Local queue

Queue module buffers messages on disk and retries delivery multiple times to another target to ensure reliable delivery.

It is also responsible for generation of DSN messages in case of delivery failures.

Arguments

First argument specifies directory to use for storage. Relative paths are relative to the StateDirectory.

Configuration directives

target.queue {
    target remote
    location ...
    max_parallelism 16
    max_tries 4
    initial_retry_time 5m
    retry_time_scale 1.25
    post_init_delay 10s
    bounce {
        destination example.org {
            deliver_to &local_mailboxes
        }
        default_destination {
            reject
        }
    }

    autogenerated_msg_domain example.org
    hostname mx.example.org
    debug no
}

target block_name

Required.
Default: not specified

Delivery target to use for final delivery.

location directory

Default: StateDirectory/configuration_block_name

File system directory to use to store queued messages. Relative paths are relative to the StateDirectory.

max_parallelism integer

Default: 16

Start up to integer goroutines for message processing. Basically, this option limits amount of messages tried to be delivered concurrently.

max_tries integer

Default: 20

Attempt delivery up to integer times. Note that no more attempts will be done if a permanent error occurred during previous attempt.

Delay before the next attempt is increased exponentially using the following formula: initial_retry_time * retry_time_scale ^ (n - 1), where n is the number of attempts already made. With default settings this gives you approximately the following sequence of delays: 5mins, 6.25mins, 7.81mins, 9.76mins, 12.2mins, 15.2mins, 19mins, 23mins, ...

initial_retry_time duration

Default: 5m

Delay before the first retry after a temporary delivery failure. Subsequent retry delays are multiplied by retry_time_scale.

retry_time_scale float

Default: 1.25

Multiplier applied to the delay after each attempt, producing exponential growth of the interval between retries. See max_tries for the formula.

post_init_delay duration

Default: 10s

Minimum time to wait before retrying messages restored from the on-disk queue after start-up. If a message is scheduled to be retried sooner, its delivery is postponed until this delay has elapsed. This prevents a restart or a crash loop from immediately consuming delivery attempts.

bounce { ... }

Default: not specified

This configuration contains pipeline configuration to be used for generated DSN (Delivery Status Notification) messages.

If this is block is not present in configuration, DSNs will not be generated. Note, however, this is not what you want most of the time.

autogenerated_msg_domain domain

Default: global directive value

Domain to use in sender address for DSNs. Should be specified too if 'bounce' block is specified.

hostname domain

Default: global directive value

Hostname to use in the Reporting-MTA field of generated DSN messages. It is also used as the hostname of the bounce pipeline, if one is specified.

debug boolean

Default: no

Enable verbose logging.