Postfix/Standartkonfigurationen

topic kurze Beschreibung

Beschreibung

Dieses Dokument stellt eine Reihe typischer Postfix-Konfigurationen vor.

• Dieses Dokument sollte gelesen werden, nachdem Sie die grundlegenden Konfigurationsschritte durchgeführt haben, die im Dokument BASIC_CONFIGURATION_README beschrieben sind.
• Insbesondere sollten Sie hier nicht fortfahren, wenn Sie Postfix noch nicht für die lokale Posteinreichung und -zustellung eingerichtet haben.

Standardkonfigurationen

Standardkonfigurationen, die jeweils ein bestimmtes Problem lösen

• Postfix auf einem eigenständigen Internet-Host
• Postfix auf einem Null-Client
• Postfix in einem lokalen Netzwerk
• Postfix E-Mail-Firewall/Gateway

Zusätzliche Konfigurationen

Zusätzliche Konfigurationen für Hosts in bestimmten Umgebungen

• 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

Standardkonfigurationen

Postfix auf einem eigenständigen Internet-Host

Postfix sollte auf einem Einzelplatzrechner mit direktem Internetzugang ohne Änderungen funktionieren.

• Zumindest wird Postfix so installiert, wenn Sie den Postfix-Quellcode über http://www.postfix.org/ herunterladen.

Sie können den Befehl "postconf -n" verwenden, um herauszufinden, welche Einstellungen durch Ihre main.cf überschrieben werden.

• Abgesehen von ein paar Pfadeinstellungen sollten auf einer Standalone-Box nur wenige Parameter gesetzt werden, die über das hinausgehen, was im Dokument BASIC_CONFIGURATION_README beschrieben ist:

/etc/postfix/main.cf

# Optional: Mail als user@domainname statt user@hostname senden.
#myorigin = $mydomain

# Optional: externe NAT/Proxy-Adresse angeben.
#proxy_interfaces = 1.2.3.4

# Alternative 1: keine Weiterleitung von Mails von anderen Hosts.
mynetworks_style = host
relay_domains =

# Alternative 2: nur Mails von lokalen Clients weiterleiten.
# mynetworks = 192.168.1.0/28
# relay_domains =

Siehe auch den Abschnitt "Postfix auf Hosts ohne echten Internet-Hostnamen", wenn dies auf Ihre Konfiguration zutrifft.

Postfix auf einem Null-Client

Ein Null-Client ist ein Rechner, der nur Mails versenden kann.

• Er empfängt keine Mails aus dem Netz und stellt auch keine Mails lokal zu.
• Ein Null-Client verwendet in der Regel POP, IMAP oder NFS für den Zugriff auf Postfächer.

In diesem Beispiel wird davon ausgegangen, dass der Internet-Domänenname "example.com" lautet und dass der Rechner "hostname.example.com" heißt.

• Wie üblich werden in den Beispielen nur Parameter gezeigt, die nicht auf ihren Standardeinstellungen belassen werden.

1 /etc/postfix/main.cf:
2 myhostname = hostname.example.com
3 myorigin = $mydomain
4 relayhost = $mydomain
5 inet_interfaces = loopback-only
6 mydestination =

Übersetzung:

• Zeile 2: Setzen Sie myhostname auf hostname.example.com, falls der Rechnername nicht auf einen vollqualifizierten Domänennamen gesetzt ist (verwenden Sie den Befehl "postconf -d myhostname", um den Rechnernamen zu ermitteln).
• Zeile 2: Der Wert myhostname gibt auch den Standardwert für den Parameter mydomain an (hier: "mydomain = example.com").
• Zeile 3: Senden Sie E-Mails als "user@example.com" (statt "user@hostname.example.com"), so dass es keinen Grund gibt, E-Mails an "user@hostname.example.com" zu senden.
• Linie 4: Leiten Sie alle Mails an den Mailserver weiter, der für die Domäne "example.com" zuständig ist.
  • Dies verhindert, dass E-Mails auf dem Null-Client hängen bleiben, wenn dieser ausgeschaltet ist, während ein entferntes Ziel nicht erreichbar ist.
  • Geben Sie hier einen echten Hostnamen an, wenn Ihre "example.com"-Domäne keinen MX-Eintrag hat.
• Zeile 5: Keine Mails aus dem Netz annehmen.
• Zeile 6: Deaktivieren Sie die lokale Postzustellung.
  • Alle E-Mails gehen an den in Zeile 4 angegebenen Mailserver.

Postfix in einem lokalen Netzwerk

Dieser Abschnitt beschreibt eine lokale Netzwerkumgebung mit einem Hauptserver und mehreren anderen Systemen, die E-Mails senden und empfangen.

• Wie üblich gehen wir davon aus, dass der Internet-Domänenname "example.com" lautet.
• Alle Systeme sind so konfiguriert, dass sie E-Mails unter dem Namen "user@example.com" senden, und alle Systeme empfangen E-Mails für "user@hostname.example.com".
• Der Hauptserver empfängt auch Mails für "user@example.com".
• Wir nennen diesen Rechner "mailhost.example.com".

Ein Nachteil des Versendens von Mails als "user@example.com" ist, dass Mails für "root" und andere Systemkonten ebenfalls an den zentralen Mailhost gesendet werden.

• Mögliche Lösungen finden Sie im Abschnitt "Einige, aber nicht alle Konten lokal zustellen" weiter unten.

Wie üblich werden in den Beispielen nur Parameter gezeigt, die nicht auf ihren Standardeinstellungen belassen werden.

Zuerst stellen wir die Nicht-Mailhost-Konfiguration vor, weil sie die einfachere ist.

• Dieser Rechner sendet Mails als "user@example.com" und ist das endgültige Ziel für "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: alle nicht-lokalen Mails an mailhost weiterleiten
6 #relayhost = $mydomain

Übersetzung:

• Zeile 2: Mail als "user@example.com" senden.
• Zeile 3: Geben Sie die vertrauenswürdigen Netzwerke an.
• Zeile 4: Dieser Host leitet keine Mails aus nicht vertrauenswürdigen Netzen weiter.
• Zeile 6: Dies ist erforderlich, wenn kein direkter Internetzugang verfügbar ist.
  • Siehe auch unten, "Postfix hinter einer Firewall".

Als nächstes stellen wir die Mailhost-Konfiguration vor.

• Dieser Rechner sendet Mails als "user@example.com" und ist sowohl für "user@hostname.example.com" als auch für "user@example.com" das endgültige Ziel.

 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: alle nicht-lokalen Mails an die Firewall weiterleiten
10 #relayhost = [firewall.example.com]

Übersetzung:

• Zeile 2: Senden Sie Mails für die Domain "example.com" an den Rechner mailhost.example.com.
  • Denken Sie daran, das "." am Ende der Zeile anzugeben.
• Zeile 5: Senden Sie die E-Mail als "user@example.com".
• Zeile 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 "postconf alias_maps".

Execute the command "newaliases" whenever you change the aliases file.

Postfix email firewall/gateway

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 "postconf mail_version".

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 in 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   relay:[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.
  • This uses the "relay" delivery transport (a copy of the default "smtp" delivery transport) to forward inbound mail.
  • This can improve performance of deliveries to internal domains because they will compete for SMTP clients from the "relay" delivery transport, instead of competing with other SMTP deliveries for SMTP clients from the default "smtp" delivery transport.

Specify dbm instead of hash if your system uses dbm files instead of db files.

• To find out what lookup tables Postfix supports, use the command "postconf -m".

Execute the command "postmap /etc/postfix/relay_recipients" whenever you change the relay_recipients table.

Execute the command "postmap /etc/postfix/transport" 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.

Zusätzliche Konfigurationen

Running Postfix behind a firewall

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 "postconf mail_version".

The following example presents additional configuration. You need to combine this with basic configuration information as discussed in 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 dbm instead of hash if your system uses dbm files instead of db files. To find out what lookup tables Postfix supports, use the command "postconf -m".

Execute the command "postmap /etc/postfix/transport" whenever you edit the transport table.

Configuring Postfix as primary or backup MX host for a remote site

This section presents additional configuration. You need to combine this with basic configuration information as discussed in 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 dbm instead of hash if your system uses dbm files instead of db files. To find out what lookup tables Postfix supports, use the command "postconf -m".

Execute the command "postmap /etc/postfix/transport" 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.

Postfix on a dialup machine

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 in 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 "postconf sendmail_path" 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
  

1. Start mail deliveries.
   /usr/sbin/sendmail -q
   
2. Allow deliveries to start.
   sleep 10
   
3. 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 "sendmail -q" command every now and then while the dialup link is up, so that newly-posted mail is flushed from the queue.

Postfix on hosts without a real Internet hostname

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 "postconf mail_version".

Solution 1: Postfix version 2.2 and later

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 in 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 dbm instead of hash if your system uses dbm files instead of db files. To find out what lookup tables Postfix supports, use the command "postconf -m".

Execute the command "postmap /etc/postfix/generic" whenever you change the generic table.

Solution 2: Postfix version 2.1 and earlier

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 in 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 dbm instead of hash if your system uses dbm files instead of db files. To find out what lookup tables Postfix supports, use the command "postconf -m".

Execute the command "postmap /etc/postfix/canonical" whenever you change the canonical table.

Execute the command "postmap /etc/postfix/virtual" whenever you change the virtual table.

Quelle: https://www.postfix.org/STANDARD_CONFIGURATION_README.html Index.php?title=Kategorie:Entwurf

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