Webhooks

The monthly quota reached a threshold

Posted to the subscriptions to quota.threshold_reached at 50, 80, 95 and 100% of the monthly quota, once a month per threshold. Signed and retried like every event. The test event (POST /api/v1/webhooks/{id}/test) arrives under this type too, with data: { test: true, message } and none of the fields of the real event: check data.test first.

postWebhookquota.threshold_reached

Headers

Mailcheer-Signaturestring required

t=<unix timestamp>,v1=<hex>: v1 is the HMAC-SHA256 of "<t>.<raw body>" keyed with the subscription's secret. Reject a t more than 300 seconds away from your clock.

Mailcheer-Timestampstring required

The same t, in seconds.

Mailcheer-Event-Idstring required

The event's id — the same on every attempt and every replay: the deduplication key.

Mailcheer-Event-Typestring required

The event's type.

Mailcheer-Delivery-Idstring required

This delivery. A manual replay gets a new one.

Mailcheer-Attemptstring required

The attempt number, starting at 1.

Payload

OR

Example payload

{
  "id": "evt_3kT9xQ2mV7aB1cD4",
  "type": "quota.threshold_reached",
  "created_at": "2026-09-24T16:02:11.000Z",
  "data": {
    "threshold": 80,
    "plan": "free",
    "quota": 3000,
    "sent": 2400,
    "in_flight": 35,
    "remaining": 565,
    "resets_at": "2026-10-01T00:00:00.000Z",
    "period": "2026-09"
  }
}

Response

Any 2xx within 15 seconds acknowledges receipt. Anything else — another status, a redirect (not followed), no answer, a network error — is retried: 5 attempts in all, the next ones 30 s, 2 min, 10 min and 1 h after the previous failure.

Changes

Webhooks have no change history: a webhook is keyed by its event name rather than a path and method, so no recorded change can name it.