[ 'messenger_dsn_email' => 'sync://', // sync means no queue 'messenger_dsn_hit' => 'sync://', // sync means no queue 'messenger_dsn_failed' => null, // failed transport is optional 'messenger_retry_strategy_max_retries' => 3, // Maximum number of retries for a failed send 'messenger_retry_strategy_delay' => 1000, // Delay in milliseconds between retries 'messenger_retry_strategy_multiplier' => 2.0, // Delay multiplier between retries e.g. 1 second delay, 2 seconds, 4 seconds 'messenger_retry_strategy_max_delay' => 0, // maximum delay in milliseconds between retries ], ];