Email Queue

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Stalwart’s outbound queue. Reachable from Mail Deliverability → Queue.

What lives in the queue

  • Messages awaiting first delivery attempt.
  • Messages deferred by the recipient (4xx response): retry intervals follow Stalwart’s exponential schedule.
  • Messages held by an administrator (paused flag).

Successfully delivered or permanently bounced messages leave the queue immediately and surface in Email Logs.

Columns

  • Queue ID
  • Submitted at
  • Next attempt at
  • From, To
  • Size
  • Reason held (last 4xx response, or paused-by-admin)
  • Attempt count
  • Age

Per-row actions

  • Retry now: moves the next-attempt timestamp to “now”; Stalwart picks it up on the next queue tick.
  • Bounce: generates an immediate permanent bounce to the sender; removes from queue.
  • Hold: pause without bouncing; admin returns later to retry or bounce.
  • View headers: show the full message headers without exposing the body.

Bulk actions

Selecting multiple rows enables bulk retry, bulk bounce, bulk hold. Useful after fixing a transient outbound problem (DNS, MX block, certificate expiry on the receiving end).

Why a queue page exists

Stalwart’s CLI supports the same operations, but during an incident an operator wants a single screen that shows what is stuck, what the recipient said, and what the next attempt looks like. The queue page is that screen.

Suspended senders

If Mail Throttles suspended a sender mid-batch, queued messages from that sender appear with reason sender-suspended. They remain in the queue until the suspension is cleared.

Health

Queue depth and oldest-message age feed the service_down event source (M14) when they exceed configured thresholds (default: depth > 1000 or oldest > 4 hours).