Manual browser: virtual(8)
|VIRTUAL(8)||System Manager's Manual||VIRTUAL(8)|
NAMEvirtual - Postfix virtual domain mail delivery agent
virtual [generic Postfix daemon options]
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.
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.
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.
QMAIL MAILDIR FORMAT
When the mailbox location ends in /, the message is delivered in qmail maildir format. This format stores one message per file.
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.
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.
When the recipient has an optional address extension the email@example.com address is looked up first.
- The firstname.lastname@example.org 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.
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.
RFC 822 (ARPA Internet Text Messages)
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.
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.
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.
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 accepts 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 $virtual_mailbox_domains.
Available in Postfix version 2.5.3 and later:
- strict_mailbox_ownership (yes)
- Defer delivery when a mailbox file is not owned by its recipient.
- virtual_mailbox_lock (see 'postconf -d' output)
- How to lock a UNIX-style virtual(8) mailbox before attempting delivery.
- deliver_lock_attempts (20)
- The maximal number of attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile.
- deliver_lock_delay (1s)
- The time between attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile.
- stale_lock_time (500s)
- The time after which a stale exclusive mailbox lockfile is removed.
RESOURCE AND RATE CONTROLS
- virtual_destination_concurrency_limit ($default_destination_concurrency_limit)
- The maximal number of parallel deliveries to the same destination via the virtual message delivery transport.
- virtual_destination_recipient_limit ($default_destination_recipient_limit)
- The maximal number of recipients per message for the virtual message delivery transport.
- virtual_mailbox_limit (51200000)
- The maximal size in bytes of an individual virtual(8) mailbox or maildir file, or zero (no limit).
- config_directory (see 'postconf -d' output)
- The default location of the Postfix main.cf and master.cf configuration files.
- daemon_timeout (18000s)
- How much time a Postfix daemon process may take to handle a request 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 logging sub-second delay values.
- ipc_timeout (3600s)
- The time limit for sending or receiving information over an internal 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)
- The mail system name that is prepended to the process name in syslog records, so that "smtpd" becomes, for example, "postfix/smtpd".
qmgr(8), queue manager
bounce(8), delivery status reports
postconf(5), configuration parameters
syslogd(8), system logging
Use "postconf readme_directory" or
"postconf html_directory" to locate this information.
VIRTUAL_README, domain hosting howto
The Secure Mailer license must be distributed with this software.
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.
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
connect.com.au Pty. Ltd.
Level 3, 213 Miller St
North Sydney 2060, NSW, Australia