The recommended default: keep every dead letter. The failure has already been logged at
error level and emitted as a [:ddd, :outbox, :dead_letter] telemetry event, so someone
looks at it and replays it by hand (mix vic.outbox.replay).
A dead letter means a handler failed repeatedly, usually because of a bug or bad data, so replaying it automatically before anyone has looked at it mostly repeats the failure. Automatic replay is opt-in, for transient causes such as an outage longer than the retries:
config :vicander, :dead_letters,
max_replays: 3, # replay each dead letter at most this many times (default 0)
replay_cooldown_ms: 60_000 # wait this long after it died before replaying (default 1 min)After max_replays replays it is kept.