Pigeonhole Sieve: Vacation Extension
====================================

The Sieve vacation extension (RFC5230 [http://tools.ietf.org/html/rfc5230/])
defines a mechanism to generate automatic replies to incoming email messages.
It takes various precautions to make sure replies are only sent when
appropriate. Script authors can specify how often replies can be sent to a
particular contact. In the original vacation extension, this interval is
specified in days with a minimum of one day. When more granularity is necessary
and particularly when replies must be sent more frequently than one day, the
vacation-seconds extension (RFC6131 [http://tools.ietf.org/html/rfc5230/]) can
be used. This allows specifying the minimum reply interval in seconds with a
minimum of zero (a reply is then always sent), depending on administrator
configuration.

Configuration
=============

The *vacation* extension is available by default. In contrast, the
*vacation-seconds* extension - which implies the vacation extension when used -
is not available by default and needs to be enabled explicitly by adding it to
the 'sieve_extensions' setting. The configuration also needs to be adjusted
accordingly to allow a non-reply period of less than a day.

The *vacation* and *vacation-seconds* extensions have their own specific
settings. The settings that specify a period (currently all of them) are
specified in *s*(econds), unless followed by a *d*(ay), *h*(our) or *m*(inute)
specifier character.

The following settings can be configured for the vacation extension in the
'plugin' section (default values are indicated):

sieve_vacation_min_period = 1d :
  This specifies the minimum period that can be specified for the :days  and
  :seconds tags of the vacation command. A minimum of 0 indicates that users
  are allowed to make the Sieve interpreter send a vacation response message
  for every incoming message that meets the other reply criteria (refer to
  RFC5230). A value of zero is however not recommended.

sieve_vacation_max_period = 0 :
   This specifies the maximum period that can be specified for the :days tag of
  the vacation command. The configured value must be larger than the
  sieve_vacation_min_period setting. A value of 0 has a special meaning: it
  indicates that there is no upper limit.

sieve_vacation_default_period = 7d :
  This specifies the default period that is used when no :days or :seconds tag
  is specified. The configured value must lie between the
  sieve_vacation_min_period and sieve_vacation_max_period.

sieve_vacation_use_original_recipient = no :
  This specifies whether the original envelope recipient should be used in the
  check for implicit delivery.  The vacation command checks headers of the
  incoming message, such as To: and Cc: for the address of the recipient, to
  verify that the message is explicitly addressed at the recipient. If the
  recipient address is not found, the vacation action will not trigger a
  response to prevent sending a reply when it is not appropriate. Normally only
  the final recipient address is used in this check. This setting allows
  including the original recipient specified in the SMTP session if available.
  This is useful to handle mail accounts with aliases. Use this option with
  caution: if you are using aliases that point to more than a single account,
  senders can get multiple vacation responses for a single message. Use the
  <LDA.txt> '-a' option or the <LMTP.txt>/ <LDA.txt>
  'lda_original_recipient_header' setting to make the original SMTP recipient
  available to Sieve.

sieve_vacation_dont_check_recipient = no :
  This disables the checks for implicit delivery entirely. This means that the
  vacation command does not verify that the message is explicitly addressed at
  the recipient. Use this option with caution. Specifying 'yes' will violate
  the Sieve standards and can cause vacation replies to be sent for messages
  not directly addressed at the recipient.

sieve_vacation_send_from_recipient = no :
  This setting determines whether vacation messages are sent with the SMTP MAIL
  FROM envelope address set to the recipient address of the Sieve script owner.
  Normally this is set to<>, which is the default as recommended in the
  specification. This is meant to prevent mail loops. However, there are
  situations for which a valid sender address is required and this setting can
  be used to accommodate for those.

Invalid values for the settings above will make the Sieve interpreter log a
warning and revert to the default values.

See also <how vacation auto-reply uses addresses> [Pigeonhole.Sieve.Usage.txt].

Example
-------

---%<-------------------------------------------------------------------------
plugin {
  # Use vacation-seconds
  sieve_extensions = +vacation-seconds

  # One hour at minimum
  sieve_vacation_min_period = 1h

  # Ten days default
  sieve_vacation_default_period = 10d

  # Thirty days at maximum
  sieve_vacation_max_period = 30d
}
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2019-06-19 12:42)
