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When it triggers

This event fires when the recipient opens the email. Open tracking works by embedding a tracking pixel in the email HTML.
Open tracking is not 100% accurate. Some email clients block tracking pixels or pre-load images, which can affect results.

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Payload

{
  "type": "email.opened",
  "data": {
    "email_id": "em_abc123",
    "from": "hello@yourdomain.com",
    "to": "user@example.com",
    "subject": "Welcome to SendKit",
    "tags": [],
    "created_at": "2026-03-02T12:05:00+00:00"
  },
  "created_at": "2026-03-02T12:05:00+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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tags
array
Tags associated with the email. Each tag has name and value string fields. Returns an empty array if no tags were set.
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created_at
string
ISO 8601 timestamp of when the email was created.