VIRTUAL(5) File Formats Manual VIRTUAL(5)

virtual - Postfix virtual alias table format

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


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:

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".



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.










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



  

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

  

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

  

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












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.



  

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

  

  
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.

  












The lookup result is subject to address rewriting:











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.










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.










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.










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.










The table format does not understand quoting conventions.










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.



  

  
List of virtual aliasing tables.

  

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

  

  
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:



  

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

  

  
List of domains that this mail system considers local.

  

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

  

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

  

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










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










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










The Secure Mailer license must be distributed with this
  software.








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