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When it triggers

This event fires when the recipient’s mail server temporarily defers delivery. SendKit will continue to retry delivery automatically. If delivery eventually succeeds, you will receive an email.delivered event.

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Payload

{
  "type": "email.delivery_delayed",
  "data": {
    "email_id": "em_abc123",
    "from": "hello@yourdomain.com",
    "to": "user@example.com",
    "subject": "Welcome to SendKit",
    "created_at": "2026-03-02T12:00:04+00:00"
  },
  "created_at": "2026-03-02T12:00:04+00:00"
}

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Payload fields

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email_id
string
Unique identifier of the email.
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from
string
Sender email address.
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to
string
Recipient email address.
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subject
string
Email subject line.
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created_at
string
ISO 8601 timestamp of when the email was created.