+
+The idea is to set up a Postfix email firewall/gateway that forwards mail for
+"example.com" to an inside gateway machine but rejects mail for
+"anything.example.com". There is only one problem: with "relay_domains =
+example.com", the firewall normally also accepts mail for
+"anything.example.com". That would not be right.
+
+Note: this example requires Postfix version 2.0 and later. To find out what
+Postfix version you have, execute the command "ppoossttccoonnff mmaaiill__vveerrssiioonn".
+
+The solution is presented in multiple parts. This first part gets rid of local
+mail delivery on the firewall, making the firewall harder to break.
+
+    1 /etc/postfix/main.cf:
+    2     myorigin = example.com
+    3     mydestination =
+    4     local_recipient_maps =
+    5     local_transport = error:local mail delivery is disabled
+    6
+    7 /etc/postfix/master.cf:
+    8     Comment out the local delivery agent
+
+Translation:
+
+  * Line 2: Send mail from this machine as "user@example.com", so that no
+    reason exists to send mail to "user@firewall.example.com".
+
+  * Lines 3-8: Disable local mail delivery on the firewall machine.
+
+For the sake of technical correctness the firewall must be able to receive mail
+for postmaster@[firewall ip address]. Reportedly, some things actually expect
+this ability to exist. The second part of the solution therefore adds support
+for postmaster@[firewall ip address], and as a bonus we do abuse@[firewall ip
+address] as well. All the mail to these two accounts is forwarded to an inside
+address.
+
+    1 /etc/postfix/main.cf:
+    2     virtual_alias_maps = hash:/etc/postfix/virtual
+    3
+    4 /etc/postfix/virtual:
+    5     postmaster      postmaster@example.com
+    6     abuse           abuse@example.com
+
+Translation:
+
+  * Because mydestination is empty (see the previous example), only address
+    literals matching $inet_interfaces or $proxy_interfaces are deemed local.
+    So "localpart@[a.d.d.r]" can be matched as simply "localpart" in canonical
+    (5) and virtual(5). This avoids the need to specify firewall IP addresses
+    into Postfix configuration files.
+
+The last part of the solution does the email forwarding, which is the real
+purpose of the firewall email function.
+
+     1 /etc/postfix/main.cf:
+     2     mynetworks = 127.0.0.0/8 12.34.56.0/24
+     3     relay_domains = example.com
+     4     parent_domain_matches_subdomains =
+     5         debug_peer_list smtpd_access_maps
+
+     6a    # Postfix 2.10 and later support separate relay control and
+     7a    # spam control.
+     8a    smtpd_relay_restrictions =
+     9a        permit_mynetworks reject_unauth_destination
+    10a    smtpd_recipient_restrictions = ...spam blocking rules....
+
+     6b    # Older configurations combine relay control and spam control. To
+     7b    # use this with Postfix >= 2.10 specify "smtpd_relay_restrictions=".
+     8b    smtpd_recipient_restrictions =
+     9b        permit_mynetworks reject_unauth_destination
+    10b        ...spam blocking rules....
+
+    11     relay_recipient_maps = hash:/etc/postfix/relay_recipients
+    12     transport_maps = hash:/etc/postfix/transport
+    13
+    14 /etc/postfix/relay_recipients:
+    15     user1@example.com   x
+    16     user2@example.com   x
+    17      . . .
+    18
+    19 /etc/postfix/transport:
+    20     example.com   smtp:[inside-gateway.example.com]
+
+Translation:
+
+  * Lines 1-10: Accept mail from local systems in $mynetworks, and accept mail
+    from outside for "user@example.com" but not for
+    "user@anything.example.com". The magic is in lines 4-5.
+
+  * Lines 11, 13-16: Define the list of valid addresses in the "example.com"
+    domain that can receive mail from the Internet. This prevents the mail
+    queue from filling up with undeliverable MAILER-DAEMON messages. If you
+    can't maintain a list of valid recipients then you must specify
+    "relay_recipient_maps =" (that is, an empty value), or you must specify an
+    "@example.com x" wild-card in the relay_recipients table.
+
+  * Lines 12, 19-20: Route mail for "example.com" to the inside gateway
+    machine. The [] forces Postfix to do no MX lookup.
+
+Specify ddbbmm instead of hhaasshh if your system uses ddbbmm files instead of ddbb files.
+To find out what lookup tables Postfix supports, use the command "ppoossttccoonnff --mm".
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//rreellaayy__rreecciippiieennttss" whenever you change
+the relay_recipients table.
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//ttrraannssppoorrtt" whenever you change the
+transport table.
+
+In some installations, there may be separate instances of Postfix processing
+inbound and outbound mail on a multi-homed firewall. The inbound Postfix
+instance has an SMTP server listening on the external firewall interface, and
+the outbound Postfix instance has an SMTP server listening on the internal
+interface. In such a configuration is it is tempting to configure
+$inet_interfaces in each instance with just the corresponding interface
+address.
+
+In most cases, using inet_interfaces in this way will not work, because as
+documented in the $inet_interfaces reference manual, the smtp(8) delivery agent
+will also use the specified interface address as the source address for
+outbound connections and will be unable to reach hosts on "the other side" of
+the firewall. The symptoms are that the firewall is unable to connect to hosts
+that are in fact up. See the inet_interfaces parameter documentation for
+suggested work-arounds.
+
+DDeelliivveerriinngg ssoommee bbuutt nnoott aallll aaccccoouunnttss llooccaallllyy
+
+A drawback of sending mail as "user@example.com" (instead of
+"user@hostname.example.com") is that mail for "root" and other system accounts
+is also sent to the central mailhost. In order to deliver such accounts
+locally, you can set up virtual aliases as follows:
+
+    1 /etc/postfix/main.cf:
+    2     virtual_alias_maps = hash:/etc/postfix/virtual
+    3
+    4 /etc/postfix/virtual:
+    5     root     root@localhost
+    6     . . .
+
+Translation:
+
+  * Line 5: As described in the virtual(5) manual page, the bare name "root"
+    matches "root@site" when "site" is equal to $myorigin, when "site" is
+    listed in $mydestination, or when it matches $inet_interfaces or
+    $proxy_interfaces.
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//vviirrttuuaall" after editing the file.
+
+RRuunnnniinngg PPoossttffiixx bbeehhiinndd aa ffiirreewwaallll
+
+The simplest way to set up Postfix on a host behind a firewalled network is to
+send all mail to a gateway host, and to let that mail host take care of
+internal and external forwarding. Examples of that are shown in the local area
+network section above. A more sophisticated approach is to send only external
+mail to the gateway host, and to send intranet mail directly.
+
+Note: this example requires Postfix version 2.0 and later. To find out what
+Postfix version you have, execute the command "ppoossttccoonnff mmaaiill__vveerrssiioonn".
+
+The following example presents additional configuration. You need to combine
+this with basic configuration information as discussed the first half of this
+document.
+
+     1 /etc/postfix/main.cf:
+     2     transport_maps = hash:/etc/postfix/transport
+     3     relayhost =
+     4     # Optional for a machine that isn't "always on"
+     5     #fallback_relay = [gateway.example.com]
+     6
+     7 /etc/postfix/transport:
+     8     # Internal delivery.
+     9     example.com      :
+    10     .example.com     :
+    11     # External delivery.
+    12     *                smtp:[gateway.example.com]
+
+Translation:
+
+  * Lines 2, 7-12: Request that intranet mail is delivered directly, and that
+    external mail is given to a gateway. Obviously, this example assumes that
+    the organization uses DNS MX records internally. The [] forces Postfix to
+    do no MX lookup.
+
+  * Line 3: IMPORTANT: do not specify a relayhost in main.cf.
+
+  * Line 5: This prevents mail from being stuck in the queue when the machine
+    is turned off. Postfix tries to deliver mail directly, and gives
+    undeliverable mail to a gateway.
+
+Specify ddbbmm instead of hhaasshh if your system uses ddbbmm files instead of ddbb files.
+To find out what lookup tables Postfix supports, use the command "ppoossttccoonnff --mm".
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//ttrraannssppoorrtt" whenever you edit the
+transport table.
+
+CCoonnffiigguurriinngg PPoossttffiixx aass pprriimmaarryy oorr bbaacckkuupp MMXX hhoosstt ffoorr aa rreemmoottee ssiittee
+
+This section presents additional configuration. You need to combine this with
+basic configuration information as discussed the first half of this document.
+
+When your system is SECONDARY MX host for a remote site this is all you need:
+
+     1 DNS:
+     2     the.backed-up.domain.tld        IN      MX 100 your.machine.tld.
+     3
+     4 /etc/postfix/main.cf:
+     5     relay_domains = . . . the.backed-up.domain.tld
+
+     6a    # Postfix 2.10 and later support separate relay control and
+     7a    # spam control.
+     8a    smtpd_relay_restrictions =
+     9a        permit_mynetworks reject_unauth_destination
+    10a    smtpd_recipient_restrictions = ...spam blocking rules....
+
+     6b    # Older configurations combine relay control and spam control. To
+     7b    # use this with Postfix >= 2.10 specify "smtpd_relay_restrictions=".
+     8b    smtpd_recipient_restrictions =
+     9b        permit_mynetworks reject_unauth_destination
+    10b        ...spam blocking rules....
+
+    11     # You must specify your NAT/proxy external address.
+    12     #proxy_interfaces = 1.2.3.4
+    13
+    14     relay_recipient_maps = hash:/etc/postfix/relay_recipients
+    15
+    16 /etc/postfix/relay_recipients:
+    17     user1@the.backed-up.domain.tld   x
+    18     user2@the.backed-up.domain.tld   x
+    19      . . .
+
+When your system is PRIMARY MX host for a remote site you need the above, plus:
+
+    20 /etc/postfix/main.cf:
+    21     transport_maps = hash:/etc/postfix/transport
+    22
+    23 /etc/postfix/transport:
+    24     the.backed-up.domain.tld       relay:[their.mail.host.tld]
+
+Important notes:
+
+  * Do not list the.backed-up.domain.tld in mydestination.
+
+  * Do not list the.backed-up.domain.tld in virtual_alias_domains.
+
+  * Do not list the.backed-up.domain.tld in virtual_mailbox_domains.
+
+  * Lines 1-9: Forward mail from the Internet for "the.backed-up.domain.tld" to
+    the primary MX host for that domain.
+
+  * Line 12: This is a must if Postfix receives mail via a NAT relay or proxy
+    that presents a different IP address to the world than the local machine.
+
+  * Lines 14-18: Define the list of valid addresses in the "the.backed-
+    up.domain.tld" domain. This prevents your mail queue from filling up with
+    undeliverable MAILER-DAEMON messages. If you can't maintain a list of valid
+    recipients then you must specify "relay_recipient_maps =" (that is, an
+    empty value), or you must specify an "@the.backed-up.domain.tld x" wild-
+    card in the relay_recipients table.
+
+  * Line 24: The [] forces Postfix to do no MX lookup.
+
+Specify ddbbmm instead of hhaasshh if your system uses ddbbmm files instead of ddbb files.
+To find out what lookup tables Postfix supports, use the command "ppoossttccoonnff --mm".
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//ttrraannssppoorrtt" whenever you change the
+transport table.
+
+NOTE for Postfix < 2.2: Do not use the fallback_relay feature when relaying
+mail for a backup or primary MX domain. Mail would loop between the Postfix MX
+host and the fallback_relay host when the final destination is unavailable.
+
+  * In main.cf specify "relay_transport = relay",
+  * In master.cf specify "-o fallback_relay =" at the end of the relay entry.
+  * In transport maps, specify "relay:nexthop..." as the right-hand side for
+    backup or primary MX domain entries.
+
+These are default settings in Postfix version 2.2 and later.
+
+PPoossttffiixx oonn aa ddiiaalluupp mmaacchhiinnee
+
+This section applies to dialup connections that are down most of the time. For
+dialup connections that are up 24x7, see the local area network section above.
+
+This section presents additional configuration. You need to combine this with
+basic configuration information as discussed the first half of this document.
+
+If you do not have your own hostname and IP address (usually with dialup, cable
+TV or DSL connections) then you should also study the section on "Postfix on
+hosts without a real Internet hostname".
+
+  * Route all outgoing mail to your network provider.
+    If your machine is disconnected most of the time, there isn't a lot of
+    opportunity for Postfix to deliver mail to hard-to-reach corners of the
+    Internet. It's better to give the mail to a machine that is connected all
+    the time. In the example below, the [] prevents Postfix from trying to look
+    up DNS MX records.
+
+    /etc/postfix/main.cf:
+        relayhost = [smtprelay.someprovider.com]
+
+  * Disable spontaneous SMTP mail delivery (if using on-demand dialup IP only).
+
+    Normally, Postfix attempts to deliver outbound mail at its convenience. If
+    your machine uses on-demand dialup IP, this causes your system to place a
+    telephone call whenever you submit new mail, and whenever Postfix retries
+    to deliver delayed mail. To prevent such telephone calls from being placed,
+    disable spontaneous SMTP mail deliveries.
+
+    /etc/postfix/main.cf:
+        defer_transports = smtp (Only for on-demand dialup IP hosts)
+
+  * Disable SMTP client DNS lookups (dialup LAN only).
+
+    /etc/postfix/main.cf:
+        disable_dns_lookups = yes (Only for on-demand dialup IP hosts)
+
+  * Flush the mail queue whenever the Internet link is established.
+    Put the following command into your PPP or SLIP dialup scripts:
+
+    /usr/sbin/sendmail -q (whenever the Internet link is up)
+
+    The exact location of the Postfix sendmail command is system-specific. Use
+    the command "ppoossttccoonnff sseennddmmaaiill__ppaatthh" to find out where the Postfix sendmail
+    command is located on your machine.
+
+    In order to find out if the mail queue is flushed, use something like:
+
+    #!/bin/sh
+
+    # Start mail deliveries.
+    /usr/sbin/sendmail -q
+
+    # Allow deliveries to start.
+    sleep 10
+
+    # Loop until all messages have been tried at least once.
+    while mailq | grep '^[^ ]*\*' >/dev/null
+    do
+        sleep 10
+    done
+
+    If you have disabled spontaneous SMTP mail delivery, you also need to run
+    the "sseennddmmaaiill --qq" command every now and then while the dialup link is up,
+    so that newly-posted mail is flushed from the queue.
+
+PPoossttffiixx oonn hhoossttss wwiitthhoouutt aa rreeaall IInntteerrnneett hhoossttnnaammee
+
+This section is for hosts that don't have their own Internet hostname.
+Typically these are systems that get a dynamic IP address via DHCP or via
+dialup. Postfix will let you send and receive mail just fine between accounts
+on a machine with a fantasy name. However, you cannot use a fantasy hostname in
+your email address when sending mail into the Internet, because no-one would be
+able to reply to your mail. In fact, more and more sites refuse mail addresses
+with non-existent domain names.
+
+Note: the following information is Postfix version dependent. To find out what
+Postfix version you have, execute the command "ppoossttccoonnff mmaaiill__vveerrssiioonn".
+
+SSoolluuttiioonn 11:: PPoossttffiixx vveerrssiioonn 22..22 aanndd llaatteerr
+
+Postfix 2.2 uses the generic(5) address mapping to replace local fantasy email
+addresses by valid Internet addresses. This mapping happens ONLY when mail
+leaves the machine; not when you send mail between users on the same machine.
+
+The following example presents additional configuration. You need to combine
+this with basic configuration information as discussed the first half of this
+document.
+
+    1 /etc/postfix/main.cf:
+    2     smtp_generic_maps = hash:/etc/postfix/generic
+    3
+    4 /etc/postfix/generic:
+    5     his@localdomain.local             hisaccount@hisisp.example
+    6     her@localdomain.local             heraccount@herisp.example
+    7     @localdomain.local                hisaccount+local@hisisp.example
+
+When mail is sent to a remote host via SMTP:
+
+  * Line 5 replaces his@localdomain.local by his ISP mail address,
+
+  * Line 6 replaces her@localdomain.local by her ISP mail address, and
+
+  * Line 7 replaces other local addresses by his ISP account, with an address
+    extension of +local (this example assumes that the ISP supports "+" style
+    address extensions).
+
+Specify ddbbmm instead of hhaasshh if your system uses ddbbmm files instead of ddbb files.
+To find out what lookup tables Postfix supports, use the command "ppoossttccoonnff --mm".
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//ggeenneerriicc" whenever you change the
+generic table.
+
+SSoolluuttiioonn 22:: PPoossttffiixx vveerrssiioonn 22..11 aanndd eeaarrlliieerr
+
+The solution with older Postfix systems is to use valid Internet addresses
+where possible, and to let Postfix map valid Internet addresses to local
+fantasy addresses. With this, you can send mail to the Internet and to local
+fantasy addresses, including mail to local fantasy addresses that don't have a
+valid Internet address of their own.
+
+The following example presents additional configuration. You need to combine
+this with basic configuration information as discussed the first half of this
+document.
+
+     1 /etc/postfix/main.cf:
+     2     myhostname = hostname.localdomain
+     3     mydomain = localdomain
+     4
+     5     canonical_maps = hash:/etc/postfix/canonical
+     6
+     7     virtual_alias_maps = hash:/etc/postfix/virtual
+     8
+     9 /etc/postfix/canonical:
+    10     your-login-name    your-account@your-isp.com
+    11
+    12 /etc/postfix/virtual:
+    13     your-account@your-isp.com       your-login-name
+
+Translation:
+
+  * Lines 2-3: Substitute your fantasy hostname here. Do not use a domain name
+    that is already in use by real organizations on the Internet. See RFC 2606
+    for examples of domain names that are guaranteed not to be owned by anyone.
+
+  * Lines 5, 9, 10: This provides the mapping from "your-login-
+    name@hostname.localdomain" to "your-account@your-isp.com". This part is
+    required.
+
+  * Lines 7, 12, 13: Deliver mail for "your-account@your-isp.com" locally,
+    instead of sending it to the ISP. This part is not required but is
+    convenient.
+
+Specify ddbbmm instead of hhaasshh if your system uses ddbbmm files instead of ddbb files.
+To find out what lookup tables Postfix supports, use the command "ppoossttccoonnff --mm".
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//ccaannoonniiccaall" whenever you change the
+canonical table.
+
+Execute the command "ppoossttmmaapp //eettcc//ppoossttffiixx//vviirrttuuaall" whenever you change the
+virtual table.
+