diff options
Diffstat (limited to 'README_FILES/ADDRESS_REWRITING_README')
| -rw-r--r-- | README_FILES/ADDRESS_REWRITING_README | 840 |
1 files changed, 840 insertions, 0 deletions
diff --git a/README_FILES/ADDRESS_REWRITING_README b/README_FILES/ADDRESS_REWRITING_README new file mode 100644 index 0000000..a0ccc20 --- /dev/null +++ b/README_FILES/ADDRESS_REWRITING_README @@ -0,0 +1,840 @@ +PPoossttffiixx AAddddrreessss RReewwrriittiinngg + +------------------------------------------------------------------------------- + +PPoossttffiixx aaddddrreessss rreewwrriittiinngg ppuurrppoossee + +Address rewriting is at the heart of the Postfix mail system. Postfix rewrites +addresses for many different purposes. Some are merely cosmetic, and some are +necessary to deliver correctly formatted mail to the correct destination. +Examples of address rewriting in Postfix are: + + * Transform an incomplete address into a complete address. For example, + transform "username" into "username@example.com", or transform + "username@hostname" into "username@hostname.example.com". + + * Replace an address by an equivalent address. For example, replace + "username@example.com" by "firstname.lastname@example.com" when sending + mail, and do the reverse transformation when receiving mail. + + * Replace an internal address by an external address. For example, replace + "username@localdomain.local" by "isp-account@isp.example" when sending mail + from a home computer to the Internet. + + * Replace an address by multiple addresses. For example, replace the address + of an alias by the addresses listed under that alias. + + * Determine how and where to deliver mail for a specific address. For + example, deliver mail for "username@example.com" with the smtp(8) delivery + agent, to the hosts that are listed in the DNS as the mail servers for the + domain "example.com". + +Although Postfix currently has no address rewriting language, it can do +surprisingly powerful address manipulation via table lookup. Postfix typically +uses lookup tables with fixed strings to map one address to one or multiple +addresses, and typically uses regular expressions to map multiple addresses to +one or multiple addresses. Fixed-string lookup tables may be in the form of +local files, or in the form of NIS, LDAP or SQL databases. The DATABASE_README +document gives an introduction to Postfix lookup tables. + +Topics covered in this document: + + * To rewrite message headers or not, or to label as invalid + * Postfix address rewriting overview + * Address rewriting when mail is received + + o Rewrite addresses to standard form + o Canonical address mapping + o Address masquerading + o Automatic BCC recipients + o Virtual aliasing + + * Address rewriting when mail is delivered + + o Resolve address to destination + o Mail transport switch + o Relocated users table + + * Address rewriting with remote delivery + + o Generic mapping for outgoing SMTP mail + + * Address rewriting with local delivery + + o Local alias database + o Local per-user .forward files + o Local catch-all address + + * Debugging your address manipulations + +TToo rreewwrriittee mmeessssaaggee hheeaaddeerrss oorr nnoott,, oorr ttoo llaabbeell aass iinnvvaalliidd + +Postfix versions 2.1 and earlier always rewrite message header addresses, and +append Postfix's own domain information to addresses that Postfix considers +incomplete. While rewriting message header addresses is OK for mail with a +local origin, it is undesirable for remote mail: + + * Message header address rewriting is frowned upon by mail standards, + * Appending Postfix's own domain produces incorrect results with some + incomplete addresses, + * Appending Postfix's own domain sometimes creates the appearance that spam + is sent by local users. + +Postfix versions 2.2 give you the option to either not rewrite message headers +from remote SMTP clients at all, or to label incomplete addresses in such +message headers as invalid. Here is how it works: + + * Postfix always rewrites message headers from local SMTP clients and from + the Postfix sendmail command, and appends its own domain to incomplete + addresses. The local_header_rewrite_clients parameter controls what SMTP + clients Postfix considers local (by default, only local network interface + addresses). + * Postfix never rewrites message header addresses from remote SMTP clients + when the remote_header_rewrite_domain parameter value is empty (the default + setting). + * Otherwise, Postfix rewrites message headers from remote SMTP clients, and + appends the remote_header_rewrite_domain value to incomplete addresses. + This feature can be used to append a reserved domain such as + "domain.invalid", so that incomplete addresses cannot be mistaken for local + addresses. + +PPoossttffiixx aaddddrreessss rreewwrriittiinngg oovveerrvviieeww + +The figure below zooms in on those parts of Postfix that are most involved with +address rewriting activity. See the OVERVIEW document for an overview of the +complete Postfix architecture. Names followed by a number are Postfix daemon +programs, while unnumbered names represent Postfix queues or internal sources +of mail messages. + + trivial- trivial- + rewrite(8) rewrite(8) + (std form) (resolve) + + ^ | ^ | + | v | v + + smtpd(8) smtp(8) + + qmqpd(8) >- cleanup(8) -> incoming -> active -> qmgr(8) -< lmtp(8) + + pickup(8) local(8) + + ^ ^ | + | | v + + bounces + forwarding deferred + notices + +The table below summarizes all Postfix address manipulations. If you're reading +this document for the first time, skip forward to "Address rewriting when mail +is received". Once you've finished reading the remainder of this document, the +table will help you to quickly find what you need. + + _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ + |AAddddrreessss |SSccooppee |DDaaeemmoonn |GGlloobbaall ttuurrnn--oonn |SSeelleeccttiivvee ttuurrnn--ooffff ccoonnttrrooll | + |mmaanniippuullaattiioonn| | |ccoonnttrrooll | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Rewrite | |trivial-|append_at_myorigin, | | + |addresses to|all mail|rewrite |append_dot_mydomain,|local_header_rewrite_clients,| + |standard | |(8) |swap_bangpath, |remote_header_rewrite_domain | + |form | | |allow_percent_hack | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Canonical | |cleanup | |receive_override_options, | + |address |all mail|(8) |canonical_maps |local_header_rewrite_clients,| + |mapping | | | |remote_header_rewrite_domain | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Address | |cleanup | |receive_override_options, | + |masquerading|all mail|(8) |masquerade_domains |local_header_rewrite_clients,| + | | | | |remote_header_rewrite_domain | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Automatic | |cleanup |always_bcc, | | + |BCC |new mail|(8) |sender_bcc_maps, |receive_override_options | + |recipients | | |recipient_bcc_maps | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Virtual |all mail|cleanup |virtual_alias_maps |receive_override_options | + |aliasing | |(8) | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Resolve | |trivial-| | | + |address to |all mail|rewrite |none |none | + |destination | |(8) | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Mail | |trivial-| | | + |transport |all mail|rewrite |transport_maps |none | + |switch | |(8) | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Relocated | |trivial-| | | + |users table |all mail|rewrite |relocated_maps |none | + | | |(8) | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Generic |outgoing| | | | + |mapping |SMTP |smtp(8) |smtp_generic_maps |none | + |table |mail | | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Local alias |local | | | | + |database |mail |local(8)|alias_maps |none | + | |only | | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Local per- |local | | | | + |user |mail |local(8)|forward_path |none | + |.forward |only | | | | + |files | | | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + |Local catch-|local | | | | + |all address |mail |local(8)|luser_relay |none | + | |only | | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ | + +AAddddrreessss rreewwrriittiinngg wwhheenn mmaaiill iiss rreecceeiivveedd + +The cleanup(8) server receives mail from outside of Postfix as well as mail +from internal sources such as forwarded mail, undeliverable mail that is +bounced to the sender, and postmaster notifications about problems with the +mail system. + +The cleanup(8) server transforms the sender, recipients and message content +into a standard form before writing it to an incoming queue file. The server +cleans up sender and recipient addresses in message headers and in the +envelope, adds missing message headers such as From: or Date: that are required +by mail standards, and removes message headers such as Bcc: that should not be +present. The cleanup(8) server delegates the more complex address manipulations +to the trivial-rewrite(8) server as described later in this document. + +Address manipulations at this stage are: + + * Rewrite addresses to standard form + * Canonical address mapping + * Address masquerading + * Automatic BCC recipients + * Virtual aliasing + +RReewwrriittee aaddddrreesssseess ttoo ssttaannddaarrdd ffoorrmm + +Before the cleanup(8) daemon runs an address through any address mapping lookup +table, it first rewrites the address to the standard +"user@fully.qualified.domain" form, by sending the address to the trivial- +rewrite(8) daemon. The purpose of rewriting to standard form is to reduce the +number of entries needed in lookup tables. + +The Postfix trivial-rewrite(8) daemon implements the following hard-coded +address manipulations: + + Rewrite "@hosta,@hostb:user@site" to "user@site" + In case you wonder what this is, the address form above is called a + route address, and specifies that mail for "user@site" be delivered via + "hosta" and "hostb". Usage of this form has been deprecated for a long + time. Postfix has no ability to handle route addresses, other than to + strip off the route part. + + NOTE: Postfix versions 2.2 and later rewrite message headers from + remote SMTP clients only if the client matches the + local_header_rewrite_clients parameter, or if the + remote_header_rewrite_domain configuration parameter specifies a non- + empty value. To get the behavior before Postfix 2.2, specify + "local_header_rewrite_clients = static:all". + + Rewrite "site!user" to "user@site" + This feature is controlled by the boolean swap_bangpath parameter + (default: yes). The purpose is to rewrite UUCP-style addresses to + domain style. This is useful only when you receive mail via UUCP, but + it probably does not hurt otherwise. + + NOTE: Postfix versions 2.2 and later rewrite message headers from + remote SMTP clients only if the client matches the + local_header_rewrite_clients parameter, or if the + remote_header_rewrite_domain configuration parameter specifies a non- + empty value. To get the behavior before Postfix 2.2, specify + "local_header_rewrite_clients = static:all". + + Rewrite "user%domain" to "user@domain" + This feature is controlled by the boolean allow_percent_hack parameter + (default: yes). Typically, this is used in order to deal with + monstrosities such as "user%domain@otherdomain". + + NOTE: Postfix versions 2.2 and later rewrite message headers from + remote SMTP clients only if the client matches the + local_header_rewrite_clients parameter, or if the + remote_header_rewrite_domain configuration parameter specifies a non- + empty value. To get the behavior before Postfix 2.2, specify + "local_header_rewrite_clients = static:all". + + Rewrite "user" to "user@$myorigin" + This feature is controlled by the boolean append_at_myorigin parameter + (default: yes). You should never turn off this feature, because a lot + of Postfix components expect that all addresses have the form + "user@domain". + + NOTE: Postfix versions 2.2 and later rewrite message headers from + remote SMTP clients only if the client matches the + local_header_rewrite_clients parameter; otherwise they append the + domain name specified with the remote_header_rewrite_domain + configuration parameter, if one is specified. To get the behavior + before Postfix 2.2, specify "local_header_rewrite_clients = static: + all". + + If your machine is not the main machine for $myorigin and you wish to + have some users delivered locally without going via that main machine, + make an entry in the virtual alias table that redirects + "user@$myorigin" to "user@$myhostname". See also the "delivering some + users locally" section in the STANDARD_CONFIGURATION_README document. + + Rewrite "user@host" to "user@host.$mydomain" + This feature is controlled by the boolean append_dot_mydomain parameter + (default: yes). The purpose is to get consistent treatment of different + forms of the same hostname. + + NOTE: Postfix versions 2.2 and later rewrite message headers from + remote SMTP clients only if the client matches the + local_header_rewrite_clients parameter; otherwise they append the + domain name specified with the remote_header_rewrite_domain + configuration parameter, if one is specified. To get the behavior + before Postfix 2.2, specify "local_header_rewrite_clients = static: + all". + + Some will argue that rewriting "host" to "host.domain" is bad. That is + why it can be turned off. Others like the convenience of having + Postfix's own domain appended automatically. + + Rewrite "user@site." to "user@site" (without the trailing dot). + A single trailing dot is silently removed. However, an address that + ends in multiple dots will be rejected as an invalid address. + + NOTE: Postfix versions 2.2 and later rewrite message headers from + remote SMTP clients only if the client matches the + local_header_rewrite_clients parameter, or if the + remote_header_rewrite_domain configuration parameter specifies a non- + empty value. To get the behavior before Postfix 2.2, specify + "local_header_rewrite_clients = static:all". + +CCaannoonniiccaall aaddddrreessss mmaappppiinngg + +The cleanup(8) daemon uses the canonical(5) tables to rewrite addresses in +message envelopes and in message headers. By default all header and envelope +addresses are rewritten; this is controlled with the canonical_classes +configuration parameter. + +NOTE: Postfix versions 2.2 and later rewrite message headers from remote SMTP +clients only if the client matches the local_header_rewrite_clients parameter, +or if the remote_header_rewrite_domain configuration parameter specifies a non- +empty value. To get the behavior before Postfix 2.2, specify +"local_header_rewrite_clients = static:all". + +Address rewriting is done for local and remote addresses. The mapping is useful +to replace login names by "Firstname.Lastname" style addresses, or to clean up +invalid domains in mail addresses produced by legacy mail systems. + +Canonical mapping is disabled by default. To enable, edit the canonical_maps +parameter in the main.cf file and specify one or more lookup tables, separated +by whitespace or commas. + +Example: + + /etc/postfix/main.cf: + canonical_maps = hash:/etc/postfix/canonical + + /etc/postfix/canonical: + wietse Wietse.Venema + +For static mappings as shown above, lookup tables such as hash:, ldap:, mysql: +or pgsql: are sufficient. For dynamic mappings you can use regular expression +tables. This requires that you become intimately familiar with the ideas +expressed in regexp_table(5), pcre_table(5) and canonical(5). + +In addition to the canonical maps which are applied to both sender and +recipient addresses, you can specify canonical maps that are applied only to +sender addresses or to recipient addresses. + +Example: + + /etc/postfix/main.cf: + sender_canonical_maps = hash:/etc/postfix/sender_canonical + recipient_canonical_maps = hash:/etc/postfix/recipient_canonical + +The sender and recipient canonical maps are applied before the common canonical +maps. The sender_canonical_classes and recipient_canonical_classes parameters +control what addresses are subject to sender_canonical_maps and +recipient_canonical_maps mappings, respectively. + +Sender-specific rewriting is useful when you want to rewrite ugly sender +addresses to pretty ones, and still want to be able to send mail to the those +ugly address without creating a mailer loop. + +Canonical mapping can be turned off selectively for mail received by smtpd(8), +qmqpd(8), or pickup(8), by overriding main.cf settings in the master.cf file. +This feature is available in Postfix version 2.1 and later. + +Example: + + /etc/postfix/master.cf: + 127.0.0.1:10026 inet n - n - - smtpd + -o receive_override_options=no_address_mappings + +Note: do not specify whitespace around the "=" here. + +AAddddrreessss mmaassqquueerraaddiinngg + +Address masquerading is a method to hide hosts inside a domain behind their +mail gateway, and to make it appear as if the mail comes from the gateway +itself, instead of from individual machines. + +NOTE: Postfix versions 2.2 and later rewrite message headers from remote SMTP +clients only if the client matches the local_header_rewrite_clients parameter, +or if the remote_header_rewrite_domain configuration parameter specifies a non- +empty value. To get the behavior before Postfix 2.2, specify +"local_header_rewrite_clients = static:all". + +Address masquerading is disabled by default, and is implemented by the cleanup +(8) server. To enable, edit the masquerade_domains parameter in the main.cf +file and specify one or more domain names separated by whitespace or commas. +When Postfix tries to masquerade a domain, it processes the list from left to +right, and processing stops at the first match. + +Example: + + /etc/postfix/main.cf: + masquerade_domains = foo.example.com example.com + +strips "any.thing.foo.example.com" to "foo.example.com", but strips +"any.thing.else.example.com" to "example.com". + +A domain name prefixed with "!" means do not masquerade this domain or its +subdomains: + + /etc/postfix/main.cf: + masquerade_domains = !foo.example.com example.com + +does not change "any.thing.foo.example.com" and "foo.example.com", but strips +"any.thing.else.example.com" to "example.com". + +The masquerade_exceptions configuration parameter specifies what user names +should not be subjected to address masquerading. Specify one or more user names +separated by whitespace or commas. + +Example: + + /etc/postfix/main.cf: + masquerade_exceptions = root + +By default, Postfix makes no exceptions. + +Subtle point: by default, address masquerading is applied only to message +headers and to envelope sender addresses, but not to envelope recipients. This +allows you to use address masquerading on a mail gateway machine, while still +being able to forward mail from outside to users on individual machines. + +In order to subject envelope recipient addresses to masquerading, too, specify +(Postfix version 1.1 and later): + + /etc/postfix/main.cf: + masquerade_classes = envelope_sender, envelope_recipient, + header_sender, header_recipient + +If you rewrite the envelope recipient like this, Postfix will no longer be able +to send mail to individual machines. + +Address masquerading can be turned off selectively for mail received by smtpd +(8), qmqpd(8), or pickup(8), by overriding main.cf settings in the master.cf +file. This feature is available in Postfix version 2.1 and later. + +Example: + + /etc/postfix/master.cf: + 127.0.0.1:10026 inet n - n - - smtpd + -o receive_override_options=no_address_mappings + +Note: do not specify whitespace around the "=" here. + +AAuuttoommaattiicc BBCCCC rreecciippiieennttss + +After applying the canonical and masquerade mappings, the cleanup(8) daemon can +generate optional BCC (blind carbon-copy) recipients. Postfix provides three +mechanisms: + + always_bcc = address + Deliver a copy of all mail to the specified address. In Postfix + versions before 2.1, this feature is implemented by smtpd(8), qmqpd(8), + or pickup(8). + sender_bcc_maps = type:table + Search the specified "type:table" lookup table with the envelope sender + address for an automatic BCC address. This feature is available in + Postfix 2.1 and later. + recipient_bcc_maps = type:table + Search the specified "type:table" lookup table with the envelope + recipient address for an automatic BCC address. This feature is + available in Postfix 2.1 and later. + +Note: automatic BCC recipients are produced only for new mail. To avoid mailer +loops, automatic BCC recipients are not generated for mail that Postfix +forwards internally, nor for mail that Postfix generates itself. + +Automatic BCC recipients (including always_bcc) can be turned off selectively +for mail received by smtpd(8), qmqpd(8), or pickup(8), by overriding main.cf +settings in the master.cf file. This feature is available in Postfix version +2.1 and later. + +Example: + + /etc/postfix/master.cf: + 127.0.0.1:10026 inet n - n - - smtpd + -o receive_override_options=no_address_mappings + +Note: do not specify whitespace around the "=" here. + +VViirrttuuaall aalliiaassiinngg + +Before writing the recipients to the queue file, the cleanup(8) daemon uses the +optional virtual(5) alias tables to redirect mail for recipients. The mapping +affects only envelope recipient addresses; it has no effect on message headers +or envelope sender addresses. Virtual alias lookups are useful to redirect mail +for virtual alias domains to real user mailboxes, and to redirect mail for +domains that no longer exist. Virtual alias lookups can also be used to +transform " Firstname.Lastname " back into UNIX login names, although it seems +that local aliases may be a more appropriate vehicle. See the VIRTUAL_README +document for an overview of methods to host virtual domains with Postfix. + +Virtual aliasing is disabled by default. To enable, edit the virtual_alias_maps +parameter in the main.cf file and specify one or more lookup tables, separated +by whitespace or commas. + +Example: + + /etc/postfix/main.cf: + virtual_alias_maps = hash:/etc/postfix/virtual + + /etc/postfix/virtual: + Wietse.Venema wietse + +Addresses found in virtual alias maps are subjected to another iteration of +virtual aliasing, but are not subjected to canonical mapping, in order to avoid +loops. + +For static mappings as shown above, lookup tables such as hash:, ldap:, mysql: +or pgsql: are sufficient. For dynamic mappings you can use regular expression +tables. This requires that you become intimately familiar with the ideas +expressed in regexp_table(5), pcre_table(5) and virtual(5). + +Virtual aliasing can be turned off selectively for mail received by smtpd(8), +qmqpd(8), or pickup(8), by overriding main.cf settings in the master.cf file. +This feature is available in Postfix version 2.1 and later. + +Example: + + /etc/postfix/master.cf: + 127.0.0.1:10026 inet n - n - - smtpd + -o receive_override_options=no_address_mappings + +Note: do not specify whitespace around the "=" here. + +At this point the message is ready to be stored into the Postfix incoming +queue. + +AAddddrreessss rreewwrriittiinngg wwhheenn mmaaiill iiss ddeelliivveerreedd + +The Postfix queue manager sorts mail according to its destination and gives it +to Postfix delivery agents such as local(8), smtp(8), or lmtp(8). Just like the +cleanup(8) server, the Postfix queue manager delegates the more complex address +manipulations to the trivial-rewrite(8) server. + +Address manipulations at this stage are: + + * Resolve address to destination + * Mail transport switch + * Relocated users table + +Each Postfix delivery agent tries to deliver the mail to its destination, while +encapsulating the sender, recipients, and message content according to the +rules of the SMTP, LMTP, etc. protocol. When mail cannot be delivered, it is +either returned to the sender or moved to the deferred queue and tried again +later. + +Address manipulations when mail is delivered via the smtp(8) delivery agent: + + * Generic mapping for outgoing SMTP mail + +Address manipulations when mail is delivered via the local(8) delivery agent: + + * Local alias database + * Local per-user .forward files + * Local catch-all address + +The remainder of this document presents each address manipulation step in more +detail, with specific examples or with pointers to documentation with examples. + +RReessoollvvee aaddddrreessss ttoo ddeessttiinnaattiioonn + +The Postfix qmgr(8) queue manager selects new mail from the incoming queue or +old mail from the deferred queue, and asks the trivial-rewrite(8) address +rewriting and resolving daemon where it should be delivered. + +As of version 2.0, Postfix distinguishes four major address classes. Each class +has its own list of domain names, and each class has its own default delivery +method, as shown in the table below. See the ADDRESS_CLASS_README document for +the fine details. Postfix versions before 2.0 only distinguish between local +delivery and everything else. + + _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ + |DDeessttiinnaattiioonn ddoommaaiinn lliisstt |DDeeffaauulltt ddeelliivveerryy mmeetthhoodd|AAvvaaiillaabbiilliittyy| + |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ | + |$mydestination, $inet_interfaces,|$local_transport |Postfix 1.0 | + |$proxy_interfaces | | | + |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ | + |$virtual_mailbox_domains |$virtual_transport |Postfix 2.0 | + |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ | + |$relay_domains |$relay_transport |Postfix 2.0 | + |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ | + |none |$default_transport |Postfix 1.0 | + |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ | + +MMaaiill ttrraannssppoorrtt sswwiittcchh + +Once the trivial-rewrite(8) daemon has determined a default delivery method it +searches the optional transport(5) table for information that overrides the +message destination and/or delivery method. Typical use of the transport(5) +table is to send mail to a system that is not connected to the Internet, or to +use a special SMTP client configuration for destinations that have special +requirements. See, for example, the STANDARD_CONFIGURATION_README and +UUCP_README documents, and the examples in the transport(5) manual page. + +Transport table lookups are disabled by default. To enable, edit the +transport_maps parameter in the main.cf file and specify one or more lookup +tables, separated by whitespace or commas. + +Example: + + /etc/postfix/main.cf: + transport_maps = hash:/etc/postfix/transport + +RReellooccaatteedd uusseerrss ttaabbllee + +Next, the trivial-rewrite(8) address rewriting and resolving daemon runs each +recipient through the relocated(5) database. This table provides information on +how to reach users that no longer have an account, or what to do with mail for +entire domains that no longer exist. When mail is sent to an address that is +listed in this table, the message is returned to the sender with an informative +message. + +The relocated(5) database is searched after transport(5) table lookups, in +anticipation of transport(5) tables that can replace one recipient address by a +different one. + +Lookups of relocated users are disabled by default. To enable, edit the +relocated_maps parameter in the main.cf file and specify one or more lookup +tables, separated by whitespace or commas. + +Example: + + /etc/postfix/main.cf: + relocated_maps = hash:/etc/postfix/relocated + + /etc/postfix/relocated: + username@example.com otheruser@elsewhere.tld + +As of Postfix version 2, mail for a relocated user will be rejected by the SMTP +server with the reason "user has moved to otheruser@elsewhere.tld". Older +Postfix versions will receive the mail first, and then return it to the sender +as undeliverable, with the same reason. + +GGeenneerriicc mmaappppiinngg ffoorr oouuttggooiinngg SSMMTTPP mmaaiill + +Some hosts have no valid Internet domain name, and instead use a name such as +localdomain.local. This can be a problem when you want to send mail over the +Internet, because many mail servers reject mail addresses with invalid domain +names. + +With the smtp_generic_maps parameter you can specify generic(5) lookup tables +that replace local mail addresses by valid Internet addresses when mail leaves +the machine via SMTP. The generic(5) mapping replaces envelope and header +addresses, and is non-recursive. It does not happen when you send mail between +addresses on the local machine. + +This feature is available in Postfix version 2.2 and later. + +Example: + + /etc/postfix/main.cf: + smtp_generic_maps = hash:/etc/postfix/generic + + /etc/postfix/generic: + his@localdomain.local hisaccount@hisisp.example + her@localdomain.local heraccount@herisp.example + @localdomain.local hisaccount+local@hisisp.example + +When mail is sent to a remote host via SMTP, this replaces +his@localdomain.local by his ISP mail address, replaces her@localdomain.local +by her ISP mail address, and replaces other local addresses by his ISP account, +with an address extension of +local (this example assumes that the ISP supports +"+" style address extensions). + +LLooccaall aalliiaass ddaattaabbaassee + +When mail is to be delivered locally, the local(8) delivery agent runs each +local recipient name through the aliases(5) database. The mapping does not +affect addresses in message headers. Local aliases are typically used to +implement distribution lists, or to direct mail for standard aliases such as +postmaster to real people. The table can also be used to map +"Firstname.Lastname" addresses to login names. + +Alias lookups are enabled by default. The default configuration depends on the +operating system environment, but it is typically one of the following: + + /etc/postfix/main.cf: + alias_maps = hash:/etc/aliases + alias_maps = dbm:/etc/aliases, nis:mail.aliases + +The pathname of the alias database file is controlled with the alias_database +configuration parameter. The value is system dependent. Usually it is one of +the following: + + /etc/postfix/main.cf: + alias_database = hash:/etc/aliases (4.4BSD, LINUX) + alias_database = dbm:/etc/aliases (4.3BSD, SYSV<4) + alias_database = dbm:/etc/mail/aliases (SYSV4) + +An aliases(5) file can specify that mail should be delivered to a local file, +or to a command that receives the message in the standard input stream. For +security reasons, deliveries to command and file destinations are performed +with the rights of the alias database owner. A default userid, default_privs, +is used for deliveries to commands or files in "root"-owned aliases. + +LLooccaall ppeerr--uusseerr ..ffoorrwwaarrdd ffiilleess + +With delivery via the local(8) delivery agent, users can control their own mail +delivery by specifying destinations in a file called .forward in their home +directories. The syntax of these files is the same as with the local aliases(5) +file, except that the left-hand side of the alias (lookup key and colon) are +not present. + +LLooccaall ccaattcchh--aallll aaddddrreessss + +When the local(8) delivery agent finds that a message recipient does not exist, +the message is normally returned to the sender ("user unknown"). Sometimes it +is desirable to forward mail for non-existing recipients to another machine. +For this purpose you can specify an alternative destination with the +luser_relay configuration parameter. + +Alternatively, mail for non-existent recipients can be delegated to an entirely +different message transport, as specified with the fallback_transport +configuration parameter. For details, see the local(8) delivery agent +documentation. + +Note: if you use the luser_relay feature in order to receive mail for non-UNIX +accounts, then you must specify: + + /etc/postfix/main.cf: + local_recipient_maps = + +(i.e. empty) in the main.cf file, otherwise the Postfix SMTP server will reject +mail for non-UNIX accounts with "User unknown in local recipient table". See +the LOCAL_RECIPIENT_README file for more information on this. + +luser_relay can specify one address. It is subjected to "$name" expansions. +Examples: + + $user@other.host + The bare username, without address extension, is prepended to + "@other.host". For example, mail for "username+foo" is sent to + "username@other.host". + + $local@other.host + The entire original recipient localpart, including address extension, + is prepended to "@other.host". For example, mail for "username+foo" is + sent to "username+foo@other.host". + + sysadmin+$user + The bare username, without address extension, is appended to + "sysadmin". For example, mail for "username+foo" is sent to + "sysadmin+username". + + sysadmin+$local + The entire original recipient localpart, including address extension, + is appended to "sysadmin". For example, mail for "username+foo" is sent + to "sysadmin+username+foo". + +DDeebbuuggggiinngg yyoouurr aaddddrreessss mmaanniippuullaattiioonnss + +Postfix version 2.1 and later can produce mail delivery reports for debugging +purposes. These reports not only show sender/recipient addresses after address +rewriting and alias expansion or forwarding, they also show information about +delivery to mailbox, delivery to non-Postfix command, responses from remote +SMTP servers, and so on. + +Postfix can produce two types of mail delivery reports for debugging: + + * What-if: report what would happen, but do not actually deliver mail. This + mode of operation is requested with: + + $ //uussrr//ssbbiinn//sseennddmmaaiill --bbvv aaddddrreessss...... + Mail Delivery Status Report will be mailed to <your login name>. + + * What happened: deliver mail and report successes and/or failures, including + replies from remote SMTP servers. This mode of operation is requested with: + + $ //uussrr//ssbbiinn//sseennddmmaaiill --vv aaddddrreessss...... + Mail Delivery Status Report will be mailed to <your login name>. + +These reports contain information that is generated by Postfix delivery agents. +Since these run as daemon processes and do not interact with users directly, +the result is sent as mail to the sender of the test message. The format of +these reports is practically identical to that of ordinary non-delivery +notifications. + +As an example, below is the delivery report that is produced with the command +"sendmail -bv postfix-users@postfix.org". The first part of the report contains +human-readable text. In this case, mail would be delivered via mail.cloud9.net, +and the SMTP server replies with "250 Ok". Other reports may show delivery to +mailbox, or delivery to non-Postfix command. + + Content-Description: Notification + Content-Type: text/plain + + This is the mail system at host spike.porcupine.org. + + Enclosed is the mail delivery report that you requested. + + The mail system + + <postfix-users@postfix.org>: delivery via mail.cloud9.net[168.100.1.4]: 250 + 2.1.5 Ok + +The second part of the report is in machine-readable form, and includes the +following information: + + * The envelope sender address (wietse@porcupine.org). + * The envelope recipient address (postfix-users@postfix.org). If the + recipient address was changed by Postfix then Postfix also includes the + original recipient address. + * The delivery status. + +Some details depend on Postfix version. The example below is for Postfix +version 2.3 and later. + + Content-Description: Delivery report + Content-Type: message/delivery-status + + Reporting-MTA: dns; spike.porcupine.org + X-Postfix-Queue-ID: 84863BC0E5 + X-Postfix-Sender: rfc822; wietse@porcupine.org + Arrival-Date: Sun, 26 Nov 2006 17:01:01 -0500 (EST) + + Final-Recipient: rfc822; postfix-users@postfix.org + Action: deliverable + Status: 2.1.5 + Remote-MTA: dns; mail.cloud9.net + Diagnostic-Code: smtp; 250 2.1.5 Ok + +The third part of the report contains the message that Postfix would have +delivered, including From: and To: message headers, so that you can see any +effects of address rewriting on those. Mail submitted with "sendmail -bv" has +no body content so none is shown in the example below. + + Content-Description: Message + Content-Type: message/rfc822 + + Received: by spike.porcupine.org (Postfix, from userid 1001) + id 84863BC0E5; Sun, 26 Nov 2006 17:01:01 -0500 (EST) + Subject: probe + To: postfix-users@postfix.org + Message-Id: <20061126220101.84863BC0E5@spike.porcupine.org> + Date: Sun, 26 Nov 2006 17:01:01 -0500 (EST) + From: wietse@porcupine.org (Wietse Venema) + |