Use Undo Send, Send Later and Outbox

Standard Compose can use a short Undo Send buffer and can also schedule a future delivery time.

1. Configure the default undo window under Settings.
2. Compose the message normally.
3. Optionally choose a future Send later date/time.
4. After queuing, use the Inbox notification or Outbox & scheduled to cancel while the message is still queued.

Once the worker claims or sends the message, it can no longer be cancelled. Failed queued messages are retried up to the platform retry limit and then remain visible in Outbox for review.