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VIRTUAL(8postfix) VIRTUAL(8postfix) 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 ser- vices. Originally based on the Postfix local(8) delivery agent, this agent looks up recipients with map lookups of their full recipient ad- dress, 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 vir- tual_mailbox_maps configuration parameters (see below). The vir- tual_mailbox_maps table is indexed by the recipient address as de- scribed 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" enve- lope 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 mail- box 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 vir- tual_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 in- put 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 suc- cessful lookup. o When the recipient has an optional address extension the user+extension AT domain.tld address is looked up first. With Postfix versions before 2.1, the optional address extension is always ignored. o The user AT domain.tld address, without address extension, is looked up next. o 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 ade- quately 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) or postlogd(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 postmas- ter 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 informa- tion to the result of table lookup. Postfix should have lookup tables that can return multiple result at- tributes. In order to avoid the inconvenience of maintaining three ta- bles, 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 ac- cepts 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 $virtual_mailbox_domains. Available in Postfix version 2.5.3 and later: strict_mailbox_ownership (yes) Defer delivery when a mailbox file is not owned by its recipi- ent. LOCKING CONTROLS virtual_mailbox_lock (see 'postconf -d' output) How to lock a UNIX-style virtual(8) mailbox before attempting delivery. deliver_lock_attempts (20) The maximal number of attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile. deliver_lock_delay (1s) The time between attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile. stale_lock_time (500s) The time after which a stale exclusive mailbox lockfile is re- moved. RESOURCE AND RATE CONTROLS virtual_mailbox_limit (51200000) The maximal size in bytes of an individual virtual(8) mailbox or maildir file, or zero (no limit). Implemented in the qmgr(8) daemon: virtual_destination_concurrency_limit ($default_destination_concur- rency_limit) The maximal number of parallel deliveries to the same destina- tion via the virtual message delivery transport. virtual_destination_recipient_limit ($default_destination_recipi- ent_limit) The maximal number of recipients per message for the virtual message delivery transport. MISCELLANEOUS CONTROLS config_directory (see 'postconf -d' output) The default location of the Postfix main.cf and master.cf con- figuration files. daemon_timeout (18000s) How much time a Postfix daemon process may take to handle a re- quest before it is terminated by a built-in watchdog timer. delay_logging_resolution_limit (2) The maximal number of digits after the decimal point when log- ging sub-second delay values. ipc_timeout (3600s) The time limit for sending or receiving information over an in- ternal communication channel. max_idle (100s) The maximum amount of time that an idle Postfix daemon process waits for an incoming connection before terminating voluntarily. max_use (100) The maximal number of incoming connections that a Postfix daemon process will service before terminating voluntarily. process_id (read-only) The process ID of a Postfix command or daemon process. process_name (read-only) The process name of a Postfix command or daemon process. queue_directory (see 'postconf -d' output) The location of the Postfix top-level queue directory. syslog_facility (mail) The syslog facility of Postfix logging. syslog_name (see 'postconf -d' output) A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd". Available in Postfix version 3.0 and later: virtual_delivery_status_filter ($default_delivery_status_filter) Optional filter for the virtual(8) delivery agent to change the delivery status code or explanatory text of successful or unsuc- cessful deliveries. Available in Postfix version 3.3 and later: enable_original_recipient (yes) Enable support for the original recipient address after an ad- dress 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. Available in Postfix 3.5 and later: info_log_address_format (external) The email address form that will be used in non-debug logging (info, warning, etc.). SEE ALSO qmgr(8), queue manager bounce(8), delivery status reports postconf(5), configuration parameters postlogd(8), Postfix logging 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 AT connect.au connect.com.au Pty. Ltd. Level 3, 213 Miller St North Sydney 2060, NSW, Australia VIRTUAL(8postfix) VIRTUAL(5) File Formats Manual VIRTUAL(5) 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 un- like 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: o To redirect mail for one address to one or more addresses. o 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 recipi- ent 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. Ex- ecute 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 di- rected to TCP-based server. In those case, the lookups are done in a slightly different way as described below under "REGULAR EXPRESSION TA- BLES" 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 corre- sponding 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 se- quence 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 $proxy_interfaces. This functionality overlaps with functionality of the local aliases(5) database. The difference is that virtual(5) mapping can be applied to non-local addresses. @domain address, address, ... Redirect mail for other users in domain to address. This form has the lowest precedence. Note: @domain is a wild-card. With this form, the Postfix SMTP server accepts mail for any recipient in domain, regardless of whether that recipient exists. This may turn your mail system into a backscatter source: Postfix first accepts mail for non-existent recipients and then tries to return that mail as "undeliverable" to the often forged sender address. To avoid backscatter with mail for a wild-card domain, replace the wild-card mapping with explicit 1:1 mappings, or add a re- ject_unverified_recipient restriction for that domain: smtpd_recipient_restrictions = ... reject_unauth_destination check_recipient_access inline:{example.com=reject_unverified_recipient} unverified_recipient_reject_code = 550 In the above example, Postfix may contact a remote server if the recipient is aliased to a remote address. RESULT ADDRESS REWRITING The lookup result is subject to address rewriting: o When the result has the form @otherdomain, the result becomes the same user in otherdomain. This works only for the first ad- dress in a multi-address lookup result. o When "append_at_myorigin=yes", append "@$myorigin" to addresses without "@domain". o 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 un- matched 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 re- cipient 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 AT 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 AT virtual-alias.domain postmaster user1 AT virtual-alias.domain address1 user2 AT 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 de- nied", 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 AT virtual-alias.domain, and rejects mail for unknown-user@vir- tual-alias.domain as undeliverable. Instead of specifying the virtual alias domain name via the vir- tual_alias_maps table, you may also specify it via the main.cf vir- tual_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 ad- dress being looked up. Thus, user@domain mail addresses are not broken up into their user and @domain constituent parts, nor is user+foo bro- ken 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 interpo- lated as $1, $2 and so on. TCP-BASED TABLES This section describes how the table lookups change when lookups are directed to a TCP-based server. For a description of the TCP client/server lookup protocol, see tcp_table(5). This feature is not available up to and including Postfix version 2.4. Each lookup operation uses the entire address once. Thus, user@domain mail addresses are not broken up into their user and @domain con- stituent parts, nor is user+foo broken up into user and foo. Results are the same as with indexed file lookups. BUGS The table format does not understand quoting conventions. CONFIGURATION PARAMETERS The following main.cf parameters are especially relevant to this topic. See the Postfix main.cf file for syntax details and for default values. Use the "postfix reload" command after a configuration change. virtual_alias_maps ($virtual_maps) Optional lookup tables that alias specific mail addresses or do- mains to other local or remote address. virtual_alias_domains ($virtual_alias_maps) Postfix is final destination for the specified list of virtual alias domains, that is, domains for which all addresses are aliased to addresses in other local or remote domains. propagate_unmatched_extensions (canonical, virtual) What address lookup tables copy an address extension from the lookup key to the lookup result. Other parameters of interest: inet_interfaces (all) The network interface addresses that this mail system receives mail on. mydestination ($myhostname, localhost.$mydomain, localhost) The list of domains that are delivered via the $local_transport mail delivery transport. myorigin ($myhostname) The domain name that locally-posted mail appears to come from, and that locally posted mail is delivered to. owner_request_special (yes) Enable special treatment for owner-listname entries in the aliases(5) file, and don't split owner-listname and listname-re- quest address localparts when the recipient_delimiter is set to "-". proxy_interfaces (empty) The network interface addresses that this mail system receives mail on by way of a proxy or network address translation unit. 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 VIRTUAL(5)
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