Soft bounce threshold before suppression

Soft bounces are temporary delivery failures (mailbox full, server temporarily unavailable) that resolve on their own in most cases. Suppressing on the first soft bounce is over-aggressive and discards valid contacts experiencing transient issues. Ignoring soft bounces entirely is the opposite failure: repeated soft bounces to the same address indicate a systemic problem — the mailbox may have been abandoned, full indefinitely, or the server may be filtering your sender. Without a counter and threshold, soft-bouncing addresses accumulate undetected on the active list, raising your overall bounce rate and generating misleading delivery stats.

Implement a soft bounce counter with a configurable window and threshold:

const SOFT_BOUNCE_THRESHOLD = parseInt(process.env.SOFT_BOUNCE_THRESHOLD ?? '3')
const SOFT_BOUNCE_WINDOW_DAYS = parseInt(process.env.SOFT_BOUNCE_WINDOW_DAYS ?? '7')

async function handleSoftBounce(email: string, eventId: string) {
  const windowStart = new Date(Date.now() - SOFT_BOUNCE_WINDOW_DAYS * 86_400_000)
  const recentCount = await db.bounceEvent.count({
    where: { email, bounce_type: 'soft', occurred_at: { gte: windowStart } }
  })
  await db.bounceEvent.create({
    data: { email, bounce_type: 'soft', occurred_at: new Date(), source_event_id: eventId }
  })
  if (recentCount + 1 >= SOFT_BOUNCE_THRESHOLD) {
    await suppressContact(email, 'soft_bounce_threshold')
  }
}

Reset the counter on successful delivery to that address. Default threshold of 3 within 7 days matches industry guidance; tune via environment variables rather than hardcoding.