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What is a complained event?

A complained event is generated when a recipient files a spam complaint about an email message. This indicates that the recipient considers the email to be unwanted or unsolicited. The recipient’s email address is automatically added to your suppression list so you won’t accidentally send mail to them again, but you should remove the address from your mailing list as well. For more information, see suppressions and unsubscribe handling.

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What to do if you receive a complained event

If you receive a complained event, you should remove the recipient’s email address from your mailing list to avoid sending to them again in the future. If you receive a large number of complaints, you should investigate the cause and take action to reduce your complaint rate. This could involve improving the quality of your email content, ensuring that you have proper permission to email your recipients, or making it easier for recipients to unsubscribe from your emails.
If you receive a large number of complaints, your sending may be restricted or your account may be suspended. It’s important to monitor your complaint rate and take action to reduce it if necessary.

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Fields for complained events

  • email: Sender email address.
  • customer_handle: Your account ID.
  • timestamp: Unix timestamp of the event.
  • event: The type of event, complained in this case.
  • recipients: List of recipient email addresses that filed complaints.
  • campaign_id (optional): The campaign ID associated with the message, if applicable.
  • request_id (optional): A unique identifier generated to track the original HTTP request. This will be blank if the message is sent via SMTP instead of the API.
  • smtp_id: A unique identifier used to track the message, matching the Message-Id header.

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Example complained event

{
    "email": "sender@example.com",
    "customer_handle": "examplecorp",
    "timestamp": 1700000000,
    "event": "complained",
    "recipients": [
        "recipient@example.net"
    ],
    "campaign_id": "spring-sale-2026",
    "request_id": "4b06083a23724f279c8d11a370e641f8",
    "smtp_id": "<c8d0c0e8412a4e9e9687814d9a7c67da@example.com>"
}