Webhooks

email.failed

Fires when an email fails to send due to an error such as an invalid recipient, domain issue, or a reached quota.

The email.failed event fires when an email failed to send due to an error. Common causes include invalid recipients, API key problems, domain verification issues, or hitting your daily sending quota.

The data.failed object carries a machine-readable reason you can branch on.

{
  "type": "email.failed",
  "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",
    "failed": {
      "reason": "reached_daily_quota"
    },
    "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.failedobjectoptional

Failure details (see below).

data.failed.reasonstringoptional

Reason for the failure, e.g. reached_daily_quota.

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.