Webhooks

email.opened

Fires the first time a recipient opens the email. Requires open tracking on the sending domain.

The email.opened event fires the first time a recipient opens the email. It is delivered at most once per recipient per email — later opens by the same recipient are recorded against the open count but do not fire another event. It requires open tracking to be enabled on the sending domain.

Open rates are not always accurate — image-blocking, prefetching, and privacy proxies can both suppress and inflate opens. Treat opens as a directional signal, not an exact count.

{
  "type": "email.opened",
  "created_at": "2026-06-22T23:41:12.126Z",
  "data": {
    "campaign_id": "8b146471-e88e-4322-86af-016cd36fd216",
    "created_at": "2026-06-22T23:41:11.894719+00:00",
    "email_id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794",
    "message_id": "<111-222-333@email.example.com>",
    "from": "Acme <onboarding@example.com>",
    "to": ["recipient@example.com"],
    "subject": "Sending this example",
    "template_id": "43f68331-0622-4e15-8202-246a0388854b"
  }
}

Payload

typestringoptional

The event type that triggered the webhook.

created_atstringoptional

ISO 8601 timestamp when the webhook event was created.

dataobjectoptional

Event-specific data. The fields below live inside this object.

data.campaign_idstringoptional

Identifier for the campaign, if applicable.

data.created_atstringoptional

ISO 8601 timestamp when the email was created.

data.email_idstringoptional

Unique identifier for this email.

data.message_idstringoptional

RFC Message-ID header value for the email.

data.fromstringoptional

Sender address; may include a display name.

data.tostring[]optional

Recipient email address(es).

data.subjectstringoptional

Email subject line.

data.template_idstringoptional

Identifier of the template used, if applicable.

This is one of several events MailBlastr can deliver. See the full list of webhook event types.