Webhooks

email.delivery_delayed

Fires when an email could not be delivered due to a temporary issue and will be retried.

The email.delivery_delayed event fires when an email couldn't be delivered due to a temporary issue — for example a full recipient inbox, greylisting, or a transient problem on the receiving server.

A delay is not a failure: MailBlastr keeps retrying delivery. You may still receive a later `email.delivered` or `email.bounced` for the same email_id.

{
  "type": "email.delivery_delayed",
  "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",
    "tags": {
      "category": "confirm_email"
    }
  }
}

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.

data.tagsobjectoptional

Object of tag key-value pairs associated with the email.

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