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VIRTUAL(8) System Manager's Manual VIRTUAL(8)

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





  

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

  

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

  

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

  

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

  

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




Available in Postfix version 2.0 and later:



  

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

  

  
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:



  

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








LOCKING CONTROLS





  

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

  

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

  

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

  

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








RESOURCE AND RATE CONTROLS





  

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

  

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

  

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








MISCELLANEOUS CONTROLS





  

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

  

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

  

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

  

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

  

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

  

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

  

  
The process ID of a Postfix command or daemon process.

  

  
The process name of a Postfix command or daemon process.

  

  
The location of the Postfix top-level queue directory.

  

  
The syslog facility of Postfix logging.

  

  
The mail system name that is prepended to the process name in syslog
      records, so that "smtpd" becomes, for example,
      "postfix/smtpd".








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