1VIRTUAL(5)                    File Formats Manual                   VIRTUAL(5)
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NAME

6       virtual - Postfix virtual alias table format
7

SYNOPSIS

9       postmap /etc/postfix/virtual
10
11       postmap -q "string" /etc/postfix/virtual
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13       postmap -q - /etc/postfix/virtual <inputfile
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DESCRIPTION

16       The  optional  virtual(5)  alias table rewrites recipient addresses for
17       all local, all virtual, and all remote mail destinations.  This is  un‐
18       like  the  aliases(5)  table  which is used only for local(8) delivery.
19       Virtual aliasing is  recursive,  and  is  implemented  by  the  Postfix
20       cleanup(8) daemon before mail is queued.
21
22       The main applications of virtual aliasing are:
23
24       •      To redirect mail for one address to one or more addresses.
25
26       •      To  implement  virtual  alias  domains  where  all addresses are
27              aliased to addresses in other domains.
28
29              Virtual alias domains are not to be confused  with  the  virtual
30              mailbox domains that are implemented with the Postfix virtual(8)
31              mail delivery agent. With virtual mailbox domains, each  recipi‐
32              ent address can have its own mailbox.
33
34       Virtual  aliasing  is applied only to recipient envelope addresses, and
35       does not affect message headers.  Use canonical(5) mapping  to  rewrite
36       header and envelope addresses in general.
37
38       Normally,  the  virtual(5) alias table is specified as a text file that
39       serves as input to the postmap(1) command.  The result, an indexed file
40       in dbm or db format, is used for fast searching by the mail system. Ex‐
41       ecute the command "postmap /etc/postfix/virtual" to rebuild an  indexed
42       file after changing the corresponding text file.
43
44       When  the  table  is provided via other means such as NIS, LDAP or SQL,
45       the same lookups are done as for ordinary indexed files.
46
47       Alternatively, the table can be provided as  a  regular-expression  map
48       where  patterns are given as regular expressions, or lookups can be di‐
49       rected to a TCP-based server. In those case, the lookups are done in  a
50       slightly different way as described below under "REGULAR EXPRESSION TA‐
51       BLES" or "TCP-BASED TABLES".
52

CASE FOLDING

54       The search string is folded to lowercase before database lookup. As  of
55       Postfix  2.3,  the search string is not case folded with database types
56       such as regexp: or pcre: whose lookup fields can match both  upper  and
57       lower case.
58

TABLE FORMAT

60       The input format for the postmap(1) command is as follows:
61
62       pattern address, address, ...
63              When  pattern  matches  a mail address, replace it by the corre‐
64              sponding address.
65
66       blank lines and comments
67              Empty lines and whitespace-only lines are ignored, as are  lines
68              whose first non-whitespace character is a `#'.
69
70       multi-line text
71              A  logical  line  starts  with  non-whitespace text. A line that
72              starts with whitespace continues a logical line.
73

TABLE SEARCH ORDER

75       With lookups from indexed files such as DB or DBM,  or  from  networked
76       tables  such as NIS, LDAP or SQL, each user@domain query produces a se‐
77       quence of query patterns as described below.
78
79       Each query pattern is sent to each specified lookup table before trying
80       the next query pattern, until a match is found.
81
82       user@domain address, address, ...
83              Redirect  mail  for  user@domain  to address.  This form has the
84              highest precedence.
85
86       user address, address, ...
87              Redirect mail for user@site to address when  site  is  equal  to
88              $myorigin,  when site is listed in $mydestination, or when it is
89              listed in $inet_interfaces or $proxy_interfaces.
90
91              This functionality overlaps with the functionality of the  local
92              aliases(5)  database.  The difference is that virtual(5) mapping
93              can be applied to non-local addresses.
94
95       @domain address, address, ...
96              Redirect mail for other users in domain to address.   This  form
97              has the lowest precedence.
98
99              Note:  @domain  is a wild-card. With this form, the Postfix SMTP
100              server accepts mail for any recipient in domain,  regardless  of
101              whether  that  recipient exists.  This may turn your mail system
102              into a  backscatter  source:  Postfix  first  accepts  mail  for
103              non-existent  recipients  and  then tries to return that mail as
104              "undeliverable" to the often forged sender address.
105
106              To avoid backscatter with mail for a wild-card  domain,  replace
107              the  wild-card  mapping with explicit 1:1 mappings, or add a re‐
108              ject_unverified_recipient restriction for that domain:
109
110                  smtpd_recipient_restrictions =
111                      ...
112                      reject_unauth_destination
113                      check_recipient_access
114                          inline:{example.com=reject_unverified_recipient}
115                  unverified_recipient_reject_code = 550
116
117              In the above example, Postfix may contact a remote server if the
118              recipient is aliased to a remote address.
119

RESULT ADDRESS REWRITING

121       The lookup result is subject to address rewriting:
122
123       •      When  the  result  has the form @otherdomain, the result becomes
124              the same user in otherdomain.  This works only for the first ad‐
125              dress in a multi-address lookup result.
126
127       •      When  "append_at_myorigin=yes", append "@$myorigin" to addresses
128              without "@domain".
129
130       •      When "append_dot_mydomain=yes", append ".$mydomain" to addresses
131              without ".domain".
132

ADDRESS EXTENSION

134       When a mail address localpart contains the optional recipient delimiter
135       (e.g., user+foo@domain), the  lookup  order  becomes:  user+foo@domain,
136       user@domain, user+foo, user, and @domain.
137
138       The  propagate_unmatched_extensions  parameter  controls whether an un‐
139       matched address extension (+foo) is propagated to the result of a table
140       lookup.
141

VIRTUAL ALIAS DOMAINS

143       Besides  virtual  aliases,  the virtual alias table can also be used to
144       implement virtual alias domains. With a virtual alias domain,  all  re‐
145       cipient addresses are aliased to addresses in other domains.
146
147       Virtual  alias  domains are not to be confused with the virtual mailbox
148       domains that are implemented with the Postfix virtual(8) mail  delivery
149       agent.  With  virtual  mailbox domains, each recipient address can have
150       its own mailbox.
151
152       With a virtual alias domain, the virtual domain has its own  user  name
153       space.  Local (i.e. non-virtual) usernames are not visible in a virtual
154       alias domain. In particular, local aliases(5) and local  mailing  lists
155       are not visible as localname@virtual-alias.domain.
156
157       Support for a virtual alias domain looks like:
158
159       /etc/postfix/main.cf:
160           virtual_alias_maps = hash:/etc/postfix/virtual
161
162       Note:  some  systems use dbm databases instead of hash.  See the output
163       from "postconf -m" for available database types.
164
165       /etc/postfix/virtual:
166           virtual-alias.domain    anything (right-hand content does not matter)
167           postmaster@virtual-alias.domain postmaster
168           user1@virtual-alias.domain      address1
169           user2@virtual-alias.domain      address2, address3
170
171       The virtual-alias.domain anything entry is required for a virtual alias
172       domain.  Without  this  entry,  mail is rejected with "relay access de‐
173       nied", or bounces with "mail loops back to myself".
174
175       Do not specify virtual alias domain names in the main.cf  mydestination
176       or relay_domains configuration parameters.
177
178       With  a  virtual alias domain, the Postfix SMTP server accepts mail for
179       known-user@virtual-alias.domain, and rejects mail for unknown-user@vir‐
180       tual-alias.domain as undeliverable.
181
182       Instead  of  specifying  the  virtual  alias  domain  name via the vir‐
183       tual_alias_maps table, you may also specify it  via  the  main.cf  vir‐
184       tual_alias_domains configuration parameter.  This latter parameter uses
185       the same syntax as the main.cf mydestination configuration parameter.
186

REGULAR EXPRESSION TABLES

188       This section describes how the table lookups change when the  table  is
189       given  in the form of regular expressions. For a description of regular
190       expression lookup table syntax, see regexp_table(5) or pcre_table(5).
191
192       Each pattern is a regular expression that is applied to the entire  ad‐
193       dress  being looked up. Thus, user@domain mail addresses are not broken
194       up into their user and @domain constituent parts, nor is user+foo  bro‐
195       ken up into user and foo.
196
197       Patterns  are  applied  in the order as specified in the table, until a
198       pattern is found that matches the search string.
199
200       Results are the same as with indexed file lookups, with the  additional
201       feature  that parenthesized substrings from the pattern can be interpo‐
202       lated as $1, $2 and so on.
203

TCP-BASED TABLES

205       This section describes how the table lookups change  when  lookups  are
206       directed   to  a  TCP-based  server.  For  a  description  of  the  TCP
207       client/server lookup  protocol,  see  tcp_table(5).   This  feature  is
208       available in Postfix 2.5 and later.
209
210       Each  lookup operation uses the entire address once.  Thus, user@domain
211       mail addresses are not broken up  into  their  user  and  @domain  con‐
212       stituent parts, nor is user+foo broken up into user and foo.
213
214       Results are the same as with indexed file lookups.
215

BUGS

217       The table format does not understand quoting conventions.
218

CONFIGURATION PARAMETERS

220       The following main.cf parameters are especially relevant to this topic.
221       See the Postfix main.cf file for syntax details and for default values.
222       Use the "postfix reload" command after a configuration change.
223
224       virtual_alias_maps ($virtual_maps)
225              Optional lookup tables that alias specific mail addresses or do‐
226              mains to other local or remote addresses.
227
228       virtual_alias_domains ($virtual_alias_maps)
229              Postfix is the final destination for the specified list of  vir‐
230              tual alias domains, that is, domains for which all addresses are
231              aliased to addresses in other local or remote domains.
232
233       propagate_unmatched_extensions (canonical, virtual)
234              What address lookup tables copy an address  extension  from  the
235              lookup key to the lookup result.
236
237       Other parameters of interest:
238
239       inet_interfaces (all)
240              The  network  interface addresses that this mail system receives
241              mail on.
242
243       mydestination ($myhostname, localhost.$mydomain, localhost)
244              The list of domains that are delivered via the  $local_transport
245              mail delivery transport.
246
247       myorigin ($myhostname)
248              The  domain  name that locally-posted mail appears to come from,
249              and that locally posted mail is delivered to.
250
251       owner_request_special (yes)
252              Enable special  treatment  for  owner-listname  entries  in  the
253              aliases(5) file, and don't split owner-listname and listname-re‐
254              quest address localparts when the recipient_delimiter is set  to
255              "-".
256
257       proxy_interfaces (empty)
258              The  network  interface addresses that this mail system receives
259              mail on by way of a proxy or network address translation unit.
260

SEE ALSO

262       cleanup(8), canonicalize and enqueue mail
263       postmap(1), Postfix lookup table manager
264       postconf(5), configuration parameters
265       canonical(5), canonical address mapping
266

README FILES

268       Use "postconf readme_directory" or "postconf html_directory" to  locate
269       this information.
270       ADDRESS_REWRITING_README, address rewriting guide
271       DATABASE_README, Postfix lookup table overview
272       VIRTUAL_README, domain hosting guide
273

LICENSE

275       The Secure Mailer license must be distributed with this software.
276

AUTHOR(S)

278       Wietse Venema
279       IBM T.J. Watson Research
280       P.O. Box 704
281       Yorktown Heights, NY 10598, USA
282
283       Wietse Venema
284       Google, Inc.
285       111 8th Avenue
286       New York, NY 10011, USA
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