#++
# NAME
#	virtual 5
# SUMMARY
#	Postfix virtual alias table format
# SYNOPSIS
#	\fBpostmap /etc/postfix/virtual\fR
#
#	\fBpostmap -q "\fIstring\fB" /etc/postfix/virtual\fR
#
#	\fBpostmap -q - /etc/postfix/virtual <\fIinputfile\fR
# DESCRIPTION
#	The optional \fBvirtual\fR(5) alias table rewrites recipient
#	addresses for all local, all virtual, and all remote mail
#	destinations.
#	This is unlike the \fBaliases\fR(5) table which is used
#	only for \fBlocal\fR(8) delivery.  Virtual aliasing is
#	recursive, and is implemented by the Postfix \fBcleanup\fR(8)
#	daemon before mail is queued.
#
#	The main applications of virtual aliasing are:
# .IP \(bu
#	To redirect mail for one address to one or more addresses.
# .IP \(bu
#	To implement virtual alias domains where all addresses are aliased
#	to addresses in other domains.
# .sp
#	Virtual alias domains are not to be confused with the virtual mailbox
#	domains that are implemented with the Postfix \fBvirtual\fR(8) mail
#	delivery agent. With virtual mailbox domains, each recipient address
#	can have its own mailbox.
# .PP
#	Virtual aliasing is applied only to recipient
#	envelope addresses, and does not affect message headers.
#	Use \fBcanonical\fR(5)
#	mapping to rewrite header and envelope addresses in general.
#
#	Normally, the \fBvirtual\fR(5) alias table is specified as a text file
#	that serves as input to the \fBpostmap\fR(1) command.
#	The result, an indexed file in \fBdbm\fR or \fBdb\fR format,
#	is used for fast searching by the mail system. Execute the command
#	"\fBpostmap /etc/postfix/virtual\fR" 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
# .ad
# .fi
#	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
# .ad
# .fi
#	The input format for the \fBpostmap\fR(1) command is as follows:
# .IP "\fIpattern address, address, ...\fR"
#	When \fIpattern\fR matches a mail address, replace it by the
#	corresponding \fIaddress\fR.
# .IP "blank lines and comments"
#	Empty lines and whitespace-only lines are ignored, as
#	are lines whose first non-whitespace character is a `#'.
# .IP "multi-line text"
#	A logical line starts with non-whitespace text. A line that
#	starts with whitespace continues a logical line.
# TABLE SEARCH ORDER
# .ad
# .fi
#	With lookups from indexed files such as DB or DBM, or from networked
#	tables such as NIS, LDAP or SQL, patterns are tried in the order as
#	listed below:
# .IP "\fIuser\fR@\fIdomain address, address, ...\fR"
#	Redirect mail for \fIuser\fR@\fIdomain\fR to \fIaddress\fR.
#	This form has the highest precedence.
# .IP "\fIuser address, address, ...\fR"
#	Redirect mail for \fIuser\fR@\fIsite\fR to \fIaddress\fR when
#	\fIsite\fR is equal to $\fBmyorigin\fR, when \fIsite\fR is listed in
#	$\fBmydestination\fR, or when it is listed in $\fBinet_interfaces\fR
#	or $\fBproxy_interfaces\fR.
#	.sp
#	This functionality overlaps with functionality of the local
#	\fIaliases\fR(5) database. The difference is that \fBvirtual\fR(5)
#	mapping can be applied to non-local addresses.
# .IP "@\fIdomain address, address, ...\fR"
#	Redirect mail for other users in \fIdomain\fR to \fIaddress\fR.
#	This form has the lowest precedence.
# .sp
#	Note: @\fIdomain\fR is a wild-card. With this form, the
#	Postfix SMTP server accepts
#	mail for any recipient in \fIdomain\fR, 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
# .ad
# .fi
#	The lookup result is subject to address rewriting:
# .IP \(bu
#	When the result has the form @\fIotherdomain\fR, the
#	result becomes the same \fIuser\fR in \fIotherdomain\fR.
#	This works only for the first address in a multi-address
#	lookup result.
# .IP \(bu
#	When "\fBappend_at_myorigin=yes\fR", append "\fB@$myorigin\fR"
#	to addresses without "@domain".
# .IP \(bu
#	When "\fBappend_dot_mydomain=yes\fR", append
#	"\fB.$mydomain\fR" to addresses without ".domain".
# ADDRESS EXTENSION
# .fi
# .ad
#	When a mail address localpart contains the optional recipient delimiter
#	(e.g., \fIuser+foo\fR@\fIdomain\fR), the lookup order becomes:
#	\fIuser+foo\fR@\fIdomain\fR, \fIuser\fR@\fIdomain\fR, \fIuser+foo\fR,
#	\fIuser\fR, and @\fIdomain\fR.
#
#	The \fBpropagate_unmatched_extensions\fR parameter controls whether
#	an unmatched address extension (\fI+foo\fR) is propagated to the
#	result of table lookup.
# VIRTUAL ALIAS DOMAINS
# .ad
# .fi
#	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 \fBvirtual\fR(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
#	\fBaliases\fR(5) and local mailing lists are not visible as
#	\fIlocalname@virtual-alias.domain\fR.
#
#	Support for a virtual alias domain looks like:
#
# .nf
#	/etc/postfix/main.cf:
#	    virtual_alias_maps = hash:/etc/postfix/virtual
# .fi
#
#	Note: some systems use \fBdbm\fR databases instead of \fBhash\fR.
#	See the output from "\fBpostconf -m\fR" for available database types.
#
# .nf
#	/etc/postfix/virtual:
#	    \fIvirtual-alias.domain	anything\fR (right-hand content does not matter)
#	    \fIpostmaster@virtual-alias.domain	postmaster\fR
#	    \fIuser1@virtual-alias.domain	address1\fR
#	    \fIuser2@virtual-alias.domain	address2, address3\fR
# .fi
# .sp
#	The \fIvirtual-alias.domain anything\fR entry is required for a
#	virtual alias domain. \fBWithout this entry, mail is rejected
#	with "relay access denied", or bounces with 
#	"mail loops back to myself".\fR
#
#	Do not specify virtual alias domain names in the \fBmain.cf
#	mydestination\fR or \fBrelay_domains\fR configuration parameters.
#
#	With a virtual alias domain, the Postfix SMTP server
#	accepts mail for \fIknown-user@virtual-alias.domain\fR, and rejects
#	mail for \fIunknown-user\fR@\fIvirtual-alias.domain\fR as undeliverable.
#
#	Instead of specifying the virtual alias domain name via
#	the \fBvirtual_alias_maps\fR table, you may also specify it via
#	the \fBmain.cf virtual_alias_domains\fR configuration parameter.
#	This latter parameter uses the same syntax as the \fBmain.cf
#	mydestination\fR configuration parameter.
# REGULAR EXPRESSION TABLES
# .ad
# .fi
#	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 \fBregexp_table\fR(5)
#	or \fBpcre_table\fR(5).
#
#	Each pattern is a regular expression that is applied to the entire
#	address being looked up. Thus, \fIuser@domain\fR mail addresses are not
#	broken up into their \fIuser\fR and \fI@domain\fR constituent parts,
#	nor is \fIuser+foo\fR broken up into \fIuser\fR and \fIfoo\fR.
#
#	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 \fB$1\fR, \fB$2\fR and so on.
# TCP-BASED TABLES
# .ad
# .fi
#	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 \fBtcp_table\fR(5).
#	This feature is not available up to and including Postfix version 2.4.
#
#	Each lookup operation uses the entire address once.  Thus,
#	\fIuser@domain\fR mail addresses are not broken up into their
#	\fIuser\fR and \fI@domain\fR constituent parts, nor is
#	\fIuser+foo\fR broken up into \fIuser\fR and \fIfoo\fR.
#
#	Results are the same as with indexed file lookups.
# BUGS
#	The table format does not understand quoting conventions.
# CONFIGURATION PARAMETERS
# .ad
# .fi
#	The following \fBmain.cf\fR parameters are especially relevant to
#	this topic. See the Postfix \fBmain.cf\fR file for syntax details
#	and for default values. Use the "\fBpostfix reload\fR" command after
#	a configuration change.
# .IP \fBvirtual_alias_maps\fR
#	List of virtual aliasing tables.
# .IP \fBvirtual_alias_domains\fR
#	List of virtual alias domains. This uses the same syntax
#	as the \fBmydestination\fR parameter.
# .IP \fBpropagate_unmatched_extensions\fR
#	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 \fBcanonical\fR, \fBvirtual\fR, \fBalias\fR,
#	\fBforward\fR, \fBinclude\fR, or \fBgeneric\fR.
# .PP
#	Other parameters of interest:
# .IP \fBinet_interfaces\fR
#	The network interface addresses that this system receives mail on.
#	You need to stop and start Postfix when this parameter changes.
# .IP \fBmydestination\fR
#	List of domains that this mail system considers local.
# .IP \fBmyorigin\fR
#	The domain that is appended to any address that does not have a domain.
# .IP \fBowner_request_special\fR
#	Give special treatment to \fBowner-\fIxxx\fR and \fIxxx\fB-request\fR
#	addresses.
# .IP \fBproxy_interfaces\fR
#	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
# .ad
# .fi
#	Use "\fBpostconf readme_directory\fR" or
#	"\fBpostconf html_directory\fR" to locate this information.
# .na
# .nf
#	ADDRESS_REWRITING_README, address rewriting guide
#	DATABASE_README, Postfix lookup table overview
#	VIRTUAL_README, domain hosting guide
# LICENSE
# .ad
# .fi
#	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
#--