Pigeonhole Sieve: Vacation Extension

The Sieve vacation extension RFC 5230 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 RFC 6131 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.


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 RFC 5230). 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 -a option or the LMTP 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.


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