email.delivery_delayed

Event triggered whenever the email couldn't be delivered due to a temporary issue.

Delivery delays can occur, for example, when the recipient's inbox is full, or when the receiving email server experiences a transient issue.

All webhook payloads follow a consistent top-level structure with event-specific data nested within the data object.

• type (string) — The event type that triggered the webhook (e.g., email.delivery_delayed).

• created_at (string) — ISO 8601 timestamp when the webhook event was created.

• data (object) — Event-specific data containing detailed information about the event. The data object for the email.delivery_delayed event contains the following parameters:

  object parameters

  • broadcast_id (string) — Unique identifier for the broadcast campaign (if applicable)
  • created_at (string) — ISO 8601 timestamp when the email was created
  • email_id (string) — Unique identifier for the specific email
  • message_id (string) — RFC Message-ID header value for the email
  • from (string) — Sender's email address. For sent events, this matches the value passed at send time and may include a display name (e.g., Name <email@domain.com>). For received events, this is the bare email address only; the display name from the original From: header is preserved in headers.from on the retrieve endpoint.
  • to (array) — Array of impacted recipient email addresses
  • subject (string) — Email subject line
  • template_id (string) — Unique identifier for the template used (if applicable)
  • tags (Record<string, string>) — Object of tag key-value pairs associated with the email.

    Example:

    {
      "category": "welcome",
      "user_id": "1234567890"
    }

{
  "type": "email.delivery_delayed",
  "created_at": "2026-02-22T23:41:12.126Z",
  "data": {
    "broadcast_id": "8b146471-e88e-4322-86af-016cd36fd216",
    "created_at": "2026-02-22T23:41:11.894Z",
    "email_id": "56761188-7520-42d8-8898-ff6fc54ce618",
    "message_id": "<111-222-333@email.example.com>",
    "from": "Acme <onboarding@resend.dev>",
    "to": ["delivered@resend.dev"],
    "subject": "Sending this example",
    "template_id": "43f68331-0622-4e15-8202-246a0388854b",
    "tags": {
      "category": "confirm_email"
    }
  }
}