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[MAN] virtual

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Content-type: text/html; charset=UTF-8 Man page of VIRTUAL

VIRTUAL

Section: File Formats (5)
Index Return to Main Contents
 

NAME

virtual - Postfix virtual alias table format  

SYNOPSIS

postmap /etc/postfix/virtual

postmap -q "string" /etc/postfix/virtual

postmap -q - /etc/postfix/virtual <inputfile
 

DESCRIPTION

The optional virtual(5) alias table rewrites recipient addresses for all local, all virtual, and all remote mail destinations. This is unlike the aliases(5) table which is used only for local(8) delivery. Virtual aliasing is recursive, and is implemented by the Postfix cleanup(8) daemon before mail is queued.

The main applications of virtual aliasing are:

•
To redirect mail for one address to one or more addresses.
•
To implement virtual alias domains where all addresses are aliased to addresses in other domains.

Virtual alias domains are not to be confused with the virtual mailbox domains that are implemented with the Postfix virtual(8) mail delivery agent. With virtual mailbox domains, each recipient address can have its own mailbox.

Virtual aliasing is applied only to recipient envelope addresses, and does not affect message headers. Use canonical(5) mapping to rewrite header and envelope addresses in general.

Normally, the virtual(5) alias table is specified as a text file that serves as input to the postmap(1) command. The result, an indexed file in dbm or db format, is used for fast searching by the mail system. Execute the command "postmap /etc/postfix/virtual" to rebuild an indexed file after changing the corresponding text file.

When the table is provided via other means such as NIS, LDAP or SQL, the same lookups are done as for ordinary indexed files.

Alternatively, the table can be provided as a regular-expression map where patterns are given as regular expressions, or lookups can be directed to TCP-based server. In those case, the lookups are done in a slightly different way as described below under "REGULAR EXPRESSION TABLES" or "TCP-BASED TABLES".  

CASE FOLDING



The search string is folded to lowercase before database
lookup. As of Postfix 2.3, the search string is not case
folded with database types such as regexp: or pcre: whose
lookup fields can match both upper and lower case.
 

TABLE FORMAT






The input format for the postmap(1) command is as follows:



pattern address, address, ...

When pattern matches a mail address, replace it by the
corresponding address.

blank lines and comments

Empty lines and whitespace-only lines are ignored, as
are lines whose first non-whitespace character is a `#'.

multi-line text

A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.


 

TABLE SEARCH ORDER






With lookups from indexed files such as DB or DBM, or from networked
tables such as NIS, LDAP or SQL, each user@domain
query produces a sequence of query patterns as described below.


Each query pattern is sent to each specified lookup table
before trying the next query pattern, until a match is
found.



user@domain address, address, ...

Redirect mail for user@domain to address.
This form has the highest precedence.

user address, address, ...

Redirect mail for user@site to address when
site is equal to $myorigin, when site is listed in
$mydestination, or when it is listed in $inet_interfaces
or $proxy_interfaces.


This functionality overlaps with functionality of the local
aliases(5) database. The difference is that virtual(5)
mapping can be applied to non-local addresses.

@domain address, address, ...

Redirect mail for other users in domain to address.
This form has the lowest precedence.


Note: @domain is a wild-card. With this form, the
Postfix SMTP server accepts
mail for any recipient in domain, regardless of whether
that recipient exists.  This may turn your mail system into
a backscatter source: Postfix first accepts mail for
non-existent recipients and then tries to return that mail
as "undeliverable" to the often forged sender address.


 

RESULT ADDRESS REWRITING






The lookup result is subject to address rewriting:



•

When the result has the form @otherdomain, the
result becomes the same user in otherdomain.
This works only for the first address in a multi-address
lookup result.

•

When "append_at_myorigin=yes", append "@$myorigin"
to addresses without "@domain".

•

When "append_dot_mydomain=yes", append
".$mydomain" to addresses without ".domain".


 

ADDRESS EXTENSION







When a mail address localpart contains the optional recipient delimiter
(e.g., user+foo@domain), the lookup order becomes:
user+foo@domain, user@domain, user+foo,
user, and @domain.


The propagate_unmatched_extensions parameter controls whether
an unmatched address extension (+foo) is propagated to the
result of table lookup.
 

VIRTUAL ALIAS DOMAINS






Besides virtual aliases, the virtual alias table can also be used
to implement virtual alias domains. With a virtual alias domain, all
recipient addresses are aliased to addresses in other domains.


Virtual alias domains are not to be confused with the virtual mailbox
domains that are implemented with the Postfix virtual(8) mail
delivery agent. With virtual mailbox domains, each recipient address
can have its own mailbox.


With a virtual alias domain, the virtual domain has its
own user name space. Local (i.e. non-virtual) usernames are not
visible in a virtual alias domain. In particular, local
aliases(5) and local mailing lists are not visible as
localname@virtual-alias.domain.


Support for a virtual alias domain looks like:



/etc/postfix/main.cf:
    virtual_alias_maps = hash:/etc/postfix/virtual





Note: some systems use dbm databases instead of hash.
See the output from "postconf -m" for available database types.



/etc/postfix/virtual:
    virtual-alias.domain    anything (right-hand content does not matter)
    postmaster@virtual-alias.domain postmaster
    user1@virtual-alias.domain      address1
    user2@virtual-alias.domain      address2, address3





The virtual-alias.domain anything entry is required for a
virtual alias domain. Without this entry, mail is rejected
with "relay access denied", or bounces with
"mail loops back to myself".


Do not specify virtual alias domain names in the main.cf
mydestination or relay_domains configuration parameters.


With a virtual alias domain, the Postfix SMTP server
accepts mail for known-user@virtual-alias.domain, and rejects
mail for unknown-user@virtual-alias.domain as undeliverable.


Instead of specifying the virtual alias domain name via
the virtual_alias_maps table, you may also specify it via
the main.cf virtual_alias_domains configuration parameter.
This latter parameter uses the same syntax as the main.cf
mydestination configuration parameter.
 

REGULAR EXPRESSION TABLES






This section describes how the table lookups change when the table
is given in the form of regular expressions. For a description of
regular expression lookup table syntax, see regexp_table(5)
or pcre_table(5).


Each pattern is a regular expression that is applied to the entire
address being looked up. Thus, user@domain mail addresses are not
broken up into their user and @domain constituent parts,
nor is user+foo broken up into user and foo.


Patterns are applied in the order as specified in the table, until a
pattern is found that matches the search string.


Results are the same as with indexed file lookups, with
the additional feature that parenthesized substrings from the
pattern can be interpolated as $1, $2 and so on.
 

TCP-BASED TABLES






This section describes how the table lookups change when lookups
are directed to a TCP-based server. For a description of the TCP
client/server lookup protocol, see tcp_table(5).
This feature is not available up to and including Postfix version 2.4.


Each lookup operation uses the entire address once.  Thus,
user@domain mail addresses are not broken up into their
user and @domain constituent parts, nor is
user+foo broken up into user and foo.


Results are the same as with indexed file lookups.
 

BUGS




The table format does not understand quoting conventions.
 

CONFIGURATION PARAMETERS






The following main.cf parameters are especially relevant to
this topic. See the Postfix main.cf file for syntax details
and for default values. Use the "postfix reload" command after
a configuration change.



virtual_alias_maps

List of virtual aliasing tables.

virtual_alias_domains

List of virtual alias domains. This uses the same syntax
as the mydestination parameter.

propagate_unmatched_extensions

A list of address rewriting or forwarding mechanisms that propagate
an address extension from the original address to the result.
Specify zero or more of canonical, virtual, alias,
forward, include, or generic.





Other parameters of interest:



inet_interfaces

The network interface addresses that this system receives mail on.
You need to stop and start Postfix when this parameter changes.

mydestination

List of domains that this mail system considers local.

myorigin

The domain that is appended to any address that does not have a domain.

owner_request_special

Give special treatment to owner-xxx and xxx-request
addresses.

proxy_interfaces

Other interfaces that this machine receives mail on by way of a
proxy agent or network address translator.


 

SEE ALSO




cleanup(8), canonicalize and enqueue mail
postmap(1), Postfix lookup table manager
postconf(5), configuration parameters
canonical(5), canonical address mapping

 

README FILES






Use "postconf readme_directory" or
"postconf html_directory" to locate this information.


ADDRESS_REWRITING_README, address rewriting guide
DATABASE_README, Postfix lookup table overview
VIRTUAL_README, domain hosting guide

 

LICENSE






The Secure Mailer license must be distributed with this software.
 

AUTHOR(S)




Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA

Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA





 
Index




NAME


SYNOPSIS


DESCRIPTION


CASE FOLDING


TABLE FORMAT


TABLE SEARCH ORDER


RESULT ADDRESS REWRITING


ADDRESS EXTENSION


VIRTUAL ALIAS DOMAINS


REGULAR EXPRESSION TABLES


TCP-BASED TABLES


BUGS


CONFIGURATION PARAMETERS


SEE ALSO


README FILES


LICENSE


AUTHOR(S)





This document was created by
man2html,
using the manual pages.

Time: 04:45:55 GMT, September 16, 2022


Content-type: text/html; charset=UTF-8


Man page of VIRTUAL


VIRTUAL

Section: Misc. Reference Manual Pages (8postfix)
Index
Return to Main Contents




 

NAME


virtual
-
Postfix virtual domain mail delivery agent
 

SYNOPSIS




virtual [generic Postfix daemon options]

 

DESCRIPTION




The virtual(8) delivery agent is designed for virtual mail
hosting services. Originally based on the Postfix local(8)
delivery
agent, this agent looks up recipients with map lookups of their
full recipient address, instead of using hard-coded unix password
file lookups of the address local part only.


This delivery agent only delivers mail.  Other features such as
mail forwarding, out-of-office notifications, etc., must be
configured via virtual_alias maps or via similar lookup mechanisms.
 

MAILBOX LOCATION






The mailbox location is controlled by the virtual_mailbox_base
and virtual_mailbox_maps configuration parameters (see below).
The virtual_mailbox_maps table is indexed by the recipient
address as described under TABLE SEARCH ORDER below.


The mailbox pathname is constructed as follows:



  $virtual_mailbox_base/$virtual_mailbox_maps(recipient)





where recipient is the full recipient address.
 

UNIX MAILBOX FORMAT






When the mailbox location does not end in /, the message
is delivered in UNIX mailbox format.   This format stores multiple
messages in one textfile.


The virtual(8) delivery agent prepends a "From sender
time_stamp" envelope header to each message, prepends a
Delivered-To: message header with the envelope recipient
address,
prepends an X-Original-To: header with the recipient address as
given to Postfix,
prepends a Return-Path: message header with the
envelope sender address, prepends a > character to lines
beginning with "From ", and appends an empty line.


The mailbox is locked for exclusive access while delivery is in
progress. In case of problems, an attempt is made to truncate the
mailbox to its original length.
 

QMAIL MAILDIR FORMAT






When the mailbox location ends in /, the message is delivered
in qmail maildir format. This format stores one message per file.


The virtual(8) delivery agent prepends a Delivered-To:
message header with the final envelope recipient address,
prepends an X-Original-To: header with the recipient address as
given to Postfix, and prepends a
Return-Path: message header with the envelope sender address.


By definition, maildir format does not require application-level
file locking during mail delivery or retrieval.
 

MAILBOX OWNERSHIP






Mailbox ownership is controlled by the virtual_uid_maps
and virtual_gid_maps lookup tables, which are indexed
with the full recipient address. Each table provides
a string with the numerical user and group ID, respectively.


The virtual_minimum_uid parameter imposes a lower bound on
numerical user ID values that may be specified in any
virtual_uid_maps.
 

CASE FOLDING






All delivery decisions are made using the full recipient
address, folded to lower case. See also the next section
for a few exceptions with optional address extensions.
 

TABLE SEARCH ORDER






Normally, a lookup table is specified as a text file that
serves as input to the postmap(1) command. The result, an
indexed file in dbm or db format, is used for fast
searching by the mail system.


The search order is as follows. The search stops
upon the first successful lookup.



•

When the recipient has an optional address extension the
user+extension@domain.tld address is looked up first.


With Postfix versions before 2.1, the optional address extension
is always ignored.

•

The user@domain.tld address, without address extension,
is looked up next.

•

Finally, the recipient @domain is looked up.





When the table is provided via other means such as NIS, LDAP
or SQL, the same lookups are done as for ordinary indexed files.


Alternatively, a table can be provided as a regular-expression
map where patterns are given as regular expressions. In that case,
only the full recipient address is given to the regular-expression
map.
 

SECURITY






The virtual(8) delivery agent is not security sensitive, provided
that the lookup tables with recipient user/group ID information are
adequately protected. This program is not designed to run chrooted.


The virtual(8) delivery agent disallows regular expression
substitution of $1 etc. in regular expression lookup tables,
because that would open a security hole.


The virtual(8) delivery agent will silently ignore requests
to use the proxymap(8) server. Instead it will open the
table directly. Before Postfix version 2.2, the virtual
delivery agent will terminate with a fatal error.
 

STANDARDS




RFC 822 (ARPA Internet Text Messages)

 

DIAGNOSTICS




Mail bounces when the recipient has no mailbox or when the
recipient is over disk quota. In all other cases, mail for
an existing recipient is deferred and a warning is logged.


Problems and transactions are logged to syslogd(8).
Corrupted message files are marked so that the queue
manager can move them to the corrupt queue afterwards.


Depending on the setting of the notify_classes parameter,
the postmaster is notified of bounces and of other trouble.
 

BUGS




This delivery agent supports address extensions in email
addresses and in lookup table keys, but does not propagate
address extension information to the result of table lookup.


Postfix should have lookup tables that can return multiple result
attributes. In order to avoid the inconvenience of maintaining
three tables, use an LDAP or MYSQL database.
 

CONFIGURATION PARAMETERS






Changes to main.cf are picked up automatically, as
virtual(8)
processes run for only a limited amount of time. Use the command
"postfix reload" to speed up a change.


The text below provides only a parameter summary. See
postconf(5) for more details including examples.
 

MAILBOX DELIVERY CONTROLS









virtual_mailbox_base (empty)

A prefix that the virtual(8) delivery agent prepends to all pathname
results from $virtual_mailbox_maps table lookups.

virtual_mailbox_maps (empty)

Optional lookup tables with all valid addresses in the domains that
match $virtual_mailbox_domains.

virtual_minimum_uid (100)

The minimum user ID value that the virtual(8) delivery agent accepts
as a result from $virtual_uid_maps table lookup.

virtual_uid_maps (empty)

Lookup tables with the per-recipient user ID that the virtual(8)
delivery agent uses while writing to the recipient's mailbox.

virtual_gid_maps (empty)

Lookup tables with the per-recipient group ID for virtual(8) mailbox
delivery.





Available in Postfix version 2.0 and later:



virtual_mailbox_domains ($virtual_mailbox_maps)

Postfix is final destination for the specified list of domains;
mail is delivered via the $virtual_transport mail delivery transport.

virtual_transport (virtual)

The default mail delivery transport and next-hop destination for
final delivery to domains listed with $virtual_mailbox_domains.





Available in Postfix version 2.5.3 and later:



strict_mailbox_ownership (yes)

Defer delivery when a mailbox file is not owned by its recipient.


 

LOCKING CONTROLS









virtual_mailbox_lock (see 'postconf -d' output)

How to lock a UNIX-style virtual(8) mailbox before attempting
delivery.

deliver_lock_attempts (20)

The maximal number of attempts to acquire an exclusive lock on a
mailbox file or bounce(8) logfile.

deliver_lock_delay (1s)

The time between attempts to acquire an exclusive lock on a mailbox
file or bounce(8) logfile.

stale_lock_time (500s)

The time after which a stale exclusive mailbox lockfile is removed.


 

RESOURCE AND RATE CONTROLS









virtual_mailbox_limit (51200000)

The maximal size in bytes of an individual virtual(8) mailbox or
maildir file, or zero (no limit).





Implemented in the qmgr(8) daemon:



virtual_destination_concurrency_limit ($default_destination_concurrency_limit)

The maximal number of parallel deliveries to the same destination
via the virtual message delivery transport.

virtual_destination_recipient_limit ($default_destination_recipient_limit)

The maximal number of recipients per message for the virtual
message delivery transport.


 

MISCELLANEOUS CONTROLS









config_directory (see 'postconf -d' output)

The default location of the Postfix main.cf and master.cf
configuration files.

daemon_timeout (18000s)

How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.

delay_logging_resolution_limit (2)

The maximal number of digits after the decimal point when logging
sub-second delay values.

ipc_timeout (3600s)

The time limit for sending or receiving information over an internal
communication channel.

max_idle (100s)

The maximum amount of time that an idle Postfix daemon process waits
for an incoming connection before terminating voluntarily.

max_use (100)

The maximal number of incoming connections that a Postfix daemon
process will service before terminating voluntarily.

process_id (read-only)

The process ID of a Postfix command or daemon process.

process_name (read-only)

The process name of a Postfix command or daemon process.

queue_directory (see 'postconf -d' output)

The location of the Postfix top-level queue directory.

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (see 'postconf -d' output)

A prefix that is prepended to the process name in syslog
records, so that, for example, "smtpd" becomes "prefix/smtpd".





Available in Postfix version 3.0 and later:



virtual_delivery_status_filter ($default_delivery_status_filter)

Optional filter for the virtual(8) delivery agent to change the
delivery status code or explanatory text of successful or unsuccessful
deliveries.





Available in Postfix version 3.3 and later:



enable_original_recipient (yes)

Enable support for the original recipient address after an
address is rewritten to a different address (for example with
aliasing or with canonical mapping).

service_name (read-only)

The master.cf service name of a Postfix daemon process.


 

SEE ALSO




qmgr(8), queue manager
bounce(8), delivery status reports
postconf(5), configuration parameters
syslogd(8), system logging

 

README_FILES




Use "postconf readme_directory" or
"postconf html_directory" to locate this information.
VIRTUAL_README, domain hosting howto

 

LICENSE






The Secure Mailer license must be distributed with this software.
 

HISTORY






This delivery agent was originally based on the Postfix local delivery
agent. Modifications mainly consisted of removing code that either
was not applicable or that was not safe in this context: aliases,
~user/.forward files, delivery to "|command" or to /file/name.


The Delivered-To: message header appears in the qmail
system by Daniel Bernstein.


The maildir structure appears in the qmail system
by Daniel Bernstein.
 

AUTHOR(S)




Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA

Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA

Andrew McNamara
andrewm@connect.com.au
connect.com.au Pty. Ltd.
Level 3, 213 Miller St
North Sydney 2060, NSW, Australia





 
Index




NAME


SYNOPSIS


DESCRIPTION


MAILBOX LOCATION


UNIX MAILBOX FORMAT


QMAIL MAILDIR FORMAT


MAILBOX OWNERSHIP


CASE FOLDING


TABLE SEARCH ORDER


SECURITY


STANDARDS


DIAGNOSTICS


BUGS


CONFIGURATION PARAMETERS


MAILBOX DELIVERY CONTROLS


LOCKING CONTROLS


RESOURCE AND RATE CONTROLS


MISCELLANEOUS CONTROLS


SEE ALSO


README_FILES


LICENSE


HISTORY


AUTHOR(S)





This document was created by
man2html,
using the manual pages.

Time: 04:46:02 GMT, September 16, 2022








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